Better host detection/handling for Rust/Clang toolchains

This CL will cause a toolchain to raise an exception if a host hasn't
been explicitly set and autodetection fails.

Test: ./build.py
Change-Id: Ib3bde3bf75701d3779011649b84d3dfbc0019f00

5 files changed, 66 insertions, 34 deletions

diff --git a/src/android_rust/build_platform.py b/src/android_rust/build_platform.py
index 6cc7678..f2ab4e0 100644
--- a/src/android_rust/build_platform.py
+++ b/src/android_rust/build_platform.py
@@ -18,20 +18,28 @@
 building under for the purpose of selecting the correct paths and targets.
 """
 
+from enum import Enum
 import platform
 
 
-def system() -> str:
+class PlatformType(Enum):
+    DARWIN = 1
+    LINUX = 2
+    WINDOWS = 3
+
+
+def system() -> PlatformType:
     """Returns a canonicalized OS type of the machine executing the script.
     Will be one of 'linux', 'darwin', or 'windows'."""
-    sys = platform.system()
-    if sys == "Linux":
-        return "linux"
-    if sys == "Darwin":
-        return "darwin"
-    if sys == "Windows":
-        return "windows"
-    raise RuntimeError("Unknown System: " + sys)
+    match platform.system():
+        case "Darwin":
+            return PlatformType.DARWIN
+        case "Linux":
+            return PlatformType.LINUX
+        case "Windows":
+            return PlatformType.WINDOWS
+        case sys:
+            raise RuntimeError(f"Unknown System: {sys}")
 
 
 def is_linux() -> bool:
@@ -49,26 +57,27 @@ def is_windows() -> bool:
 def prebuilt() -> str:
     """Returns the prebuilt subdirectory for prebuilts which do not use
     subarch specialization."""
-    return system() + "-x86"
+    return system().name.lower() + "-x86"
 
 
 def prebuilt_full() -> str:
     """Returns the prebuilt subdirectory for prebuilts which have subarch
     specialization available.
     """
-    return system() + "-x86_64"
+    return system().name.lower() + "-x86_64"
 
 
 def triple() -> str:
     """Returns the target triple of the build environment."""
-    build_os = system()
-    if build_os == "linux":
-        return "x86_64-unknown-linux-gnu"
-    if build_os == "darwin":
-        return "x86_64-apple-darwin"
-    if build_os == "windows":
-        return "x86_64-pc-windows-gnu"
-    raise RuntimeError("Unknown OS: " + build_os)
+    match system():
+        case PlatformType.LINUX:
+            return "x86_64-unknown-linux-gnu"
+        case PlatformType.DARWIN:
+            return "x86_64-apple-darwin"
+        case PlatformType.WINDOWS:
+            return "x86_64-pc-windows-gnu"
+        case _:
+            raise RuntimeError("Unreachable")
 
 
 def rpath_origin() -> str:
diff --git a/src/android_rust/paths.py b/src/android_rust/paths.py
index 3201240..ec6c8ed 100644
--- a/src/android_rust/paths.py
+++ b/src/android_rust/paths.py
@@ -21,11 +21,11 @@ import android_rust.build_platform as build_platform
 RUST_STAGE0_VERSION: str = "1.77.1"
 RUST_STAGE0_TRIPLE: str
 match build_platform.system():
-    case "darwin":
+    case build_platform.PlatformType.DARWIN:
         RUST_STAGE0_TRIPLE = "x86_64-apple-darwin"
-    case "linux":
+    case build_platform.PlatformType.LINUX:
         RUST_STAGE0_TRIPLE = "x86_64-unknown-linux-gnu"
-    case "windows":
+    case build_platform.PlatformType.WINDOWS:
         RUST_STAGE0_TRIPLE = "x86_64-pc-windows-gnu"
     case _:
         RUST_STAGE0_TRIPLE = "unreachable"
diff --git a/src/android_rust/toolchains.py b/src/android_rust/toolchains.py
index fa9585e..cbf2f2d 100644
--- a/src/android_rust/toolchains.py
+++ b/src/android_rust/toolchains.py
@@ -12,9 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import inspect
 from pathlib import Path
 
+from android_rust.build_platform import PlatformType
 from android_rust.paths import CLANG_VERSION, LLVM_PREBUILT_PATH_HOST, LLVM_PREBUILT_PATH_LINUX, LLVM_PREBUILT_PATH_WINDOWS, RUST_HOST_STAGE0_PATH
 
 
@@ -32,10 +32,21 @@ class ClangToolchain:
         "readelf",
     ]
 
