[sorinirimies]

Summary

find_rustc_codegen_spirv panicked when the backend dylib wasn't in the library search path. SpirvBuilder::build already returns Result<_, SpirvBuilderError>, so this is now a proper error.

 fn find_rustc_codegen_spirv() -> Result<PathBuf, SpirvBuilderError>
   if cfg!(feature = "rustc_codegen_spirv")
-    ... else panic!("Could not find {filename} in library path")
+    find_rustc_codegen_spirv_in_paths(dylib_path())
+      .ok_or(RustcCodegenSpirvDylibNotFound { filename })

New variant: SpirvBuilderError::RustcCodegenSpirvDylibNotFound { filename: String } — "could not find {filename} in the dynamic library search path".

Evidence

New tests in dylib_lookup:

finds_nothing_in_empty_or_missing_dirs   ok
ignores_unrelated_dylibs                 ok
not_found_error_names_the_dylib          ok

cargo test -p spirv-builder --features watch,clap: 7 passed. Clippy -D warnings clean (default, --no-default-features, watch,clap).

Merge Danger

Door: two-way

Blast Radius: small — SpirvBuilderError is #[non_exhaustive], so the new variant is non-breaking. Callers that relied on the panic now get an Err.

[sorinirimies]

Reproduction

multibuilder run outside the target dir with no dylib search path, so the backend can't be found:

cargo build -p multibuilder && cd /tmp && env -u DYLD_FALLBACK_LIBRARY_PATH <repo>/target/debug/multibuilder

Before (main) — panic inside spirv-builder:

thread 'main' panicked at crates/spirv-builder/src/lib.rs:870:9:
Could not find librustc_codegen_spirv.dylib in library path

After (this PR) — SpirvBuilder::build returns Err; the only panic is the example's own .unwrap():

thread 'main' panicked at examples/multibuilder/src/main.rs:9:34:
called `Result::unwrap()` on an `Err` value: RustcCodegenSpirvDylibNotFound { filename: "librustc_codegen_spirv.dylib" }