[pigeon] added more errors for improper usage (#393)

2025-06-26 02:19:24 +08:00 · 2021-06-29 12:27:59 -07:00
parent 59160ba428
commit 4996352511
7 changed files with 910 additions and 287 deletions
--- a/packages/pigeon/CHANGELOG.md
+++ b/packages/pigeon/CHANGELOG.md
@ -2,6 +2,7 @@

 * [front-end] Added a more explicit error if generic fields are used.
 * [front-end] Added a more explicit error for static fields.
+* [front-end] Added more errors for incorrect usage of Pigeon (previously they were just ignored).

 ## 0.3.0

--- a/packages/pigeon/lib/ast.dart
+++ b/packages/pigeon/lib/ast.dart
@ -21,7 +21,10 @@ class Method extends Node {
    required this.name,
    required this.returnType,
    required this.argType,
+    this.isArgNullable = false,
    this.isAsynchronous = false,
+    this.isReturnNullable = false,
+    this.offset,
  });

  /// The name of the method.
@ -30,12 +33,21 @@ class Method extends Node {
  /// The data-type of the return value.
  String returnType;

+  /// True if the method can return a null value.
+  bool isReturnNullable;
+
  /// The data-type of the argument.
  String argType;

+  /// True if the argument has a null tag `?`.
+  bool isArgNullable;
+
  /// Whether the receiver of this method is expected to return synchronously or not.
  bool isAsynchronous;

+  /// The offset in the source file where the field appears.
+  int? offset;
+
  @override
  String toString() {
    return '(Api name:$name returnType:$returnType argType:$argType isAsynchronous:$isAsynchronous)';
@ -76,6 +88,8 @@ class Field extends Node {
  Field({
    required this.name,
    required this.dataType,
+    required this.isNullable,
+    this.typeArguments,
    this.offset,
  });

@ -88,6 +102,12 @@ class Field extends Node {
  /// The offset in the source file where the field appears.
  int? offset;

+  /// True if the datatype is nullable (ex `int?`).
+  bool isNullable;
+
+  /// Type parameters used for generics.
+  List<Field>? typeArguments;
+
  @override
  String toString() {
    return '(Field name:$name dataType:$dataType)';
--- a/packages/pigeon/lib/pigeon_lib.dart
+++ b/packages/pigeon/lib/pigeon_lib.dart
@ -391,7 +391,7 @@ List<Error> _validateAst(Root root, String source) {
  final List<String> customEnums = root.enums.map((Enum x) => x.name).toList();
  for (final Class klass in root.classes) {
    for (final Field field in klass.fields) {
-      if (field.dataType.contains('<')) {
+      if (field.typeArguments != null) {
        result.add(Error(
          message:
              'Unsupported datatype:"${field.dataType}" in class "${klass.name}". Generic fields aren\'t yet supported (https://github.com/flutter/flutter/issues/63468).',
@ -410,15 +410,33 @@ List<Error> _validateAst(Root root, String source) {
  }
  for (final Api api in root.apis) {
    for (final Method method in api.methods) {
+      if (method.isReturnNullable) {
+        result.add(Error(
+          message:
+              'Nullable return types types aren\'t supported for Pigeon methods: "${method.argType}" in API: "${api.name}" method: "${method.name}',
+          lineNumber: _calculateLineNumberNullable(source, method.offset),
+        ));
+      }
+      if (method.isArgNullable) {
+        result.add(Error(
+          message:
+              'Nullable argument types aren\'t supported for Pigeon methods: "${method.argType}" in API: "${api.name}" method: "${method.name}',
+          lineNumber: _calculateLineNumberNullable(source, method.offset),
+        ));
+      }
      if (_validTypes.contains(method.argType)) {
        result.add(Error(
-            message:
-                'Unsupported argument type: "${method.argType}" in API: "${api.name}" method: "${method.name}'));
+          message:
+              'Primitive argument types aren\'t yet supported (https://github.com/flutter/flutter/issues/66467): "${method.argType}" in API: "${api.name}" method: "${method.name}',
+          lineNumber: _calculateLineNumberNullable(source, method.offset),
+        ));
      }
      if (_validTypes.contains(method.returnType)) {
        result.add(Error(
-            message:
-                'Unsupported return type: "${method.returnType}" in API: "${api.name}" method: "${method.name}'));
+          message:
+              'Primitive return types aren\'t yet supported (https://github.com/flutter/flutter/issues/66467): "${method.returnType}" in API: "${api.name}" method: "${method.name}',
+          lineNumber: _calculateLineNumberNullable(source, method.offset),
+        ));
      }
    }
  }
@ -426,6 +444,17 @@ List<Error> _validateAst(Root root, String source) {
  return result;
 }

