DAS plugins: Only analyze (and hence visit) .dart files

In it's current form, the lint rules are given _every_ file in the
context root, including things like CHANGELOG.md, YAML files, etc, and
it tries to parse them as Dart source.

Change-Id: I0bd5a682fa4f22b857520bb99e7a3d8990c93e37
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/396041
Commit-Queue: Samuel Rawlins <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Auto-Submit: Samuel Rawlins <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: srawlins

pkg/analysis_server_plugin/lib/src/plugin_server.dart

@@ -29,6 +29,7 @@ import 'package:analyzer/src/dart/element/type_system.dart';
 import 'package:analyzer/src/lint/linter.dart';
 import 'package:analyzer/src/lint/linter_visitor.dart';
 import 'package:analyzer/src/lint/registry.dart';
+import 'package:analyzer/src/util/file_paths.dart' as file_paths;
 import 'package:analyzer_plugin/channel/channel.dart';
 import 'package:analyzer_plugin/protocol/protocol.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart' as protocol;
@@ -190,7 +191,14 @@ class PluginServer {
     required AnalysisContextCollection contextCollection,
   }) async {
     await _forAnalysisContexts(contextCollection, (analysisContext) async {
-      var paths = analysisContext.contextRoot.analyzedFiles().toList();
+      var paths = analysisContext.contextRoot
+          .analyzedFiles()
+          // TODO(srawlins): Enable analysis on other files, even if only
+          // YAML files for analysis options and pubspec analysis and quick
+          // fixes.
+          .where((p) => file_paths.isDart(_resourceProvider.pathContext, p))
+          .toList();
+
       await _analyzeFiles(
         analysisContext: analysisContext,
         paths: paths,