JSON module support #4407

littledan · 2019-03-02T16:46:48Z

This patch provides JSON modules as a single default export, with
parse errors checked before instantiating the module graph.

Note, editorially, it's unclear whether JSON modules should be
considered a type of "module script", with a settings object, fetch
options, base URL, etc or not. This patch considers them "module
scripts", but leaves those record fields unset (as they are unused).

This patch is based on
tc39/proposal-built-in-modules#44
which hasn't landed yet, so the references are a bit awkward, and
this patch should not land until that one does.

Closes #4315
Closes WICG/webcomponents#770

/acknowledgements.html ( diff )
/infrastructure.html ( diff )
/scripting.html ( diff )
/timers-and-user-prompts.html ( diff )
/webappapis.html ( diff )

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annevk · 2019-03-03T08:23:16Z

This also resolves WICG/webcomponents#770.

littledan · 2019-03-03T09:33:17Z

Once we settle on a wording here, it would be very easy to specify CSS modules, if we're settled on @justinfagnani's proposed semantics to give it a single default export of the parsed stylesheet. I don't see any open questions on the HTML side.

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domenic

Very interesting. After seeing the results, I'm quite unsure about calling JSON modules "scripts", although I would have suggested that course of action beforehand.

Implicitly, this seems to add a bunch of "assert: X is not a JSON module script" at the beginning of tons of algorithms that take a script. And I'm not sure all those asserts are satisfied, e.g., it seems like by doing <script type="module" src="foo.json"></script> we could end up at https://html.spec.whatwg.org/#execute-the-script-block with the script's script being a JSON module script.

In general, I think there are multiple direct and indirect callers of "fetch a single module script" which assume they are getting back something with all the appropriate struct fields set.

Probably these callers at least need a settings object. I'm unsure about the other fields.

An alternate approach would be to not have a "script" for JSON modules, and only have something you can put in the module map. I'm not sure if that would be better or worse. Probably worse...

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domenic · 2019-03-05T20:49:39Z

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-   script">module scripts</span>; or null. In the former two cases, it represents a parsed script;
+   script">module scripts</span>; a <span>Synthetic Module Record</span> for <span
+   data-x="JSON module script">JSON module scripts</span>; or null. In the
+   former two cases, it represents a parsed script; in the third case, a parsed JSON document;
   null represents a failure parsing.</p></dd>


I think it's OK to leave "a parsed script" covering all three cases, since we still consider these scripts.

littledan · 2019-03-06T18:28:33Z

Thanks for the review. In ced9b08 , module scripts are renamed JavaScript module scripts, and I caught a number of errors going through and making this change; added a number of asserts, and re-added the settings object.

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Ms2ger · 2019-05-06T15:27:08Z

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+
+   <li><p>Upon rejection of <var>jsonPromise</var> with <var>reason</var>, set <var>script</var>'s
+   <span data-x="concept-script-parse-error">parse error</span> to <var>reason</var>, and return
+   <var>script</var>.</p></li>


You can't return anything to the caller of this algorithm from within a rejection/fulfillment handler.

Well, some other pieces of spec text use "asynchronously" to get through this. Do you think that would be possible here?

domenic

I saw the update today to do things arguably more correct, and thought I'd do a pass. My conclusion is that you should go back to the incorrect way of consuming the body :)

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littledan

Thanks for all the suggestions, @domenic. I've done my best to apply them; feel free to push more corrections if you have ideas.

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This patch provides JSON modules as a single default export, with parse errors checked before instantiating the module graph. Note, editorially, it's unclear whether JSON modules should be considered a type of "module script", with a settings object, fetch options, base URL, etc or not. This patch considers them "module scripts", but leaves those record fields unset (as they are unused). This patch is based on tc39/proposal-built-in-modules#44 which hasn't landed yet, so the references are a bit awkward, and this patch should not land until that one does. Closes whatwg#4315

This patch creates a common concept of a "module script", unifying JavaScript module scripts with JSON module scripts (and future concepts like style sheet module scripts, WebAssembly module scripts, etc.) The name change includes the following fixes: - Clarify that <link rel=modulepreload> works for JSON module scripts. - Check for Cyclic Module Records in fetching module descendants and finding the first parse error. - Initialize the settings object and error to rethrow in JSON module scripts, both of which are used by algorithms in HTML. - Add various asserts to make it clear why we can use things when we do. Module scripts may be renamed to simply "modules" in a future patch.

- Tweaks to <script> element stuff - Add example - Add Myles to acks for raising whatwg#4315. - Tighten definition of JS and JSON module script a bit

domenic

OK, this LGTM. Remaining things:

Tests
Implementation bugs
Finding a better home than https://proposal-javascript-standard-library-domenic.now.sh/ for Synthetic Module Records.

I'll tag "do not merge yet" for the last one.

See <whatwg/html#4407>.

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- Delete double space - Change my name from "Dan" to "Daniel" in acknowledgements

Ms2ger · 2019-05-17T10:01:38Z

Tests
- Add some initial tests for JSON modules. web-platform-tests/wpt#16734
Implementation bugs
Finding a better home than https://proposal-javascript-standard-library-domenic.now.sh/ for Synthetic Module Records.
- Define Synthetic Module Records webidl#722

Based on text written by Domenic at tc39/proposal-built-in-modules#44. These will be used by HTML in whatwg/html#4407.

