Merge pull request #28290 from rflorian/add-codefix-cannot-find-name-in-for-loop

Add codefix for 'Cannot find name' diagnostic

src/compiler/diagnosticMessages.json

@@ -5079,6 +5079,14 @@
         "category": "Message",
         "code": 95080
     },
+    "Add 'const' to unresolved variable": {
+        "category": "Message",
+        "code": 95081
+    },
+    "Add 'const' to all unresolved variables": {
+        "category": "Message",
+        "code": 95082
+    },
     "No value exists in scope for the shorthand property '{0}'. Either declare one or provide an initializer.": {
         "category": "Error",
         "code": 18004

src/services/codefixes/addMissingConst.ts

@@ -0,0 +1,109 @@
+/* @internal */
+namespace ts.codefix {
+    const fixId = "addMissingConst";
+    const errorCodes = [
+        Diagnostics.Cannot_find_name_0.code,
+        Diagnostics.No_value_exists_in_scope_for_the_shorthand_property_0_Either_declare_one_or_provide_an_initializer.code
+    ];
+
+    registerCodeFix({
+        errorCodes,
+        getCodeActions: (context) => {
+            const changes = textChanges.ChangeTracker.with(context, t => makeChange(t, context.sourceFile, context.span.start, context.program));
+            if (changes.length > 0) {
+                return [createCodeFixAction(fixId, changes, Diagnostics.Add_const_to_unresolved_variable, fixId, Diagnostics.Add_const_to_all_unresolved_variables)];
+            }
+        },
+        fixIds: [fixId],
+        getAllCodeActions: context => {
+            const fixedNodes = new NodeSet();
+            return codeFixAll(context, errorCodes, (changes, diag) => makeChange(changes, diag.file, diag.start, context.program, fixedNodes));
+        },
+    });
+
+    function makeChange(changeTracker: textChanges.ChangeTracker, sourceFile: SourceFile, pos: number, program: Program, fixedNodes?: NodeSet<Node>) {
+        const token = getTokenAtPosition(sourceFile, pos);
+        const forInitializer = findAncestor(token, node =>
+            isForInOrOfStatement(node.parent) ? node.parent.initializer === node :
+            isPossiblyPartOfDestructuring(node) ? false : "quit"
+        );
+        if (forInitializer) return applyChange(changeTracker, forInitializer, sourceFile, fixedNodes);
+
+        const parent = token.parent;
+        if (isBinaryExpression(parent) && isExpressionStatement(parent.parent)) {
+            return applyChange(changeTracker, token, sourceFile, fixedNodes);
+        }
+
+        if (isArrayLiteralExpression(parent)) {
+            const checker = program.getTypeChecker();
+            if (!every(parent.elements, element => arrayElementCouldBeVariableDeclaration(element, checker))) {
+                return;
+            }
+
+            return applyChange(changeTracker, parent, sourceFile, fixedNodes);
+        }
+
+        const commaExpression = findAncestor(token, node =>
+            isExpressionStatement(node.parent) ? true :
+            isPossiblyPartOfCommaSeperatedInitializer(node) ? false : "quit"
+        );
+        if (commaExpression) {
+            const checker = program.getTypeChecker();
+            if (!expressionCouldBeVariableDeclaration(commaExpression, checker)) {
+                return;
+            }
+
+            return applyChange(changeTracker, commaExpression, sourceFile, fixedNodes);
+        }
+    }
+
+    function applyChange(changeTracker: textChanges.ChangeTracker, initializer: Node, sourceFile: SourceFile, fixedNodes?: NodeSet<Node>) {
+        if (!fixedNodes || fixedNodes.tryAdd(initializer)) {
+            changeTracker.insertModifierBefore(sourceFile, SyntaxKind.ConstKeyword, initializer);
+        }
+    }
+
+    function isPossiblyPartOfDestructuring(node: Node): boolean {
+        switch (node.kind) {
+            case SyntaxKind.Identifier:
+            case SyntaxKind.ArrayLiteralExpression:
+            case SyntaxKind.ObjectLiteralExpression:
+            case SyntaxKind.PropertyAssignment:
+            case SyntaxKind.ShorthandPropertyAssignment:
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    function arrayElementCouldBeVariableDeclaration(expression: Expression, checker: TypeChecker): boolean {
+        const identifier =
+            isIdentifier(expression) ? expression :
+            isAssignmentExpression(expression, /*excludeCompoundAssignment*/ true) && isIdentifier(expression.left) ? expression.left :
+            undefined;
+        return !!identifier && !checker.getSymbolAtLocation(identifier);
+    }
+
+    function isPossiblyPartOfCommaSeperatedInitializer(node: Node): boolean {
+        switch (node.kind) {
+            case SyntaxKind.Identifier:
+            case SyntaxKind.BinaryExpression:
+            case SyntaxKind.CommaToken:
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    function expressionCouldBeVariableDeclaration(expression: Node, checker: TypeChecker): boolean {
+        if (!isBinaryExpression(expression)) {
+            return false;
+        }
+
+        if (expression.operatorToken.kind === SyntaxKind.CommaToken) {
+            return every([expression.left, expression.right], expression => expressionCouldBeVariableDeclaration(expression, checker));
+        }
+
+        return isIdentifier(expression.left) && !checker.getSymbolAtLocation(expression.left);
+    }
+}

src/services/tsconfig.json

@@ -45,6 +45,7 @@
         "codeFixProvider.ts",
         "refactorProvider.ts",
         "codefixes/addConvertToUnknownForNonOverlappingTypes.ts",
+        "codefixes/addMissingConst.ts",
         "codefixes/addMissingInvocationForDecorator.ts",
         "codefixes/addNameToNamelessParameter.ts",
         "codefixes/annotateWithTypeFromJSDoc.ts",