Shard web tests; enable semantics tests on the Web (#42203)

Shard web tests; enable semantics tests on the Web

.cirrus.yml

@@ -152,10 +152,31 @@ task:
       container:
         cpu: 8
         memory: 24G
-    - name: web_tests-linux
-      allow_failures: true
+    - name: web_tests-linux-shard-0
+      use_compute_credits: $CIRRUS_USER_COLLABORATOR == 'true'
       env:
         SHARD: web_tests
+        WEB_SHARD: 0
+      test_script:
+        - dart --enable-asserts ./dev/bots/test.dart
+      container:
+        cpu: 4
+        memory: 12G
+    - name: web_tests-linux-shard-1
+      use_compute_credits: $CIRRUS_USER_COLLABORATOR == 'true'
+      env:
+        SHARD: web_tests
+        WEB_SHARD: 1
+      test_script:
+        - dart --enable-asserts ./dev/bots/test.dart
+      container:
+        cpu: 4
+        memory: 12G
+    - name: web_tests-linux-shard-2
+      use_compute_credits: $CIRRUS_USER_COLLABORATOR == 'true'
+      env:
+        SHARD: web_tests
+        WEB_SHARD: 2
       test_script:
         - dart --enable-asserts ./dev/bots/test.dart
       container:

dev/bots/test.dart

@@ -445,7 +445,6 @@ Future<void> _runWebTests() async {
     'test/material',
     'test/painting',
     'test/rendering',
-    'test/semantics',
     'test/widgets',
   ];
 
@@ -686,10 +685,16 @@ class EvalResult {
   final int exitCode;
 }
 
+/// The number of Cirrus jobs that run web tests in parallel.
+///
+/// WARNING: if you change this number, also change .cirrus.yml
+/// and make sure it runs _all_ shards.
+const int _kWebShardCount = 3;
+
 Future<void> _runFlutterWebTest(String workingDirectory, {
   List<String> tests,
 }) async {
-  final List<String> allTests = <String>[];
+  List<String> allTests = <String>[];
   for (String testDirPath in tests) {
     final Directory testDir = Directory(path.join(workingDirectory, testDirPath));
     allTests.addAll(
@@ -699,6 +704,20 @@ Future<void> _runFlutterWebTest(String workingDirectory, {
         .map((File file) => path.relative(file.path, from: workingDirectory))
     );
   }
+
+  // If a shard is specified only run tests in that shard.
+  final int webShard = int.tryParse(Platform.environment['WEB_SHARD'] ?? 'n/a');
+  if (webShard != null) {
+    if (webShard >= _kWebShardCount) {
+      throw 'WEB_SHARD must be <= _kWebShardCount, but was $webShard';
+    }
+    final List<String> shard = <String>[];
+    for (int i = webShard; i < allTests.length; i += _kWebShardCount) {
+      shard.add(allTests[i]);
+    }
+    allTests = shard;
+  }
+
   print(allTests.join('\n'));
   print('${allTests.length} tests total');