[camera_android_camerax][tool] Integrate dart_code_linter for cyclomatic complexity checks

.repo_tool_config.yaml

@@ -20,6 +20,9 @@ allowed_dependencies:
   # A pin can be either an exact version, or a range with an explicit, inclusive
   # max version, which must a version that already exists, not a future version.
   pinned:
+    # Cyclomatic complexity linter for camera_android_camerax
+    - dart_code_linter
+
     # Test-only dependency, so does not impact package clients, and
     # has limited impact so could be easily removed if there are
     # ever maintenance issues in the future.

packages/camera/camera_android_camerax/analysis_options.yaml

@@ -0,0 +1,16 @@
+include: ../../../analysis_options.yaml
+
+analyzer:
+  exclude:
+    - build/**
+    - android/**
+    - ios/**
+    - web/**
+    - windows/**
+    - macos/**
+    - linux/**
+
+dart_code_linter:
+  metrics:
+    cyclomatic-complexity: 15
+

packages/camera/camera_android_camerax/pubspec.yaml

@@ -27,6 +27,7 @@ dependencies:
 
 dev_dependencies:
   build_runner: ^2.2.0
+  dart_code_linter: 4.1.5
   dart_skills_lint:
     git:
       url: https://github.com/flutter/skills.git

script/configs/custom_analysis.yaml

@@ -34,3 +34,6 @@
 - rfw/example
 # Disables docs requirements, as it is test code.
 - web_benchmarks/testing/test_app
+# Uses custom analysis to enable the cyclomatic complexity linter plugin.
+- camera/camera_android_camerax
+

script/tool/lib/src/analyze_command.dart

@@ -5,6 +5,7 @@
 import 'dart:io' as io;
 
 import 'package:file/file.dart';
+import 'package:yaml/yaml.dart';
 
 import 'common/core.dart';
 import 'common/file_filters.dart';
@@ -330,10 +331,75 @@ class AnalyzeCommand extends PackageLoopingCommand {
       ...skillsErrors,
     ];
 
-    if (errors.isNotEmpty) {
-      return PackageResult.fail(errors);
+    final customCheckRunners = <_CustomLinter>[
+      _CustomLinter(dependencyName: 'dart_code_linter', run: _runDartCodeLinterForPackage),
+    ];
+
+    // Skip custom linters during downgrade as metrics are redundant and vulnerable to dependency issues.
+    if (!getBoolArg(_downgradeFlag)) {
+      final Pubspec pubspec = package.parsePubspec();
+      for (final runner in customCheckRunners) {
+        final bool hasDependency = pubspec.devDependencies.containsKey(runner.dependencyName);
+        if (hasDependency) {
+          errors.addAll(await runner.run(package));
+        }
+      }
     }
-    return PackageResult.success();
+
+    return errors.isEmpty ? PackageResult.success() : PackageResult.fail(errors);
+  }
+
+  /// Retrieves the configured cyclomatic complexity threshold from the local
+  /// `analysis_options.yaml` if it exists and is configured.
+  int? _getLinterThreshold(RepositoryPackage package) {
+    final File optionsFile = package.directory.childFile('analysis_options.yaml');
+    if (!optionsFile.existsSync()) {
+      return null;
+    }
+    try {
+      final Object? yaml = loadYaml(optionsFile.readAsStringSync());
+      if (yaml is YamlMap) {
+        final Object? linter = yaml['dart_code_linter'];
+        if (linter is YamlMap) {
+          final Object? metrics = linter['metrics'];
+          if (metrics is YamlMap) {
+            final Object? complexity = metrics['cyclomatic-complexity'];
+            if (complexity is int) {
+              return complexity;
+            }
+          }
+        }
+      }
+    } catch (_) {
+      // Ignore errors parsing invalid/incomplete files.
+    }
+    return null;
+  }
+
+  /// Runs the `dart_code_linter` metrics analyzer on the package.
+  ///
+  /// Assumes `dart_code_linter` is present in `dev_dependencies`.
+  Future<List<String>> _runDartCodeLinterForPackage(RepositoryPackage package) async {
+    if (!package.libDirectory.existsSync()) {
+      return <String>[];
+    }
+    print('Running dart_code_linter:metrics analysis...');
+    final int linterExitCode = await processRunner.runAndStream(_dartBinaryPath, <String>[
+      'run',
+      'dart_code_linter:metrics',
+      'analyze',
+      'lib',
+      '--set-exit-on-violation-level=warning',
+    ], workingDir: package.directory);
+    if (linterExitCode != 0) {
+      final int? threshold = _getLinterThreshold(package);
+      final thresholdMessage = threshold != null ? ' (configured threshold: $threshold)' : '';
+      return <String>[
+        'Metrics violations found$thresholdMessage. See the package\'s local "analysis_options.yaml" for configured thresholds.',
+      ];
+    }
+
+    return <String>[];
   }
 
   /// Validates that `.agents/skills` contains Dart code if configured for skills analysis.
@@ -485,3 +551,17 @@ class AnalyzeCommand extends PackageLoopingCommand {
     return errors.isEmpty ? PackageResult.success() : PackageResult.fail(errors);
   }
 }
+
+/// Represents a custom linter check that is executed during package analysis.
+class _CustomLinter {
+  const _CustomLinter({required this.dependencyName, required this.run});
+
+  /// The name of the package dependency that triggers this custom check.
+  ///
+  /// The check is only executed if this dependency is listed in the package's
+  /// `dev_dependencies`.
+  final String dependencyName;
+
+  /// The runner function that executes the custom check.
+  final Future<List<String>> Function(RepositoryPackage) run;
+}