Bug-fix: export default decorated class parsed as class expression

[nveenjain]

Q	A
Fixed Issues?	Fixes #7123
Patch: Bug Fix?	Yes
Major: Breaking Change?	No
Minor: New Feature?	No
Tests Added + Pass?	Yes
Documentation PR	No
Any Dependency Changes?	No
License	MIT

Now decorators are checked just after checking for exported classes, then they are processed and then class is processed.

[nicolo-ribaudo]

@nveenjain As you can see by travis-ci, the output of a fixture of a babel plugin changed. If you delete the output.js file and run make test-only, it will be updated automaticaly.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/6638/

[nveenjain]

@nicolo-ribaudo Fixed that. It took some time as i was struggling with rebasing.

[nicolo-ribaudo]

Q: Why do we need to this.startNode() instead of using expr?

[nveenjain]

i think expr will still point to the node which is of decorators. After parsing decorators, current node will point to class Node which is needed to be parsed.

[nicolo-ribaudo]

The parseDecorator function (called by parseDecorators) creates its own node, so expr won't be used. If you have tried and using expr breaks something leave it as it is now, otherwise don't create an unnecessary node 😉

[nveenjain]

Yes, it creates its own node which according to me, is required.
For example

export default @dec class x{}

In the code above expr will point to the node having start at 15 (when expr is assigned then current node is still tt.at) so when class is parsed without creating an extra node, it's current start will be pointed by 15 which acc. to me should be 20. that's why we need to create extra Node, which will point to current location of class i.e. 20. I've seen that class declaration/expression nodes start at the starting of class keyword. I maybe wrong though.. 😬

[nveenjain]

@nicolo-ribaudo, i cross-checked by using expr instead of creating a new node, and tested it for following input:-

export default @dec class A {}

, i got this output:-

[ Node {
    type: 'ExportDefaultDeclaration',
    start: 0,
    end: 30,
    loc: SourceLocation { start: [Object], end: [Object] },
    declaration:
     Node {
       type: 'ClassDeclaration',
       start: 15,
       end: 30,
       loc: [Object],
       decorators: [Array],
       id: [Object],
       superClass: null,
       body: [Object] } } ]

However the ouptut must be :-

[ Node {
    type: 'ExportDefaultDeclaration',
    start: 0,
    end: 30,
    loc: SourceLocation { start: [Object], end: [Object] },
    declaration:
     Node {
       type: 'ClassDeclaration',
       start: 20,
       end: 30,
       loc: [Object],
       decorators: [Array],
       id: [Object],
       superClass: null,
       body: [Object] } } ]

I think we need to create new node. However, suggestions/corrections are appreciated 🙂

[nicolo-ribaudo]

I tested and decorators are included in the class location:

"use strict";

const babylon = require("./packages/babylon");

const code = "@deco class Foo {}";

const ast = babylon.parse(code, { plugins: ["decorators2"] });

console.log(JSON.stringify(ast.program.body[0], null, 2));

{
  "type": "ClassDeclaration",
  "start": 0,
  "end": 18,
  "loc": {
    "start": {
      "line": 1,
      "column": 0
    },
    "end": {
      "line": 1,
      "column": 18
    }
  },
  "decorators": [
    {
      "type": "Decorator",
      "start": 0,
      "end": 5,
      "loc": {
        "start": {
          "line": 1,
          "column": 0
        },
        "end": {
          "line": 1,
          "column": 5
        }
      },
      "expression": {
        "type": "Identifier",
        "start": 1,
        "end": 5,
        "loc": {
          "start": {
            "line": 1,
            "column": 1
          },
          "end": {
            "line": 1,
            "column": 5
          },
          "identifierName": "deco"
        },
        "name": "deco"
      }
    }
  ],
  "id": {
    "type": "Identifier",
    "start": 12,
    "end": 15,
    "loc": {
      "start": {
        "line": 1,
        "column": 12
      },
      "end": {
        "line": 1,
        "column": 15
      },
      "identifierName": "Foo"
    },
    "name": "Foo"
  },
  "superClass": null,
  "body": {
    "type": "ClassBody",
    "start": 16,
    "end": 18,
    "loc": {
      "start": {
        "line": 1,
        "column": 16
      },
      "end": {
        "line": 1,
        "column": 18
      }
    },
    "body": []
  }
}

[nveenjain]

Updated the PR 😃 . Thanks, got to learn something while doing this.

[nicolo-ribaudo]

Last thing, you passed too many parameters here. It should be expr, true, true like the line above.

[nveenjain]

@nicolo-ribaudo , sorry for bothering, but is anything still wrong in PR?

[nicolo-ribaudo]

It's good 🙂