Fix property access on an object literal #17919
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Why only empty object literal? |
henrymercer
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henrymercer
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src/compiler/factory.ts
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| const emittedExpression = skipPartiallyEmittedExpressions(expression); | ||
| if (isLeftHandSideExpression(emittedExpression) | ||
| && (emittedExpression.kind !== SyntaxKind.NewExpression || (<NewExpression>emittedExpression).arguments)) { | ||
| && (!isNewExpression(emittedExpression) || (<NewExpression>emittedExpression).arguments) | ||
| && !isObjectLiteralExpression(emittedExpression)) { |
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this is only true if this is an expression statement. i.e.
var x = {a: 1}.a; // OK
{a: 1}.a; // Error
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This is an incorrect fix as it aggressively adds parenthesis around object literals in positions where a property access was previously legal.
The issue only occurs when the object literal is the left-most expression in an expression statement. For the most part, we already handle this case in parenthesizeExpressionForExpressionStatement:
// ts
(<any>{}).x;
// js
({}.x);However, It does look like there is a bug in parenthesizeExpressionForExpressionStatement when the outermost expression is a call.
You can see an example of the issue here: http://www.typescriptlang.org/play/index.html#src=%2F%2F%20ok%0D%0A(%3Cany%3E%7B%7D).x%3B%0D%0A%2F%2F%20error%0D%0A(%3Cany%3E%7B%7D).x()%3B%0D%0A
The easiest fix is to just lift the else block in factory.ts, line 3944 so that it performs the check for leftmost expression unconditionally.
| @@ -37,13 +37,13 @@ x = [true][0]; | |||
| x; // boolean | |||
| _a = [1][0], x = _a === void 0 ? "" : _a; | |||
| x; // string | number | |||
| (x = { x: true }.x); | |||
| (x = ({ x: true }).x); | |||
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The parenthesis aren't needed here.
Modify parenthesizeExpressionForExpressionStatement to add brackets around an expression statement in which the left-most expression is an object literal.
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Thanks @rbuckton, adding the parentheses around the whole property access expression in |
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Thanks for the contribution! |
Fixes #10129.
Currently a property access on an object literal e.g.
{ a : 1 }can compile to{ a : 1 }.x, which is incorrect syntax. This fixes object literal property accesses to compile to({ a : 1 }.x), and fixes existing tests that have been using this incorrect syntax.