module: deprecate trailing slash pattern mappings #40039

guybedford · 2021-09-08T18:41:49Z

This PR deprecates the ability for pattern mappings to be able to resolve import specifiers ending in / like import('pkg/subpath/'), with a new deprecation warning and message.

The primary motivation here is that the import maps specification does not support trailing / mappings resolving.

For example:

<!doctype html>
<script type="importmap">
{
  "imports": {
    "pkg/subpath/": "/pkg/index.js"
  }
}
</script>
<script type="module">
import 'pkg/subpath/';
</script>

will give the browser console error:

Ignored an import map value of "pkg/subpath/": Since specifierKey ended in a slash, so must the address: /pkg/index.js

See WICG/import-maps#244 for more background here.

Since we deprecated folder subpaths, there are no common patterns of trailing / usage yet. It is only with the introduction of pattern trailers in #39635 that it is now easy to define maps like:

{
  "exports": {
    "./*/": "./*/index.js"
  }
}

to support import('pkg/asdf/') resolving to pkg/asdf/index.js for any name.

The risk is that users start defining packages like this and then these packages will never be supportable in import maps environments. By deprecating this now we can avoid this outcome.

guybedford · 2021-09-08T18:42:15Z

@nodejs/modules

doc/api/deprecations.md

Co-authored-by: Antoine du Hamel <[email protected]>

doc/api/deprecations.md

Co-authored-by: Antoine du Hamel <[email protected]>

ljharb · 2021-09-08T21:51:54Z

What about core modules? It's a very common pattern to require, eg fs/ to indicate that the user wants node_modules/fs and not the core fs module.

… or does this only apply to exports?

What about wanting to disambiguate foo.js from foo/index.js, and wanting the user to do $pkg/foo vs $pkg/foo/?

guybedford · 2021-09-08T21:54:52Z

@ljharb now that we have node:fs I think that's the better pattern for distinction going forward.

And yes, disambiguation of pkg/foo versus pkg/foo/ in the import maps specification not being possible is exactly the issue here.

test/es-module/test-esm-exports-deprecations.mjs

Co-authored-by: Antoine du Hamel <[email protected]>

ljharb · 2021-09-08T22:28:03Z

@guybedford for a core module, yes, i can use node: as a prefix, but i'd still need fs/ to be able to get at node_modules/fs - the prefix doesn't change that.

And yes, disambiguation of pkg/foo versus pkg/foo/ in the import maps specification not being possible is exactly the issue here.

Why are we reducing the usefulness of node because an entirely different specification - one node doesn't even follow - lacks functionality?

aduh95 · 2021-09-08T22:51:35Z

To be clear, you mean being able to do something like that, correct?

{
  "imports": {
    "#fs": "fs/"
  }
}

And import '#fs' would load node_modules/fs package. But I don't think this PR forbids that, does it?

guybedford · 2021-09-09T00:54:12Z

Note that import 'fs/' resolving node_modules/fs/index.js is deprecated due to folder mappings.

So this is just fs/subpath/ use cases.

Why are we reducing the usefulness of node because an entirely different specification - one node doesn't even follow - lacks functionality?

So this PR only reduces the functionality of a feature landed two days ago with pattern trailers.

nodejs-github-bot · 2021-09-09T00:58:01Z

CI: https://ci.nodejs.org/job/node-test-pull-request/39873/

ljharb · 2021-09-09T06:01:04Z

By deprecated, you mean in ESM, or in CJS?

Either way, if I have a folder in node_modules/fs with a package.json with an "exports" with a dot in it, how do you propose i both require and import it?

In CJS, require('fs/') would be the answer; you seem to be suggesting that in ESM there's no non-deprecated answer. That seems like a problem.

guybedford · 2021-09-12T20:39:02Z

By deprecated, you mean in ESM, or in CJS?

We deprecated it specifically for ESM per the folder mappings deprecation PR.

Yes, ESM does deprecate the ability to load npm packages with the same names as core modules, but this is completely off topic at this point for this PR - I'd suggest opening another issue to discuss that.

PR-URL: #40039 Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Geoffrey Booth <[email protected]>

guybedford · 2021-09-15T06:59:37Z

Landed in 7216fb1.

PR-URL: #40039 Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Geoffrey Booth <[email protected]>

module: deprecate trailing slash pattern mappings

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nodejs-github-bot added esm Issues and PRs related to the ECMAScript Modules implementation. needs-ci PRs that need a full CI run. labels Sep 8, 2021

guybedford requested a review from bmeck September 8, 2021 18:42

fixup: exports deprecation check tests

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fixup: make documentation-only deprecation

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guybedford added deprecations Issues and PRs related to deprecations. and removed semver-major PRs that contain breaking changes and should be released in the next major version. deprecations Issues and PRs related to deprecations. labels Sep 8, 2021

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fixup: deprecation docs

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fixup: log

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weswigham mentioned this pull request Sep 15, 2021

Initial import/export/self-name support weswigham/TypeScript#68

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module: deprecate trailing slash pattern mappings

7216fb1

PR-URL: #40039 Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Geoffrey Booth <[email protected]>

guybedford closed this Sep 15, 2021

guybedford deleted the restrict-exports-slash branch September 15, 2021 06:59

guybedford mentioned this pull request Sep 15, 2021

module: runtime deprecate trailing slash patterns #40117

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merceyz mentioned this pull request Sep 15, 2021

Changes to Node.js exports specification lukeed/resolve.exports#11

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BethGriggs pushed a commit that referenced this pull request Sep 21, 2021

module: deprecate trailing slash pattern mappings

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PR-URL: #40039 Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Geoffrey Booth <[email protected]>

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module: deprecate trailing slash pattern mappings

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PR-URL: #40039 Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Geoffrey Booth <[email protected]>

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v16.10.0 proposal #40175

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