+class _FindInitializer extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
+  dart_ast.Expression? initializer;
+  @override
+  Object? visitVariableDeclaration(dart_ast.VariableDeclaration node) {
+    if (node.initializer != null) {
+      initializer = node.initializer;
+    }
+    return null;
+  }
+}
+
 class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
  _RootBuilder(this.source, this.ignoresInvalidImports);

@ -472,30 +501,11 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
      }
    }

-    final List<Class> classesWithNullTagStripped = _classes.map((Class aClass) {
-      return Class(
-          name: aClass.name,
-          fields: aClass.fields.map((Field field) {
-            String datatype = field.dataType;
-            if (datatype.endsWith('?')) {
-              datatype = datatype.substring(0, datatype.length - 1);
-            } else {
-              // TODO(aaclarke): Provide an error when not using a nullable type.
-              // _errors.add(Error(
-              //     message:
-              //         'Field ${aClass.name}.${field.name} must be nullable.'));
-            }
-            return Field(
-                name: field.name, dataType: datatype, offset: field.offset);
-          }).toList());
-    }).toList();
-
    final List<String> classesToCheck = List<String>.from(referencedTypes);
    while (classesToCheck.isNotEmpty) {
      final String next = classesToCheck.last;
      classesToCheck.removeLast();
-      final Class aClass = classesWithNullTagStripped.firstWhere(
-          (Class x) => x.name == next,
+      final Class aClass = _classes.firstWhere((Class x) => x.name == next,
          orElse: () => Class(name: '', fields: <Field>[]));
      for (final Field field in aClass.fields) {
        if (!referencedTypes.contains(field.dataType) &&
@ -510,8 +520,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
        ? (Class x) => !referencedTypes.contains(x.name)
        : (Class x) =>
            !referencedTypes.contains(x.name) && !typeFilter.contains(x.name);
-    final List<Class> referencedClasses =
-        List<Class>.from(classesWithNullTagStripped);
+    final List<Class> referencedClasses = List<Class>.from(_classes);
    referencedClasses.removeWhere(classRemover);

