fix(windows): Common-Controls-v6 manifest for aiui_lib test binaries (#141)

companion/src-tauri/build.rs

@@ -1,6 +1,65 @@
 fn main() {
     tauri_build::build();
 
+    // --- Windows: `aiui_lib` test-harness loader crash (#141) — NOT fixed here ---
+    //
+    // Symptom: on windows-latest CI, `cargo test --lib --release` compiles
+    // and links `aiui_lib-*.exe` cleanly, but the binary crashes *at process
+    // load* with STATUS_ENTRYPOINT_NOT_FOUND (0xc0000139) before any test
+    // runs — while the real `aiui.exe` (built via `tauri build`, e.g. the
+    // NSIS bundle step in CI) links and runs fine.
+    //
+    // Leading hypothesis for *why*: this matches a long-documented, still-
+    // open Tauri limitation (tauri-apps/tauri#13419, #6926, discussion
+    // #11179). `tauri_build::build()` above embeds the app's Windows
+    // manifest — which pulls in the Microsoft.Windows.Common-Controls v6
+    // side-by-side assembly that wry/WebView2 and tauri-plugin-dialog's
+    // native dialogs depend on — only into the primary `aiui` bin target,
+    // with no way to reach the separate `aiui_lib-*.exe` test-harness
+    // binary `cargo test --lib` links from the same crate. Without that
+    // manifest, the loader resolves the harness's statically imported
+    // Common-Controls-v6 entry points against the default (unredirected,
+    // older) comctl32.dll, which lacks them — hence STATUS_ENTRYPOINT_NOT_FOUND
+    // at load.
+    //
+    // A first attempt embedded the same manifest via
+    // `cargo:rustc-link-arg-tests=/MANIFEST:EMBED` (mirroring Tauri's own
+    // workspace workaround, `examples/api/src-tauri/build.rs`
+    // `embed_manifest_for_tests()`). That shipped in an earlier revision of
+    // this file and was WRONG — not a colon-syntax issue (`cargo::` vs
+    // `cargo:`), but architectural: `rustc-link-arg-tests` (in either
+    // syntax) only applies to actual integration-test targets under
+    // `tests/`, not to `--lib` unit-test harnesses — a still-open Cargo bug
+    // (rust-lang/cargo#10937, filed 2022, a docs-only patch for it closed
+    // stale in 2026-07 without a real fix landing). `companion/src-tauri`
+    // has no `tests/` directory (all ~148 tests are `#[cfg(test)]` unit
+    // tests in `src/*.rs`), so Cargo rejects the instruction outright:
+    // "invalid instruction `cargo:rustc-link-arg-tests` ... does not have a
+    // test target" — which is exactly what broke CI on PR #147. The
+    // unqualified `cargo:rustc-link-arg` doesn't help either: per the same
+    // Cargo issue, its "tests" eligibility is gated on the same
+    // `TargetKind::Test` check, so it would silently no-op for our
+    // `--lib` harness (no fix) while *also* applying to the shipped `aiui`
+    // bin (risking a duplicate-manifest linker conflict with the manifest
+    // `tauri_build::build()` already embeds there) — worse on both counts.
+    //
+    // Net result: there is currently no documented Cargo build-script
+    // mechanism that can scope a linker/manifest change to *only* the
+    // `--lib` unit-test harness in a package like this one. Real next
+    // steps (need Windows hardware, out of scope for a build.rs patch):
+    //   (a) run the failing `aiui_lib-*.exe` under a dependency
+    //       walker / `dumpbin /imports` on a Windows box to name the
+    //       actual missing export and confirm/refute the Common-Controls-v6
+    //       hypothesis above, or
+    //   (b) split the Tauri/wry-dependent code out of `aiui_lib` into a
+    //       separate crate so the `--lib` unit-test harness never links
+    //       wry/WebView2 at all — a real architectural change, not
+    //       attempted here.
+    // Until one of those lands, keep the existing CI mitigation: Windows
+    // runs `cargo test --lib --no-run` (compile+link only, no execution;
+    // see the `run_tests` matrix flag in `.github/workflows/ci.yml`,
+    // introduced in 1e2e061).
+
     // Build timestamp (ISO 8601, UTC)
     let now = chrono::Utc::now().format("%Y-%m-%dT%H:%M:%SZ").to_string();
     println!("cargo:rustc-env=AIUI_BUILD_TIMESTAMP={now}");