feat(Diagnostics): Add proposed DiagnosticTag.Deprecated enum member

src/vs/editor/browser/widget/codeEditorWidget.ts

@@ -1851,4 +1851,6 @@ registerThemingParticipant((theme, collector) => {
 	if (unnecessaryBorder) {
 		collector.addRule(`.${SHOW_UNUSED_ENABLED_CLASS} .monaco-editor .${ClassName.EditorUnnecessaryDecoration} { border-bottom: 2px dashed ${unnecessaryBorder}; }`);
 	}
+
+	collector.addRule(`.monaco-editor .${ClassName.EditorDeprecatedInlineDecoration} { text-decoration: line-through; }`);
 });

src/vs/editor/common/model/intervalTree.ts

@@ -17,7 +17,8 @@ export const enum ClassName {
 	EditorWarningDecoration = 'squiggly-warning',
 	EditorErrorDecoration = 'squiggly-error',
 	EditorUnnecessaryDecoration = 'squiggly-unnecessary',
-	EditorUnnecessaryInlineDecoration = 'squiggly-inline-unnecessary'
+	EditorUnnecessaryInlineDecoration = 'squiggly-inline-unnecessary',
+	EditorDeprecatedInlineDecoration = 'squiggly-inline-deprecated'
 }
 
 export const enum NodeColor {

src/vs/editor/common/services/markerDecorationsServiceImpl.ts

@@ -221,6 +221,9 @@ export class MarkerDecorationsService extends Disposable implements IMarkerDecor
 			if (marker.tags.indexOf(MarkerTag.Unnecessary) !== -1) {
 				inlineClassName = ClassName.EditorUnnecessaryInlineDecoration;
 			}
+			if (marker.tags.indexOf(MarkerTag.Deprecated) !== -1) {
+				inlineClassName = ClassName.EditorDeprecatedInlineDecoration;
+			}
 		}
 
 		return {

src/vs/editor/common/standalone/standaloneEnums.ts

@@ -7,7 +7,8 @@
 
 
 export enum MarkerTag {
-	Unnecessary = 1
+	Unnecessary = 1,
+	Deprecated = 2
 }
 
 export enum MarkerSeverity {

src/vs/monaco.d.ts

@@ -27,7 +27,8 @@ declare namespace monaco {
 
 
 	export enum MarkerTag {
-		Unnecessary = 1
+		Unnecessary = 1,
+		Deprecated = 2
 	}
 
 	export enum MarkerSeverity {

src/vs/platform/markers/common/markers.ts

@@ -39,6 +39,7 @@ export interface IRelatedInformation {
 
 export const enum MarkerTag {
 	Unnecessary = 1,
+	Deprecated = 2
 }
 
 export enum MarkerSeverity {

src/vs/vscode.proposed.d.ts

@@ -1274,4 +1274,18 @@ declare module 'vscode' {
 	}
 
 	//#endregion
+
+	//#region Deprecated support
+
+	export enum DiagnosticTag {
+		/**
+		 * Deprecated or obsolete code
+		 *
+		 * Can be used to style with strikeout or other "obsolete" styling. See:
+		 * https://github.com/microsoft/vscode/issues/50972
+		 */
+		Deprecated = 2,
+	}
+
+	//#endregion
 }

src/vs/workbench/api/common/extHostTypeConverters.ts

@@ -108,6 +108,8 @@ export namespace DiagnosticTag {
 		switch (value) {
 			case types.DiagnosticTag.Unnecessary:
 				return MarkerTag.Unnecessary;
+			case types.DiagnosticTag.Deprecated:
+				return MarkerTag.Deprecated;
 		}
 		return undefined;
 	}

src/vs/workbench/api/common/extHostTypes.ts

@@ -773,6 +773,7 @@ export class SnippetString {
 
 export enum DiagnosticTag {
 	Unnecessary = 1,
+	Deprecated = 2
 }
 
 export enum DiagnosticSeverity {