Fix 'as const'-like behavior in JSDoc type cast #45464

rbuckton · 2021-08-16T02:29:42Z

We almost support as const like casts in JavaScript files, but end up reporting errors because we either pick up the /** @type {} */ from the parenthesized expression when looking for effective type nodes, or by not handling it at all for contextual types. This fixes both scenarios.

Fixes #45463
Fixes #30445

rbuckton · 2021-08-16T02:31:28Z

src/compiler/checker.ts

@@ -25858,7 +25858,9 @@ namespace ts {
                case SyntaxKind.ParenthesizedExpression: {
                    // Like in `checkParenthesizedExpression`, an `/** @type {xyz} */` comment before a parenthesized expression acts as a type cast.
                    const tag = isInJSFile(parent) ? getJSDocTypeTag(parent) : undefined;
-                    return tag ? getTypeFromTypeNode(tag.typeExpression.type) : getContextualType(parent as ParenthesizedExpression, contextFlags);
+                    return !tag ? getContextualType(parent as ParenthesizedExpression, contextFlags) :


I inverted the order here so that we have one condition per branch (i.e., !a ? x : b ? y : z) instead of nested conditions (i.e., a ? b ? y : x : z).

weswigham

Conceptually this looks OK, except for the odd baseline changes. But I could swear we discussed weather we should support const casts in JS back when we first added const casts, and the original answer was "no" (meaning the fix would have been properly parsing const as a type reference/erroring on the keyword if we wanted to stick with that).

tests/baselines/reference/importTypeInJSDoc.types

tests/baselines/reference/jsdocTypeTagCast.types

sandersn

Couple of things in the tests need to be changed, plus I didn't understand one branch of filterOwnedJSDocTags

src/compiler/utilities.ts

tests/baselines/reference/importTypeInJSDoc.types

tests/baselines/reference/jsdocTypeTagCast.types

orta

Love it, thanks - I'll get this added to the JSDoc reference when it's in 👍🏻

orta · 2021-08-24T11:43:19Z

@typescript-bot pack this

typescript-bot · 2021-08-24T11:43:22Z

Heya @orta, I've started to run the tarball bundle task on this PR at 6504a34. You can monitor the build here.

typescript-bot · 2021-08-24T12:02:29Z

Hey @orta, I've packed this into an installable tgz. You can install it for testing by referencing it in your package.json like so:

{
    "devDependencies": {
        "typescript": "https://typescript.visualstudio.com/cf7ac146-d525-443c-b23c-0d58337efebc/_apis/build/builds/109187/artifacts?artifactName=tgz&fileId=040AC2E0D39470A1CBEB58F9F08DDA3348CDB0ACA6F228B610CAEC0A4F6C001802&fileName=/typescript-4.5.0-insiders.20210824.tgz"
    }
}

and then running npm install.

There is also a playground for this build and an npm module you can use via "typescript": "npm:@typescript-deploys/pr-build@4.5.0-pr-45464-2".;

orta · 2021-08-24T13:15:22Z

As this is definitely going to get asked in the future, is it possible for both of these to work? e.g. sans-parens

const isConst = /** @type {const} */ ({
    hello: "world, not string"
})

isConst
// ^? - { readonly hello: "world, not string" }

const isString = /** @type {const} */ {
    hello: "world, not string"
}

isString
// ^? - { hello: string }

Playground

sandersn · 2021-08-24T18:06:15Z

Probably yes -- but it's an expansion of the Clojure cast syntax that no other tool would recognise, so we should really consider the entire design space if we decide to make casts easier to write.

rbuckton · 2021-08-27T23:10:35Z

The parens are also useful for performance reasons, otherwise we'd have to check every leading JSDoc comment of every expression in a JS file.

What I'd like is a shorter cast syntax (even with the parens). Something like /** {type} */(expr) (removing the @type). I know we allow you to write /** @type type */(expr) (dropping the {}), but that still feels awkward.

I'd also like a way to emulate postfix-! in JSDoc, because the only options currently are a cast (which could be difficult to write from an inferred type), or a generic identity function that removes null | undefined. Not sure what a good jsdoc syntax might be for that though, since there really isn't precedent in Clojure or jsdoc.app.

Something like one of these:

/** @type {!} */(foo.bar).baz; // just the `!` prefix
/** @notnull */(foo.bar).baz; // a keyword-like tag
/** @! */(foo.bar).baz; // or some type of shorthand
/** {!} */(foo.bar).baz;

I'll have to see if there's an open issue for this and, if not, create one.

rbuckton · 2021-08-27T23:14:03Z

@typescript-bot test this
@typescript-bot user test this

Checking rwc and community tests, though I don't think this should affect anything currently.

typescript-bot · 2021-08-27T23:14:06Z

Heya @rbuckton, I've started to run the extended test suite on this PR at 6504a34. You can monitor the build here.

typescript-bot · 2021-08-27T23:14:06Z

Heya @rbuckton, I've started to run the parallelized community code test suite on this PR at 6504a34. You can monitor the build here.

