[ci] cache Gradle distributions on MSBuild test agents

[jonathanpeppers]

Summary

Internal build 3030679 had six AndroidGradleProjectTests failures spread across two macOS test agents (Xamarin.Android.Build.Tests - macOS-9 and macOS-10). Every one reported:

error XAGRDL1000: Executable 'gradlew' not found in project directory
'.../temp/gradle/BuildAppNativeAOT/'

The real failure was upstream, in the Gradle wrapper invoked by AndroidGradleProject.Create():

Running: .../build-tools/gradle/gradlew init --dsl kotlin ... --no-daemon
Exception in thread "main" java.io.IOException: Server returned HTTP response code: 504 for URL:
  https://github.com/gradle/gradle-distributions/releases/download/v9.4.1/gradle-9.4.1-bin.zip
Exit Code: 1

services.gradle.org redirects distribution downloads to GitHub releases, and GitHub returned a transient 504 on those two agents. Every Gradle test on those agents failed; the same test cases passed on all other shards.

Two things made a single transient 504 fatal:

• cache-gradle.yaml only cached $HOME/.gradle/caches. The Gradle wrapper stores downloaded distributions in $HOME/.gradle/wrapper/dists, which was never cached — so every agent re-downloaded the distribution from GitHub on every run.
• run-msbuild-tests.yaml did not include cache-gradle.yaml at all, even though AndroidGradleProjectTests runs the Gradle wrapper there. The MSBuild test agents had no Gradle caching whatsoever.

Changes

• cache-gradle.yaml gains a second Cache@2 task for $HOME/.gradle/wrapper/dists, keyed only on build-tools/gradle/gradle/wrapper/gradle-wrapper.properties since that file alone determines the distribution version. The existing dependency cache keeps its broader key.
• run-msbuild-tests.yaml now includes cache-gradle.yaml, after setup-test-environment.yaml (which performs the checkout the cache key globs against).

Notes

This is complementary to #12199. That PR removes the gradle init call and the extra 9.3.1 distribution download, but the repo wrapper's own distribution (9.4.1) is still fetched from services.gradle.org on first use, so caching it is still needed.

The Linux Xamarin.Android.Build.Tests jobs are filtered to BuildTest/PackagingTest/XASdkTests/AndroidDependenciesTests and do not run AndroidGradleProjectTests, so they are left alone.

Testing

• Both templates parse as valid YAML.
• Caching behavior is only observable on CI; the effect should be a cache Gradle distributions hit on subsequent MSBuild test runs.

[Copilot]

Pull request overview

This PR improves CI reliability for AndroidGradleProjectTests by ensuring the Gradle wrapper’s downloaded distribution ZIPs are cached on MSBuild test agents, reducing sensitivity to transient download failures from services.gradle.org → GitHub redirects.

Changes:

• Add a second Cache@2 entry in cache-gradle.yaml to persist $HOME/.gradle/wrapper/dists (Gradle distributions), keyed solely on gradle-wrapper.properties.
• Include cache-gradle.yaml in run-msbuild-tests.yaml so MSBuild test jobs get the same Gradle caching behavior as other pipelines.
• Update cache-gradle.yaml’s default xaSourcePath to $(System.DefaultWorkingDirectory) to match the MSBuild test template defaults.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
build-tools/automation/yaml-templates/run-msbuild-tests.yaml	Adds the Gradle cache template so MSBuild test agents restore/save Gradle caches before running tests that invoke gradlew.
build-tools/automation/yaml-templates/cache-gradle.yaml	Introduces a dedicated cache for Gradle wrapper distributions (~/.gradle/wrapper/dists) keyed by gradle-wrapper.properties.

[jonathanpeppers]

/review

[github-actions]

✅ Android PR Reviewer completed successfully!

[github-actions]

✅ LGTM

Clean, well-scoped CI change that correctly addresses the root cause from build 3030679 (transient GitHub 504 while the Gradle wrapper downloaded its distribution).

Verified:

• The dists cache path $HOME/.gradle/wrapper/dists matches the wrapper config — build-tools/gradle/gradle/wrapper/gradle-wrapper.properties sets distributionPath=wrapper/dists with distributionBase=GRADLE_USER_HOME (→ $HOME/.gradle). ✔️
• Keying the dists cache solely on gradle-wrapper.properties is correct — that file's distributionUrl (currently gradle-9.4.1-bin.zip) fully determines the distribution version. ✔️
• Separating the two caches (dependencies keyed on build files + Java.Interop hash; distributions keyed only on the wrapper) is the right invalidation model. ✔️
• Placement in run-msbuild-tests.yaml after setup-test-environment.yaml is correct — that template performs the submodules: recursive checkout the cache key globs and the git log external/Java.Interop step depend on. ✔️
• Windows pwsh and macOS/Linux bash branches both set GRADLE_DISTS_DIR consistently. ✔️

Notes:

• CI is still pending on the head commit; this review reflects a static analysis only.
• One 💡 inline suggestion about monotonic growth of the dists cache across version bumps — informational, not blocking.

Severity counts: ❌ 0 · ⚠️ 0 · 💡 1

Nice, targeted fix with excellent inline documentation explaining the why.

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