Protect flutter analyze --suggestions from erroring on missing AGP value. (#137719)

Fixes #137600 
Protect flutter analyze --suggestions from null error when AGP value is missing
Update template with a reference to new agp definition location 
Look for AGP version being set in settings.gradle (change to templates happened in https://github.com/flutter/flutter/commit/dbe0ccd8853dabdcb0f94ce2cdef892a1b10e48a#diff-20537fb84ee37894a3f3d9723a06bcf2674290ee25aa83332c2524a1f7546a6d

packages/flutter_tools/lib/src/android/gradle_utils.dart

@@ -71,19 +71,31 @@ const String maxKnownAgpVersion = '8.3';
 // compatible Java version.
 const String oldestDocumentedJavaAgpCompatibilityVersion = '4.2';
 
+// Constant used in [_buildAndroidGradlePluginRegExp] and
+// [_settingsAndroidGradlePluginRegExp] to identify the version section.
+const String _versionGroupName = 'version';
+
+// AGP can be defined in build.gradle
 // Expected content:
 // "classpath 'com.android.tools.build:gradle:7.3.0'"
-// Parentheticals are use to group which helps with version extraction.
-// "...build:gradle:(...)" where group(1) should be the version string.
-final RegExp _androidGradlePluginRegExp =
-  RegExp(r'com\.android\.tools\.build:gradle:(\d+\.\d+\.\d+)');
+// ?<version> is used to name the version group which helps with extraction.
+final RegExp _buildAndroidGradlePluginRegExp =
+    RegExp(r'com\.android\.tools\.build:gradle:(?<version>\d+\.\d+\.\d+)');
+
+// AGP can be defined in settings.gradle.
+// Expected content:
+// "id "com.android.application" version "{{agpVersion}}""
+// ?<version> is used to name the version group which helps with extraction.
+final RegExp _settingsAndroidGradlePluginRegExp = RegExp(
+    r'^\s+id\s+"com.android.application"\s+version\s+"(?<version>\d+\.\d+\.\d+)"',
+    multiLine: true);
 
 // Expected content format (with lines above and below).
 // Version can have 2 or 3 numbers.
 // 'distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.2-all.zip'
 // '^\s*' protects against commented out lines.
 final RegExp distributionUrlRegex =
-  RegExp(r'^\s*distributionUrl\s*=\s*.*\.zip', multiLine: true);
+    RegExp(r'^\s*distributionUrl\s*=\s*.*\.zip', multiLine: true);
 
 // Modified version of the gradle distribution url match designed to only match
 // gradle.org urls so that we can guarantee any modifications to the url
@@ -199,7 +211,7 @@ String getGradleVersionForAndroidPlugin(Directory directory, Logger logger) {
     return templateDefaultGradleVersion;
   }
   final String buildFileContent = buildFile.readAsStringSync();
-  final Iterable<Match> pluginMatches = _androidGradlePluginRegExp.allMatches(buildFileContent);
+  final Iterable<Match> pluginMatches = _buildAndroidGradlePluginRegExp.allMatches(buildFileContent);
   if (pluginMatches.isEmpty) {
     logger.printTrace("$buildFile doesn't provide an AGP version, assuming Gradle version: $templateDefaultGradleVersion");
     return templateDefaultGradleVersion;
@@ -309,8 +321,9 @@ OS:           Mac OS X 13.2.1 aarch64
 /// Returns the Android Gradle Plugin (AGP) version that the current project
 /// depends on when found, null otherwise.
 ///
-/// The Android plugin version is specified in the [build.gradle] file within
-/// the project's Android directory ([androidDirectory]).
+/// The Android plugin version is specified in the [build.gradle] or
+/// [settings.gradle] file within the project's
+/// Android directory ([androidDirectory]).
 String? getAgpVersion(Directory androidDirectory, Logger logger) {
   final File buildFile = androidDirectory.childFile('build.gradle');
   if (!buildFile.existsSync()) {
@@ -318,15 +331,34 @@ String? getAgpVersion(Directory androidDirectory, Logger logger) {
     return null;
   }
   final String buildFileContent = buildFile.readAsStringSync();
-  final Iterable<Match> pluginMatches =
-      _androidGradlePluginRegExp.allMatches(buildFileContent);
-  if (pluginMatches.isEmpty) {
-    logger.printTrace("$buildFile doesn't provide an AGP version");
+  final RegExpMatch? buildMatch =
+      _buildAndroidGradlePluginRegExp.firstMatch(buildFileContent);
+  if (buildMatch != null) {
+    final String? androidPluginVersion =
+        buildMatch.namedGroup(_versionGroupName);
+    logger.printTrace('$buildFile provides AGP version: $androidPluginVersion');
+    return androidPluginVersion;
+  }
+  logger.printTrace(
+      "$buildFile doesn't provide an AGP version. Checking settings.");
+  final File settingsFile = androidDirectory.childFile('settings.gradle');
+  if (!settingsFile.existsSync()) {
+    logger.printTrace('$settingsFile does not exist.');
     return null;
   }
-  final String? androidPluginVersion = pluginMatches.first.group(1);
-  logger.printTrace('$buildFile provides AGP version: $androidPluginVersion');
-  return androidPluginVersion;
+  final String settingsFileContent = settingsFile.readAsStringSync();
+  final RegExpMatch? settingsMatch =
+      _settingsAndroidGradlePluginRegExp.firstMatch(settingsFileContent);
+
+  if (settingsMatch != null) {
+    final String? androidPluginVersion =
+        settingsMatch.namedGroup(_versionGroupName);
+    logger.printTrace(
+        '$settingsFile provides AGP version: $androidPluginVersion');
+    return androidPluginVersion;
+  }
+  logger.printTrace("$settingsFile doesn't provide an AGP version.");
+  return null;
 }
 
