Fix finding third party analysis options.

Change-Id: If6792018fa9a4a64316be034dfa4b6e14c2e03d8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/166124
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Keerti Parthasarathy <[email protected]>

Author: keertip

pkg/analyzer/lib/src/dart/micro/resolve_file.dart

@@ -462,10 +462,17 @@ class FileResolver {
   }) {
     YamlMap optionMap;
 
-    var optionsFile = performance.run('findOptionsFile', (_) {
-      var folder = resourceProvider.getFile(path).parent;
-      return _findOptionsFile(folder);
-    });
+    var separator = resourceProvider.pathContext.separator;
+    var isThirdParty =
+        path.contains('${separator}third_party${separator}dart$separator');
+
+    File optionsFile;
+    if (!isThirdParty) {
+      optionsFile = performance.run('findOptionsFile', (_) {
+        var folder = resourceProvider.getFile(path).parent;
+        return _findOptionsFile(folder);
+      });
+    }
 
     if (optionsFile != null) {
       performance.run('getOptionsFromFile', (_) {
@@ -479,9 +486,7 @@ class FileResolver {
     } else {
       var source = performance.run('defaultOptions', (_) {
         if (workspace is WorkspaceWithDefaultAnalysisOptions) {
-          var separator = resourceProvider.pathContext.separator;
-          if (path
-              .contains('${separator}third_party${separator}dart$separator')) {
+          if (isThirdParty) {
             return sourceFactory.forUri(
               WorkspaceWithDefaultAnalysisOptions.thirdPartyUri,
             );

pkg/analyzer/test/src/dart/micro/simple_file_resolver_test.dart

@@ -312,6 +312,13 @@ analyzer:
     implicit-casts: false
 ''');
 
+    newFile('/workspace/thid_party/dart/aaa/analysis_options.yaml',
+        content: r'''
+analyzer:
+  strong-mode:
+    implicit-casts: true
+''');
+
     var aPath = convertPath('/workspace/third_party/dart/aaa/lib/a.dart');
     await assertErrorsInFile(aPath, r'''
 num a = 0;