Summary

Angular v22 changed the safe-navigation operator (?.) in template expressions to yield undefined via native optional chaining, gated behind the legacyOptionalChaining compiler option (angular/angular@2896c93cc1). OXC unconditionally emitted the legacy == null ? null ternary, so every ?. expression in a v22+ project got the wrong runtime value (null instead of undefined). This is a silent, time-bombed regression for anyone upgrading to v22.

This PR makes OXC version-aware and faithful to the reference compiler's emitted output.

Closes #317.

What changed

• legacyOptionalChaining option added to TransformOptions (NAPI + Rust + index.d.ts) and threaded through ingest into both ComponentCompilationJob and HostBindingCompilationJob. The effective value is explicit_override ?? version_default, where the version default is derived from angularVersion:
  • major < 22 → legacy (null)
  • major ≥ 22 → modern (native ?., undefined)
  • unknown → legacy (Angular's conservative fallback)
• optional flag added to the resolved IR read/call nodes (ResolvedPropertyRead / ResolvedKeyedRead / ResolvedCall) and passed through reify so it renders as native ?. / ?.[] / ?.().
• expand_safe_reads rewritten to branch per node: legacy builds the SafeTernary (== null ? null); modern rewrites each safe access into the equivalent optional resolved read (no temporaries needed — native ?. evaluates the receiver once).
• $safeNavigationMigration(...) escape hatch: a wrapped subtree is forced back to legacy null semantics even on a modern target, and the wrapper is stripped. Detected post-resolve_names (where the receiver's names are already resolved), so no new IR node or extra phase was needed.

Deviations from the issue text (both to match the reference compiler)

• The modern form is native optional chaining (ctx.user?.name), not the == null ? undefined ternary the issue described. Both yield undefined; native ?. is what Angular actually emits.
• The shipped v22 magic function is $safeNavigationMigration(...), not $null(...) — the referenced commit's message said $null, but the code (in v22.0.0-next.10) named it $safeNavigationMigration.

Out of scope

Partial/linker output keeps legacy semantics for now; threading the legacyOptionalChaining facade field through partial emit is deferred (issue required-work #4). Wiring a user's tsconfig angularCompilerOptions.legacyOptionalChaining → this NAPI option lives in the JS build-plugin layer.

Verification

Output was diffed against Angular's own compliance goldens (r3_view_compiler/safe_access) by running the exact fixture templates through OXC at v22:

• Modern deep chains match character-for-character (ctx.p?.a?.b?.c?.d, ctx.p?.["a"]?.["b"]..., and the mixed-optional/plain cases).
• The $safeNavigationMigration legacy expansion reproduces the golden including the same temporary name (tmp_3_0) and chain structure.
• A template mixing an unwrapped span (modern) and a wrapped span (legacy) reproduced the golden's per-span split.

The only difference anywhere is OXC's emitter wrapping ternaries in extra parentheses — pre-existing style, semantically identical.

Test plan

• cargo build --workspace (incl. NAPI crate) — clean
• cargo test -p oxc_angular_compiler — all green; existing safe-nav snapshots unchanged (version-unknown stays legacy)
• cargo fmt --check — clean
• Added 6 integration tests: modern interpolation/chain/mixed-chain/call (v22), legacy on v21, and the $safeNavigationMigration escape hatch
• JS/node-side tests not run (no behavioral changes in the JS layer)

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