feat: add support for preserving comments in code #967

tido64 · 2023-04-17T09:32:59Z

Summary

Add support for preserving comments in code. Useful for preserving /*#__PURE__*/ annotations that aid tree shaking.

Test plan

	Size
Before	1567764
After	1258413
Diff	-309351

robhogan · 2023-04-17T09:39:14Z

Thanks! This seems pretty well defined - I wonder whether we could just go straight to stable with this. WDYT @motiz88?

motiz88 · 2023-04-17T09:52:52Z

This seems pretty well defined - I wonder whether we could just go straight to stable with this.

@robhogan: Makes sense to me. I guess this is something all transformers (even non-Babel-based ones) would be able to implement, so no concerns there. The only real gap IMO is that we should document this in https://facebook.github.io/metro/docs/configuration/#transformer-options if stable. To avoid confusion, I wouldn't explicitly mention tree-shaking, and instead just briefly describe what the option itself does.

packages/metro-transform-worker/src/__tests__/index-test.js

Useful for preserving `/*#__PURE__*/` annotations that aid tree shaking.

motiz88 · 2023-04-21T18:30:48Z

packages/metro-config/src/defaults/index.js

@@ -111,6 +111,7 @@ const getDefaultValues = (projectRoot: ?string): ConfigT => ({
      },
      output: {
        ascii_only: true,
+        comments: false,


I don't see a need to specify this explicitly.

Our default minifier, Terser, has a documented default of "some", set here, so this overrides that and may be an unwanted change in behaviour. Per 1, let's just remove this explicit Metro default.

Suggested change

comments: false,

Previously, we had comments: false in Babel, which basically omits all comments, so no comments ever reach the minifier. To preserve that behaviour, we need to set comments: false here. If you still want to remove it, that's fine with me, but it will produce a different output than today.

I see! Yeah, in that case we should probably land this with a behaviour-preserving default so it can go out as a patch, then align with terser's default in the next major. (Would you mind sending a separate PR with that?)

The only thing I don't get is: if this is supposed to be behaviour-preserving, why did the buildGraph test snapshot change? Do we have a good test covering the actual default from Metro's config?

It changed because it's unminified, so the comments have yet to be stripped out.

I can send out a separate PR to remove this line.

Thanks for merging this PR! Here's the follow-up: #972

facebook-github-bot · 2023-04-24T07:50:46Z

@motiz88 has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

facebook-github-bot · 2023-04-24T11:32:07Z

@motiz88 merged this pull request in 8d8f317.