-    def __init__(self, base_dir: Path):
+    def __init__(self, base_dir: Path, host: PlatformType | None = None):
+        if host is None:
+            if "linux-x86" in base_dir.parts:
+                host = PlatformType.LINUX
+            elif "darwin-x86" in base_dir.parts:
+                host = PlatformType.DARWIN
+            elif "windows-x86" in base_dir.parts:
+                host = PlatformType.WINDOWS
+            else:
+                raise RuntimeError(f"Toolchain host autodetection failed for {base_dir}")
+
         self.base_dir = base_dir
         self.bin_dir = base_dir / "bin"
-        self.exe = ".exe" if self.is_windows() else ""
+        self.host = host
+        self.exe = ".exe" if self.host == PlatformType.WINDOWS else ""
 
         for method_name in self.__class__.PATH_METHODS:
             path = getattr(self, method_name)()
@@ -109,10 +120,10 @@ class ClangToolchain:
     #
 
     def is_linux(self) -> bool:
-        return "linux" in str(self.base_dir)
+        return self.host == PlatformType.LINUX
 
     def is_windows(self) -> bool:
-        return "windows" in str(self.base_dir)
+        return self.host == PlatformType.WINDOWS
 
 
 class RustToolchain:
@@ -121,10 +132,21 @@ class RustToolchain:
         "rustc",
     ]
 
-    def __init__(self, base_dir: Path):
+    def __init__(self, base_dir: Path, host: PlatformType | None = None):
+        if host is None:
+            if "linux-x86" in base_dir.parts:
+                host = PlatformType.LINUX
+            elif "darwin-x86" in base_dir.parts:
+                host = PlatformType.DARWIN
+            elif "windows-x86" in base_dir.parts:
+                host = PlatformType.WINDOWS
+            else:
+                raise RuntimeError(f"Toolchain host autodetection failed for {base_dir}")
+
         self.base_dir = base_dir
         self.bin_dir = base_dir / "bin"
-        self.exe = ".exe" if self.is_windows() else ""
+        self.host = host
+        self.exe = ".exe" if self.host == PlatformType.WINDOWS else ""
 
         for method_name in self.__class__.PATH_METHODS:
             path = getattr(self, method_name)()
@@ -146,10 +168,10 @@ class RustToolchain:
     #
 
     def is_linux(self) -> bool:
-        return "linux" in str(self.base_dir)
+        return self.host == PlatformType.LINUX
 
     def is_windows(self) -> bool:
-        return "windows" in str(self.base_dir)
+        return self.host == PlatformType.WINDOWS
 
 
 LLVM_TOOLCHAIN_HOST = ClangToolchain(LLVM_PREBUILT_PATH_HOST)
diff --git a/src/android_rust/upstream_tests.py b/src/android_rust/upstream_tests.py
index 31b16ab..67a316c 100644
--- a/src/android_rust/upstream_tests.py
+++ b/src/android_rust/upstream_tests.py
@@ -17,6 +17,7 @@ from pathlib import Path
 
 
 import android_rust.build_platform as build_platform
+from android_rust.build_platform import PlatformType
 
 disabled_tests = [
     "--exclude", Path("compiler/rustc_target"),
@@ -96,7 +97,7 @@ disabled_tests = [
 ]
 
 match build_platform.system():
-    case "darwin":
+    case PlatformType.DARWIN:
         # Darwin failures on 1.73.0 due to dylib error
         # https://buganizer.corp.google.com/issues/311035877
         disabled_tests += [
diff --git a/tools/build.py b/tools/build.py
index ad8d204..2c9cc6e 100755
--- a/tools/build.py
+++ b/tools/build.py
@@ -332,7 +332,7 @@ def initialize_rust_stage0(args: argparse.Namespace) -> None:
         archive_extract(args.rust_stage0, extract_dir)
         args.rust_stage0 = extract_dir
 
-    args.rust_stage0 = RustToolchain(args.rust_stage0)
+    args.rust_stage0 = RustToolchain(args.rust_stage0, host=build_platform.system())
 
 
 def extract_ndk_archive(archive_path: Path) -> Path:
@@ -599,7 +599,7 @@ def main(argv: list[str] | None = None) -> int:
     #
 
     if args.host == build_platform.triple():
-        new_toolchain = RustToolchain(OUT_PATH_PACKAGE)
+        new_toolchain = RustToolchain(OUT_PATH_PACKAGE, host=build_platform.system())
         cargo_deny = cargo.Crate(
             WORKSPACE_PATH / "toolchain" / "cargo-deny",
             env,