example

DevHub example

An Expo app that tests the build cache provider of DevHub (@rootnative/devhub/cache-provider) with npx expo run:android and npx expo run:ios. The app config turns on the provider:

"buildCacheProvider": { "plugin": "@rootnative/devhub/cache-provider" }

The app is not a demo. It shows one line of text.

The store of the example

The scripts of this app keep the builds in .devhub/ in this folder, not in your own DevHub store. with-store.mjs sets DEVHUB_HOME to that folder, and then starts expo or devhub. Git ignores the folder. pnpm clean deletes it.

A command that you run with npx does not get this setting, and uses your own store.

Before the test

1. In the root folder of the repository, run pnpm install and pnpm run build. The app loads the provider from packages/devhub/dist/. After a change to the package, build it again.
2. For Android, start an emulator, or connect a phone with USB. For iOS, start a simulator on a Mac.

The test

Run each command in this folder.

Step	Command	Result
1	pnpm android	› DevHub: No stored build has the android fingerprint …. Gradle builds the app. After the app starts: › DevHub: Stored the build <id> in the DevHub store.
2	pnpm android	› DevHub: Expo CLI installs the stored build <id>, and does not build the app. Gradle does not run.
3	Change orientation in app.json from portrait to default. Then pnpm android.	The fingerprint is new, so Gradle builds the app. The android folder is older than app.json, so DevHub gives a warning and does not store the build.
4	Delete the android folder. Then pnpm android.	Expo CLI runs prebuild, Gradle builds the app, and DevHub stores a second build.
5	Set orientation back to portrait. Delete the android folder. Then pnpm android.	Expo CLI runs prebuild. The fingerprint of step 1 is back, so Expo CLI installs the build of step 1. Gradle does not run.
6	pnpm devhub list, then pnpm devhub match	The two local builds of this app. The build of step 1 matches.

For iOS, use pnpm ios, and delete the ios folder, in steps 1 to 5. Xcode builds the app in place of Gradle. Expo CLI uses the provider only for a simulator, not for an iOS device. Expo SDK 58 needs Xcode 26 for a local iOS build.

node gate.mjs android and node gate.mjs ios do steps 1 to 6 with no person at the device, and check the output and the store after each run. Each run uses --no-bundler, so the app opens with no JavaScript. The script always puts app.json back. The workflow gate-cache-provider.yml runs it on GitHub Actions.

The native folders

expo run makes the android and ios folders with prebuild in step 1. Git ignores them, so @expo/fingerprint does not read them, and they do not change the fingerprint.

Expo CLI runs prebuild only when the folder is missing. A change to a native input in app.json therefore does not go into a folder that exists, and Gradle or Xcode builds the old native code with the new fingerprint. DevHub does not store such a build (step 3). Delete the folder, or run npx expo prebuild --clean, after each change to the app config.

To give the device, add --device <name>, for example pnpm android --device Test_AVD_34. Without --device, a stored Android build must hold the native code of each ready device, because Expo CLI does not tell the provider which device it uses.