[![Mend Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com) This PR contains the following updates: | Package | Change | Age | Adoption | Passing | Confidence | |---|---|---|---|---|---| | [metro](https://togithub.com/facebook/metro) | [`0.76.0` -> `0.76.6`](https://renovatebot.com/diffs/npm/metro/0.76.0/0.76.6) | [![age](https://badges.renovateapi.com/packages/npm/metro/0.76.6/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/npm/metro/0.76.6/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/npm/metro/0.76.6/compatibility-slim/0.76.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/npm/metro/0.76.6/confidence-slim/0.76.0)](https://docs.renovatebot.com/merge-confidence/) | | [metro-resolver](https://togithub.com/facebook/metro) | [`0.76.0` -> `0.76.6`](https://renovatebot.com/diffs/npm/metro-resolver/0.76.0/0.76.6) | [![age](https://badges.renovateapi.com/packages/npm/metro-resolver/0.76.6/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/npm/metro-resolver/0.76.6/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/npm/metro-resolver/0.76.6/compatibility-slim/0.76.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/npm/metro-resolver/0.76.6/confidence-slim/0.76.0)](https://docs.renovatebot.com/merge-confidence/) | --- ### Release Notes <details> <summary>facebook/metro</summary> ### [`v0.76.6`](https://togithub.com/facebook/metro/releases/tag/v0.76.6) [Compare Source](https://togithub.com/facebook/metro/compare/v0.76.5...v0.76.6) - **\[Types]** Update config and `Server` types to use broader types from `connect` package (facebook/metro@d20d7c8 by [@huntie](https://togithub.com/huntie)) - **\[Types]** Fix TypeScript name for `createConnectMiddleware` export (facebook/metro@06682f8 by [@huntie](https://togithub.com/huntie)) - **\[Deprecation]** Deprecate `server.enhanceMiddleware` option (facebook/metro@22e85fd by [@huntie](https://togithub.com/huntie)) > NOTE: Experimental features are not covered by semver and can change at any time. - **\[Experimental]** Add `unstable_extraMiddleware` option to `runServer` API (facebook/metro@d0d5543 by [@huntie](https://togithub.com/huntie)) **Full Changelog**: facebook/metro@v0.76.5...v0.76.6 ### [`v0.76.5`](https://togithub.com/facebook/metro/releases/tag/v0.76.5) [Compare Source](https://togithub.com/facebook/metro/compare/v0.76.4...v0.76.5) - **\[Feature]** Support URLs for both bundling and symbolication requests using `//&` instead of `?` as a query string delimiter (facebook/metro@bd357c8 by [@robhogan](https://togithub.com/robhogan)) - **\[Fix]** Fix crash on a module added+modified+removed between updates (facebook/metro@5d7305e by [@robhogan](https://togithub.com/robhogan)) - **\[Fix]** Fix missed modification on module removed+modified+added between updates (facebook/metro@5d7305e by [@robhogan](https://togithub.com/robhogan)) - **\[Fix]** Emit source URLs in a format that will not be stripped by JavaScriptCore (facebook/metro@bce6b27ef8ac7c41e0a3e990eb71747cc0e6f606by [@robhogan](https://togithub.com/robhogan)) - **\[Performance]** Prune unmodified modules from delta updates before sending them to the client (facebook/metro@e24c6ae by [@robhogan](https://togithub.com/robhogan)) > NOTE: Experimental features are not covered by semver and can change at any time. - **\[Experimental]** Fix `babel/runtime` issue when using Package Exports (facebook/metro@905d773 by [@huntie](https://togithub.com/huntie)) **Full Changelog**: facebook/metro@v0.76.4...v0.76.5 ### [`v0.76.4`](https://togithub.com/facebook/metro/releases/tag/v0.76.4) [Compare Source](https://togithub.com/facebook/metro/compare/v0.76.3...v0.76.4) - **\[Feature]**: Support the [`x_google_ignoreList`](https://developer.chrome.com/articles/x-google-ignore-list/) source map extension. ([facebook/metro#973, [`82bd64a`](https://togithub.com/facebook/metro/commit/82bd64a9720174a9e2a02fb73bbef292153e20f1) by [@motiz88](https://togithub.com/motiz88)) - **\[Feature]**: Support bundling KTX files as image assets. ([facebook/metro#975 by [@rshest](https://togithub.com/rshest)) - **\[Fix]**: Fix crash on a module added+modified+removed between updates. ([`5d7305e`](https://togithub.com/facebook/metro/commit/5d7305e2f3a9f5f4aebc889a452afb03b1db12a7) by [@robhogan](https://togithub.com/robhogan)) - **\[Fix]**: Fix missed modification on module removed+modified+added