Enable prefer_single_quotes in analyzer_plugin

Change-Id: I9cdda6df810ac20c9737d12951ad53a72e6b4f3c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/132621
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer_plugin/analysis_options.yaml

@@ -39,7 +39,7 @@ linter:
     - prefer_is_empty
     - prefer_is_not_empty
     - prefer_iterable_whereType
-    #- prefer_single_quotes # 2076
+    - prefer_single_quotes
     - prefer_spread_collections
     - recursive_getters
     - slash_for_doc_comments

pkg/analyzer_plugin/lib/src/utilities/null_string_sink.dart

@@ -8,11 +8,11 @@ class NullStringSink implements StringSink {
   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 = '']) {}
 }

pkg/analyzer_plugin/test/integration/support/integration_tests.dart

@@ -514,7 +514,7 @@ class Server {
     _pendingCommands[id] = completer;
     String line = json.encode(command);
     _recordStdio('SEND: $line');
-    _process.stdin.add(utf8.encoder.convert("$line\n"));
+    _process.stdin.add(utf8.encoder.convert('$line\n'));
     return completer.future;
   }
 
@@ -615,7 +615,7 @@ class Server {
   /// [debugStdio] has been called.
   void _recordStdio(String line) {
     double elapsedTime = currentElapseTime;
-    line = "$elapsedTime: $line";
+    line = '$elapsedTime: $line';
     if (_debuggingStdio) {
       print(line);
     }

pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart

@@ -634,7 +634,7 @@ class CodegenProtocolVisitor extends DartCodegenVisitor with CodeGenerator {
             writeln(' else {');
             indent(() {
               writeln(
-                  "throw jsonDecoder.mismatch(jsonPath, $fieldNameString);");
+                  'throw jsonDecoder.mismatch(jsonPath, $fieldNameString);');
             });
             writeln('}');
           } else {

pkg/analyzer_plugin/tool/spec/to_html.dart

@@ -283,7 +283,7 @@ class ToHtmlVisitor extends HierarchicalApiVisitor
   }
 
   void generateNotificationsIndex(Iterable<Notification> notifications) {
-    h5(() => write("Notifications"));
+    h5(() => write('Notifications'));
     element('div', {'class': 'subindex'}, () {
       element('ul', {}, () {
         for (var notification in notifications) {
@@ -302,7 +302,7 @@ class ToHtmlVisitor extends HierarchicalApiVisitor
       return;
     }
     h3(() {
-      write("Refactorings");
+      write('Refactorings');
       write(' (');
       link('refactorings', () => write('\u2191'));
       write(')');
@@ -322,7 +322,7 @@ class ToHtmlVisitor extends HierarchicalApiVisitor
   }
 
   void generateRequestsIndex(Iterable<Request> requests) {
-    h5(() => write("Requests"));
+    h5(() => write('Requests'));
     element('ul', {}, () {
       for (var request in requests) {
         if (!request.experimental) {
@@ -367,7 +367,7 @@ class ToHtmlVisitor extends HierarchicalApiVisitor
 
   void generateTypesIndex(Set<String> types) {
     h3(() {
-      write("Types");
+      write('Types');
       write(' (');
       link('types', () => write('\u2191'));
       write(')');