    final List<Enum> referencedEnums = List<Enum>.from(_enums);
@ -646,6 +655,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
  Object? visitMethodDeclaration(dart_ast.MethodDeclaration node) {
    final dart_ast.FormalParameterList parameters = node.parameters!;
    late String argType;
+    bool isNullable = false;
    if (parameters.parameters.isEmpty) {
      argType = 'void';
    } else {
@ -655,6 +665,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
          // ignore: always_specify_types
          .firstWhere((e) => e is dart_ast.TypeName) as dart_ast.TypeName;
      argType = typeName.name.name;
+      isNullable = typeName.question != null;
    }
    final bool isAsynchronous = _hasMetadata(node.metadata, 'async');
    if (_currentApi != null) {
@ -662,7 +673,15 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
          name: node.name.name,
          returnType: node.returnType.toString(),
          argType: argType,
-          isAsynchronous: isAsynchronous));
+          isReturnNullable: node.returnType!.question != null,
+          isArgNullable: isNullable,
+          isAsynchronous: isAsynchronous,
+          offset: node.offset));
+    } else if (_currentClass != null) {
+      _errors.add(Error(
+          message:
+              'Methods aren\'t supported in Pigeon data classes ("${node.name.name}").',
+          lineNumber: _calculateLineNumber(source, node.offset)));
    }
    node.visitChildren(this);
    return null;
@ -689,20 +708,59 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
                'Pigeon doesn\'t support static fields ("${node.toString()}"), consider using enums.',
            lineNumber: _calculateLineNumber(source, node.offset)));
      } else if (type is dart_ast.NamedType) {
-        _currentClass!.fields.add(Field(
-          name: node.fields.variables[0].name.name,
-          dataType: type.toString(),
-          offset: node.offset,
-        ));
+        final _FindInitializer findInitializerVisitor = _FindInitializer();
+        node.visitChildren(findInitializerVisitor);
+        if (findInitializerVisitor.initializer != null) {
+          _errors.add(Error(
+              message:
+                  'Initialization isn\'t supported for fields in Pigeon data classes ("$node"), just use nullable types with no initializer (example "int? x;").',
+              lineNumber: _calculateLineNumber(source, node.offset)));
+        } else {
+          final dart_ast.TypeArgumentList? typeArguments = type.typeArguments;
+          _currentClass!.fields.add(Field(
+            name: node.fields.variables[0].name.name,
+            dataType: type.name.name,
+            isNullable: type.question != null,
+            // TODO(aaclarke): This probably has to be recursive at some point.
+            // ignore: prefer_null_aware_operators
+            typeArguments: typeArguments == null
+                ? null
+                : typeArguments.arguments
+                    .map((dart_ast.TypeAnnotation e) => Field(
+                          name: '',
+                          dataType: (e.childEntities.first
+                                  as dart_ast.SimpleIdentifier)
+                              .name,
+                          isNullable: e.question != null,
+                          offset: e.offset,
+                        ))
+                    .toList(),
+            offset: node.offset,
+          ));
+        }
      } else {
        _errors.add(Error(
            message: 'Expected a named type but found "${node.toString()}".',
            lineNumber: _calculateLineNumber(source, node.offset)));
      }
+    } else if (_currentApi != null) {
+      _errors.add(Error(
+          message: 'Fields aren\'t supported in Pigeon API classes ("$node").',
+          lineNumber: _calculateLineNumber(source, node.offset)));
    }
    node.visitChildren(this);
    return null;
  }
+
+  @override
+  Object? visitConstructorDeclaration(dart_ast.ConstructorDeclaration node) {
+    final String type = _currentApi != null ? 'API classes' : 'data classes';
+    _errors.add(Error(
+        message: 'Constructors aren\'t supported in $type ("$node").',
+        lineNumber: _calculateLineNumber(source, node.offset)));
+    node.visitChildren(this);
+    return null;
+  }
 }

