[iOS][swiftpm] stop baking an absolute HERMES_CLI_PATH into the app pbxproj - #58292

Summary:

npx react-native spm add writes HERMES_CLI_PATH into the app's committed project.pbxproj — the absolute path of hermesc in the hermes-compiler npm package, as resolved on whichever machine ran the command. So every SwiftPM-converted app commits one developer's disk layout.

Nothing needs it: react-native-xcode.sh already resolves hermesc at build time through react-native's own dependency graph when the current value is not a file. A relative setting can't replace it either — $(REACT_NATIVE_PATH)/../hermes-compiler breaks on a symlinked react-native, and $(SRCROOT)/../node_modules/… breaks on hoisted monorepos.

So this deletes resolveHermesCliPathSetting(), along with the hermesCliPath parameter it fed on injectSpmIntoPbxproj and mergeReactBuildSettings. Already-injected projects self-clean on the next spm add/update, which strips every scalar recorded in .spm-injected.json before re-injecting.

Scope: SwiftPM only

Both pieces involved arrived with SwiftPM in #57332 and first shipped in 0.87.0 — scripts/spm/generate-spm-xcodeproj.js (the whole file, including the write) and the NODE_HERMESC build-time fallback in react-native-xcode.sh.

Everything CocoaPods relies on is older and untouched, all present in 0.86.0: the pod-derived HERMES_CLI_PATH default, the "hermesc could not be found" error, and the hermesc -emit-binary call. A CocoaPods build cannot be affected by this change.

That parameter shipped in 0.87.0 and 0.87.1, but SwiftPM is Preview-labelled, so removing it is in scope. Nothing in the repo passed it except the deleted resolver.

Known limitation

The fallback is gated on PODS_ROOT being absent, so a SwiftPM app that keeps side-by-side non-RN pods skips it and needs an explicit HERMES_CLI_PATH. Evaluating that gate verbatim out of the unchanged script:

Set it in an xcconfig, not the pbxproj: createdScalars cleanup removes by key, so it would drop a hand-edited value too. Keying the gate on the hermes-engine directory would close this — left as a follow-up so this PR doesn't touch the bundling script.

Changelog:

[IOS] [FIXED] - SwiftPM: stop baking an absolute, machine-specific HERMES_CLI_PATH into the app's pbxproj; resolve hermesc at build time instead

Test Plan:

Red first — with the source reverted, the new entry-point test fails on a seeded hermes-compiler fixture: ✕ writes no HERMES_CLI_PATH, in any configuration or the marker (1 failed, 76 passed).

yarn jest packages/react-native/scripts/spm --no-cache -i
Test Suites: 18 passed, 18 total
Tests:       835 passed, 835 total

yarn flow-check (0 errors), plus yarn eslint --max-warnings 0 and yarn prettier --check on the four changed files.

End to end: a 0.87.1 SwiftPM app (@shopify/react-native-skia example, no Pods) with the HERMES_CLI_PATH lines removed from its pbxproj builds in Release, the fallback resolving hermesc from node_modules/hermes-compiler. That build ran against an earlier revision of this branch which also widened the shell gate; with no Pods/ it is row 1, where both conditions behave identically. There is no shell test harness, and the script is unchanged here.

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