How is Skip emulator installation supposed to work?

[dfabulich]

Recently, a few newbies have shown up on Slack reporting that Skip builds are failing, refusing to install to attached devices. I attempted to reproduce these issues in UTM.app.

I wasn't able to reproduce the real issue in UTM, because UTM can't run the Android emulator at all! I ran smack into the "HVF error: HV_UNSUPPORTED" issue.

• Support for M1 Silicon - HVF error: HV_UNSUPPORTED ReactiveCircus/android-emulator-runner#350
  That affects Github Actions, and it affects Android Studio itself in UTM. (@marcprux I don't suppose you know of a good workaround…?!)

While I was investigating this, I filed these issues:

• skip doctor/skip checkup doesn't attempt to connect to the Android emulator skipstone#186
• skip android emulator create fails on fresh install skipstone#187
• skip android emulator list fails on fresh install skipstone#188
• skip android emulator launch fails if you haven't used skip to create an emulator skipstone#189

I didn't catch any of these in my previous round of UTM testing, because my goal at that time was just to get skip checkup to pass. It does kinda sorta pass now, except for this issue I filed a while ago:

• skip doctor should suggest using xcode-select if the command-line tools are selected #609
  • There's an open PR for this. doctor: Print xcode-select hint if active dev dir is CommandLineTools skipstone#180

Once I manually ran sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer, skip checkup passed, but it passed because of skipstone#186 … it passed because we didn't check the status of the emulator.

I'm embarrassed to say that I didn't even know that Skip had a skip android emulator command, not least because I almost never use skip android, because I normally use Skip Lite exclusively, and do almost all of my builds with xcodebuild, even when I am using Skip Fuse.

I feel like we're kinda at a fork in the road about this. I can see four-ish primary approaches:

1. Document how to use Android Studio's GUI. Use screenshots to guide users through the process of installing the correct SDK platforms (plus source!), build tools, and emulator, and then show them how to create and launch an emulated device. This is what expo.dev does.
2. Document how to use Android Studio's GUI, but only as far as walking users through the process of installing the CLI Tools. We could then use Android Studio's sdkmanager to ensure that adequate versions of build-tools and platforms had been installed, use avdmanager to ensure that an emulator had been created (and that the emulator was running).
3. We could try to hackily automate installing the CLI tools in Android Studio. I've hacked up a script that downloads CLI tools directly from dl.google.com, extracts them into a temp directory, and then runs /tmp/cmdline-tools/bin/sdkmanager --sdk_root=$HOME/Library/Android/sdk. (This requires a working macOS JVM like Temurin.) We can run it once with --licenses and then again to install "cmdline-tools;latest", which installs the CLI tools into Android Studio's managed Android home. When it's done, Android Studio's SDK acknowledges that the CLI tools have been installed.
   This works surprisingly well on Android Studio Panda 1 | 2025.3.1 Patch 1, but it's extremely hacky. It feels like it could break in any minor point release of Android Studio.
4. Try harder to vendorize the Android SDK. In this story, we'd install our own copy of the Android CLI tools (perhaps using Homebrew's android-commandlinetools), then use its sdkmanager to install emulator build-tools and platform-tools, adding them to the PATH ourselves. We'd use avdmanager to create our own emulator and run it. Android Studio would know nothing about it. (We'd also need to wire up a JVM like Temurin.)

I think these approaches are roughly sorted in order of my preference.

[dfabulich]

I talked myself into trying out option 3 in skiptools/skipstone#194

[marcprux]

There are a few reasons for the skip android emulator command (which was added recently in skiptools/skipstone@6a8d283):

1. Enable the user to get started with Skip without necessarily installing and running Android Studio ahead of time. We have found that for iOS-oriented users, the Studio prerequisite can be off-putting.
2. Simplify the getting started instructions by having a single command that will launch the emulator and start watching adb logcat at the same time to be able to see logging messages
3. (Aspirational) Have a robust way to launch the emulator along with a Skip app automatically when the app is run, similar to how Xcode automatically launches an iOS Simulator.
4. (Eventually) Have a way to install and launch the emulator on CI without needing to rely on https://github.com/ReactiveCircus/android-emulator-runner (e.g., to support alternative CI systems)

There are a variety of possible configurations that make command-line driving of the Android emulator tricky. There are subtle differences in where the emulator images are sought, which can vary based on various configurations: the path to the emulator command being launched (which will be different depending on whether is using used from the Homebrew installation or through Android Studio, and potentially also different if emulator was installed via the sdkmanager). It also appears to have different behavior based on the setting of the ANDROID_SDK_ROOT environment (which might be different than ANDROID_HOME). For a very old examination of these issues, see https://stackoverflow.com/questions/39645178/panic-broken-avd-system-path-check-your-android-sdk-root-value

We can take a look at skiptools/skipstone#194 to try to robustify the process, but if that fails, we may need to revert to the previous advice of just doing it all through Android Studio.