DAS plugins: Test how an unsupported request is handled.

Change-Id: If214c32f396867a5af0a3bfcc40946121c895aef
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/442285
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>

Author: srawlins

pkg/analysis_server/lib/src/plugin/plugin_manager.dart

@@ -1127,6 +1127,15 @@ class PluginSession {
       // If a RequestError is returned in the response, report this as an
       // exception.
       if (response.error case var error?) {
+        if (error.code == RequestErrorCode.UNKNOWN_REQUEST) {
+          // The plugin doesn't support this request. It may just be using an
+          // older version of the `analysis_server_plugin` package.
+          info.instrumentationService.logInfo(
+            "Plugin cannot handle request '${request.method}' with parameters: "
+            '$parameters.',
+          );
+          return;
+        }
         var stackTrace = StackTrace.fromString(error.stackTrace!);
         var exception = PluginException(error.message);
         info.reportException(

pkg/analysis_server_plugin/test/src/plugin_server_test.dart

@@ -12,6 +12,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart' as protocol;
 import 'package:analyzer_plugin/protocol/protocol_constants.dart' as protocol;
 import 'package:analyzer_plugin/protocol/protocol_generated.dart' as protocol;
+import 'package:analyzer_plugin/protocol/protocol_generated.dart';
 import 'package:analyzer_plugin/utilities/assist/assist.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
 import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
@@ -180,6 +181,20 @@ bool b = false;
     _expectAnalysisError(params.errors.single, message: 'No doubles message');
   }
 
+  Future<void> test_unsupportedRequest() async {
+    writeAnalysisOptionsWithPlugin();
+    newFile(filePath, 'bool b = false;');
+
+    await channel
+        .sendRequest(protocol.AnalysisSetContextRootsParams([contextRoot]));
+
+    // This request is unsupported.
+    var response = await channel.sendRequest(
+        protocol.CompletionGetSuggestionsParams(filePath, 0 /* offset */));
+
+    expect(response.error?.code, RequestErrorCode.UNKNOWN_REQUEST);
+  }
+
   Future<void> test_updateContent_addOverlay() async {
     writeAnalysisOptionsWithPlugin();
     newFile(filePath, 'int b = 7;');