Allow .asset.json files to be treated as assets #1391
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This patch in conjunction with adding `asset.json` to `assetExts` allows JSON files to be treated as assets. This is helpful in cases where the JSON file is large and would cause too much bloat in the main bundle. Perhaps because `json` was previously in the `assetExts` array (removed in facebook#593) it was necessary to have a special code path for transforming `.json` files rather than letting standard asset transformation take priority. However this logic prevents large JSON files from being treated as assets (i.e. not included in the bundle) even when using a custom extension like `.asset.json`. There is a test for `asset.json` that hints this should be supported, but the transform prevents it from working in practice (see https://github.com/facebook/metro/blob/412771475c540b6f85d75d9dcd5a39a6e0753582/packages/metro-resolver/src/__tests__/assets-test.js#L67).
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Summary
This patch in conjunction with adding
asset.jsontoassetExtsallows JSON files to be treated as assets. This is helpful in cases where the JSON file is large and would cause too much bloat in the main bundle.Perhaps because
jsonwas previously in theassetExtsarray (removed in #593) it was necessary to have a special code path for transforming.jsonfiles rather than letting standard asset transformation take priority. However this logic prevents large JSON files from being treated as assets (i.e. not included in the bundle) even when using a custom extension like.asset.json. There is a test forasset.jsonthat hints this should be supported, but the transform prevents it from working in practice (seemetro/packages/metro-resolver/src/__tests__/assets-test.js
Line 67 in 4127714
Edit: After experimenting with this more, I found that in my use-case using async imports like
import("./foo.json")instead works and splits the.jsonfile out into another bundle. With that strategy this PR isn't necessary, so perhaps it's better to just close this.Changelog:
Test plan