[expo-asset] Load local expo-updates manifest assets

[jonsamp]

Why

Fixes 4081

Closes ENG-2748, ENG-2288

As described in the issues above, there was one issue that was causing problems:

• The expo-asset library could not load local assets when using an expo-updates manifest
• Using React Native <Image />'s defaultSource prop would cause an app to error.

This PR exposes the manifest2.extra.expoGo.debuggerHost to the selectAssetSources function, which returns the correct local asset URLs. This makes it possible to run expo start --force-manifest-type=expo-updates and to load assets.

How

For expo-asset to know the correct local URL, we must pass it the URL of the currently running local session. For classic manifests, we pass in the manifest.bundleUrl (example: http://127.0.0.1:19000/node_modules/expo/AppEntry.bundle?platform=ios&dev=true&hot=false&minify=false). The expo-asset library code then takes the pathname (http://127.0.0.1:19000) and uses that to construct the asset URL.

In similar fashion, I decided to take the manifest2.extra.expoGo.debuggerHost property (example: 127.0.0.1:19000) for expo-updates manifests. If this property is likely to change, we should pass another prop when running Expo CLI that is more specific, but using this one since I think it is likely stable.

Test Plan

1. Run unit tests inside expo-asset.
2. In apps/sandbox, add the following App.js file and some images named image-one.png and image-two.png:

   import ImageOne from './image-one.png';
   import ImageTwo from './image-two.png';
   
   // ...
   <Image defaultSource={ImageOne} source={ImageTwo} style={{ height: 200, width: 300 }} />

3. Install dependencies with yarn, then run the server with expo start --force-manifest-type=expo-updates and open the app in Expo Go in a simulator. You should see an image appear. You can also write console.log(Image.resolveAssetSource(ImageOne)), and make sure that the URL starts with a URL like "https://127.0.0.1:19000/...".
4. Then, try running the server with expo start --force-manifest-type=classic, to make sure that classic updates are unaffected.

[linear]

ENG-2748 Manifest type "expo-updates" does not show images in development

expo/expo-cli#4081

ENG-2288 Using w/modern manifests in development produces expo-asset error with a production CloudFront URL

We don't yet know why this happens but it's definitely something we need to fix.

A minimum, complete, reproducible example: https://github.com/jonsamp/mcr-expo-manifest-image-default-source

I have a hunch this code is involved:

https://github.com/expo/expo/blame/master/packages/expo-asset/src/AssetSources.ts#L86

Note: defaultSource does not work on Android in development (according to RN docs) so it makes sense that we're only seeing this on iOS

[esamelson]

Looks good to me (aside from the one detail) -- thanks so much for fixing this, @jonsamp!! And for the comprehensive test plan 🙏 🙏

It looks like we should probably take a pass over the rest of the getManifest() calls in this file as well, to make them compatible with manifest2 (could also consider removing the hardcoded cloudfront URL altogether, although it has useful to have a last resort fallback at times) -- but this seems great as a hotfix for the current issue.