 int? _calculateLineNumberNullable(String contents, int? offset) {
--- a/packages/pigeon/test/dart_generator_test.dart
+++ b/packages/pigeon/test/dart_generator_test.dart
@ -15,6 +15,7 @@ void main() {
        Field(
          name: 'field1',
          dataType: 'dataType1',
+          isNullable: true,
        ),
      ],
    );
@ -57,17 +58,26 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
@ -80,11 +90,23 @@ void main() {
    final Root root = Root(apis: <Api>[], classes: <Class>[
      Class(
        name: 'Input',
-        fields: <Field>[Field(name: 'input', dataType: 'String')],
+        fields: <Field>[
+          Field(
+            name: 'input',
+            dataType: 'String',
+            isNullable: true,
+          )
+        ],
      ),
      Class(
        name: 'Nested',
-        fields: <Field>[Field(name: 'nested', dataType: 'Input')],
+        fields: <Field>[
+          Field(
+            name: 'nested',
+            dataType: 'Input',
+            isNullable: true,
+          )
+        ],
      )
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
@ -110,17 +132,26 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
@ -135,14 +166,19 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'void',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
@ -157,14 +193,19 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'void',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
@ -183,14 +224,19 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'void',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
@ -205,14 +251,19 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'EnumClass',
+          isArgNullable: false,
          returnType: 'EnumClass',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'EnumClass',
-          fields: <Field>[Field(name: 'enum1', dataType: 'Enum')]),
+      Class(name: 'EnumClass', fields: <Field>[
+        Field(
+          name: 'enum1',
+          dataType: 'Enum',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[
      Enum(
        name: 'Enum',
@ -237,14 +288,19 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'EnumClass',
+          isArgNullable: false,
          returnType: 'EnumClass',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'EnumClass',
-          fields: <Field>[Field(name: 'enum1', dataType: 'Enum')]),
+      Class(name: 'EnumClass', fields: <Field>[
+        Field(
+          name: 'enum1',
+          dataType: 'Enum',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[
      Enum(
        name: 'Enum',
@ -271,14 +327,19 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'void',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
@ -296,23 +357,33 @@ void main() {
            Method(
              name: 'doSomething',
              argType: 'Input',
+              isArgNullable: false,
              returnType: 'Output',
              isAsynchronous: false,
            ),
            Method(
              name: 'voidReturner',
              argType: 'Input',
+              isArgNullable: false,
              returnType: 'void',
              isAsynchronous: false,
            )
          ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer mainCodeSink = StringBuffer();
    final StringBuffer testCodeSink = StringBuffer();
@ -342,6 +413,7 @@ void main() {
        Field(
          name: 'field1',
          dataType: 'dataType1',
+          isNullable: true,
        ),
      ],
    );
@ -362,17 +434,26 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: true,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
@ -389,17 +470,26 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'void',
          isAsynchronous: true,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
@ -415,17 +505,26 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: true,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
@ -440,14 +539,19 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'void',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: true,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateDart(const DartOptions(isNullSafe: false), root, sink);
--- a/packages/pigeon/test/java_generator_test.dart
+++ b/packages/pigeon/test/java_generator_test.dart
@ -14,6 +14,7 @@ void main() {
        Field(
          name: 'field1',
          dataType: 'int',
+          isNullable: true,
        ),
      ],
    );
@ -63,6 +64,7 @@ void main() {
        Field(
          name: 'field1',
          dataType: 'int',
+          isNullable: true,
        )
      ],
    );
@ -86,17 +88,18 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: true,
          returnType: 'Output',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(name: 'input', dataType: 'String', isNullable: true)
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(name: 'output', dataType: 'String', isNullable: true)
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -110,14 +113,14 @@ void main() {
  test('all the simple datatypes header', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
      Class(name: 'Foobar', fields: <Field>[
-        Field(name: 'aBool', dataType: 'bool'),
-        Field(name: 'aInt', dataType: 'int'),
-        Field(name: 'aDouble', dataType: 'double'),
-        Field(name: 'aString', dataType: 'String'),
-        Field(name: 'aUint8List', dataType: 'Uint8List'),
-        Field(name: 'aInt32List', dataType: 'Int32List'),
-        Field(name: 'aInt64List', dataType: 'Int64List'),
-        Field(name: 'aFloat64List', dataType: 'Float64List'),
+        Field(name: 'aBool', dataType: 'bool', isNullable: true),
+        Field(name: 'aInt', dataType: 'int', isNullable: true),
+        Field(name: 'aDouble', dataType: 'double', isNullable: true),
+        Field(name: 'aString', dataType: 'String', isNullable: true),
+        Field(name: 'aUint8List', dataType: 'Uint8List', isNullable: true),
+        Field(name: 'aInt32List', dataType: 'Int32List', isNullable: true),
+        Field(name: 'aInt64List', dataType: 'Int64List', isNullable: true),
+        Field(name: 'aFloat64List', dataType: 'Float64List', isNullable: true),
      ]),
    ], enums: <Enum>[]);

@ -141,17 +144,18 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(name: 'input', dataType: 'String', isNullable: true)
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(name: 'output', dataType: 'String', isNullable: true)
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -167,14 +171,15 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'void',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(name: 'input', dataType: 'String', isNullable: true)
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -190,14 +195,15 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'void',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(name: 'input', dataType: 'String', isNullable: true)
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -214,14 +220,15 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'void',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(name: 'output', dataType: 'String', isNullable: true)
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -237,14 +244,15 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'void',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: false,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(name: 'output', dataType: 'String', isNullable: true)
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -256,9 +264,9 @@ void main() {

  test('gen list', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Foobar',
-          fields: <Field>[Field(name: 'field1', dataType: 'List')]),
+      Class(name: 'Foobar', fields: <Field>[
+        Field(name: 'field1', dataType: 'List', isNullable: true)
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -270,9 +278,9 @@ void main() {

