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Cannot set property 'hasAwait' of null

See original GitHub issue

ESLint Version: v6.4.0
Node Version: v12.10.0
npm Version: 6.10.3

What parser (default, Babel-ESLint, etc.) are you using?

@typescript-eslint/parser

Please show your full configuration: eslintrc

$ eslint  --ext .ts --ext .tsx src/
TypeError: Cannot set property 'hasAwait' of null
Occurred while linting /home/mha/Projects/chat/src/components/ChatMessage.tsx:127
    at AwaitExpression (/home/mha/Projects/chat/node_modules/eslint/lib/rules/require-await.js:95:36)
    at /home/mha/Projects/chat/node_modules/eslint/lib/linter/safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (/home/mha/Projects/chat/node_modules/eslint/lib/linter/safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (/home/mha/Projects/chat/node_modules/eslint/lib/linter/node-event-generator.js:253:26)
    at NodeEventGenerator.applySelectors (/home/mha/Projects/chat/node_modules/eslint/lib/linter/node-event-generator.js:282:22)
    at NodeEventGenerator.enterNode (/home/mha/Projects/chat/node_modules/eslint/lib/linter/node-event-generator.js:296:14)
    at CodePathAnalyzer.enterNode (/home/mha/Projects/chat/node_modules/eslint/lib/linter/code-path-analysis/code-path-analyzer.js:646:23)
    at /home/mha/Projects/chat/node_modules/eslint/lib/linter/linter.js:936:32
    at Array.forEach (<anonymous>)

Issue Analytics

State:
Created 4 years ago
Comments:11 (7 by maintainers)

Top GitHub Comments

1reaction

mdjermanoviccommented, Sep 18, 2019

The project is actually using @typescript-eslint/require-await rule, not directly require-await. This rule internally uses the core require-await and also has some additional logic from the typing information (allows async functions without await in some cases).

Docs: @typescript-eslint/require-await.md

Source code: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/src/rules/require-await.ts

It doesn’t appear in the stack trace because it just returns a reference to AwaitExpression. When the line AwaitExpression: rules.AwaitExpression in the distribution code is replaced with something like AwaitExpression(node){ rules.AwaitExpression(node); }, it does appear in the stack trace.

While the core rule doesn’t crash on this code, the @typescript-eslint wrapper does, because it has a bit different selectors - FunctionExpression[async = true] instead of just FunctionExpression.

1reaction

kaicataldocommented, Sep 18, 2019

This isn’t currently handled by the rule because this is a parser error in the default parser and in Babel’s parser (see demo). I don’t think it would be a bad thing to update the rule to not crash here, but I think the real fix should be that @typescript-eslint/parser should throw a parser error here.