[web] Fail if Skia Gold is required but unavailable (#29792)

Author: mdebbar

lib/web_ui/dev/run.dart

@@ -29,13 +29,23 @@ class RunCommand extends Command<bool> with ArgUtils<bool> {
       defaultsTo: false,
       help: 'Lists all available build steps.',
     );
+    argParser.addFlag(
+      'require-skia-gold',
+      defaultsTo: false,
+      help: 'Whether we require Skia Gold to be available or not. When this '
+            'flag is true, the tests will fail if Skia Gold is not available.',
+    );
   }
 
   @override
   String get name => 'run';
 
   bool get isListSteps => boolArg('list');
 
+  /// When running screenshot tests, require Skia Gold to be available and
+  /// reachable.
+  bool get requireSkiaGold => boolArg('require-skia-gold');
+
   @override
   String get description => 'Runs a build step.';
 
@@ -52,6 +62,7 @@ class RunCommand extends Command<bool> with ArgUtils<bool> {
           browserName: browserName,
           isDebug: false,
           doUpdateScreenshotGoldens: false,
+          requireSkiaGold: requireSkiaGold,
           overridePathToCanvasKit: null,
         ),
     };

lib/web_ui/dev/steps/run_tests_step.dart

@@ -38,6 +38,7 @@ class RunTestsStep implements PipelineStep {
     required this.browserName,
     required this.isDebug,
     required this.doUpdateScreenshotGoldens,
+    required this.requireSkiaGold,
     this.testFiles,
     required this.overridePathToCanvasKit,
   }) : _browserEnvironment = getBrowserEnvironment(browserName);
@@ -48,6 +49,9 @@ class RunTestsStep implements PipelineStep {
   final bool doUpdateScreenshotGoldens;
   final String? overridePathToCanvasKit;
 
+  /// Require Skia Gold to be available and reachable.
+  final bool requireSkiaGold;
+
   final BrowserEnvironment _browserEnvironment;
 
   /// Global list of shards that failed.
@@ -184,12 +188,13 @@ class RunTestsStep implements PipelineStep {
       browserName: browserName,
     );
 
-    if (!await _checkSkiaClient(skiaClient)) {
-      print('WARNING: Unable to use Skia Client in this environment.');
-      return null;
+    if (await _checkSkiaClient(skiaClient)) {
+      return skiaClient;
     }
 
-    return skiaClient;
+    if (requireSkiaGold) {
+      throw ToolExit('Skia Gold is required but is unavailable.');
+    }
   }
 
   /// Checks whether the Skia Client is usable in this environment.

lib/web_ui/dev/test_runner.dart

@@ -51,6 +51,13 @@ class TestCommand extends Command<bool> with ArgUtils<bool> {
               'won\'t be consistent with CIs when this flag is set. flutter '
               'command should be set in the PATH for this flag to be useful.'
               'This flag can also be used to test local Flutter changes.')
+      ..addFlag(
+        'require-skia-gold',
+        defaultsTo: false,
+        help:
+            'Whether we require Skia Gold to be available or not. When this '
+            'flag is true, the tests will fail if Skia Gold is not available.',
+      )
       ..addFlag(
         'update-screenshot-goldens',
         defaultsTo: false,
@@ -117,6 +124,10 @@ class TestCommand extends Command<bool> with ArgUtils<bool> {
   /// The name of the browser to run tests in.
   String get browserName => stringArg('browser');
 
+  /// When running screenshot tests, require Skia Gold to be available and
+  /// reachable.
+  bool get requireSkiaGold => boolArg('require-skia-gold');
+
   /// When running screenshot tests writes them to the file system into
   /// ".dart_tool/goldens".
   bool get doUpdateScreenshotGoldens => boolArg('update-screenshot-goldens');
@@ -144,6 +155,7 @@ class TestCommand extends Command<bool> with ArgUtils<bool> {
         testFiles: testFiles,
         isDebug: isDebug,
         doUpdateScreenshotGoldens: doUpdateScreenshotGoldens,
+        requireSkiaGold: requireSkiaGold,
         overridePathToCanvasKit: overridePathToCanvasKit,
       ),
     ]);