typescript-bot · 2021-08-27T23:52:47Z

The user suite test run you requested has finished and failed. I've opened a PR with the baseline diff from master.

rbuckton · 2021-08-28T01:17:48Z

user test baselines are fine (changes are minor and unrelated)

rbuckton · 2021-08-28T01:21:44Z

rwc baselines look fine.

mohd-akram · 2021-09-12T08:13:27Z

Any idea on when this will be available in TypeScript? It's very useful and hopefully could be released soon.

orta · 2021-09-13T13:33:42Z

TypeScript has a set release schedule, the next release details are here: #45418

mohd-akram · 2021-09-13T13:38:41Z

Ah, I was hoping this could be released as part of a 4.4 bugfix release.

phil294 · 2021-09-15T15:14:04Z

What's the reasoning for not leveraging JSDoc's (currently unused) @constant (short: @const) identifier for this?

sandersn · 2021-09-15T17:07:46Z

TS treats Closure cast syntax as the JSDoc cast syntax, so it's feature parity with TS as const casts.

If @const is truly unused in JSDoc, and likely to remain that way, it might be worth adding it as an alternate syntax. But you'd need to open a new issue with a proposal and exploration of the design problems. A couple I can think of:

would @const only apply to declarations, like most tags?
do people have existing uses of @const that would break in TS?
will JSDoc ever want to use @const for some other meaning?

gaurav5430 · 2021-09-16T14:14:50Z

TypeScript has a set release schedule, the next release details are here: #45418

can't see it in the plans for 4.5
is that right or am I missing something ?

sandersn · 2021-09-16T17:31:39Z

@gaurav5430 Fixes don't show up in the iteration plan as far as I know.

chunjin666 · 2022-07-02T10:30:26Z

Not working in v4.7.4, how can i get this feature.

orta · 2022-07-02T13:09:37Z

Confirming that it is working in 4.7.4

I'd recommend filing a full bug report if you have a case where it is not working as expected

chunjin666 · 2022-07-02T14:40:46Z

I'm very sorry, It's my fault. 8 month ago I learned this feature and try a lot times not work (now I find out the reason is my ts verstion is 4.4.4 that time). And recently I tried agin, but it was in a ts enviroment, and I find this pr. Thanks very mutch, My type programing experience in js project is perfectly satisfied. At 2022-07-02 21:09:48, "Orta Therox" ***@***.***> wrote: Confirming that it is working in 4.7.4 I'd recommend filing a full bug report if you have a case where it is not working as expected — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you commented.Message ID: ***@***.***>

I18n.pluralRulesMap keys are variable so “string” wasn’t compatible when the compiler thought we were using fixed string literals Might be worth another look at `Object.keys()` in future with: * microsoft/TypeScript#45464

rbuckton requested review from sandersn, DanielRosenwasser and weswigham August 16, 2021 02:29

typescript-bot assigned rbuckton Aug 16, 2021

typescript-bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Aug 16, 2021

rbuckton commented Aug 16, 2021

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weswigham reviewed Aug 16, 2021

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sandersn requested changes Aug 16, 2021

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rbuckton force-pushed the fixConstCastInJs branch from 7b70f43 to db3ef67 Compare August 17, 2021 03:09

Fix 'as const'-like behavior in JSDoc type cast

6504a34

rbuckton force-pushed the fixConstCastInJs branch from db3ef67 to 6504a34 Compare August 17, 2021 03:25

sandersn approved these changes Aug 19, 2021

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orta approved these changes Aug 24, 2021

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sandersn added this to Not started in PR Backlog Aug 25, 2021

sandersn moved this from Not started to Needs merge in PR Backlog Aug 25, 2021

typescript-bot mentioned this pull request Aug 27, 2021

🤖 User test baselines have changed for fixConstCastInJs typescript-bot/TypeScript#200

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rbuckton merged commit 107c556 into main Aug 28, 2021

andrewbranch mentioned this pull request Sep 17, 2021

JSDoc support for String array to Object key #45902

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BobobUnicorn pushed a commit to BobobUnicorn/TypeScript that referenced this pull request Oct 24, 2021

Fix 'as const'-like behavior in JSDoc type cast (microsoft#45464)

bd6a94d

AustinGil mentioned this pull request Feb 4, 2022

const assertions in JSDoc #30445

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JounQin mentioned this pull request Mar 6, 2022

const assertions is not supported gajus/eslint-plugin-jsdoc#846

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MartinJohns mentioned this pull request May 21, 2022

Support exact matching array types from JSON files #49194

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btaillon-coveo mentioned this pull request Nov 25, 2022

ci: add prerelease process coveo/ui-kit#2561

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Fix 'as const'-like behavior in JSDoc type cast #45464

Fix 'as const'-like behavior in JSDoc type cast #45464

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Fix 'as const'-like behavior in JSDoc type cast #45464

Fix 'as const'-like behavior in JSDoc type cast #45464

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