Add code fix to remove unused label (#24037)

* Add code fix to remove unused label

* Test with trivia and fix indentation with dedented label

Author: Andy

src/compiler/diagnosticMessages.json

@@ -4261,5 +4261,13 @@
     "Add missing typeof": {
         "category": "Message",
         "code": 95052
+    },
+    "Remove unused label": {
+        "category": "Message",
+        "code": 95053
+    },
+    "Remove all unused labels": {
+        "category": "Message",
+        "code": 95054
     }
 }

src/harness/tsconfig.json

@@ -106,6 +106,7 @@
         "../services/codefixes/fixForgottenThisPropertyAccess.ts",
         "../services/codefixes/fixUnusedIdentifier.ts",
         "../services/codefixes/fixUnreachableCode.ts",
+        "../services/codefixes/fixUnusedLabel.ts",
         "../services/codefixes/fixJSDocTypes.ts",
         "../services/codefixes/fixAwaitInSyncFunction.ts",
         "../services/codefixes/disableJsDiagnostics.ts",

src/server/tsconfig.json

@@ -102,6 +102,7 @@
         "../services/codefixes/fixForgottenThisPropertyAccess.ts",
         "../services/codefixes/fixUnusedIdentifier.ts",
         "../services/codefixes/fixUnreachableCode.ts",
+        "../services/codefixes/fixUnusedLabel.ts",
         "../services/codefixes/fixJSDocTypes.ts",
         "../services/codefixes/fixAwaitInSyncFunction.ts",
         "../services/codefixes/disableJsDiagnostics.ts",

src/server/tsconfig.library.json

@@ -108,6 +108,7 @@
         "../services/codefixes/fixForgottenThisPropertyAccess.ts",
         "../services/codefixes/fixUnusedIdentifier.ts",
         "../services/codefixes/fixUnreachableCode.ts",
+        "../services/codefixes/fixUnusedLabel.ts",
         "../services/codefixes/fixJSDocTypes.ts",
         "../services/codefixes/fixAwaitInSyncFunction.ts",
         "../services/codefixes/disableJsDiagnostics.ts",

src/services/codefixes/fixUnusedLabel.ts

@@ -0,0 +1,25 @@
+/* @internal */
+namespace ts.codefix {
+    const fixId = "fixUnusedLabel";
+    const errorCodes = [Diagnostics.Unused_label.code];
+    registerCodeFix({
+        errorCodes,
+        getCodeActions(context) {
+            const changes = textChanges.ChangeTracker.with(context, t => doChange(t, context.sourceFile, context.span.start));
+            return [createCodeFixAction(fixId, changes, Diagnostics.Remove_unused_label, fixId, Diagnostics.Remove_all_unused_labels)];
+        },
+        fixIds: [fixId],
+        getAllCodeActions: context => codeFixAll(context, errorCodes, (changes, diag) => doChange(changes, diag.file, diag.start)),
+    });
+
+    function doChange(changes: textChanges.ChangeTracker, sourceFile: SourceFile, start: number): void {
+        const token = getTokenAtPosition(sourceFile, start, /*includeJsDocComment*/ false);
+        const labeledStatement = cast(token.parent, isLabeledStatement);
+        const pos = token.getStart(sourceFile);
+        const statementPos = labeledStatement.statement.getStart(sourceFile);
+        // If label is on a separate line, just delete the rest of that line, but not the indentation of the labeled statement.
+        const end = positionsAreOnSameLine(pos, statementPos, sourceFile) ? statementPos
+            : skipTrivia(sourceFile.text, findChildOfKind(labeledStatement, SyntaxKind.ColonToken, sourceFile)!.end, /*stopAfterLineBreak*/ true);
+        changes.deleteRange(sourceFile, { pos, end });
+    }
+}

src/services/tsconfig.json

@@ -99,6 +99,7 @@
         "codefixes/fixForgottenThisPropertyAccess.ts",
         "codefixes/fixUnusedIdentifier.ts",
         "codefixes/fixUnreachableCode.ts",
+        "codefixes/fixUnusedLabel.ts",
         "codefixes/fixJSDocTypes.ts",
         "codefixes/fixAwaitInSyncFunction.ts",
         "codefixes/disableJsDiagnostics.ts",

tests/cases/fourslash/codeFixUnusedLabel.ts

@@ -0,0 +1,11 @@
+/// <reference path='fourslash.ts' />
+
+// @noUnusedLocals: true
+
+/////* a */label/* b */:/* c */while (1) {}
+
+verify.codeFix({
+    description: "Remove unused label",
+    newFileContent:
+`/* a */while (1) {}`,
+});

tests/cases/fourslash/codeFixUnusedLabel_all.ts

@@ -0,0 +1,21 @@
+/// <reference path='fourslash.ts' />
+
+// @noUnusedLocals: true
+
+////label1: while (1) {}
+////
+////function f() {
+////label2:
+////    while (1) {}
+////}
+
+verify.codeFixAll({
+    fixId: "fixUnusedLabel",
+    fixAllDescription: "Remove all unused labels",
+    newFileContent:
+`while (1) {}
+
+function f() {
+    while (1) {}
+}`,
+});