fix(metadata-generator): emit UIKit metadata for Mac Catalyst

[farfromrefug]

Summary

Two defects in build-step-metadata-generator.py stop a Mac Catalyst build from producing usable metadata. Both were found by building a real app for platform=macOS,variant=Mac Catalyst and fixing whatever failed next.

• Generation crashes before it starts. With EFFECTIVE_PLATFORM_NAME=-maccatalyst the script looks up MACCATALYST_DEPLOYMENT_TARGET, which Xcode does not export unless the project sets it explicitly, so it dies with KeyError: 'MACCATALYST_DEPLOYMENT_TARGET'. It now falls back to IPHONEOS_DEPLOYMENT_TARGET.

• The generated metadata contains no UIKit. UIKit and the other iOS-flavoured frameworks live under System/iOSSupport in the macOS SDK. Xcode passes those to the real compile with -iframework, which never reaches FRAMEWORK_SEARCH_PATHS, so the generator parses the macOS SDK with no UIKit in scope and emits metadata without it. Every UIKit class then fails at runtime with ReferenceError: UIDevice is not defined — the app dies during require() of the first module touching UIKit. Those two search paths are now added for -maccatalyst only.

Testing

Built a real app (OSS Weather) as a Mac Catalyst app on Apple Silicon. With both fixes it builds, signs and launches as a native macOS app — menu bar, resizable window, network and CoreLocation working.

Symbols in the generated Mac Catalyst metadata, before and after:

symbol	before	after
UIDevice	0	2
UIContentSizeCategoryExtraSmall	0	1

iOS device and simulator builds are unaffected — the new search paths are behind the -maccatalyst check, and the deployment-target change is a fallback that only fires when the platform-specific variable is absent.

Note for reviewers

The IS_UIKITFORMAC check in generate_metadata is dead code: Xcode's variable has been IS_MACCATALYST for several releases, so that branch never runs and the else branch builds arm64-apple-ios<sdk>-macabi, which is what actually works today. I left it alone rather than switch to an untested code path, but it is worth a follow-up.

Summary by CodeRabbit

• Bug Fixes
  • Deployment metadata generation now uses a fallback deployment target when a platform-specific value is unavailable.
  • macCatalyst builds can now locate iOS frameworks and subframeworks correctly.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 19269f96-a249-4bb9-8707-02f83ba9280e

📥 Commits

Reviewing files that changed from the base of the PR and between bddaacb and 658f5b1.

📒 Files selected for processing (1)

• metadata-generator/build-step-metadata-generator.py

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📝 Walkthrough

Walkthrough

The build-step metadata generator now falls back to IPHONEOS_DEPLOYMENT_TARGET when a platform-specific deployment target is unavailable. macCatalyst builds now include iOSSupport framework and subframework directories in framework search paths.

Changes

Deployment metadata generation

Layer / File(s)	Summary
Deployment target and framework path handling metadata-generator/build-step-metadata-generator.py	The generator uses IPHONEOS_DEPLOYMENT_TARGET as a fallback and adds iOSSupport framework paths for macCatalyst builds.

Estimated code review effort: 2 (Simple) | ~10 minutes

Poem

A rabbit checked the build path twice,
Found fallback targets, neat and precise.
For Catalyst, paths now grow,
Through iOSSupport they safely flow.
Hop, hop—metadata is nice!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the metadata-generator fix for emitting UIKit metadata during Mac Catalyst builds.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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