Add supported Luci builders for cocoon repo

app_dart/lib/src/datastore/cocoon_config.dart

@@ -72,11 +72,7 @@ class Config {
 
   // Gets supported luci builders based on github http request.
   Future<List<Map<String, dynamic>>> _getLuciBuilders(String bucket) async {
-    final String builderContent =
-        await getBuilders(Providers.freshHttpClient, loggingService, twoSecondLinearBackoff, bucket);
-    final Map<String, dynamic> builderMap = json.decode(builderContent) as Map<String, dynamic>;
-    final List<dynamic> builderList = builderMap['builders'] as List<dynamic>;
-    return builderList.map((dynamic builder) => builder as Map<String, dynamic>).toList();
+    return await getBuilders(Providers.freshHttpClient, loggingService, twoSecondLinearBackoff, bucket);
   }
 
   Future<String> _getSingleValue(String id) async {

app_dart/lib/src/foundation/utils.dart

@@ -84,9 +84,18 @@ Future<RepositorySlug> repoNameForBuilder(List<Map<String, dynamic>> builders, S
 }
 
 /// Gets supported luci builders based on [bucket] via GitHub http request.
-Future<String> getBuilders(HttpClientProvider branchHttpClientProvider, Logging log,
+Future<List<Map<String, dynamic>>> getBuilders(HttpClientProvider branchHttpClientProvider, Logging log,
     GitHubBackoffCalculator gitHubBackoffCalculator, String bucket) async {
   final String filename = bucket == 'try' ? 'luci_try_builders.json' : 'luci_prod_builders.json';
-  final String content = await remoteFileContent(branchHttpClientProvider, log, gitHubBackoffCalculator, filename);
-  return content ?? '{"builders":[]}';
+  String builderContent = await remoteFileContent(branchHttpClientProvider, log, gitHubBackoffCalculator, filename);
+  builderContent ??= '{"builders":[]}';
+  Map<String, dynamic> builderMap;
+  try {
+    builderMap = json.decode(builderContent) as Map<String, dynamic>;
+  } on FormatException catch (e) {
+    log.error('error: $e');
+    builderMap = <String, dynamic>{'builders': <dynamic>[]};
+  }
+  final List<dynamic> builderList = builderMap['builders'] as List<dynamic>;
+  return builderList.map((dynamic builder) => builder as Map<String, dynamic>).toList();
 }

app_dart/test/foundation/utils_test.dart

@@ -18,16 +18,17 @@ const String branchRegExp = '''
       flutter-1.1-candidate.1
       ''';
 const String luciBuilders = '''
-      builders: [
-        {
-          test1:value1,
-          test2:value2,
-        },{
-          test1:value3,
-          test2:value4,
-          test3:value5,
-        }
-      ]
+      {
+        "builders":[
+            {
+              "name":"Cocoon",
+              "repo":"cocoon"
+            }, {
+              "name":"Cocoon2",
+              "repo":"cocoon"
+            }
+        ]
+      }
       ''';
 
 void main() {
@@ -116,30 +117,29 @@ void main() {
       });
       test('returns luci builders', () async {
         lucBuilderHttpClient.request.response.body = luciBuilders;
-        final String builders =
+        final List<Map<String, dynamic>> builders =
             await getBuilders(() => lucBuilderHttpClient, log, (int attempt) => Duration.zero, 'try');
-        expect(builders, '''
-      builders: [
-        {
-          test1:value1,
-          test2:value2,
-        },{
-          test1:value3,
-          test2:value4,
-          test3:value5,
-        }
-      ]
-      ''');
+        expect(builders.length, 2);
+        expect(builders[0]['name'], 'Cocoon');
+        expect(builders[0]['repo'], 'cocoon');
+      });
+
+      test('logs error and returns empty list when json file is invalid', () async {
+        lucBuilderHttpClient.request.response.body = '{"builders":[';
+        final List<Map<String, dynamic>> builders =
+            await getBuilders(() => lucBuilderHttpClient, log, (int attempt) => Duration.zero, 'try');
+        expect(log.records.where(hasLevel(LogLevel.ERROR)), isNotEmpty);
+        expect(builders.length, 0);
       });
 
       test('returns empty list when http request fails', () async {
         int retry = 0;
         lucBuilderHttpClient.onIssueRequest = (FakeHttpClientRequest request) => retry++;
         lucBuilderHttpClient.request.response.statusCode = HttpStatus.serviceUnavailable;
         lucBuilderHttpClient.request.response.body = luciBuilders;
-        final String builders =
+        final List<Map<String, dynamic>> builders =
             await getBuilders(() => lucBuilderHttpClient, log, (int attempt) => Duration.zero, 'try');
-        expect(builders, '{"builders":[]}');
+        expect(builders.length, 0);
       });
     });
 

dev/README.md

@@ -0,0 +1,22 @@
+This directory contains resources that the Flutter team uses during 
+the development of cocoon.
+
+## Luci builder file
+`cocoon_try_builders.json` contains the supported luci try builders 
+for cocoon. It follows format:
+```json
+{
+    "builders":[
+        {
+            "name":"xxx",
+            "repo":"cocoon"
+        }
+    ]
+}
+```
+This file will be mainly used in [`flutter/cocoon`](https://github.com/flutter/cocoon)
+to trigger LUCI presubmit tasks.
+
+If any new changes, please validate json contents by running
+`dart validat_json.dart cocoon_try_builders.json`.
+

dev/cocoon_try_builders.json

@@ -0,0 +1,8 @@
+{
+   "builders":[
+      {
+         "name":"Cocoon",
+         "repo":"cocoon"
+      }
+   ]
+}

dev/validate_json.dart

@@ -0,0 +1,38 @@
+// Copyright 2020 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:convert';
+import 'dart:io' show File;
+
+/// Validates if the input builders JSON file has valid contents.
+///
+/// Examples:
+/// dart validate_json.dart /path/to/json/file
+Future<bool> main(List<String> args) async {
+  final String jsonString = await File(args[0]).readAsString();
+  Map<String, dynamic> decodedJson;
+  bool decodedStatus = true;
+  try {
+    decodedJson = json.decode(jsonString) as Map<String, dynamic>;
+    final List<dynamic> builders = decodedJson['builders'] as List<dynamic>;
+    if (builders == null) {
+      print('Json format is violated: no "builders" exists. Please follow');
+      print('''
+      {
+        "builders":[
+          {
+            "name":"xxx",
+            "repo":"cocoon"
+          }
+        ]
+      }''');
+      return decodedStatus = false;
+    }
+  } on FormatException catch (e) {
+    print('error: $e');
+    return decodedStatus = false;
+  }
+  print('Success.');
+  return decodedStatus;
+}