between updates. ([`5d7305e`](https://togithub.com/facebook/metro/commit/5d7305e2f3a9f5f4aebc889a452afb03b1db12a7) by [@robhogan](https://togithub.com/robhogan)) **Full Changelog**: facebook/metro@v0.76.3...v0.76.4 ### [`v0.76.3`](https://togithub.com/facebook/metro/releases/tag/v0.76.3) [Compare Source](https://togithub.com/facebook/metro/compare/v0.76.2...v0.76.3) - **\[Feature]**: Support custom `__loadBundleAsync` implementations in the default `asyncRequire` function. See the [lazy bundling RFC](https://togithub.com/react-native-community/discussions-and-proposals/blob/main/proposals/0605-lazy-bundling.md) for more details. (facebook/metro@ac3adce, facebook/metro@f07ce5c by [@motiz88](https://togithub.com/motiz88)) - **\[Feature]**: Support `lazy` parameter in bundle requests. See the [lazy bundling RFC](https://togithub.com/react-native-community/discussions-and-proposals/blob/main/proposals/0605-lazy-bundling.md) for more details. (facebook/metro@4ef14f9 by [@motiz88](https://togithub.com/motiz88)) - **\[Feature]**: Preserve comments in unminified builds, while continuing to strip all comments from minified builds. ([facebook/metro#967 by [@tido64](https://togithub.com/tido64)) - **\[Deprecated]**: The `transformer.asyncRequireModulePath` config option is deprecated. Use [`__loadBundleAsync`](https://togithub.com/react-native-community/discussions-and-proposals/blob/main/proposals/0605-lazy-bundling.md#\__loadbundleasync-in-metro) instead.(facebook/metro@c7b684f by [@motiz88](https://togithub.com/motiz88)) > NOTE: Experimental features are not covered by semver and can change at any time. - **\[Experimental]** Package Exports unstable_conditionNames now defaults to \['require', 'import'] (facebook/metro@e70ceef by [@huntie](https://togithub.com/huntie)) - **\[Experimental]** Removed `server.experimentalImportBundleSupport` config option. (facebook/metro@4ef14f9 by [@motiz88](https://togithub.com/motiz88)) **Full Changelog**: facebook/metro@v0.76.2...v0.76.3 ### [`v0.76.2`](https://togithub.com/facebook/metro/releases/tag/v0.76.2) [Compare Source](https://togithub.com/facebook/metro/compare/v0.76.1...v0.76.2) - **\[Feature]**: Added customizeStack hook to Metro's `/symbolicate` endpoint to allow custom frame skipping logic on a stack level. (facebook/metro@ce266dd by [@GijsWeterings](https://togithub.com/GijsWeterings)) - **\[Feature]**: Re-export `metro-core`'s `Terminal` from `metro`. (facebook/metro@86e3f93 by [@robhogan](https://togithub.com/robhogan)) - **\[Feature]**: Re-export `metro-config`'s `resolveConfig` from `metro`. (facebook/metro@cc16664 by [@robhogan](https://togithub.com/robhogan)) - **\[Types]**: Remove dependency on `@types/babel__code-frame`. (facebook/metro@41cdc03 by [@robhogan](https://togithub.com/robhogan)) - **\[Types]**: Remove dependency on `@types/ws`. (facebook/metro@7deb525 by [@robhogan](https://togithub.com/robhogan)) - **\[Types]**: Fix TypeScript types entry point for metro-source-map. (facebook/metro@3238bbc by [@huntie](https://togithub.com/huntie)) - **\[Deprecated]**: Deprecate `ResolutionContext.getPackageForModule`. (facebook/metro@2d0a01c by [@huntie](https://togithub.com/huntie)) > NOTE: Experimental features are not covered by semver and can change at any time. - **\[Experimental]**: Pass full path and query params to `asyncRequire` for lazy bundles. (facebook/metro@61a30b7 by [@motiz88](https://togithub.com/motiz88)) - **\[Experimental]**: Fix bug where Package Exports warnings may have been logged for nested `node_modules` path candidates. (facebook/metro@29c77bf by [@huntie](https://togithub.com/huntie)) - **\[Experimental]**: Fix `package.json` discovery against root package specifiers for Package Exports. (facebook/metro@b995303 by [@huntie](https://togithub.com/huntie), fixes [facebook/metro#965 reported by [@shamilovtim](https://togithub.com/shamilovtim)) **Full Changelog**: facebook/metro@v0.76.1...v0.76.2 ### [`v0.76.1`](https://togithub.com/facebook/metro/releases/tag/v0.76.1) [Compare Source](https://togithub.com/facebook/metro/compare/v0.76.0...v0.76.1) - **\[Feature]**: Support custom transformer/resolver options in `metro build` and `runBuild` API. (facebook/metro@fcfecc9 by [@motiz88](https://togithub.com/motiz88)) - **\[Feature]**: `metro get-dependencies --entryFile <entryFile>` can now be