Build fails due to hard-coded dependency on unavailable Swift snapshot (main-snapshot-2026-01-16)

[akkie76]

I have spent a significant amount of time debugging it. I can confirm the root cause and would like to share my findings to help move this issue forward.

The Root Cause

The project is currently unbuildable because it has a hard-coded dependency on a specific, and now unavailable, Swift development snapshot.

1. Hard-coded Version
   The hello-swift-java/hashing-lib/build.gradle file explicitly requires main-snapshot-2026-01-16.

def sdkName = "swift-DEVELOPMENT-SNAPSHOT-2026-01-16-a_android.artifactbundle"
def swiftVersion = "main-snapshot-2026-01-16"

2. Unavailable Toolchain
   This specific snapshot is no longer available for download from swift.org. Attempting to install it via swiftly fails with the following error:

$ swiftly install main-snapshot-2026-01-16
Error: main-snapshot-2026-01-16 does not exist at URL https://download.swift.org/development/xcode/swift-DEVELOPMENT-SNAPSHOT-2026-01-16-a/swift-DEVELOPMENT-SNAPSHOT-2026-01-16-a-osx.pkg, exiting

Conclusion

Because the required Swift toolchain cannot be installed, the build process fails immediately with exit code 1 when swiftly is invoked. This issue is not related to local caches or environment misconfiguration; it is a fundamental dependency problem.

Suggested Path Forward

To make this project usable again, the Gradle build scripts (build.gradle) and possibly the Swift package manifests (Package.swift) across the project need to be updated to use a currently available Swift toolchain (either a recent stable release or a newer development snapshot).

Thank you for maintaining this project. I hope this information helps in resolving the issue.

[finagolfin]

I do not see that non-existent Jan. 16 snapshot date used anywhere in this repo: can you link to where you see it, because your example above does not show that date? I think you probably modified that date locally incorrectly or some thing like that.

[akkie76]

@finagolfin

Hi, thank you for the follow-up.
To clarify the situation and explain why I concluded this is a dependency issue, here is a summary of the debugging steps I performed.

I am aware that the build.gradle file in the current main branch is set to the following versions. My debugging process started from this state, but it failed, which is why I undertook the steps below.

def sdkName = "swift-DEVELOPMENT-SNAPSHOT-2026-01-07-a_android.artifactbundle"
def swiftVersion = "main-snapshot-2026-01-07"

However, the build failed even with this configuration. To demonstrate the exhaustive debugging I performed, here is a summary of my steps.

Summary of Debugging Steps

1. Error Identification:

The build consistently failed with the generic error emit-module command failed with exit code 1.

2. Root Cause Analysis (Version Mismatch):

After enabling verbose logging, the direct cause was identified as compiled module was created by an older version of the compiler. This indicated a version mismatch between the Swift toolchain being used and the Android Swift SDK the project was referencing.

3. Aligning build.gradle Version:

Initially, the Swift version required by my build.gradle file (main-snapshot-2026-01-16) was different from the version I had installed (main-snapshot-2026-01-07). I tried to resolve this by changing the build.gradle file to match my installed version (01-07).

4. Complete Cache Purge:

When the error persisted, I suspected stale configurations were the problem. I performed a full cache purge multiple times, which included:

• Running ./gradlew clean.
• Manually deleting the local Swift Package Manager cache (the .build directory).
• Manually deleting the global Swift Package Manager cache (e.g., ~/Library/Caches/org.swift.swiftpm/).

5. Toolchain Re-installation:

Because the issue remained even after clearing all caches, I considered the possibility of a corrupted toolchain. I used swiftly to uninstall and then reinstall the toolchain.

6. Final Root Cause Confirmation:

After all the above steps failed, I reverted my build.gradle to require main-snapshot-2026-01-16 and attempted to install it as a final step. This is when the definitive error appeared:

$ swiftly install main-snapshot-2026-01-16
Error: main-snapshot-2026-01-16 does not exist at URL ...

Conclusion

This final error confirms that the project depends on a specific development snapshot (main-snapshot-2026-01-16) that is no longer available for download from Swift.org.My previous debugging steps were logical, but the core issue was not my local environment; it was the availability of the tool itself, which is a dependency of the project.

I hope this summary clarifies the situation. Thank you.

[finagolfin]

Yeah, makes sense, I myself was also surprised that swiftly will download toolchain snapshots that are not official tags, which are the only ones we provide SDK snapshots for.

Can you try again now with the latest Jan. 31 toolchain and SDK snapshot and see if that works, after modifying that gradle script to use that tag? I think that should fix your issues, then I'll add a note to the doc so others don't hit this later.

[akkie76]

I tried installing the SNAPSHOT-2026-01-31 SDK, but it still doesn’t seem to build.

Is there something wrong with my environment?

$ swiftly list                                                                      
Installed release toolchains
----------------------------
Swift 6.1.0 (in use) (default)

Installed snapshot toolchains
-----------------------------
main-snapshot-2026-01-31

Available system toolchains
---------------------------
xcode

swift sdk install https://download.swift.org/development/wasm-sdk/swift-DEVELOPMENT-SNAPSHOT-2026-01-31-a/swift-DEVELOPMENT-SNAPSHOT-2026-01-31-a_wasm.artifactbundle.tar.gz --checksum f6424fc0c1421fc7fddb5fddd2dfacd0e7fbb2485bee3789c2b4372a9ba0cf7f

def sdkName = "swift-DEVELOPMENT-SNAPSHOT-2026-01-31-a_android.artifactbundle"
def swiftVersion = "main-snapshot-2026-01-31"

Error

No Swift SDK found matching query `aarch64-unknown-linux-android28` and host triple `arm64-apple-macosx`. Use `swift sdk list` command to see available Swift SDKs.
Execution failed for task ':hello-swift-java-hashing-lib:buildSwiftArm64-v8a'.
> Process 'command '/Users/me/.swiftly/bin/swiftly'' finished with non-zero exit value 1

[finagolfin]

Yes, you must set the latest snapshot toolchain as the one "in use" by swiftly, as the Getting Started instructions linked from the example doc show, ie swiftly use main-snapshot.

[finagolfin]

Now that we updated to the 6.3 release, I don't think people will hit this much. Can you try the updated instructions, @akkie76, and let us know if all works well for you now?