See <whatwg/html#4407>.

…, a=testonly Automatic update from web-platform-tests Add some initial tests for JSON modules. See <whatwg/html#4407>. -- wp5At-commits: f510720b12c7d0dd3e0639bac35aceb237c2221c wpt-pr: 16734

See <whatwg/html#4407>.

…, a=testonly Automatic update from web-platform-tests Add some initial tests for JSON modules. See <whatwg/html#4407>. -- wp5At-commits: f510720b12c7d0dd3e0639bac35aceb237c2221c wpt-pr: 16734 UltraBlame original commit: d18767ce41b850b8929ad67e8367a5fb80eda67d

littledan · 2019-11-12T01:27:40Z

This patch has already been reverted, but I'm wondering if it'd be blocked by nosniff, since we never changed the destination to something that isn't script-like for JSON modules. (I don't even know if there is an appropriate destination type in fetch, or if we should add a new one.)

annevk · 2019-11-12T08:22:29Z

I think you're right that it would've been blocked. I'm surprised that didn't come up as implementation feedback.

littledan force-pushed the json-modules branch from 079f527 to 3d3e219 Compare March 2, 2019 23:39

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annevk mentioned this pull request Mar 4, 2019

JSON "modules" WICG/webcomponents#770

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MylesBorins mentioned this pull request Mar 6, 2019

esm: add experimental .json support to loader nodejs/ecmascript-modules#43

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domenic mentioned this pull request May 4, 2019

JSON modules #4315

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annevk added the needs tests Moving the issue forward requires someone to write tests label May 6, 2019

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littledan changed the title ~~[WIP] JSON module support~~ JSON module support May 6, 2019

littledan added 8 commits May 7, 2019 13:56

Remove errant 1.

602cf44

JSON is "a parsed script"

5c52c2d

Fix markup error

42a5675

Improving formatting, fixing typos

eab8fe5

Fix usage of "consume body", which returns a Promise

712d7e6

Various editorial improvements from Domenic's review

888fe2b

domenic force-pushed the json-modules branch from 7c4189f to 78f7c40 Compare May 7, 2019 19:13

A few more things

d9e4d84

- Tweaks to <script> element stuff - Add example - Add Myles to acks for raising whatwg#4315. - Tighten definition of JS and JSON module script a bit

domenic force-pushed the json-modules branch from 78f7c40 to d9e4d84 Compare May 7, 2019 19:14

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domenic added the do not merge yet Pull request must not be merged per rationale in comment label May 7, 2019

Ms2ger mentioned this pull request May 8, 2019

Add specification for Synthetic Module Records tc39/proposal-built-in-modules#44

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Ms2ger added a commit to web-platform-tests/wpt that referenced this pull request May 8, 2019

Add some initial tests for JSON modules.

a3863c4

See <whatwg/html#4407>.

Ms2ger added a commit to web-platform-tests/wpt that referenced this pull request May 8, 2019

Add some initial tests for JSON modules.

535c067

See <whatwg/html#4407>.

Ms2ger mentioned this pull request May 8, 2019

Add some initial tests for JSON modules. web-platform-tests/wpt#16734

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Minor editorial tweaks

3534110

- Delete double space - Change my name from "Dan" to "Daniel" in acknowledgements

domenic pushed a commit to whatwg/webidl that referenced this pull request May 17, 2019

Define Synthetic Module Records

495ff31

Based on text written by Domenic at tc39/proposal-built-in-modules#44. These will be used by HTML in whatwg/html#4407.

domenic added addition/proposal New features or enhancements topic: script and removed do not merge yet Pull request must not be merged per rationale in comment needs tests Moving the issue forward requires someone to write tests labels May 17, 2019

Refer to Web IDL

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domenic merged commit db03474 into whatwg:master May 17, 2019

littledan mentioned this pull request May 19, 2019

JSON modules w3ctag/design-reviews#375

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Ms2ger added a commit to web-platform-tests/wpt that referenced this pull request May 20, 2019

Add some initial tests for JSON modules.

88d9468

See <whatwg/html#4407>.

Ms2ger added a commit to web-platform-tests/wpt that referenced this pull request May 20, 2019

Add some initial tests for JSON modules.

f510720

See <whatwg/html#4407>.

joeldenning mentioned this pull request Jun 7, 2019

Support JSON files as valid ESM modules. systemjs/systemjs#1949

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marcoscaceres pushed a commit to web-platform-tests/wpt that referenced this pull request Jul 23, 2019

Add some initial tests for JSON modules.

b1f00b0

See <whatwg/html#4407>.

littledan mentioned this pull request Nov 17, 2019

What is the right destination type for non-JS modules? whatwg/fetch#967

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hober mentioned this pull request Dec 10, 2019

HTML horizontal review: Modules w3ctag/design-reviews#460

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summercms mentioned this pull request Sep 4, 2021

Support JSON5 Modules #7021

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JSON module support #4407

JSON module support #4407

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JSON module support #4407

JSON module support #4407

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