Enable prefer_single_quotes in analysis_server_client

Change-Id: I08211c5fd63f69978772558582459fbe5b730743
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/132623
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server_client/analysis_options.yaml

@@ -40,7 +40,7 @@ linter:
     - prefer_is_empty
     - prefer_is_not_empty
     - prefer_iterable_whereType
-    #- prefer_single_quotes # 3434
+    - prefer_single_quotes
     - prefer_spread_collections
     - recursive_getters
     - slash_for_doc_comments

pkg/analysis_server_client/lib/server.dart

@@ -142,7 +142,7 @@ class Server {
     _pendingCommands[id] = completer;
     String line = json.encode(command);
     _listener?.requestSent(line);
-    _process.stdin.add(utf8.encoder.convert("$line\n"));
+    _process.stdin.add(utf8.encoder.convert('$line\n'));
     return completer.future;
   }
 

pkg/analysis_server_client/lib/src/protocol/protocol_base.dart

@@ -435,7 +435,7 @@ class Response {
   Response.invalidAnalysisRoot(Request request, String rootPath)
       : this(request.id,
             error: RequestError(RequestErrorCode.INVALID_ANALYSIS_ROOT,
-                "Invalid analysis root: $rootPath"));
+                'Invalid analysis root: $rootPath'));
 
   /// Initialize a newly created instance to represent an error condition caused
   /// by a [request] that specifies an execution context whose context root does
@@ -443,7 +443,7 @@ class Response {
   Response.invalidExecutionContext(Request request, String contextId)
       : this(request.id,
             error: RequestError(RequestErrorCode.INVALID_EXECUTION_CONTEXT,
-                "Invalid execution context: $contextId"));
+                'Invalid execution context: $contextId'));
 
   /// Initialize a newly created instance to represent the
   /// INVALID_FILE_PATH_FORMAT error condition.

pkg/analysis_server_client/test/server_test.dart

@@ -201,11 +201,11 @@ class MockStdin implements IOSink {
   void write(Object obj) {}
 
   @override
-  void writeAll(Iterable objects, [String separator = ""]) {}
+  void writeAll(Iterable objects, [String separator = '']) {}
 
   @override
   void writeCharCode(int charCode) {}
 
   @override
-  void writeln([Object obj = ""]) {}
+  void writeln([Object obj = '']) {}
 }