[Dependency Cache] Enable Dependency Cache on CI

[ParaskP7]

Project Thread: paaHJt-7CE-p2 (Stretch Goal)
Related: WCAndroid#133303 + JP/WPAndroid#21584
Depends On: a8c-ci-toolkit#135 -> a8c-ci-toolkit#138
Required By: buildkite-ci#581

---

Description

This PR enables dependency cache on CI for this project. 💾

The dependency cache mechanism is split between:

• A weekly scheduled save cache build (see commit and buildkite-ci#581 PR), which targets the below tasks only:
  • Apps (assembleDebug)
  • Lint (:app:lintDebug :automotive:lintDebug :wear:lintDebug)
  • Unit Tests (assembleDebugUnitTest)
  • Android Tests (assembleDebugAndroidTest)
• A restore cache step that is run on targeted pipeline.yml related jobs, via their corresponding individual scripts:
  • Mobile App (prototype-build.sh)
  • Lint (lint.sh)
  • Unit Tests (run-unit-tests.sh)
  • Android tests (run-instrumented-tests.sh)

PS: Dependency cache isn't enabled on the release-builds.yml pipeline just yet, but just temporarily, and until we become comfortable with running this new process on the main pipeline.yml pipeline.

---

Future Improvement

Me and @wzieba has been discussing on DMs about some possible future improvement, which are including but are not limited to the below list:

1. Only execute the assemble android test task, which depends on assemble task anyway, and would most likely resolve most of the dependencies, for all other tasks to benefit from. However, this needs further testing to make sure that running other tasks such us lint and assemble unit test are providing little to no help.
2. Create a custom Gradle task and utilize Gradle's init scripts (init.d). Using the init script, go through all available modules for a project, and then, using that custom Gradle task, resolve all dependencies for all tasks that are available per module. We could take some inspiration from plugins such as this.
3. Instead of scheduling the dependency cache build to run weekly (buildkite-ci#581), make it run more often, possibly scheduling it to even run daily. However, since dependencies are not being updated too often, and, even when they do on that specific week, it would only be for a few of them. This will indeed cause some extra network requests, but most of the dependencies cached would still benefit from the existing and weekly refreshed dependency cache.
4. Enable dependency cache on the release-builds.yml pipeline.

---

Testing Instructions

• Save Cache:

  • Triggering schedules/dependency-cache.yml manually via this build:
    • Starts downloading the dependencies per task.
    • Caches the dependencies successfully.
      • Duration: 45s
      • Size: 607.47 MB
    • Total time it takes for the dependency cache job to complete: 17m 9s
  • Sending a Slack notification (#android-core-notifs):
    • On success, notifying that: The dependency cache has been updated. (p1737386018597179-slack-C0787KRDYDC)
    • On failure, notifying that: Failure to update the dependency cache. (p1737382895136969-slack-C0787KRDYDC)

• Restore Cache:

Job	BT (Without)	BT (With)	BT (Diff*)	NR (Without)	NR (With)	RC (Without)	RC (With)	Win
Assemble Release	6m 49s	5m 47s	-2m 2s	1m 6s	0s (ish)	0s	16s	50s
Mobile App	7m 5s	5m 0s	-2m 5s	1m 6s	0s (ish)	0s	12s	54s
Lint	6m 47s	5m 10s	-1m 37s	1m 1s	0s (ish)	0s	14s	47s
Unit Tests	5m 45s	4m 24s	-1m 21s	1m 6s	0s	0s	14s	50s
UI Tests	11m 17s	10m 56s	-21s	1m 10s	0s	0s	14s	56s

Note

• Without: Without Dependency Cache
• With: With Dependency Cache
• BT: Build Time
• NR: Network Requests
• RC: Restore Cache
• Win: NR (Without) - RC (With)

Warning

(*): The BT (Diff) presented above is relative, so don't read too much into it, it might not match with the WIN, which is a much more solid number. But still, it is nice to have and compare those two number together. To to be clear about that, although I tried to pick the most representative builds, without and with the dependency cache mechanism in place, there are other factors that can make any build faster, or slower for that matter (like build cache, firebase test lab, etc), so again, don't read too much into it.

---

Checklist N/A

I have tested any UI changes... N/A

[wpmobilebot]

📲 You can test the changes from this Pull Request in 📱 Mobile by scanning the QR code below to install the corresponding build.

	App Name	📱 Mobile
	Build Type	debugProd
	Commit	afedd3f
	Direct Download	pocketcasts-app-prototype-build-pr3463-afedd3f.apk

📲 You can test the changes from this Pull Request in 🚗 Automotive by scanning the QR code below to install the corresponding build.

	App Name	🚗 Automotive
	Build Type	debugProd
	Commit	afedd3f
	Direct Download	pocketcasts-automotive-prototype-build-pr3463-afedd3f.apk

📲 You can test the changes from this Pull Request in ⌚ Wear by scanning the QR code below to install the corresponding build.

	App Name	⌚ Wear
	Build Type	debugProd
	Commit	afedd3f
	Direct Download	pocketcasts-wear-prototype-build-pr3463-afedd3f.apk

[wzieba]

Looks good!