PackageToJS: Derive WASI and shared memory support from wasm imports - #807
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The SwiftBuild backend's build directory doesn't encode the target triple, so detect the traits derived from it by parsing the imports of the product binary instead. The imports are now parsed as a part of the packaging build graph.
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```
$ echo "@preconcurrency import var Foundation.stderr" | swiftly run +main-snapshot-2026-08-11 swiftc - -o /dev/null
<stdin>:1:28: error: ambiguous name 'stderr' in module 'Foundation'
1 | @preconcurrency import var Foundation.stderr
| `- error: ambiguous name 'stderr' in module 'Foundation'
2 |
Glibc.stderr:1:32: note: found this candidate
1 | nonisolated(unsafe) public var stderr: UnsafeMutablePointer<FILE>! { get }
| `- note: found this candidate
/usr/include/stdio.h:151:14: note: found this candidate
149 | extern FILE *stdin; /* Standard input stream. */
150 | extern FILE *stdout; /* Standard output stream. */
151 | extern FILE *stderr; /* Standard error output stream. */
| `- note: found this candidate
152 | /* C89/C99 say they're macros. Make them happy. */
153 | #define stdin stdin
```
swiftlang/swift#89891
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Flattening the tarball into /usr/local makes SwiftPM derive a bogus toolchain root, so the swiftbuild build system cannot find swiftc.
Only memory imports were collected, so `WasmFeatures.isWASI` never saw `wasi_snapshot_preview1` and the generated node.js dropped the WASI import while still constructing a WASI instance.
…ystem `swift package js test` assumed the native build system's single combined `<Package>PackageTests` binary: it looked for one `.wasm`/`.xctest` under `.build/<config>/`, packaged it, and ran it. SwiftBuild produces no combined test binary. It emits one `<TestTarget>-test-runner.wasm` per test target under `.build/out/Products/`, plus an aggregate target that only orchestrates building them, so the old lookup failed with "Failed to find 'JavaScriptKitPackageTests.wasm'". (cherry picked from commit c12c7e9)
Because SwiftBuild mode produces a linked executable for each test target. (cherry picked from commit 0a1f926)
`js test` generates the glue from every test target's skeletons, but the SwiftBuild build system links one binary per test target, so the eager registration hit a missing export.
The per-runner `bridge-js.js` copied to the base output directory for test preludes imports its JavaScript modules relative to itself, so copy the `bridge-js-modules` directory next to it.
kateinoigakukun
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August 21, 2026 17:56
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The SwiftBuild backend's build directory doesn't encode the target triple, so detect the traits derived from it by parsing the imports of the product binary instead. The imports are now parsed as a part of the packaging build graph.