fix: address PR #344 review feedback

- Reuse extracted macOS binaries in OUT_DIR instead of re-downloading on
  every build-script rerun (previous regression would break offline/CI).
- Switch build-script directives from `cargo::` back to `cargo:` for
  consistency with the rest of the build scripts.
- Propagate I/O errors from `Artifact::ensure_in` instead of unwrapping
  in `SpyImpl::init_in`.
- Inherit `target = "target"` for the fspy_preload cdylib artifact deps
  through the workspace so `cargo autoinherit` is idempotent.

Author: claude

Cargo.toml

@@ -75,8 +75,8 @@ bundled_artifact_build = { path = "crates/bundled_artifact_build" }
 flate2 = "1.0.35"
 fspy = { path = "crates/fspy" }
 fspy_detours_sys = { path = "crates/fspy_detours_sys" }
-fspy_preload_unix = { path = "crates/fspy_preload_unix", artifact = "cdylib" }
-fspy_preload_windows = { path = "crates/fspy_preload_windows", artifact = "cdylib" }
+fspy_preload_unix = { path = "crates/fspy_preload_unix", artifact = "cdylib", target = "target" }
+fspy_preload_windows = { path = "crates/fspy_preload_windows", artifact = "cdylib", target = "target" }
 fspy_seccomp_unotify = { path = "crates/fspy_seccomp_unotify" }
 fspy_shared = { path = "crates/fspy_shared" }
 fspy_shared_unix = { path = "crates/fspy_shared_unix" }

crates/bundled_artifact_build/src/lib.rs

@@ -8,7 +8,7 @@ pub const ENV_PREFIX: &str = "BUNDLED_ARTIFACT_";
 /// Publish an artifact at `path` so `bundled_artifact`'s `artifact!($name)`
 /// macro can embed it.
 ///
-/// Emits three `cargo::…` directives:
+/// Emits three `cargo:…` directives:
 /// `rerun-if-changed={path}`,
 /// `rustc-env=BUNDLED_ARTIFACT_{name}_PATH={path}`, and
 /// `rustc-env=BUNDLED_ARTIFACT_{name}_HASH={hex}`. The runtime resolves these
@@ -27,11 +27,11 @@ pub fn register(name: &str, path: &Path) {
     {
         // Emit rerun-if-changed before reading so cargo still sees it even if
         // reading the file below panics.
-        println!("cargo::rerun-if-changed={path_str}");
+        println!("cargo:rerun-if-changed={path_str}");
         let bytes =
             fs::read(path).unwrap_or_else(|e| panic!("failed to read artifact at {path_str}: {e}"));
         let hash = format!("{:x}", xxhash_rust::xxh3::xxh3_128(&bytes));
-        println!("cargo::rustc-env={ENV_PREFIX}{name}_PATH={path_str}");
-        println!("cargo::rustc-env={ENV_PREFIX}{name}_HASH={hash}");
+        println!("cargo:rustc-env={ENV_PREFIX}{name}_PATH={path_str}");
+        println!("cargo:rustc-env={ENV_PREFIX}{name}_HASH={hash}");
     }
 }

crates/fspy/Cargo.toml

@@ -63,8 +63,8 @@ fspy_test_bin = { path = "../fspy_test_bin", artifact = "bin", target = "x86_64-
 anyhow = { workspace = true }
 bundled_artifact_build = { workspace = true }
 flate2 = { workspace = true }
-fspy_preload_unix = { path = "../fspy_preload_unix", artifact = "cdylib", target = "target" }
-fspy_preload_windows = { path = "../fspy_preload_windows", artifact = "cdylib", target = "target" }
+fspy_preload_unix = { workspace = true }
+fspy_preload_windows = { workspace = true }
 sha2 = { workspace = true }
 tar = { workspace = true }
 

crates/fspy/build.rs

@@ -120,15 +120,20 @@ fn fetch_macos_binaries(out_dir: &Path) -> anyhow::Result<()> {
 
     for BinaryDownload { name, url, path_in_targz, expected_sha256 } in downloads {
         let dest = out_dir.join(name);
-        let tarball = download(url).context(format!("Failed to download {url}"))?;
-        let actual_sha256 = sha256_hex(&tarball);
-        assert_eq!(
-            &actual_sha256, expected_sha256,
-            "sha256 of {url} does not match — update expected value in MACOS_BINARY_DOWNLOADS",
-        );
-        let data = unpack_tar_gz(Cursor::new(tarball), path_in_targz)
-            .context(format!("Failed to extract {path_in_targz} from {url}"))?;
-        fs::write(&dest, &data).with_context(|| format!("writing {}", dest.display()))?;
+        // Reuse the extracted binary if it's already in OUT_DIR; the sha256
+        // of the tarball was verified on the initial download. This avoids
+        // hitting the network on incremental build-script reruns.
+        if !dest.exists() {
+            let tarball = download(url).context(format!("Failed to download {url}"))?;
+            let actual_sha256 = sha256_hex(&tarball);
+            assert_eq!(
+                &actual_sha256, expected_sha256,
+                "sha256 of {url} does not match — update expected value in MACOS_BINARY_DOWNLOADS",
+            );
+            let data = unpack_tar_gz(Cursor::new(tarball), path_in_targz)
+                .context(format!("Failed to extract {path_in_targz} from {url}"))?;
+            fs::write(&dest, &data).with_context(|| format!("writing {}", dest.display()))?;
+        }
         bundled_artifact_build::register(name, &dest);
     }
     Ok(())
@@ -142,7 +147,7 @@ fn register_preload_cdylib() -> anyhow::Result<()> {
     };
     // The cdylib path is content-addressed by cargo; when its content changes
     // the path changes. Track it so we re-publish the hash on update.
-    println!("cargo::rerun-if-env-changed={env_name}");
+    println!("cargo:rerun-if-env-changed={env_name}");
     let dylib_path = env::var_os(env_name).with_context(|| format!("{env_name} not set"))?;
     bundled_artifact_build::register("fspy_preload", Path::new(&dylib_path));
     Ok(())

crates/fspy/src/windows/mod.rs

@@ -51,7 +51,7 @@ pub struct SpyImpl {
 
 impl SpyImpl {
     pub fn init_in(path: &Path) -> io::Result<Self> {
-        let dll_path = INTERPOSE_CDYLIB.ensure_in(path, ".dll", false).unwrap();
+        let dll_path = INTERPOSE_CDYLIB.ensure_in(path, ".dll", false)?;
 
         let wide_dll_path = dll_path.as_os_str().encode_wide().collect::<Vec<u16>>();
         let mut ansi_dll_path =