Support Flow `this` parameter annotations #12234

dsainati1 · 2020-10-21T18:48:59Z

This adds support for this parameter annotations.

Example:

function foo (this: number) {}

This is already supported in the Flow parser: facebook/flow@8efdc8c

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

babel-bot · 2020-10-21T18:52:27Z

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/40277/

codesandbox-ci · 2020-10-21T18:57:30Z

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kaicataldo · 2020-10-21T23:28:00Z

Looks like this is currently failing CI's linting step due to a Flow issue. Mind fixing the typing issue so that we can review? :)

JLHwung

Can you add an integration test with transform-parameters like we did in #9714?

packages/babel-generator/src/generators/flow.js

packages/babel-plugin-transform-flow-strip-types/src/index.js

JLHwung · 2020-10-22T20:43:21Z

packages/babel-parser/src/plugins/flow.js

@@ -1461,6 +1524,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>

          node.params = tmp.params;
          node.rest = tmp.rest;
+          node.this = tmp._this;


Can you also update

babel/packages/babel-parser/src/types.js

Line 161 in d6816f0

export type BodilessFunctionOrMethodBase = HasDecorators & {

? Since we have a new "this" property in the AST node.

The new "this" property is only present in the FunctionTypeAnnotation node. For regular function nodes the "this" is the first member of the parameter list (to match the Flow parser's behavior).

This also matches the AST we use for this type annotations in TS.

packages/babel-parser/src/plugins/flow.js

dsainati1 · 2020-10-23T14:39:54Z

Not sure what the create react app failure is, seems unrelated to these changes.

existentialism · 2020-10-23T14:41:51Z

@dsainati1 it's def unrelated, we're seeing it on all recent prs (terser/terser#854)

dsainati1 · 2020-11-04T14:41:40Z

Any updates on this?

nicolo-ribaudo · 2020-11-04T14:48:46Z

We'll release this in the next minor version.

nicolo-ribaudo · 2021-01-31T01:54:13Z

@dsainati1 Could you rebase this, or enabling "Allow edit by maintainers" in the right sidebar?
I tried rebasing and pushing, but I got a permission error.

dsainati1 · 2021-01-31T23:04:41Z

I have the "Allow edit by maintainers" box checked.

JLHwung · 2021-02-05T20:42:47Z

@dsainati1 Although "Allow edit by maintainers" is checked, we can not push to your repo because the PR is from the default branch main. I have rebased on the upstream and pushed to https://github.com/JLHwung/babel/tree/dsainati1/main Can you reset to this ref and force push?

dsainati1 · 2021-02-05T23:16:32Z

OK I think I got it, but let me know if you still need something from me here.

dsainati1 · 2021-02-08T17:52:02Z

Hmmm it seems the estree-throws test is failing on this revision, but it is unclear to me what this means. All the other tests pass without issue. Any thoughts?

JLHwung · 2021-02-08T18:54:00Z

@dsainati1 If an estree-throws test throws, it means the related test case will fail when you enable both estree and flow plugin. The use case is that people could use @babel/eslint-parser on a Flow project.

For debug purpose you can add "estree" to options.json

{
  "plugins": ["estree", "flow"]
}

dsainati1 · 2021-02-08T22:01:21Z

Given that this test was not failing when I submitted this PR initially, I am not sure what would have changed between now and then that causes this test to fail. Are there any recent changes I should know about that would result in different behavior here?

JLHwung · 2021-02-09T00:59:43Z

The test was likely broken before you rebased, but it was not reported then because before 8478027 we never ensure that the parser tests throw same errors when estree plugin is added to the test options.

JLHwung · 2021-02-09T01:03:17Z

packages/babel-parser/src/plugins/flow.js

@@ -1160,6 +1182,12 @@ export default (superClass: Class<Parser>): Class<Parser> =>
          if (kind === "get" || kind === "set") {
            this.flowCheckGetterSetterParams(node);
          }
+          if (node.key.name === "constructor" && node.value.this) {


As you can see from https://astexplorer.net/#/gist/e4e0c3380467882e445d5ddd8193feac/8bf60fc83e55d1fff70cd5b0ad4d3255e9fb5691, when estree plugin is enabled, the AST is slightly different. node.value becomes a function expression. The error is thrown, very likely because node.value.this is no longer true when estree is enabled.

Can you add a new test case on string literal constructor?

class A { "constructor"() {} }

It is semantically equivalent to the identifier constructor.

dsainati1 added 5 commits October 20, 2020 17:06

initial parsing

68fdc0d

Finish parsing

2764479

update babel-plugin-transform-flow-strip-types

c37faeb

update babel-types

5972bfb

update babel-generator

82cc6fc

existentialism added area: flow PR: New Feature 🚀 A type of pull request used for our changelog categories labels Oct 21, 2020

fix flow typing

a5d7d68

JLHwung reviewed Oct 22, 2020

View reviewed changes

respond to PR comments

d600156

nicolo-ribaudo added this to the v7.13.0 milestone Nov 4, 2020

hzoo approved these changes Dec 4, 2020

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nicolo-ribaudo approved these changes Jan 31, 2021

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Merge remote-tracking branch 'upstream/main' into main

1b56201

JLHwung reviewed Feb 9, 2021

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github-actions bot added the outdated A closed issue/PR that is archived due to age. Recommended to make a new issue label May 24, 2021

github-actions bot locked as resolved and limited conversation to collaborators May 24, 2021

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Support Flow `this` parameter annotations #12234

Support Flow `this` parameter annotations #12234

dsainati1 commented Oct 21, 2020 •

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Support Flow this parameter annotations #12234

Support Flow this parameter annotations #12234

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Support Flow `this` parameter annotations #12234

Support Flow `this` parameter annotations #12234

dsainati1 commented Oct 21, 2020 •

edited by gitpod-io bot

babel-bot commented Oct 21, 2020 •

edited

codesandbox-ci bot commented Oct 21, 2020 •

edited

kaicataldo commented Oct 21, 2020 •

edited

JLHwung commented Feb 5, 2021 •

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JLHwung Feb 9, 2021 •

edited