  test('gen map', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Foobar',
-          fields: <Field>[Field(name: 'field1', dataType: 'Map')]),
+      Class(name: 'Foobar', fields: <Field>[
+        Field(name: 'field1', dataType: 'Map', isNullable: true)
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -289,6 +297,7 @@ void main() {
        Field(
          name: 'nested',
          dataType: 'Nested',
+          isNullable: true,
        )
      ],
    );
@ -298,6 +307,7 @@ void main() {
        Field(
          name: 'data',
          dataType: 'int',
+          isNullable: true,
        )
      ],
    );
@ -324,17 +334,18 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: true,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(name: 'input', dataType: 'String', isNullable: true)
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(name: 'output', dataType: 'String', isNullable: true)
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -357,17 +368,18 @@ void main() {
        Method(
          name: 'doSomething',
          argType: 'Input',
+          isArgNullable: false,
          returnType: 'Output',
          isAsynchronous: true,
        )
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(name: 'input', dataType: 'String', isNullable: true)
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(name: 'output', dataType: 'String', isNullable: true)
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
@ -391,6 +403,7 @@ void main() {
        Field(
          name: 'enum1',
          dataType: 'Enum1',
+          isNullable: true,
        ),
      ],
    );
--- a/packages/pigeon/test/objc_generator_test.dart
+++ b/packages/pigeon/test/objc_generator_test.dart
@ -9,9 +9,13 @@ import 'package:test/test.dart';
 void main() {
  test('gen one class header', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Foobar',
-          fields: <Field>[Field(name: 'field1', dataType: 'String')]),
+      Class(name: 'Foobar', fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(const ObjcOptions(), root, sink);
@ -22,9 +26,13 @@ void main() {

  test('gen one class source', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Foobar',
-          fields: <Field>[Field(name: 'field1', dataType: 'String')]),
+      Class(name: 'Foobar', fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(const ObjcOptions(header: 'foo.h'), root, sink);
@ -76,8 +84,16 @@ void main() {
        Class(
          name: 'Foobar',
          fields: <Field>[
-            Field(name: 'field1', dataType: 'String'),
-            Field(name: 'enum1', dataType: 'Enum1'),
+            Field(
+              name: 'field1',
+              dataType: 'String',
+              isNullable: true,
+            ),
+            Field(
+              name: 'enum1',
+              dataType: 'Enum1',
+              isNullable: true,
+            ),
          ],
        ),
      ],
@ -102,15 +118,27 @@ void main() {
  test('gen one api header', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'Output')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'Output')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(const ObjcOptions(), root, sink);
@ -125,15 +153,27 @@ void main() {
  test('gen one api source', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'Output')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'Output')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(const ObjcOptions(header: 'foo.h'), root, sink);
@ -147,14 +187,46 @@ void main() {
  test('all the simple datatypes header', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
      Class(name: 'Foobar', fields: <Field>[
-        Field(name: 'aBool', dataType: 'bool'),
-        Field(name: 'aInt', dataType: 'int'),
-        Field(name: 'aDouble', dataType: 'double'),
-        Field(name: 'aString', dataType: 'String'),
-        Field(name: 'aUint8List', dataType: 'Uint8List'),
-        Field(name: 'aInt32List', dataType: 'Int32List'),
-        Field(name: 'aInt64List', dataType: 'Int64List'),
-        Field(name: 'aFloat64List', dataType: 'Float64List'),
+        Field(
+          name: 'aBool',
+          dataType: 'bool',
+          isNullable: true,
+        ),
+        Field(
+          name: 'aInt',
+          dataType: 'int',
+          isNullable: true,
+        ),
+        Field(
+          name: 'aDouble',
+          dataType: 'double',
+          isNullable: true,
+        ),
+        Field(
+          name: 'aString',
+          dataType: 'String',
+          isNullable: true,
+        ),
+        Field(
+          name: 'aUint8List',
+          dataType: 'Uint8List',
+          isNullable: true,
+        ),
+        Field(
+          name: 'aInt32List',
+          dataType: 'Int32List',
+          isNullable: true,
+        ),
+        Field(
+          name: 'aInt64List',
+          dataType: 'Int64List',
+          isNullable: true,
+        ),
+        Field(
+          name: 'aFloat64List',
+          dataType: 'Float64List',
+          isNullable: true,
+        ),
      ]),
    ], enums: <Enum>[]);

@ -180,7 +252,11 @@ void main() {
  test('bool source', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
      Class(name: 'Foobar', fields: <Field>[
-        Field(name: 'aBool', dataType: 'bool'),
+        Field(
+          name: 'aBool',
+          dataType: 'bool',
+          isNullable: true,
+        ),
      ]),
    ], enums: <Enum>[]);

