fix: gate whoami to exclude iOS/tvOS/watchOS — fixes aarch64-apple-ios linker error

[ArthurZucker]

Problem

Building any crate that depends on xet-core for aarch64-apple-ios (or the iOS simulator) fails at link time:

Undefined symbols for architecture arm64:
  "_SCDynamicStoreCopyComputerName", referenced from:
      objc2_system_configuration in libapp.a (whoami)
ld: symbol(s) not found for architecture arm64

Root cause

whoami v2 declares objc2-system-configuration as a dependency for all target_vendor = "apple" targets — including iOS, tvOS, and watchOS. That crate wraps SystemConfiguration.framework, which exposes SCDynamicStoreCopyComputerName. The symbol exists on macOS but is not available on iOS/tvOS/watchOS, so the linker fails.

Dependency chain: data → cas_client → file_utils → xet-runtime → whoami → objc2-system-configuration → SCDynamicStoreCopyComputerName 💥

Why the fix is safe

The only use of whoami in xet-runtime is in privilege_context.rs::permission_warning() — a diagnostic helper that prints a chown hint when a permission-denied error occurs. iOS, tvOS, and watchOS have no POSIX multi-user model, so:

1. sudo chown is meaningless on those platforms
2. The diagnostic message is purely informational, not load-bearing

Fix

xet_runtime/Cargo.toml — narrow the whoami target cfg from unix to exclude Apple mobile targets:

# before
[target.'cfg(unix)'.dependencies]
whoami = { workspace = true }

# after
[target.'cfg(all(unix, not(target_os = "ios"), not(target_os = "tvos"), not(target_os = "watchos")))'.dependencies]
whoami = { workspace = true }

privilege_context.rs — mirror the cfg gate on the call site, with a simplified fallback message for mobile targets.

Testing

# Must compile clean (no SCDynamicStoreCopyComputerName undefined symbol)
cargo build -p data --target aarch64-apple-ios
cargo build -p data --target aarch64-apple-ios-sim

# macOS behaviour unchanged
cargo test -p xet-runtime

---

Note

Low Risk
Low risk: changes are limited to target-specific dependency gating and a diagnostic-only warning message, plus a new CI cargo check for aarch64-apple-ios. Main potential impact is missing the chown hint on Apple mobile targets, where it is not applicable.

Overview
Fixes an iOS-family linker failure by tightening xet-runtime’s whoami dependency and call sites to exclude ios/tvos/watchos targets, avoiding the transitive SystemConfiguration symbol.

Adds a small regression test around permission_warning() and introduces a new CI job that runs cargo check -p xet-runtime --target aarch64-apple-ios on macOS runners to catch future target-specific build issues.

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visionOS not excluded from cfg gates like other Apple mobile targets

Low Severity

The cfg gates exclude ios, tvos, and watchos but miss visionos. Apple visionOS (aarch64-apple-visionos) has been a tier 3 Rust target since 1.79.0 and also lacks SCDynamicStoreCopyComputerName from SystemConfiguration.framework. Building for visionOS would hit the same linker error this PR fixes for the other Apple mobile platforms. Adding not(target_os = "visionos") to the dependency and code cfg gates would make the fix complete.

Additional Locations (2)

• xet_runtime/src/file_utils/privilege_context.rs#L213-L214
• xet_runtime/src/file_utils/privilege_context.rs#L226-L230

 

[julien-c]

do you intend to download models from watchOS?

[ArthurZucker]

👀 maybe maybe

[ArthurZucker]

It was failing on ios!