From 94b1c9949a13684d0de4ccdf628bfcfc7cdd7bdb Mon Sep 17 00:00:00 2001
From: Alex Hunt <alexeh@meta.com>
Date: Tue, 18 Apr 2023 03:57:34 -0700
Subject: [PATCH] Drop internal base config merge in metro-config (#36777)
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Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/36777

Changelog: [Internal]

Remove internal merge of `getDefaultConfig` (Metro base defaults) from `react-native/metro-config`. This is unnecessary given the config loading setup of RN CLI and Expo CLI, which use (or replicate) Metro's [`loadConfig`](https://github.com/facebook/metro/blob/1e47cb5b3cc289530fb18e402891f9d2816611dd/packages/metro-config/src/loadConfig.js#L182-L190) function — which will itself apply defaults appropriately.

This relates to a previously-breaking behaviour documented in the test plan of https://github.com/react-native-community/cli/pull/1896 (independently fixed and no longer load-bearing) (**read: no need to cherry pick this change**).

https://pxl.cl/2B8NS

While this has no effect under the fixed RN CLI setup, this is a worthwhile simplification to this package that better-aligns with current Metro tooling expectations.

## Notes

- `getDefaultConfig` no longer returns `ConfigT` (full config), and instead returns `MetroConfig` (partial config). This is non-breaking with the expected API of a given `metro.config.js` file.

Differential Revision: D44630645

fbshipit-source-id: e85247b145e87d7bac9eca0bcb90e85e6fec98ae
---
 packages/metro-config/index.js | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/packages/metro-config/index.js b/packages/metro-config/index.js
index c43b46a34b8cf9..e88df579040627 100644
--- a/packages/metro-config/index.js
+++ b/packages/metro-config/index.js
@@ -8,9 +8,9 @@
  * @noformat
  */
 
-/*:: import type {ConfigT} from 'metro-config'; */
+/*:: import type {MetroConfig} from 'metro-config'; */
 
-const {getDefaultConfig: getBaseConfig, mergeConfig} = require('metro-config');
+const {mergeConfig} = require('metro-config');
 
 const INTERNAL_CALLSITES_REGEX = new RegExp(
   [
@@ -37,8 +37,8 @@ const INTERNAL_CALLSITES_REGEX = new RegExp(
  */
 function getDefaultConfig(
   projectRoot /*: string */
-) /*: ConfigT */ {
-  const config = {
+) /*: MetroConfig */ {
+  return {
     resolver: {
       resolverMainFields: ['react-native', 'browser', 'main'],
       platforms: ['android', 'ios'],
@@ -76,11 +76,6 @@ function getDefaultConfig(
     },
     watchFolders: [],
   };
-
-  return mergeConfig(
-    getBaseConfig.getDefaultValues(projectRoot),
-    config,
-  );
 }
 
 module.exports = {getDefaultConfig, mergeConfig};