@ -193,12 +269,20 @@ void main() {

  test('nested class header', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Nested',
-          fields: <Field>[Field(name: 'nested', dataType: 'Input')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Nested', fields: <Field>[
+        Field(
+          name: 'nested',
+          dataType: 'Input',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(const ObjcOptions(header: 'foo.h'), root, sink);
@ -209,12 +293,20 @@ void main() {

  test('nested class source', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Nested',
-          fields: <Field>[Field(name: 'nested', dataType: 'Input')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Nested', fields: <Field>[
+        Field(
+          name: 'nested',
+          dataType: 'Input',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(const ObjcOptions(header: 'foo.h'), root, sink);
@ -225,9 +317,13 @@ void main() {

  test('prefix class header', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Foobar',
-          fields: <Field>[Field(name: 'field1', dataType: 'String')]),
+      Class(name: 'Foobar', fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(const ObjcOptions(prefix: 'ABC'), root, sink);
@ -237,9 +333,13 @@ void main() {

  test('prefix class source', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Foobar',
-          fields: <Field>[Field(name: 'field1', dataType: 'String')]),
+      Class(name: 'Foobar', fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(const ObjcOptions(prefix: 'ABC'), root, sink);
@ -250,15 +350,27 @@ void main() {
  test('prefix nested class header', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'Nested')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'Nested')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Nested',
-          fields: <Field>[Field(name: 'nested', dataType: 'Input')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Nested', fields: <Field>[
+        Field(
+          name: 'nested',
+          dataType: 'Input',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(const ObjcOptions(prefix: 'ABC'), root, sink);
@ -271,15 +383,27 @@ void main() {
  test('prefix nested class source', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'Nested')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'Nested')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Nested',
-          fields: <Field>[Field(name: 'nested', dataType: 'Input')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Nested', fields: <Field>[
+        Field(
+          name: 'nested',
+          dataType: 'Input',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(const ObjcOptions(prefix: 'ABC'), root, sink);
@ -292,15 +416,27 @@ void main() {
  test('gen flutter api header', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'Output')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'Output')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(const ObjcOptions(header: 'foo.h'), root, sink);
@ -316,15 +452,27 @@ void main() {
  test('gen flutter api source', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'Output')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'Output')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')])
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ])
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(const ObjcOptions(header: 'foo.h'), root, sink);
@ -336,12 +484,20 @@ void main() {
  test('gen host void header', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'void')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'void')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(
@ -353,12 +509,20 @@ void main() {
  test('gen host void source', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'void')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'void')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(
@ -372,12 +536,20 @@ void main() {
  test('gen flutter void return header', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'void')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'void')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(
@ -389,12 +561,20 @@ void main() {
  test('gen flutter void return source', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
-        Method(name: 'doSomething', argType: 'Input', returnType: 'void')
+        Method(
+            name: 'doSomething',
+            argType: 'Input',
+            isArgNullable: false,
+            returnType: 'void')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(
@ -407,12 +587,20 @@ void main() {
  test('gen host void arg header', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
-        Method(name: 'doSomething', argType: 'void', returnType: 'Output')
+        Method(
+            name: 'doSomething',
+            argType: 'void',
+            isArgNullable: false,
+            returnType: 'Output')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(
@ -424,12 +612,20 @@ void main() {
  test('gen host void arg source', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
-        Method(name: 'doSomething', argType: 'void', returnType: 'Output')
+        Method(
+            name: 'doSomething',
+            argType: 'void',
+            isArgNullable: false,
+            returnType: 'Output')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(
@ -441,12 +637,20 @@ void main() {
  test('gen flutter void arg header', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
-        Method(name: 'doSomething', argType: 'void', returnType: 'Output')
+        Method(
+            name: 'doSomething',
+            argType: 'void',
+            isArgNullable: false,
+            returnType: 'Output')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(
@ -461,12 +665,20 @@ void main() {
  test('gen flutter void arg header', () {
    final Root root = Root(apis: <Api>[
      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
-        Method(name: 'doSomething', argType: 'void', returnType: 'Output')
+        Method(
+            name: 'doSomething',
+            argType: 'void',
+            isArgNullable: false,
+            returnType: 'Output')
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(
@ -481,9 +693,13 @@ void main() {

  test('gen list', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Foobar',
-          fields: <Field>[Field(name: 'field1', dataType: 'List')]),
+      Class(name: 'Foobar', fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'List',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(const ObjcOptions(), root, sink);
@ -494,9 +710,13 @@ void main() {

