[analysis_server] Add "label" mapping for semantic tokens

Fixes Dart-Code/Dart-Code#5505

Change-Id: Iad8b405442c841b215d3697d87b0203bd06c0ef2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/428360
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: DanTup

pkg/analysis_server/lib/src/computer/computer_highlights.dart

@@ -132,7 +132,7 @@ class DartUnitHighlightsComputer {
     if (_addIdentifierRegion_importPrefix(nameToken, element)) {
       return;
     }
-    if (_addIdentifierRegion_label(nameToken, element)) {
+    if (_addIdentifierRegion_label(parent, nameToken, element)) {
       return;
     }
     if (_addIdentifierRegion_localVariable(nameToken, element)) {
@@ -395,11 +395,22 @@ class DartUnitHighlightsComputer {
     return false;
   }
 
-  bool _addIdentifierRegion_label(Token nameToken, Element? element) {
+  bool _addIdentifierRegion_label(
+    AstNode parent,
+    Token nameToken,
+    Element? element,
+  ) {
     if (element is! LabelElement) {
       return false;
     }
-    return _addRegion_token(nameToken, HighlightRegionType.LABEL);
+    return _addRegion_token(
+      nameToken,
+      HighlightRegionType.LABEL,
+      semanticTokenModifiers:
+          parent is! BreakStatement
+              ? {SemanticTokenModifiers.declaration}
+              : null,
+    );
   }
 
   bool _addIdentifierRegion_localVariable(Token nameToken, Element? element) {

pkg/analysis_server/lib/src/lsp/constants.dart

@@ -206,8 +206,13 @@ abstract final class CustomSemanticTokenModifiers {
   static const importPrefix = SemanticTokenModifiers('importPrefix');
 
   /// A modifier applied to parameter references to indicate they are the name/label
-  /// to allow theming them differently to the values. For example in the code
-  /// `foo({String a}) => foo(a: a)` the a's will be differentiated as:
+  /// to allow theming them differently to the values.
+  ///
+  /// This is different to [CustomSemanticTokenTypes.label] which is for labels
+  /// as used in loops/switch statements.
+  ///
+  /// In the code `foo({String a}) => foo(a: a)` the a's will be differentiated
+  /// as:
   /// - parameter.declaration
   /// - parameter.label
   /// - parameter
@@ -268,6 +273,22 @@ abstract final class CustomSemanticTokenTypes {
   static const annotation = SemanticTokenTypes('annotation');
   static const boolean = SemanticTokenTypes('boolean');
 
+  /// A token type for labels.
+  ///
+  /// This is different to [CustomSemanticTokenModifiers.label] which is for
+  /// parameter name labels.
+  ///
+  /// 'label' is listed as a standard VS Code token type at
+  /// https://code.visualstudio.com/api/language-extensions/semantic-highlight-guide
+  /// and therefore may be used by theme authors, but it's currently not defined
+  /// by LSP (and therefore missing from the code-generated SemanticTokenTypes)
+  /// so we have to define it here.
+  ///
+  /// This can be removed once
+  /// https://github.com/microsoft/language-server-protocol/issues/2137 is
+  /// resolved.
+  static const label = SemanticTokenTypes('label');
+
   /// A placeholder token type for basic source code that is not usually colored.
   ///
   /// This is used only where clients might otherwise provide their own coloring
@@ -280,7 +301,7 @@ abstract final class CustomSemanticTokenTypes {
 
   /// All custom semantic token types, used to populate the LSP Legend which must
   /// include all used types.
-  static const values = [annotation, boolean, source];
+  static const values = [annotation, boolean, label, source];
 }
 
 /// CodeActionKinds supported by the server that are not declared in the LSP spec.

pkg/analysis_server/lib/src/lsp/semantic_tokens/mapping.dart

@@ -140,6 +140,7 @@ final highlightRegionTokenTypes = {
   HighlightRegionType.INSTANCE_SETTER_DECLARATION: SemanticTokenTypes.property,
   HighlightRegionType.INSTANCE_SETTER_REFERENCE: SemanticTokenTypes.property,
   HighlightRegionType.KEYWORD: SemanticTokenTypes.keyword,
+  HighlightRegionType.LABEL: CustomSemanticTokenTypes.label,
   HighlightRegionType.LIBRARY_NAME: SemanticTokenTypes.namespace,
   HighlightRegionType.LITERAL_BOOLEAN: CustomSemanticTokenTypes.boolean,
   HighlightRegionType.LITERAL_DOUBLE: SemanticTokenTypes.number,

pkg/analysis_server/test/lsp/semantic_tokens_test.dart

@@ -1199,6 +1199,40 @@ void f() async {
     await _initializeAndVerifyTokens(content, expected);
   }
 
+  Future<void> test_label() async {
+    var content = '''
+void f() {
+myLabel:
+  while (true) {
+    break myLabel;
+  }
+}
+''';
+
+    var expected = [
+      _Token('void', SemanticTokenTypes.keyword, [
+        CustomSemanticTokenModifiers.void_,
+      ]),
+      _Token('f', SemanticTokenTypes.function, [
+        SemanticTokenModifiers.declaration,
+        SemanticTokenModifiers.static,
+      ]),
+      _Token('myLabel', CustomSemanticTokenTypes.label, [
+        SemanticTokenModifiers.declaration,
+      ]),
+      _Token('while', SemanticTokenTypes.keyword, [
+        CustomSemanticTokenModifiers.control,
+      ]),
+      _Token('true', CustomSemanticTokenTypes.boolean),
+      _Token('break', SemanticTokenTypes.keyword, [
+        CustomSemanticTokenModifiers.control,
+      ]),
+      _Token('myLabel', CustomSemanticTokenTypes.label),
+    ];
+
+    await _initializeAndVerifyTokens(content, expected);
+  }
+
   Future<void> test_lastLine_code() async {
     var content = 'String? bar;';
 

pkg/analyzer/lib/src/dart/element/element.dart

@@ -5483,8 +5483,8 @@ class LabelElementImpl2 extends ElementImpl2
     return [firstFragment];
   }
 
-  /// Return `true` if this label is associated with a `switch` member (`case
-  /// ` or`default`).
+  /// Return `true` if this label is associated with a `switch` member (`case`
+  /// or `default`).
   bool get isOnSwitchMember => _wrappedElement.isOnSwitchMember;
 
   @override
@@ -5531,8 +5531,8 @@ class LabelFragmentImpl extends FragmentImpl implements LabelFragment {
   ExecutableFragment get enclosingFragment =>
       enclosingElement3 as ExecutableFragment;
 
-  /// Return `true` if this label is associated with a `switch` member (`case
-  /// ` or`default`).
+  /// Return `true` if this label is associated with a `switch` member (`case`
+  /// or `default`).
   bool get isOnSwitchMember => _onSwitchMember;
 
   @override