fix(project): Memoize in-flight native watcher load to avoid polling race - #1578
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…race Concurrent subscribe() calls (as issued by WatchHandler via Promise.all) raced on the native-backend memoization: nativeBackendLoaded was flipped to true before the dynamic import() resolved, so callers settling before the winner assigned nativeBackend read a null value and silently fell back to the polling backend. On projects with many watched paths (e.g. the OpenUI5 testsuite), that meant nearly all source watchers polled ~42k files every 250ms, pegging idle CPU at ~250%. Memoize the in-flight promise instead of a pre-await boolean so concurrent callers await the same import and all observe the resolved backend. Add a regression test that fires concurrent subscribe() calls before the first load resolves and asserts all use the native backend.
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Concurrent subscribe() calls (as issued by WatchHandler via Promise.all) raced on the native-backend memoization: nativeBackendLoaded was flipped to true before the dynamic import() resolved, so callers settling before the winner assigned nativeBackend read a null value and silently fell back to the polling backend. On projects with many watched paths (e.g. the OpenUI5 testsuite), that meant nearly all source watchers polled ~42k files every 250ms, pegging idle CPU at ~250%.
Memoize the in-flight promise instead of a pre-await boolean so concurrent callers await the same import and all observe the resolved backend. Add a regression test that fires concurrent subscribe() calls before the first load resolves and asserts all use the native backend.