Parse destructuring private fields #13931

JLHwung · 2021-11-04T20:54:19Z

Q	A
Fixed Issues?	Implement parsing of destructuring private proposal
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?	Y
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

Todo:

typings update
syntax plugin
generator support
standalone

This PR implements parsing support for the proposal.

When parsing a binding property, it is unambiguous that { #x: x } must be a pattern so we parse the private name and push it to the object pattern.

When parsing an assignment property, { #x: x } is ambiguous because it can be an object expression or an object pattern. We register the first private key position as refExpressionErrors.privateKey and then decide to throw or discard when the ambiguity is resolved. We add expectPlugin check when the private key is consumed in the object pattern, so users won't see the error "expect experimental destructuringPrivate plugin" when the private key is used in an object literal, which can be quite misleading.

This PR includes commits from #13929, I will rebase after it gets merged.

Preview REPL (Currently it throws Unknown private name #x because the private field transform can't handle private name in property key yet.)

codesandbox-ci · 2021-11-04T20:57:12Z

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babel-bot · 2021-11-04T20:57:14Z

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/49930/

JLHwung · 2021-11-12T19:07:15Z

...babel-parser/test/fixtures/experimental/destructuring-private/valid-arrow-params/output.json

@@ -1,9 +1,6 @@
 {
  "type": "File",
  "start":0,"end":46,"loc":{"start":{"line":1,"column":0},"end":{"line":4,"column":1}},
-  "errors": [
-    "SyntaxError: Private names can only be used as the name of a class element (i.e. class C { #p = 42; #m() {} } )\n or a property of member expression (i.e. this.#p). (3:11)"
-  ],


This test has been moved to packages/babel-parser/test/fixtures/experimental/_no-plugin/destructuring-private-arrow-params/input.js and throws expected plugins instead.

This test is also duplicated to packages/babel-parser/test/fixtures/experimental/destructuring-private/valid-arrow-params/input.js as a test case for destructuring private. Here git confusingly marks that output.json is moved to destructuring-private.

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

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

...babel-parser/test/fixtures/es2022/class-private-properties/invalid-object-method/output.json

nicolo-ribaudo · 2021-11-13T10:21:53Z

...er/test/fixtures/experimental/destructuring-private/invalid-async-call-arguments/output.json

+  "type": "File",
+  "start":0,"end":46,"loc":{"start":{"line":1,"column":0},"end":{"line":4,"column":1}},
+  "errors": [
+    "SyntaxError: Private names can only be used as the name of a class element (i.e. class C { #p = 42; #m() {} } )\n or a property of member expression (i.e. this.#p). (3:16)"


When the plugin is enabled, we should update the error message to also mention destructuring.

The current error message does not cover #p in o, either. At this point I feel like listing all the valid cases in error messages is a bit verbose. Should we just say unexpected private field?

Uh yes, if adding every case it's too much lets stay vague to cover all of them.

nicolo-ribaudo

Approving, but I think the error message should be updated either to include all possible cases or none of them (half of them doesn't really make sense).

JLHwung · 2021-11-17T15:34:07Z

I agree. I will update the error message to the vague "Unexpected private field".

nicolo-ribaudo · 2021-11-17T15:38:54Z

Maybe "Private name", which is the name of the syntactic element (private field is the "thing" installed on an object that you access with its private name).

existentialism · 2021-11-19T02:28:44Z

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

@@ -2197,8 +2206,12 @@ export default class ExpressionParser extends LValParser {
    return node;
  }

+  // https://tc39.es/ecma262/#prod-PropertyName
+  // when refExpressionErrors presents, it will parse private name


Nit:

Suggested change

// when refExpressionErrors presents, it will parse private name

// when refExpressionErrors is present, it will parse private name

existentialism

Nice work!

nicolo-ribaudo · 2021-11-24T19:33:10Z

@JLHwung If you want to work on the transform, make sure to merge this to a feat-7.17.0 branch and not to main (it currently targets main).

JLHwung · 2021-11-25T20:25:16Z

Merged to feat-7.17.0/destructuring-private

* feat: parse destructuring private * add test cases * fix: register private name on destructuring * add typings * add syntax plugin * add generator test case * add syntax plugin to preset-stage-2 * fix flow errors * address review comments * fix: use private name in toAssignable * test: add case with undefined refExpressionErrors

JLHwung added PR: New Feature 🚀 A type of pull request used for our changelog categories Spec: Destructuring Private Fields labels Nov 4, 2021

JLHwung force-pushed the parse-destructuring-private branch from 5046646 to d2979d2 Compare November 5, 2021 19:26

JLHwung marked this pull request as ready for review November 5, 2021 19:37

JLHwung force-pushed the parse-destructuring-private branch 3 times, most recently from cb6eadf to 1c1b938 Compare November 12, 2021 19:03

JLHwung commented Nov 12, 2021

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nicolo-ribaudo reviewed Nov 13, 2021

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JLHwung force-pushed the parse-destructuring-private branch from 1c1b938 to 176a1ab Compare November 15, 2021 16:46

JLHwung changed the base branch from feat-7.17.0/destructuring-private to main November 15, 2021 16:50

JLHwung force-pushed the parse-destructuring-private branch 2 times, most recently from 8e2fb74 to ce9dba3 Compare November 15, 2021 20:43

nicolo-ribaudo approved these changes Nov 17, 2021

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JLHwung mentioned this pull request Nov 17, 2021

fix: update UnexpectedPrivateField error message #13975

Merged

JLHwung force-pushed the parse-destructuring-private branch 2 times, most recently from 4481524 to b1aa55a Compare November 17, 2021 19:36

existentialism reviewed Nov 19, 2021

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existentialism approved these changes Nov 19, 2021

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nicolo-ribaudo added this to the v7.17.0 milestone Nov 19, 2021

JLHwung added 6 commits November 24, 2021 11:05

feat: parse destructuring private

431c722

add test cases

e6aa04f

fix: register private name on destructuring

67908c9

add typings

be4386a

add syntax plugin

6fdaccb

add generator test case

fbe9b1c

JLHwung added 5 commits November 24, 2021 11:05

add syntax plugin to preset-stage-2

3f03eee

fix flow errors

055f74f

address review comments

8d0ac28

fix: use private name in toAssignable

7ce9408

test: add case with undefined refExpressionErrors

370efa6

JLHwung force-pushed the parse-destructuring-private branch from b1aa55a to 370efa6 Compare November 24, 2021 16:05

JLHwung changed the base branch from main to feat-7.17.0/destructuring-private November 24, 2021 19:34

JLHwung merged commit c87850c into babel:feat-7.17.0/destructuring-private Nov 25, 2021

JLHwung deleted the parse-destructuring-private branch November 25, 2021 20:25

JLHwung mentioned this pull request Nov 25, 2021

Implement parser support for destructuring-private #13999

Merged

1 task

This was referenced Feb 7, 2022

Build(deps): Bump @babel/parser from 7.16.12 to 7.17.0 prettier/prettier#12241

Merged

TODOs for @babel/parser@7.17.0 prettier/prettier#12255

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Parse destructuring private fields #13931

Parse destructuring private fields #13931

JLHwung commented Nov 4, 2021 •

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JLHwung commented Nov 25, 2021

	// when refExpressionErrors presents, it will parse private name
	// when refExpressionErrors is present, it will parse private name

Parse destructuring private fields #13931

Parse destructuring private fields #13931

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