[All] Expand artifact hub to all plugins (#4645)

- Adds artifact hub check to gradle command
- Add tests for build.gradle and settings.gradle check
- Update all example build.gradle and settings.gradle files

flutter/flutter/issues/120119

Expansion of https://github.com/flutter/packages/pull/4567

script/tool/lib/src/gradle_check_command.dart

@@ -66,6 +66,12 @@ class GradleCheckCommand extends PackageLoopingCommand {
       if (!_validateExampleTopLevelBuildGradle(package, topLevelGradleFile)) {
         succeeded = false;
       }
+      final File topLevelSettingsGradleFile =
+          _getSettingsGradleFile(androidDir);
+      if (!_validateExampleTopLevelSettingsGradle(
+          package, topLevelSettingsGradleFile)) {
+        succeeded = false;
+      }
 
       final File appGradleFile =
           _getBuildGradleFile(androidDir.childDirectory('app'));
@@ -82,6 +88,10 @@ class GradleCheckCommand extends PackageLoopingCommand {
   // Returns the gradle file in the given directory.
   File _getBuildGradleFile(Directory dir) => dir.childFile('build.gradle');
 
+  // Returns the settings gradle file in the given directory.
+  File _getSettingsGradleFile(Directory dir) =>
+      dir.childFile('settings.gradle');
+
   // Returns the main/AndroidManifest.xml file for the given package.
   File _getMainAndroidManifest(RepositoryPackage package,
       {required bool isExample}) {
@@ -120,6 +130,124 @@ class GradleCheckCommand extends PackageLoopingCommand {
     return succeeded;
   }
 
+  /// Documentation url for Artifact hub implementation in flutter repo's.
+  @visibleForTesting
+  static const String artifactHubDocumentationString =
+      r'https://github.com/flutter/flutter/wiki/Plugins-and-Packages-repository-structure#gradle-structure';
+
+  /// String printed as example of valid example root build.gradle repository
+  /// configuration that enables artifact hub env variable.
+  @visibleForTesting
+  static const String exampleRootGradleArtifactHubString = '''
+        // See $artifactHubDocumentationString for more info.
+        def artifactRepoKey = 'ARTIFACT_HUB_REPOSITORY'
+        if (System.getenv().containsKey(artifactRepoKey)) {
+            println "Using artifact hub"
+            maven { url System.getenv(artifactRepoKey) }
+        }
+''';
+
+  /// Validates that [gradleLines] reads and uses a artifiact hub repository
+  /// when ARTIFACT_HUB_REPOSITORY is set.
+  ///
+  /// Required in root gradle file.
+  bool _validateArtifactHubUsage(
+      RepositoryPackage example, List<String> gradleLines) {
+    // Gradle variable name used to hold environment variable string.
+    const String keyVariable = 'artifactRepoKey';
+    final RegExp keyPresentRegex =
+        RegExp('$keyVariable' r"\s+=\s+'ARTIFACT_HUB_REPOSITORY'");
+    final RegExp documentationPresentRegex = RegExp(
+        r'github\.com.*wiki.*Plugins-and-Packages-repository-structure.*gradle-structure');
+    final RegExp keyReadRegex =
+        RegExp(r'if.*System\.getenv.*\.containsKey.*' '$keyVariable');
+    final RegExp keyUsedRegex =
+        RegExp(r'maven.*url.*System\.getenv\(' '$keyVariable');
+
+    final bool keyPresent =
+        gradleLines.any((String line) => keyPresentRegex.hasMatch(line));
+    final bool documentationPresent = gradleLines
+        .any((String line) => documentationPresentRegex.hasMatch(line));
+    final bool keyRead =
+        gradleLines.any((String line) => keyReadRegex.hasMatch(line));
+    final bool keyUsed =
+        gradleLines.any((String line) => keyUsedRegex.hasMatch(line));
+
+    if (!(documentationPresent && keyPresent && keyRead && keyUsed)) {
+      printError('Failed Artifact Hub validation. Include the following in '
+          'example root build.gradle:\n$exampleRootGradleArtifactHubString');
+    }
+
+    return keyPresent && documentationPresent && keyRead && keyUsed;
+  }
+
+  /// Validates the top-level settings.gradle for an example app (e.g.,
+  /// some_package/example/android/settings.gradle).
+  bool _validateExampleTopLevelSettingsGradle(
+      RepositoryPackage package, File gradleSettingsFile) {
+    print('${indentation}Validating '
+        '${getRelativePosixPath(gradleSettingsFile, from: package.directory)}.');
+    final String contents = gradleSettingsFile.readAsStringSync();
+    final List<String> lines = contents.split('\n');
+    // This is tracked as a variable rather than a sequence of &&s so that all
+    // failures are reported at once, not just the first one.
+    bool succeeded = true;
+    if (!_validateArtifactHubSettingsUsage(package, lines)) {
+      succeeded = false;
+    }
+    return succeeded;
+  }
+
+  /// String printed as example of valid example root settings.gradle repository
+  /// configuration that enables artifact hub env variable.
+  @visibleForTesting
+  static String exampleRootSettingsArtifactHubString = '''
+// See $artifactHubDocumentationString for more info.
+buildscript {
+  repositories {
+    maven {
+      url "https://plugins.gradle.org/m2/"
+    }
+  }
+  dependencies {
+    classpath "gradle.plugin.com.google.cloud.artifactregistry:artifactregistry-gradle-plugin:2.2.1"
+  }
+}
+apply plugin: "com.google.cloud.artifactregistry.gradle-plugin"
+''';
+
+  /// Validates that [gradleLines] reads and uses a artifiact hub repository
+  /// when ARTIFACT_HUB_REPOSITORY is set.
+  ///
+  /// Required in root gradle file.
+  bool _validateArtifactHubSettingsUsage(
+      RepositoryPackage example, List<String> gradleLines) {
+    final RegExp documentationPresentRegex = RegExp(
+        r'github\.com.*wiki.*Plugins-and-Packages-repository-structure.*gradle-structure');
+    final RegExp artifactRegistryDefinitionRegex = RegExp(
+        r'classpath.*gradle\.plugin\.com\.google\.cloud\.artifactregistry:artifactregistry-gradle-plugin');
+    final RegExp artifactRegistryPluginApplyRegex = RegExp(
+        r'apply.*plugin.*com\.google\.cloud\.artifactregistry\.gradle-plugin');
+
+    final bool documentationPresent = gradleLines
+        .any((String line) => documentationPresentRegex.hasMatch(line));
+    final bool artifactRegistryDefined = gradleLines
+        .any((String line) => artifactRegistryDefinitionRegex.hasMatch(line));
+    final bool artifactRegistryPluginApplied = gradleLines
+        .any((String line) => artifactRegistryPluginApplyRegex.hasMatch(line));
+
+    if (!(documentationPresent &&
+        artifactRegistryDefined &&
+        artifactRegistryPluginApplied)) {
+      printError('Failed Artifact Hub validation. Include the following in '
+          'example root settings.gradle:\n$exampleRootSettingsArtifactHubString');
+    }
+
+    return documentationPresent &&
+        artifactRegistryDefined &&
+        artifactRegistryPluginApplied;
+  }
+
   /// Validates the top-level build.gradle for an example app (e.g.,
   /// some_package/example/android/build.gradle).
   bool _validateExampleTopLevelBuildGradle(
@@ -138,6 +266,9 @@ class GradleCheckCommand extends PackageLoopingCommand {
     if (!_validateKotlinVersion(package, lines)) {
       succeeded = false;
     }
+    if (!_validateArtifactHubUsage(package, lines)) {
+      succeeded = false;
+    }
     return succeeded;
   }