Add private-property-in-object support #11372

jridgewell · 2020-04-03T09:49:20Z

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

https://github.com/tc39/proposal-private-fields-in-in

The parsing is a little loose, but it's going to take a lot of effort to restrict it to only in binary expressions.

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

jridgewell · 2020-04-03T20:36:19Z

/cc @ljharb

ljharb

LGTM overall

ljharb · 2020-04-03T21:00:00Z

packages/babel-helper-create-class-features-plugin/src/fields.js

+      return;
+    }
+
+    path.replaceWith(template.expression.ast`${id}.has(${right})`);


just curious; do these field WeakMaps have WeakMap.prototype.has copied onto them? or can i intercept babel private fields, even in spec mode, by replacing WeakMap.prototype.has?

We do not secure the weak
maps, so this will do a prototype reference. Note that even get and set calls go through the prototype, too. We can't ensure the order of our evaluation, so the WeakMap could have already been patched by the time we reach the class definition.

Of course - you can't protect against first-run code, but to be spec compliant you'd have to at least protect against later code. Object.defineProperties(id, Object.getOwnPropertyDescriptors(WeakMap.prototype)) at id creation would address that.

Currently, all of our output assumes that builtins haven't been modified.

oof, ok - it's totally fine to assume they haven't been modified at module evaluation time (you don't really have a choice) but it's not fine to assume they haven't been modified later. that should be fixed asap (but not in this PR, obviously)

JLHwung

We should also throw when private in is out of the class scope.

({
  test() {
    #x in {};
  }
})

#constructor as private identifier is a syntax error when it is used in a class element. Should we also forbid #constructor in c? @ljharb

ljharb · 2020-04-03T21:47:26Z

@JLHwung I would assume obj.#constructor is a syntax error, so that #constructor in x should be as well?

nicolo-ribaudo · 2020-04-03T21:56:46Z

I think that for #constructor we will already throw when handling private names not in scope, because since it can't be declared it will ever be in scope.

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

...l-parser/test/fixtures/experimental/class-private-methods/asi-failure-generator/options.json

ljharb · 2020-04-03T23:14:33Z

I've just added an early error for #constructor to the proposed spec; thanks for the ping :-)

packages/babel-helper-create-class-features-plugin/src/fields.js

JLHwung · 2020-04-22T17:36:32Z

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

@@ -1158,7 +1171,11 @@ export default class ExpressionParser extends LValParser {
    const isPrivate = this.match(tt.hash);

    if (isPrivate) {
-      this.expectOnePlugin(["classPrivateProperties", "classPrivateMethods"]);


I think throwing missing privateIn error for the common private property case will confuse users.

class C { #p = 42; }

Instead we can expect privateIn when we see tt._in after a private name.

I don't understand the suggestion. I need to expect one of the 3 plugins here, or else I won't be able to parse the private name.

I just realize that this line is never failed due to https://github.com/babel/babel/pull/11478/files#diff-80da704a8d2fc8d339ab57f154fb225eL429, which I address in #11478.

Base on #11478 and current implementation, if users are enabling classPrivateProperties but without privateIn, the following case does not throw missing privateIn error. (REPL)

class C { #p = 42; m() { return #p in this } }

because we never really check privateIn as long as classPrivateProperties is enabled.

Can you add a test case to packages/babel-parser/test/fixtures/experimental/_no-plugin?

We check at https://github.com/babel/babel/pull/11372/files#diff-56fea09eea2de51b8291db400d2f69beR1142. Added a test, we get SyntaxError: Unexpected token at the # in #foo in {}.

Can we throw the privateIn plugin is expected when we see #foo in {} but privateIn is missing? Just like we did for classPrivateProperties.

There are several conflicting desires here:

Parsing smart pipelines, and giving good errors

Parsing invalid #foo expressions (not followed by in)

Parsing #foo in {} expressions, but not having plugin enabled

I don't have a good solution to all three of these. If you can push a commit, that'd be awesome.

Pushed a commit that should address 2) and 3).

For 1) we are printing good errors when |> is seen but no pipeline plugin. I think current situation is acceptable and since they are competing proposals we can give better errors after any of them advances.

babel-bot · 2020-04-24T04:26:12Z

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/21980/

codesandbox-ci · 2020-04-28T20:50:16Z

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nicolo-ribaudo

Thanks @JLHwung for helping!

