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Update source-map -> 0.8.0-beta.0 for compatibility with global fetch #1164

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merged 1 commit into from Apr 4, 2022

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robhogan
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@robhogan robhogan commented Mar 14, 2022

source-map@0.7.3 has an issue with buggy identification of node vs browser environment (it uses typeof fetch === 'function' to spot browsers) - See mozilla/source-map#349, mozilla/source-map#432 and fixes mozilla/source-map#350, mozilla/source-map#363.

This is an issue for React (Native) environments where fetch is often polyfilled, eg for testing or SSR. It's one of the last issues holding us back from making terser the default minifier for https://github.com/facebook/metro.

Importantly, this is also probably going to be an issue for all NodeJS users soon, as NodeJS moves forward with a native global fetch: nodejs/node#41749

Unfortunately, the only source-map release since that bug was fixed is 0.8.0-beta.0, dated Nov 2018.

Would you consider a dependency on a "prerelease", or is this a non-starter?

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@jridgewell jridgewell left a comment

This is due to SourceMapConsumer using WASM, which uses fetch or fs.readFile to get the WASM bytes to instantiate. We could instead switch to @jridgewell/trace-mapping which provides a near drop-in API (and is faster, less memory intensive, and doesn't depend on WASM).

@jridgewell jridgewell added the dependencies Pull requests that update a dependency file label Mar 14, 2022
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fabiosantoscode commented Mar 15, 2022

🤔 this sounds tempting! The memory usage of source-map is definitely a problem. Though Terser also needs to handle the production of source maps. This library could help https://www.npmjs.com/package/vlq#-buffer

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robhogan commented Mar 15, 2022

It is only the SourceMapConsumer part of source-map that's problematic though - while it'd be great to replace the source-map dependency entirely, just using something else for consumption would address the particular issue that motivated this PR.

(Specifically: source-map@0.7.3 will still incorrectly detect the environment on require('../lib/read-wasm'), but the issue doesn't manifest until readWasm() is called (and throws), which is only on instantiation of SourceMapConsumer here)

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jridgewell commented Mar 15, 2022

I tried creating a PR for @jridgewell/trace-mapping, but I see that there's a test for sections sourcemaps, which it doesn't currently support (I don't know of any build tool that produces it). I can try adding it later this week, but we can merge this PR for now.

@robhogan robhogan changed the title [RFC] Update source-map -> 0.8.0-beta.0 Update source-map -> 0.8.0-beta.0 for compatibility with global fetch Mar 21, 2022
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robhogan commented Apr 4, 2022

@jridgewell - did you get anywhere with adding sections support? Otherwise, could we go with this PR as a mitigation?

Would love to move towards terser by default for React Native 👍

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jridgewell commented Apr 4, 2022

I did not yet. I'm happy with using 0.8.0-beta for now, and I'll try updating to my package at a later time. /cc @fabiosantoscode

Implemented as AnyMap in v0.3.8. See #1181 for PR to switch.

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fabiosantoscode commented Apr 4, 2022

Sounds good to me!

@fabiosantoscode fabiosantoscode merged commit 7c98c9c into terser:master Apr 4, 2022
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fabiosantoscode commented Apr 4, 2022

Thanks for coming up with this @robhogan !

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marjorg commented Apr 20, 2022

This also closes #1030, who also deserves some credit for suggesting the fix ages ago :)

facebook-github-bot pushed a commit to facebook/metro that referenced this pull request May 30, 2022
Summary:
This update includes the removal of a direct dependency on `source-map@0.7.x`, in particular the problematic (especially for React Native) `fetch`-based browser/node environment detection described in terser/terser#1164.

This was the last item blocking us from deprecating and replacing `metro-minify-uglify`, which uses the long-depreceted [`uglify-es`](https://www.npmjs.com/package/uglify-es).

### Follow-up
I'll follow up with adding `metro-minify-terser` to `metro`'s dependencies and communicating the deprecation of `metro-minify-uglify` in OSS. Then we'll be able to switch the default and remove `metro-minify-uglify` from the deps in a release cycle or two.

Reviewed By: motiz88

Differential Revision: D36098090

fbshipit-source-id: 415431f17e8048bcd1eccd80c3faa6bbc2283cfb
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