called as `metro get-dependencies <entryFile>`. (facebook/metro@6fdce04 by [@huntie](https://togithub.com/huntie)) - **\[Feature]**: Add `Content-Type` and `Content-Length` headers for assets to Metro server. ([facebook/metro#953 by [@aleqsio](https://togithub.com/aleqsio), [facebook/metro#961 by [@byCedric](https://togithub.com/byCedric)) - **\[Feature]**: Expose `mergeConfig` util from `metro` package. (facebook/metro@aa8ec90 by [@huntie](https://togithub.com/huntie)) - **\[Fix]**: `metro-file-map`: consistently abort crawl when `end()` is called. (facebook/metro@51877a8 by [@motiz88](https://togithub.com/motiz88)) - **\[Fix]**: `metro-config`: Don't mutate argument to `loadConfig`. (facebook/metro@38ec62d by [@motiz88](https://togithub.com/motiz88)) - **\[Fix]**: Babel transformers: Provide correct absolute source path to plugins when Metro is not run from the project root. (facebook/metro@de19bbd by [@robhogan](https://togithub.com/robhogan)) - **\[Fix]**: [`resolver.assetExts`](https://facebook.github.io/metro/docs/configuration/#assetexts) will now match asset files for extension values that include a dot (`.`). (facebook/metro@6d65a32 by [@huntie](https://togithub.com/huntie)) - **\[Fix]**: Don't register an [`unhandledRejection`](https://nodejs.org/api/process.html#event-unhandledrejection) listener, fix spammy EventEmitter leak warning. (facebook/metro@833f2ff by [@motiz88](https://togithub.com/motiz88)) - **\[Types]**: Add bundled TypeScript definitions (partial) for all packages previously on DefinitelyTyped. (facebook/metro@c022c36, facebook/metro@07732e7, facebook/metro@9ee5280 by [@huntie](https://togithub.com/huntie), with [@afoxman](https://togithub.com/afoxman) and [@tido64](https://togithub.com/tido64)) - **\[Types]**: Expose `MetroConfig` type in `metro` package. (facebook/metro@d2f3664 by [@huntie](https://togithub.com/huntie)) > NOTE: Experimental features are not covered by semver and can change at any time. - **\[Experimental]**: Reorder `asyncRequire`'s parameters and make module name optional. (facebook/metro@4e5261c by [@motiz88](https://togithub.com/motiz88)) - **\[Experimental]**: Remove experimental `metro-hermes-compiler` package. (facebook/metro@833f2ff by [@motiz88](https://togithub.com/motiz88)) - **\[Experimental]**: Package Exports [`unstable_conditionNames`](https://facebook.github.io/metro/docs/configuration/#unstable_conditionnames-experimental) now defaults to `['require']`. ([facebook/metro#955 by [@huntie](https://togithub.com/huntie)) - **\[Experimental]**: Add compatibility with legacy Node.js "exports" array formats. (facebook/metro@f321cff, facebook/metro@1e47cb5 by [@huntie](https://togithub.com/huntie)) **Full Changelog**: facebook/metro@v0.76.0...v0.76.1 </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. 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metro-serializer-esbuild: /*#__PURE__*/ markers are not respected microsoft/rnx-kit#2365

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tido64 force-pushed the tido/preserve-comments branch 2 times, most recently from 967c64a to 6ba1071 Compare April 18, 2023 05:44

tido64 added 2 commits April 19, 2023 13:08

feat: add support for preserving comments in code

227989b

Useful for preserving `/*#__PURE__*/` annotations that aid tree shaking.

let the minifier handle comments

bd567e5

tido64 force-pushed the tido/preserve-comments branch from 6ba1071 to bd567e5 Compare April 19, 2023 11:08

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arushikesarwani94 mentioned this pull request Apr 25, 2023

chore : Upgrading metro dependencies to 0.76.3 react-native-community/cli#1921

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sirinartk mentioned this pull request Jun 21, 2023

[Snyk] Security upgrade yargs from 9.0.1 to 10.0.0 sirinartk/metro#64

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feat: add support for preserving comments in code #967

feat: add support for preserving comments in code #967

tido64 commented Apr 17, 2023

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feat: add support for preserving comments in code #967

feat: add support for preserving comments in code #967

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tido64 commented Apr 17, 2023

Summary

Test plan

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