JLHwung

Thanks.

jridgewell · 2020-04-28T21:27:11Z

Excellent, thanks for the help!

nicolo-ribaudo · 2020-04-28T21:36:38Z

@jridgewell Could you add a docs page for this new plugin to babel/website? You can copy one of the existing pages for other simple plugins.

jridgewell · 2020-04-29T08:43:50Z

babel/website#2235

Co-Authored-By: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

nicolo-ribaudo · 2020-05-18T19:10:31Z

Note: this is not merged to master yet.

https://github.com/tc39/proposal-private-fields-in-in Co-Authored-By: Nicolò Ribaudo <nicolo.ribaudo@gmail.com> Co-Authored-By: Huáng Jùnliàng <jlhwung@gmail.com>

nicolo-ribaudo reviewed Apr 3, 2020

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nicolo-ribaudo added this to the v7.10.0 milestone Apr 4, 2020

JLHwung reviewed Apr 10, 2020

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jridgewell force-pushed the private-prop-in-obj branch 2 times, most recently from 75e7c6f to 47dbbfd Compare April 15, 2020 04:07

nicolo-ribaudo approved these changes Apr 20, 2020

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jridgewell force-pushed the private-prop-in-obj branch from 47dbbfd to dc6872d Compare April 24, 2020 04:23

JLHwung mentioned this pull request Apr 24, 2020

Add some parser missing plugins errors #11478

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nicolo-ribaudo added the PR: Needs Docs label Apr 27, 2020

JLHwung force-pushed the private-prop-in-obj branch from f424252 to 3b282c4 Compare April 28, 2020 20:44

JLHwung force-pushed the private-prop-in-obj branch from 3b282c4 to 5103f89 Compare April 28, 2020 20:54

nicolo-ribaudo approved these changes Apr 28, 2020

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nicolo-ribaudo added the PR: Ready to be Merged A pull request with already two approvals, but waiting for the next minor release label Apr 28, 2020

jridgewell mentioned this pull request Apr 29, 2020

Add doc for private-property-in-object transform babel/website#2235

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jridgewell and others added 14 commits May 9, 2020 00:24

Assert PrivateName followed by in keyword

7d7c82d

Nit fix

beae703

Update PrivateInExpectedIn message

ae1aa9c

Co-Authored-By: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

Only parse if enabled

ac3fa34

Lint

9baa3f6

Update description

7c396f9

Mark undeclared private properties inside in-expressions

e423cda

Fix nested private in expressions

3f8eb82

Fix flow type

d1a3085

Fix nested class traversal

8c4dbe1

fix: throw expect privateIn when we see tt._in after private name

b0dcb2f

update test fixtures

fc61e67

nit refactor

dc90c7e

fix: allow escaped sequence in private in

a19930f

jridgewell force-pushed the private-prop-in-obj branch from cdc5654 to a19930f Compare May 9, 2020 04:25

Flow types...

f304cdb

nicolo-ribaudo changed the base branch from master to feat-7.10.0/private-stuff May 18, 2020 19:06

nicolo-ribaudo merged commit 4379f5c into babel:feat-7.10.0/private-stuff May 18, 2020

nicolo-ribaudo mentioned this pull request May 18, 2020

private-in-obj and integration between private and ?. #11586

Merged

3 tasks

JLHwung mentioned this pull request May 21, 2020

feat: add privatePropertyInObject to babel-standalone #11593

Merged

JLHwung mentioned this pull request May 29, 2020

fix: add new plugin names to missing plugin helpers #11643

Merged

existentialism mentioned this pull request May 31, 2020

Fix some test fixtures #11655

Merged

hzoo mentioned this pull request Jun 4, 2020

Plugins: single file plugin format (like JSX but for plugins) babel/notes#119

Open

JLHwung mentioned this pull request Jun 25, 2020

add builtins assumptions babel/website#2283

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JLHwung added the Spec: Brand Check for Private Fields label Jul 21, 2020

github-actions bot added the outdated A closed issue/PR that is archived due to age. Recommended to make a new issue label Oct 21, 2020

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Add private-property-in-object support #11372

Add private-property-in-object support #11372

jridgewell commented Apr 3, 2020 •

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Add private-property-in-object support #11372

Add private-property-in-object support #11372

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