Incorrect parsing for contextual keyword async

[svr93]

What code were you trying to parse?

import { TestBed, async } from '@angular/core/testing';

What did you expect to happen?
token type Identifier with value async

What actually happened?
token type Keyword with value async

Versions

package	version
@typescript-eslint/typescript-estree	1.11.0
TypeScript	3.4.5
node	10.14.2
npm	6.4.1

[bradzacher]

According to astexplorer that isn't what comes out?

This is the result of the parse (yes, ASTExplorer is on v1.4.2, but we haven't changed anything in the parser)
https://astexplorer.net/#/gist/6bc10f2361963d312bd8ed3e0c46b15e/f2fdc226b280857558b5a9d90c786364c76a4ebb

This is the output of parsing against master (without location info), which is against `v1.11.0`

{
  "body": [
    {
      "source": {
        "raw": "'@angular/core/testing'",
        "type": "Literal",
        "value": "@angular/core/testing",
      },
      "specifiers": [
        {
          "imported": {
            "name": "TestBed",
            "type": "Identifier",
          },
          "local": {
            "name": "TestBed",
            "type": "Identifier",
          },
          "type": "ImportSpecifier",
        },
        //////////////////////////////////
        {
          "imported": {
            "name": "async",
            "type": "Identifier",
          },
          "local": {
            "name": "async",
            "type": "Identifier",
          },
          "type": "ImportSpecifier",
        },
        //////////////////////////////////
      ],
      "type": "ImportDeclaration",
    },
  ],
  "sourceType": "module",
  "tokens": [
    {
      "type": "Keyword",
      "value": "import",
    },
    {
      "type": "Punctuator",
      "value": "{",
    },
    {
      "type": "Identifier",
      "value": "TestBed",
    },
    {
      "type": "Punctuator",
      "value": ",",
    },
    {
      "type": "Keyword",
      "value": "async",
    },
    {
      "type": "Punctuator",
      "value": "}",
    },
    {
      "type": "Identifier",
      "value": "from",
    },
    {
      "type": "String",
      "value": "'@angular/core/testing'",
    },
    {
      "type": "Punctuator",
      "value": ";",
    },
  ],
  "type": "Program",
}

As you can see, in both cases async is correctly parsed as an identifier.
The bug is not in the parser from what I can see.

[svr93]

@bradzacher Thank you for quick response!

The parser used for easy integration between TypeScript & JavaScript ecosystems. So I expect identical results with identical strings of code.
My test case:

// @ts-check
const tsParser = require('@typescript-eslint/typescript-estree');
const esParser = require('esprima')
const esParser2 = require('espree')

const code = `import { TestBed, async } from '@angular/core/testing';`;

const { tokens: tsTokens } = tsParser.parse(code, {
  tokens: true,
});
const esTokens = esParser.tokenize(code)
const esTokens2 = esParser2.tokenize(code, {ecmaVersion: 2019, sourceType: 'module'})

console.log(tsTokens.map(({ type, value }) => ({ type, value })))
console.log('---')
console.log(esTokens.map(({ type, value }) => ({ type, value })))
console.log('---')
console.log(esTokens2.map(({ type, value }) => ({ type, value })))

Result is different:

[ { type: 'Keyword', value: 'import' },
  { type: 'Punctuator', value: '{' },
  { type: 'Identifier', value: 'TestBed' },
  { type: 'Punctuator', value: ',' },
  { type: 'Keyword', value: 'async' }, // *?*
  { type: 'Punctuator', value: '}' },
  { type: 'Identifier', value: 'from' },
  { type: 'String', value: '\'@angular/core/testing\'' },
  { type: 'Punctuator', value: ';' } ]
---
[ { type: 'Keyword', value: 'import' },
  { type: 'Punctuator', value: '{' },
  { type: 'Identifier', value: 'TestBed' },
  { type: 'Punctuator', value: ',' },
  { type: 'Identifier', value: 'async' },
  { type: 'Punctuator', value: '}' },
  { type: 'Identifier', value: 'from' },
  { type: 'String', value: '\'@angular/core/testing\'' },
  { type: 'Punctuator', value: ';' } ]
---
[ { type: 'Keyword', value: 'import' },
  { type: 'Punctuator', value: '{' },
  { type: 'Identifier', value: 'TestBed' },
  { type: 'Punctuator', value: ',' },
  { type: 'Identifier', value: 'async' },
  { type: 'Punctuator', value: '}' },
  { type: 'Identifier', value: 'from' },
  { type: 'String', value: '\'@angular/core/testing\'' },
  { type: 'Punctuator', value: ';' } ]

Consistent results will help to use the available ESLint plugins for TypeScript code

[bradzacher]

I see - you should have included that in your initial issue!

Looking again at the example, yes - the tokens array does classify the async token as a keyword.

However looking at the linked issue, and the source code of the plugin, it never inspects that array, and gathers tokens via sourceCode.getTokens(node).

In practice it looks like it all works as expected?

https://astexplorer.net/#/gist/8599f450e5cab7f5711b55ab02bd4a0e/bddd5558899be19236dead04055faa4348a1f66c

[ { type: 'Keyword', value: 'import' },
  { type: 'Punctuator', value: '{' },
  { type: 'Identifier', value: 'TestBed' },
  { type: 'Punctuator', value: ',' },
  { type: 'Identifier', value: 'async' },
  { type: 'Punctuator', value: '}' },
  { type: 'Identifier', value: 'from' },
  { type: 'String', value: '\'@angular/core/testing\'' },
  { type: 'Punctuator', value: ';' } ]

[bradzacher]

Note that I have raised #681 to fix the incorrect typing of the token.

[svr93]

@bradzacher
I tried to clone this repo - https://github.com/lydell/eslint-plugin-simple-import-issue - and manually patch dependency with your PR changes.

Result: test is OK :)

diff --git a/test.js b/test.js
index 9b2896a..1139a7c 100644
--- a/test.js
+++ b/test.js
@@ -1 +1 @@
-import { TestBed, async } from '@angular/core/testing';
+import { async,TestBed } from '@angular/core/testing';

Plugin works as expected