Default unstable_renameRequire to false in base config (#1776)#1776
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Default unstable_renameRequire to false in base config (#1776)#1776robhogan wants to merge 2 commits into
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@robhogan has exported this pull request. If you are a Meta employee, you can view the originating Diff in D111627295. |
Summary:
Flip the default value of the `transformer.allowOptionalDependencies` Metro config option from `false` to `true` in `metro-config`'s own defaults.
This allows for patterns like:
```js
let dep = null;
try {
// If not installed, allowOptionalDependencies ===
// true => throw at runtime, handled by catch
// false => throw at build time
dep = require('maybe-installed-dependency');
} catch {
dep = require('./my-fallback');
}
```
Which comes up in popular packages, eg [`lru-cache`](https://github.com/isaacs/node-lru-cache/blob/16b3a916662ab449d496b7b4b4f04132565d1d28/src/diagnostics-channel-esm.mts#L24-L29).
Note that this is *already the default* in:
- `react-native/metro-config`: https://github.com/react/react-native/blob/a632f9efe24bac8b3a113c78469948f55bde0f5d/packages/metro-config/src/index.flow.js#L86
- And `expo/metro-config`: https://github.com/expo/expo/blob/ab042edb8228e3873bdbd8e04b7c61cd3e00372e/packages/%40expo/metro-config/src/ExpoMetroConfig.ts#L423
There were previously known problems with `allowOptionalDependencies` and the behaviour of subsequently declared dependencies, and they were also broken under HMR if their existence changed. These were both fixed a year ago in #1522.
The heuristic was also quite limited, for example a `try { require() }` was considered optional but an `import().catch()` was not. That was fixed in #1697.
I can't think of any good reason not to enable this and fix the misalignment with RN/Expo.
With this enabled, dependencies referenced inside `try/catch` blocks (and dynamic `import()`s with rejection handlers) are treated as optional by default: an unresolvable optional dependency no longer fails the build, matching the common expectation for guarded requires. Projects can still opt out by explicitly setting `allowOptionalDependencies: false`.
Since this change doesn't alter observable runtime behaviour (it allows bundles to build that would otherwise fail to build), I'm inclined to regard it as non-breaking.
```
- **[Feature]**: `allowOptionalDependencies` defaults to `true` to align with RN and Expo
```
Reviewed By: huntie
Differential Revision: D111577052
Summary: Flips the OSS default of the `unstable_renameRequire` transformer option from `true` to `false` in `metro-config`. With renaming disabled, the scoped `require` function is left as `require` instead of being renamed to `_$$_REQUIRE` when serializing to the IIFE module factory (the default). Tested with repeated, interleaved, RNTester dev builds with a cold transform cache: ``` metric OFF (false) ON (true) delta cold build, mean 10.65 s 11.21 s -0.56 s (~5%) cold build, median 11.09 s 11.73 s -0.64 s (~5.5%) _$$_REQUIRE renames 0 3,534 -3,534 ``` NB: Expo already sets this to `false`, so this is a no-op for Expo users. ``` - **[Performance]** Don't rename `require` in bundle output, improve cold build time ~5%` ``` Reviewed By: huntie Differential Revision: D111627295
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This pull request has been merged in e1b6a6a. |
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Summary: Removes the `unstable_renameRequire` transformer option entirely and bakes in the no-rename behaviour that is now the default across base Metro (flipped in the parent #1776) and Expo. Require renaming was vestigial from some previous static analysis, and was implemented in a particularly expensive way, with full re-traversal. ``` - **[Experimental]** Remove unstable_renameRequire - require is never renamed ``` Reviewed By: huntie Differential Revision: D111709130 fbshipit-source-id: 42fb81ed57b668e5bf38b1f2a760aad26fc26fef
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Summary:
Flips the OSS default of the
unstable_renameRequiretransformer optionfrom
truetofalseinmetro-config. With renaming disabled, the scopedrequirefunction is left asrequireinstead of being renamed to_$$_REQUIREwhen serializing to the IIFE module factory (the default).Tested with repeated, interleaved, RNTester dev builds with a cold transform cache:
NB: Expo already sets this to
false, so this is a no-op for Expo users.Reviewed By: huntie
Differential Revision: D111627295