 String _formatParseWarning(String content) {

packages/flutter_tools/lib/src/project.dart

@@ -608,15 +608,20 @@ class AndroidProject extends FlutterProjectPlatform {
     final bool compatibleGradleAgp = gradle.validateGradleAndAgp(globals.logger,
         gradleV: gradleVersion, agpV: agpVersion);
 
-    final bool compatibleJavaGradle = gradle.validateJavaAndGradle(globals.logger,
-        javaV: javaVersion, gradleV: gradleVersion);
+    final bool compatibleJavaGradle = gradle.validateJavaAndGradle(
+        globals.logger,
+        javaV: javaVersion,
+        gradleV: gradleVersion);
 
     // Begin description formatting.
     if (!compatibleGradleAgp) {
+      final String gradleDescription = agpVersion != null
+          ? 'Update Gradle to at least "${gradle.getGradleVersionFor(agpVersion)}".'
+          : '';
       description = '''
 Incompatible Gradle/AGP versions. \n
 Gradle Version: $gradleVersion, AGP Version: $agpVersion
-Update Gradle to at least "${gradle.getGradleVersionFor(agpVersion!)}".\n
+$gradleDescription\n
 See the link below for more information:
 $gradleAgpCompatUrl
 ''';

packages/flutter_tools/templates/app_shared/android-java.tmpl/build.gradle.tmpl

@@ -6,6 +6,7 @@ buildscript {
     }
 
     dependencies {
+        // AGP version is set in settings.gradle.
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }

packages/flutter_tools/templates/app_shared/android-kotlin.tmpl/build.gradle.tmpl

@@ -6,6 +6,7 @@ buildscript {
     }
 
     dependencies {
+        // AGP version is set in settings.gradle.
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }

packages/flutter_tools/test/general.shard/android/gradle_utils_test.dart

@@ -469,6 +469,51 @@ allprojects {
       );
     });
 
+    testWithoutContext('returns the AGP version when in settings', () async {
+      final Directory androidDirectory = fileSystem.directory('/android')
+        ..createSync();
+      // File must exist and can not have agp defined.
+      androidDirectory.childFile('build.gradle').writeAsStringSync(r'');
+      androidDirectory.childFile('settings.gradle').writeAsStringSync(r'''
+pluginManagement {
+    def flutterSdkPath = {
+        def properties = new Properties()
+        file("local.properties").withInputStream { properties.load(it) }
+        def flutterSdkPath = properties.getProperty("flutter.sdk")
+        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
+        return flutterSdkPath
+    }
+    settings.ext.flutterSdkPath = flutterSdkPath()
+
+    includeBuild("${settings.ext.flutterSdkPath}/packages/flutter_tools/gradle")
+
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+
+    plugins {
+        id "dev.flutter.flutter-gradle-plugin" version "1.0.0" apply false
+    }
+}
+
+plugins {
+    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
+    // Decoy value to ensure we ignore commented out lines.
+    // id "com.android.application" version "6.1.0" apply false
+    id "com.android.application" version "7.3.0" apply false
+}
+
+include ":app"
+''');
+
+      expect(
+        getAgpVersion(androidDirectory, BufferLogger.test()),
+        '7.3.0',
+      );
+    });
+
     group('validates gradle/agp versions', () {
       final List<GradleAgpTestData> testData = <GradleAgpTestData>[
         // Values too new *these need to be updated* when

packages/flutter_tools/test/general.shard/project_test.dart

@@ -659,6 +659,48 @@ dependencies {
           androidSdk: androidSdk,
         );
       });
+      group('_', () {
+        final FakeProcessManager processManager;
+        final Java java;
+        final AndroidStudio androidStudio;
+        final FakeAndroidSdkWithDir androidSdk;
+        final FileSystem fileSystem = getFileSystemForPlatform();
+        java = FakeJava(version: Version(11, 0, 2));
+        processManager = FakeProcessManager.empty();
+        androidStudio = FakeAndroidStudio();
+        androidSdk =
+            FakeAndroidSdkWithDir(fileSystem.currentDirectory);
+        fileSystem.currentDirectory
+            .childDirectory(androidStudio.javaPath!)
+            .createSync();
+        _testInMemory(
+          'null agp only',
+          () async {
+            const String gradleV = '7.0.3';
+            final FlutterProject? project = await configureGradleAgpForTest(
+              gradleV: gradleV,
+              agpV: '',
+            );
+            final CompatibilityResult value =
+                await project!.android.hasValidJavaGradleAgpVersions();
+            expect(value.success, isFalse);
+            // Should not have the valid string.
+            expect(
+                value.description,
+                isNot(
+                    contains(RegExp(AndroidProject.validJavaGradleAgpString))));
+            // On gradle/agp error print help url null value for agp.
+            expect(value.description,
+                contains(RegExp(AndroidProject.gradleAgpCompatUrl)));
+            expect(value.description, contains(RegExp(gradleV)));
+            expect(value.description, contains(RegExp('null')));
+          },
+          java: java,
+          androidStudio: androidStudio,
+          processManager: processManager,
+          androidSdk: androidSdk,
+        );
+      });
     });
 
     group('language', () {