Merge pull request #20373 from amcasey/PropertyUnderscore

Don't offer to prepend an underscore to the name of an unused private property

Author: amcasey

src/services/codefixes/fixUnusedIdentifier.ts

@@ -18,7 +18,7 @@ namespace ts.codefix {
 
             switch (token.kind) {
                 case ts.SyntaxKind.Identifier:
-                    return deleteIdentifierOrPrefixWithUnderscore(<Identifier>token);
+                    return deleteIdentifierOrPrefixWithUnderscore(<Identifier>token, context.errorCode);
 
                 case SyntaxKind.PropertyDeclaration:
                 case SyntaxKind.NamespaceImport:
@@ -54,7 +54,7 @@ namespace ts.codefix {
                 };
             }
 
-            function deleteIdentifierOrPrefixWithUnderscore(identifier: Identifier): CodeAction[] | undefined {
+            function deleteIdentifierOrPrefixWithUnderscore(identifier: Identifier, errorCode: number): CodeAction[] | undefined {
                 const parent = identifier.parent;
                 switch (parent.kind) {
                     case ts.SyntaxKind.VariableDeclaration:
@@ -76,8 +76,10 @@ namespace ts.codefix {
 
                     case ts.SyntaxKind.Parameter:
                         const functionDeclaration = <FunctionDeclaration>parent.parent;
-                        return [functionDeclaration.parameters.length === 1 ? deleteNode(parent) : deleteNodeInList(parent),
-                            prefixIdentifierWithUnderscore(identifier)];
+                        const deleteAction = functionDeclaration.parameters.length === 1 ? deleteNode(parent) : deleteNodeInList(parent);
+                        return errorCode === Diagnostics.Property_0_is_declared_but_its_value_is_never_read.code
+                            ? [deleteAction]
+                            : [deleteAction, prefixIdentifierWithUnderscore(identifier)];
 
                     // handle case where 'import a = A;'
                     case SyntaxKind.ImportEqualsDeclaration:

tests/cases/fourslash/unusedParameterInConstructor1AddUnderscore.ts

@@ -1,12 +1,12 @@
 /// <reference path='fourslash.ts' />
 
-// @noUnusedLocals: true
+// @noUnusedParameters: true
 //// class C1 {
-////    [|constructor(private p1: string, public p2: boolean, public p3: any, p5) |] { p5; }
+////    [|constructor(p1: string, public p2: boolean, public p3: any, p5) |] { p5; }
 //// }
 
 verify.codeFix({
     description: "Prefix 'p1' with an underscore.",
     index: 1,
-    newRangeContent: "constructor(private _p1: string, public p2: boolean, public p3: any, p5)",
+    newRangeContent: "constructor(_p1: string, public p2: boolean, public p3: any, p5)",
 });