[ci] Run analysis with older versions of Flutter (#5000)

script/tool/lib/src/analyze_command.dart

@@ -10,12 +10,9 @@ import 'package:yaml/yaml.dart';
 
 import 'common/core.dart';
 import 'common/package_looping_command.dart';
-import 'common/plugin_command.dart';
 import 'common/process_runner.dart';
 import 'common/repository_package.dart';
 
-const int _exitPackagesGetFailed = 3;
-
 /// A command to run Dart analysis on packages.
 class AnalyzeCommand extends PackageLoopingCommand {
   /// Creates a analysis command instance.
@@ -84,41 +81,8 @@ class AnalyzeCommand extends PackageLoopingCommand {
     return false;
   }
 
-  /// Ensures that the dependent packages have been fetched for all packages
-  /// (including their sub-packages) that will be analyzed.
-  Future<bool> _runPackagesGetOnTargetPackages() async {
-    final List<Directory> packageDirectories =
-        await getTargetPackagesAndSubpackages()
-            .map((PackageEnumerationEntry entry) => entry.package.directory)
-            .toList();
-    final Set<String> packagePaths =
-        packageDirectories.map((Directory dir) => dir.path).toSet();
-    packageDirectories.removeWhere((Directory directory) {
-      // Remove the 'example' subdirectories; 'flutter packages get'
-      // automatically runs 'pub get' there as part of handling the parent
-      // directory.
-      return directory.basename == 'example' &&
-          packagePaths.contains(directory.parent.path);
-    });
-    for (final Directory package in packageDirectories) {
-      final int exitCode = await processRunner.runAndStream(
-          flutterCommand, <String>['packages', 'get'],
-          workingDir: package);
-      if (exitCode != 0) {
-        return false;
-      }
-    }
-    return true;
-  }
-
   @override
   Future<void> initializeRun() async {
-    print('Fetching dependencies...');
-    if (!await _runPackagesGetOnTargetPackages()) {
-      printError('Unable to get dependencies.');
-      throw ToolExit(_exitPackagesGetFailed);
-    }
-
     _allowedCustomAnalysisDirectories =
         getStringListArg(_customAnalysisFlag).expand<String>((String item) {
       if (item.endsWith('.yaml')) {
@@ -138,6 +102,19 @@ class AnalyzeCommand extends PackageLoopingCommand {
 
   @override
   Future<PackageResult> runForPackage(RepositoryPackage package) async {
+    // For non-example packages, fetch dependencies. 'flutter packages get'
+    // automatically runs 'pub get' in examples as part of handling the parent
+    // directory, which is guaranteed to come first in the package enumeration.
+    if (package.directory.basename != 'example' ||
+        !RepositoryPackage(package.directory.parent).pubspecFile.existsSync()) {
+      final int exitCode = await processRunner.runAndStream(
+          flutterCommand, <String>['packages', 'get'],
+          workingDir: package.directory);
+      if (exitCode != 0) {
+        return PackageResult.fail(<String>['Unable to get dependencies']);
+      }
+    }
+
     if (_hasUnexpecetdAnalysisOptions(package)) {
       return PackageResult.fail(<String>['Unexpected local analysis options']);
     }

script/tool/lib/src/common/package_looping_command.dart

@@ -9,6 +9,8 @@ import 'package:file/file.dart';
 import 'package:git/git.dart';
 import 'package:path/path.dart' as p;
 import 'package:platform/platform.dart';
+import 'package:pub_semver/pub_semver.dart';
+import 'package:pubspec_parse/pubspec_parse.dart';
 
 import 'core.dart';
 import 'plugin_command.dart';
@@ -75,7 +77,16 @@ abstract class PackageLoopingCommand extends PluginCommand {
     Platform platform = const LocalPlatform(),
     GitDir? gitDir,
   }) : super(packagesDir,
-            processRunner: processRunner, platform: platform, gitDir: gitDir);
+            processRunner: processRunner, platform: platform, gitDir: gitDir) {
+    argParser.addOption(
+      _skipByFlutterVersionArg,
+      help: 'Skip any packages that require a Flutter version newer than '
+          'the provided version.',
+    );
+  }
+
+  static const String _skipByFlutterVersionArg =
+      'skip-if-not-supporting-flutter-version';
 
   /// Packages that had at least one [logWarning] call.
   final Set<PackageEnumerationEntry> _packagesWithWarnings =
@@ -219,6 +230,11 @@ abstract class PackageLoopingCommand extends PluginCommand {
     _otherWarningCount = 0;
     _currentPackageEntry = null;
 
+    final String minFlutterVersionArg = getStringArg(_skipByFlutterVersionArg);
+    final Version? minFlutterVersion = minFlutterVersionArg.isEmpty
+        ? null
+        : Version.parse(minFlutterVersionArg);
+
     final DateTime runStart = DateTime.now();
 
     await initializeRun();
@@ -242,7 +258,8 @@ abstract class PackageLoopingCommand extends PluginCommand {
 
       PackageResult result;
       try {
-        result = await runForPackage(entry.package);
+        result = await _runForPackageIfSupported(entry.package,
+            minFlutterVersion: minFlutterVersion);
       } catch (e, stack) {
         printError(e.toString());
         printError(stack.toString());
@@ -285,6 +302,26 @@ abstract class PackageLoopingCommand extends PluginCommand {
     return true;
   }
 
+  /// Returns the result of running [runForPackage] if the package is supported
+  /// by any run constraints, or a skip result if it is not.
+  Future<PackageResult> _runForPackageIfSupported(
+    RepositoryPackage package, {
+    Version? minFlutterVersion,
+  }) async {
+    if (minFlutterVersion != null) {
+      final Pubspec pubspec = package.parsePubspec();
+      final VersionConstraint? flutterConstraint =
+          pubspec.environment?['flutter'];
+      if (flutterConstraint != null &&
+          !flutterConstraint.allows(minFlutterVersion)) {
+        return PackageResult.skip(
+            'Does not support Flutter ${minFlutterVersion.toString()}');
+      }
+    }
+
+    return await runForPackage(package);
+  }
+
   void _printSuccess(String message) {
     captureOutput ? print(message) : printSuccess(message);
   }

script/tool/lib/src/common/plugin_command.dart

@@ -409,6 +409,9 @@ abstract class PluginCommand extends Command<void> {
   ///
   /// By default, packages excluded via --exclude will not be in the stream, but
   /// they can be included by passing false for [filterExcluded].
+  ///
+  /// Subpackages are guaranteed to be after the containing package in the
+  /// stream.
   Stream<PackageEnumerationEntry> getTargetPackagesAndSubpackages(
       {bool filterExcluded = true}) async* {
     await for (final PackageEnumerationEntry plugin