Resolve platform specific files if general file was not found

[stephan-wolf-ais]

Hi! 👋

Firstly, thanks for your work on this project! 🙂

Today I used patch-package to patch metro@0.83.6 for the project I'm working on.

We used a package which contains only platform specific resources. This means metro was not able to find files specified by i.e. icon@3x without an platform specifier. This patch solved the issue.

Here is the diff that solved my problem:

diff --git a/node_modules/metro/src/Assets.js b/node_modules/metro/src/Assets.js
index ac3302c..10f4ae1 100644
--- a/node_modules/metro/src/Assets.js
+++ b/node_modules/metro/src/Assets.js
@@ -223,9 +223,22 @@ async function getAsset(
   }
   if (fileExistsInFileMap != null) {
     if (!fileExistsInFileMap(absolutePath)) {
-      throw new Error(
-        `'${relativePath}' could not be found, because it is not within the projectRoot or watchFolders, or it is blocked via the resolver.blockList config`,
-      );
+      // When the exact file doesn't exist in the file map, check for a
+      // platform-specific variant (e.g. icon@3x.android.png instead of
+      // icon@3x.png). Some packages only ship platform-specific assets.
+      let foundPlatformVariant = false;
+      if (platform != null) {
+        const ext = _path.default.extname(absolutePath);
+        const platformPath = absolutePath.slice(0, -ext.length) + '.' + platform + ext;
+        if (fileExistsInFileMap(platformPath)) {
+          foundPlatformVariant = true;
+        }
+      }
+      if (!foundPlatformVariant) {
+        throw new Error(
+          `'${relativePath}' could not be found, because it is not within the projectRoot or watchFolders, or it is blocked via the resolver.blockList config`,
+        );
+      }
     }
   } else {
     if (!pathBelongsToRoots(absolutePath, [projectRoot, ...watchFolders])) {

This issue body was partially generated by patch-package.

[kitten]

#1694 already fixed this. The patch here looks like it's for a version prior to the hotfix releases