Fix #4530: no-string-throw fixer creates syntax errors

src/rules/noStringThrowRule.ts

@@ -73,10 +73,20 @@ function walk(ctx: Lint.WalkContext<void>): void {
         if (isThrowStatement(node)) {
             const { expression } = node;
             if (expression !== undefined && isString(expression)) {
-                ctx.addFailureAtNode(node, Rule.FAILURE_STRING, [
+                const fix = [
                     Lint.Replacement.appendText(expression.getStart(sourceFile), "new Error("),
                     Lint.Replacement.appendText(expression.getEnd(), ")"),
-                ]);
+                ];
+
+                const hasWhitespaceAfterThrow = /^throw\s+/.test(node.getText());
+                if (!hasWhitespaceAfterThrow) {
+                    const token = node.getFirstToken() as ts.Node;
+                    if (token !== undefined && token.kind === ts.SyntaxKind.ThrowKeyword) {
+                        fix.push(Lint.Replacement.appendText(token.getEnd(), " "));
+                    }
+                }
+
+                ctx.addFailureAtNode(node, Rule.FAILURE_STRING, fix);
             }
         }
         return ts.forEachChild(node, cb);

test/rules/no-string-throw/test.ts.fix

@@ -0,0 +1,24 @@
+let a: never = () => throw new Error('bla');
+
+let b: never = () => throw new Error('bla');
+
+let c: never = () => throw new Error('string1' + 'string2' + 'string3');
+
+let d: never = () => throw new Error('string' + 1);
+
+let e: never = () => throw new Error('string1' + 1 + {});
+
+let f: never = () => throw new Error(('string'));
+
+let g: never = () => throw new Error(1 + 2 + ('string'));
+
+// no warning because rule does not check for toString()
+const one = 1;
+let h: never = () => throw one.toString();
+
+let i: never = () => throw new Error(`some template string`);
+
+const someVariable = 123;
+let j: never = () => throw new Error(`template with ${someVariable} string`);
+
+throw new Error(('component requires CSS height property'));

test/rules/no-string-throw/test.ts.lint

@@ -28,3 +28,6 @@ let i: never = () => throw `some template string`;
 const someVariable = 123;
 let j: never = () => throw `template with ${someVariable} string`;
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [Throwing plain strings (not instances of Error) gives no stack traces]
+
+throw('component requires CSS height property');
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [Throwing plain strings (not instances of Error) gives no stack traces]