feat(52569): fixUnusedIdentifier: Unwanted side-effects when removing an unused destructuring declaration containing a function call (#52951)

Author: a-tarasyuk

src/services/codefixes/fixUnusedIdentifier.ts

@@ -3,6 +3,7 @@ import {
     CancellationToken,
     cast,
     CodeFixAction,
+    CodeFixContext,
     Debug,
     DiagnosticAndArguments,
     DiagnosticMessage,
@@ -14,12 +15,15 @@ import {
     forEach,
     FunctionLikeDeclaration,
     getJSDocParameterTags,
+    getNewLineOrDefaultFromHost,
+    getPrecedingNonSpaceCharacterPosition,
     getTokenAtPosition,
     Identifier,
     ImportDeclaration,
     isArrayBindingPattern,
     isBinaryExpression,
     isCallExpression,
+    isCallLikeExpression,
     isComputedPropertyName,
     isDeclarationWithTypeParameterChildren,
     isExpressionStatement,
@@ -37,11 +41,14 @@ import {
     isPrefixUnaryExpression,
     isPropertyAccessExpression,
     isSuperKeyword,
+    isVariableDeclaration,
     isVariableDeclarationList,
+    length,
     map,
     Node,
     ObjectBindingPattern,
     ParameterDeclaration,
+    probablyUsesSemicolons,
     Program,
     showModuleSpecifier,
     SourceFile,
@@ -114,7 +121,7 @@ registerCodeFix({
             }
             return [
                 createDeleteFix(textChanges.ChangeTracker.with(context, t =>
-                    t.delete(sourceFile, token.parent.parent)), Diagnostics.Remove_unused_destructuring_declaration)
+                    deleteDestructuring(context, t, sourceFile, token.parent as ObjectBindingPattern | ArrayBindingPattern)), Diagnostics.Remove_unused_destructuring_declaration),
             ];
         }
 
@@ -243,6 +250,27 @@ function deleteDestructuringElements(changes: textChanges.ChangeTracker, sourceF
     forEach(node.elements, n => changes.delete(sourceFile, n));
 }
 
+function deleteDestructuring(context: CodeFixContext, changes: textChanges.ChangeTracker, sourceFile: SourceFile, { parent }: ObjectBindingPattern | ArrayBindingPattern) {
+    if (isVariableDeclaration(parent) && parent.initializer && isCallLikeExpression(parent.initializer)) {
+        if (isVariableDeclarationList(parent.parent) && length(parent.parent.declarations) > 1) {
+            const varStatement = parent.parent.parent;
+            const pos = varStatement.getStart(sourceFile);
+            const end = varStatement.end;
+            changes.delete(sourceFile, parent);
+            changes.insertNodeAt(sourceFile, end, parent.initializer, {
+                prefix: getNewLineOrDefaultFromHost(context.host, context.formatContext.options) + sourceFile.text.slice(getPrecedingNonSpaceCharacterPosition(sourceFile.text, pos - 1), pos),
+                suffix: probablyUsesSemicolons(sourceFile) ? ";" : "",
+            });
+        }
+        else {
+            changes.replaceNode(sourceFile, parent.parent, parent.initializer);
+        }
+    }
+    else {
+        changes.delete(sourceFile, parent);
+    }
+}
+
 function tryPrefixDeclaration(changes: textChanges.ChangeTracker, errorCode: number, sourceFile: SourceFile, token: Node): void {
     // Don't offer to prefix a property.
     if (errorCode === Diagnostics.Property_0_is_declared_but_its_value_is_never_read.code) return;

tests/cases/fourslash/codeFixUnusedIdentifier_destructuring_elements7.ts

@@ -0,0 +1,20 @@
+/// <reference path="fourslash.ts" />
+
+// @noUnusedLocals: true
+// @noUnusedParameters: true
+
+////function foo() {
+////    return { a: 1 };
+////}
+////[|function bar() {
+////    const { a } = foo();
+////}|]
+
+verify.codeFix({
+    index: 0,
+    description: ts.Diagnostics.Remove_unused_destructuring_declaration.message,
+    newRangeContent:
+`function bar() {
+    foo();
+}`,
+});

tests/cases/fourslash/codeFixUnusedIdentifier_destructuring_elements8.ts

@@ -0,0 +1,24 @@
+/// <reference path="fourslash.ts" />
+
+// @noUnusedLocals: true
+// @noUnusedParameters: true
+
+////function foo() {
+////    return { a: 1 };
+////}
+////[|function bar() {
+////    const { a } = foo(),
+////           b = 1;
+////    return b;
+////}|]
+
+verify.codeFix({
+    index: 0,
+    description: ts.Diagnostics.Remove_unused_destructuring_declaration.message,
+    newRangeContent:
+`function bar() {
+    const b = 1;
+    foo();
+    return b;
+}`,
+});