  test('gen map', () {
    final Root root = Root(apis: <Api>[], classes: <Class>[
-      Class(
-          name: 'Foobar',
-          fields: <Field>[Field(name: 'field1', dataType: 'Map')]),
+      Class(name: 'Foobar', fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'Map',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(const ObjcOptions(), root, sink);
@ -511,16 +731,25 @@ void main() {
        Method(
            name: 'doSomething',
            argType: 'Input',
+            isArgNullable: false,
            returnType: 'void',
            isAsynchronous: true)
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(
@ -538,16 +767,25 @@ void main() {
        Method(
            name: 'doSomething',
            argType: 'Input',
+            isArgNullable: false,
            returnType: 'Output',
            isAsynchronous: true)
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(
@ -565,13 +803,18 @@ void main() {
        Method(
            name: 'doSomething',
            argType: 'void',
+            isArgNullable: false,
            returnType: 'Output',
            isAsynchronous: true)
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcHeader(
@ -589,6 +832,7 @@ void main() {
        Method(
            name: 'doSomething',
            argType: 'void',
+            isArgNullable: false,
            returnType: 'void',
            isAsynchronous: true)
      ])
@ -609,16 +853,25 @@ void main() {
        Method(
            name: 'doSomething',
            argType: 'Input',
+            isArgNullable: false,
            returnType: 'Output',
            isAsynchronous: true)
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(
@ -636,16 +889,25 @@ void main() {
        Method(
            name: 'doSomething',
            argType: 'Input',
+            isArgNullable: false,
            returnType: 'void',
            isAsynchronous: true)
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Input',
-          fields: <Field>[Field(name: 'input', dataType: 'String')]),
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Input', fields: <Field>[
+        Field(
+          name: 'input',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(
@ -663,6 +925,7 @@ void main() {
        Method(
            name: 'doSomething',
            argType: 'void',
+            isArgNullable: false,
            returnType: 'void',
            isAsynchronous: true)
      ])
@ -681,13 +944,18 @@ void main() {
        Method(
            name: 'doSomething',
            argType: 'void',
+            isArgNullable: false,
            returnType: 'Output',
            isAsynchronous: true)
      ])
    ], classes: <Class>[
-      Class(
-          name: 'Output',
-          fields: <Field>[Field(name: 'output', dataType: 'String')]),
+      Class(name: 'Output', fields: <Field>[
+        Field(
+          name: 'output',
+          dataType: 'String',
+          isNullable: true,
+        )
+      ]),
    ], enums: <Enum>[]);
    final StringBuffer sink = StringBuffer();
    generateObjcSource(
--- a/packages/pigeon/test/pigeon_lib_test.dart
+++ b/packages/pigeon/test/pigeon_lib_test.dart
@ -184,10 +184,12 @@ void main() {
    expect(input?.fields.length, equals(1));
    expect(input?.fields[0].name, equals('input'));
    expect(input?.fields[0].dataType, equals('String'));
+    expect(input?.fields[0].isNullable, isTrue);

    expect(output?.fields.length, equals(1));
    expect(output?.fields[0].name, equals('output'));
    expect(output?.fields[0].dataType, equals('String'));
+    expect(output?.fields[0].isNullable, isTrue);
  });

  test('invalid datatype', () {
@ -208,6 +210,7 @@ void main() {
    expect(results.root.classes[0].name, equals('ClassWithEnum'));
    expect(results.root.classes[0].fields.length, equals(1));
    expect(results.root.classes[0].fields[0].dataType, equals('Enum1'));
+    expect(results.root.classes[0].fields[0].isNullable, isTrue);
    expect(results.root.classes[0].fields[0].name, equals('enum1'));
  });

@ -232,6 +235,7 @@ void main() {
        results.root.classes.firstWhere((Class x) => x.name == 'Nested');
    expect(nested.fields.length, equals(1));
    expect(nested.fields[0].dataType, equals('Input1'));
+    expect(nested.fields[0].isNullable, isTrue);
  });

  test('flutter api', () {
@ -417,6 +421,161 @@ abstract class NotificationsHostApi {
    });
  });

