[HACK WEEK] Integrate periphery

[RafaelKayumov]

Description

Integrate Periphery to run on Buildkite CI. Follows the approach introduced here: pbzQyC-3OH-p2

• Implements the .periphery.yml setup.
• Generates and uses Scripts/Periphery/periphery_baseline.json as filter list of existing legacy unused code issues.
• Implements the Scripts/Periphery/setup-and-run-periphery.sh to prepare and use the Periphery installation
• Implements the .buildkite/commands/run-periphery.sh as a Buildkite pipeline command.
• Runs the setup-and-run-periphery.sh scan with --skip-build to reuse the build artifact from the build step
• Extends the .buildkite/commands/build-for-testing.sh step to also upload the DerivedData/Index.noindex/DataStore/ data store index for the Periphery.

---

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

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

	App Name	WooCommerce iOS Prototype
	Build Number	pr15962-147232e
	Version	22.9
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	147232e
	Installation URL	4v922dds905a8

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[itsmeichigo]

I'm a novice when it comes to app infrastructure tasks so I'll refrain from reviewing this PR. I'm just curious where I can get the reports from Periphery after this setup? (pardon the dumb question)

[RafaelKayumov]

I'm a novice when it comes to app infrastructure tasks so I'll refrain from reviewing this PR. I'm just curious where I can get the reports from Periphery after this setup? (pardon the dumb question)

You can go to the PR's Buildkite pipeline and check out the "Detect unused code" step. For example this is the one for this PR: https://buildkite.com/automattic/woocommerce-ios/builds/31502#019879ee-7dcd-453e-b5c2-1ed88921cf0f

If there are any unused code entries, the build will fail and the output will contain smth like:

woocommerce-ios/WooCommerce/Classes/Spotlight/SpotlightManager.swift:5:16: warning: Property 'unusedLetExample' is unused

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 23.0. This milestone is due in less than 2 days. Please make sure to get it merged by then or assign it to a milestone with a later deadline.

Generated by 🚫 Danger

[AliSoftware]

Approving to unblock, just left a suggestions of adding 2 flags to the periphery scan to improve the output

[EDIT] Actually implemented those suggestions myself in a separate PR so that you have all the options (merge this base PR independently and iterate on the other one later, or merge the other one in this one first if you like it before merging all to trunk… up to you)

[RafaelKayumov]

@AliSoftware Thx for contributions. I'll wait for your PR before merging.

[AliSoftware]

I'm just curious where I can get the reports from Periphery after this setup?

@itsmeichigo Quick update: following some improvements we made in #15984, the CI job now also posts a Buildkite annotation to report any Periphery warnings (example here) 🎉
So that's now another (and arguably nicer) way to see those 🙂 (though they're still in the job logs too if you prefer to look there)