Module: Import assertions improvements

[GeoffreyBooth]

Please use #40790 for “product” or “feature” discussion, so that the discussion on this PR thread can stay focused on technical feedback.

This PR implements #40790 (comment), making the following changes to Node’s support for import assertions:

• An experimental warning is now printed for all imports with explicitly declared assertion types (currently only JSON).

• In the module map, the string 'javascript' is used instead of a symbol to represent the “default” or implied type, to align with the HTML spec.

• To align with Chrome and with Prevent modules from being imported with a type: 'javascript' assertion whatwg/html#7350, assert { type: 'javascript' } throws an error. (This was the behavior before, but now it’s made explicit since we use 'javascript' internally.)

Please see #40790 for the motivation behind these changes, and please use that thread for discussion of the desired functionality. I’d like to limit the discussion on this PR thread to technical concerns. Thanks! cc @nodejs/modules @nodejs/loaders

[bmeck]

Implementation LGTM, discussion is ongoing though

[bmeck]

Since the discussion seems to be narrowed to around how to deal w/ imports that lack the assertion, and it seems it would move from early error -> working at runtime. I think we should probably land this PR and continue discussion elsewhere unless there are clear concerns about moving those early errors into working at runtime code from this implementation in this PR. I tried to read the discussion again but don't see anything that stands out to me as absolutely concerned with the implementation here.

[MylesBorins]

RSLGTM

[MylesBorins]

should we link out to the ongoing discussion in HTML spec?

[GeoffreyBooth]

I’m not sure what the best link would be. There’s WebAssembly/esm-integration#42 or tc39/proposal-import-attributes#19 or others. It also feels a little messy to link to a discussion thread as opposed to a decision outcome. But if you have a link in particular you recommend, though, I’m happy to add it.

[guybedford]

Blocking as per my comments in #40790 (comment). to summarize:

1. Separating "type": "javascript" and "type": "webassembly" risks conflating a model of security privilege with the execution model, when JS and Wasm currently share execution privileges by virtue of being able to import and execute any function. Making this distinction I believe would result in unnecessary interop frictions on import boundaries.
2. Whether "type": "webassembly" will be optional, required or even supported at all is entirely unclear and should be determined based on discussion with those in the browser and Web Assembly communities through the Web Assembly ESM Integration effort, not by Node.js jumping ahead with implementation.

I'm in contact with @GeoffreyBooth with regards to next steps on this topic.

[aduh95]

LGTM with one nit and assuming Guy concern can be resolved.

[nodejs-github-bot]

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✔  Done loading data for nodejs/node/pull/40785
----------------------------------- PR info ------------------------------------
Title      Module: Import assertions improvements (#40785)
   ⚠  Could not retrieve the email or name of the PR author's from user's GitHub profile!
Branch     GeoffreyBooth:more-import-assertion-types -> nodejs:master
Labels     module, esm, author ready, loaders
Commits    2
 - doc: fix spelling of 'WebAssembly'
 - module: import assertions improvements
Committers 1
 - Geoffrey Booth 
PR-URL: https://github.com/nodejs/node/pull/40785
Reviewed-By: James M Snell 
Reviewed-By: Bradley Farias 
Reviewed-By: Myles Borins 
Reviewed-By: Guy Bedford 
Reviewed-By: Antoine du Hamel 
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/40785
Reviewed-By: James M Snell 
Reviewed-By: Bradley Farias 
Reviewed-By: Myles Borins 
Reviewed-By: Guy Bedford 
Reviewed-By: Antoine du Hamel 
--------------------------------------------------------------------------------
   ⚠  Commits were pushed since the last review:
   ⚠  - doc: fix spelling of 'WebAssembly'
   ⚠  - module: import assertions improvements
   ℹ  This PR was created on Thu, 11 Nov 2021 05:02:37 GMT
   ✔  Approvals: 5
   ✔  - James M Snell (@jasnell) (TSC): https://github.com/nodejs/node/pull/40785#pullrequestreview-805386076
   ✔  - Bradley Farias (@bmeck): https://github.com/nodejs/node/pull/40785#pullrequestreview-811832395
   ✔  - Myles Borins (@MylesBorins) (TSC): https://github.com/nodejs/node/pull/40785#pullrequestreview-806600800
   ✔  - Guy Bedford (@guybedford): https://github.com/nodejs/node/pull/40785#pullrequestreview-811839664
   ✔  - Antoine du Hamel (@aduh95) (TSC): https://github.com/nodejs/node/pull/40785#pullrequestreview-807849260
   ✔  Last GitHub Actions successful
   ℹ  Last Full PR CI on 2021-11-24T04:02:39Z: https://ci.nodejs.org/job/node-test-pull-request/41066/
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[nodejs-github-bot]

Landed in 7633c86...6dfbf04