+  test('test method in data class error', () {
+    final Pigeon dartle = Pigeon.setup();
+    _withTempFile('compilationError.dart', (File file) {
+      file.writeAsStringSync('''
+class Foo {
+  int? x;
+  int? foo() { return x; }
+}
+
+@HostApi()
+abstract class Api {
+  Foo doit(Foo foo);
+}
+''');
+      final ParseResults results = dartle.parseFile(file.path);
+      expect(results.errors.length, 1);
+      expect(results.errors[0].lineNumber, 3);
+      expect(results.errors[0].message, contains('Method'));
+    });
+  });
+
+  test('test field initialization', () {
+    final Pigeon dartle = Pigeon.setup();
+    _withTempFile('compilationError.dart', (File file) {
+      file.writeAsStringSync('''
+class Foo {
+  int? x = 123;  
+}
+
+@HostApi()
+abstract class Api {
+  Foo doit(Foo foo);
+}
+''');
+      final ParseResults results = dartle.parseFile(file.path);
+      expect(results.errors.length, 1);
+      expect(results.errors[0].lineNumber, 2);
+      expect(results.errors[0].message, contains('Initialization'));
+    });
+  });
+
+  test('test field in api error', () {
+    final Pigeon dartle = Pigeon.setup();
+    _withTempFile('compilationError.dart', (File file) {
+      file.writeAsStringSync('''
+class Foo {
+  int? x;
+}
+
+@HostApi()
+abstract class Api {
+  int? x;
+  Foo doit(Foo foo);
+}
+''');
+      final ParseResults results = dartle.parseFile(file.path);
+      expect(results.errors.length, 1);
+      expect(results.errors[0].lineNumber, 7);
+      expect(results.errors[0].message, contains('Field'));
+    });
+  });
+
+  test('constructor in data class', () {
+    final Pigeon dartle = Pigeon.setup();
+    _withTempFile('compilationError.dart', (File file) {
+      file.writeAsStringSync('''
+class Foo {
+  int? x;
+  Foo(this.x);
+}
+
+@HostApi()
+abstract class Api {
+  Foo doit(Foo foo);
+}
+''');
+      final ParseResults results = dartle.parseFile(file.path);
+      expect(results.errors.length, 1);
+      expect(results.errors[0].lineNumber, 3);
+      expect(results.errors[0].message, contains('Constructor'));
+    });
+  });
+
+  test('nullable api arguments', () {
+    final Pigeon dartle = Pigeon.setup();
+    _withTempFile('compilationError.dart', (File file) {
+      file.writeAsStringSync('''
+class Foo {
+  int? x;
+}
+
+@HostApi()
+abstract class Api {
+  Foo doit(Foo? foo);
+}
+''');
+      final ParseResults results = dartle.parseFile(file.path);
+      expect(results.errors.length, 1);
+      expect(results.errors[0].lineNumber, 7);
+      expect(results.errors[0].message, contains('Nullable'));
+    });
+  });
+
+  test('nullable api return', () {
+    final Pigeon dartle = Pigeon.setup();
+    _withTempFile('compilationError.dart', (File file) {
+      file.writeAsStringSync('''
+class Foo {
+  int? x;
+}
+
+@HostApi()
+abstract class Api {
+  Foo? doit(Foo foo);
+}
+''');
+      final ParseResults results = dartle.parseFile(file.path);
+      expect(results.errors.length, 1);
+      expect(results.errors[0].lineNumber, 7);
+      expect(results.errors[0].message, contains('Nullable'));
+    });
+  });
+
+  test('primitive arguments', () {
+    final Pigeon dartle = Pigeon.setup();
+    _withTempFile('compilationError.dart', (File file) {
+      file.writeAsStringSync('''
+@HostApi()
+abstract class Api {
+  void doit(int foo);
+}
+''');
+      final ParseResults results = dartle.parseFile(file.path);
+      expect(results.errors.length, 1);
+      expect(results.errors[0].lineNumber, 3);
+      expect(results.errors[0].message, contains('Primitive'));
+    });
+  });
+
+  test('primitive return', () {
+    final Pigeon dartle = Pigeon.setup();
+    _withTempFile('compilationError.dart', (File file) {
+      file.writeAsStringSync('''
+@HostApi()
+abstract class Api {
+  int doit();
+}
+''');
+      final ParseResults results = dartle.parseFile(file.path);
+      expect(results.errors.length, 1);
+      expect(results.errors[0].lineNumber, 3);
+      expect(results.errors[0].message, contains('Primitive'));
+    });
+  });
+
  test('test invalid import', () {
    final Pigeon dartle = Pigeon.setup();
    _withTempFile('compilationError.dart', (File file) {