Move ensure_rust_toolchain to buildall (#83)

Rather than installing the rust toolchain in each build step that uses
rust, do it once in buildall.

Split off from #81.

pyodide_build/build_env.py

@@ -19,8 +19,7 @@
 from pyodide_build.recipe import load_all_recipes
 
 RUST_BUILD_PRELUDE = """
-rustup toolchain install ${RUST_TOOLCHAIN} && rustup default ${RUST_TOOLCHAIN}
-rustup target add wasm32-unknown-emscripten --toolchain ${RUST_TOOLCHAIN}
+rustup default ${RUST_TOOLCHAIN}
 """
 
 

pyodide_build/buildall.py

@@ -33,6 +33,7 @@
 from pyodide_build.build_env import BuildArgs
 from pyodide_build.buildpkg import needs_rebuild
 from pyodide_build.common import (
+    exit_with_stdio,
     extract_wheel_metadata_file,
     find_matching_wheels,
     find_missing_executables,
@@ -158,6 +159,8 @@ def build(self, build_args: BuildArgs, build_dir: Path) -> None:
                 # been updated and should be rebuilt even though its own
                 # files haven't been updated.
                 "--force-rebuild",
+                # We already did the rust setup in buildall
+                "--skip-rust-setup",
             ],
             check=False,
             stdout=subprocess.DEVNULL,
@@ -645,6 +648,28 @@ def run(self, n_jobs: int, already_built: set[str]) -> None:
                         self.build_queue.put((job_priority(dependent), dependent))
 
 
+def _ensure_rust_toolchain():
+    rust_toolchain = build_env.get_build_flag("RUST_TOOLCHAIN")
+    result = subprocess.run(
+        ["rustup", "toolchain", "install", rust_toolchain], check=False
+    )
+    if result.returncode == 0:
+        result = subprocess.run(
+            [
+                "rustup",
+                "target",
+                "add",
+                "wasm32-unknown-emscripten",
+                "--toolchain",
+                rust_toolchain,
+            ],
+            check=False,
+        )
+    if result.returncode != 0:
+        logger.error("ERROR: rustup toolchain install failed")
+        exit_with_stdio(result)
+
+
 def build_from_graph(
     pkg_map: dict[str, BasePackage],
     build_args: BuildArgs,
@@ -686,6 +711,12 @@ def build_from_graph(
     for pkg_name in needs_build:
         pkg_map[pkg_name].unbuilt_host_dependencies.difference_update(already_built)
 
+    needs_rust = any(
+        pkg_map[pkg_name].meta.is_rust_package() for pkg_name in needs_build
+    )
+    if needs_rust:
+        _ensure_rust_toolchain()
+
     if already_built:
         logger.info(
             "The following packages are already built: [bold]%s[/bold]",

pyodide_build/cli/build_recipes.py

@@ -4,7 +4,7 @@
 
 import typer
 
-from pyodide_build import build_env, buildall
+from pyodide_build import build_env, buildall, recipe
 from pyodide_build.build_env import BuildArgs, init_environment
 from pyodide_build.buildpkg import RecipeBuilder
 from pyodide_build.common import get_num_cores
@@ -17,6 +17,7 @@ class Args:
     build_dir: Path
     install_dir: Path
     build_args: BuildArgs
+    skip_rust_setup: bool
     force_rebuild: bool
     n_jobs: int
 
@@ -28,6 +29,7 @@ def __init__(
         install_dir: Path | str | None = None,
         build_args: BuildArgs,
         force_rebuild: bool,
+        skip_rust_setup: bool = False,
         n_jobs: int | None = None,
     ):
         cwd = Path.cwd()
@@ -41,6 +43,7 @@ def __init__(
         )
         self.build_args = build_args
         self.force_rebuild = force_rebuild
+        self.skip_rust_setup = skip_rust_setup
         self.n_jobs = n_jobs or get_num_cores()
         if not self.recipe_dir.is_dir():
             raise FileNotFoundError(f"Recipe directory {self.recipe_dir} not found")
@@ -93,6 +96,11 @@ def build_recipes_no_deps(
         "--continue",
         help="Continue a build from the middle. For debugging. Implies '--force-rebuild'",
     ),
+    skip_rust_setup: bool = typer.Option(
+        False,
+        "--skip-rust-setup",
+        help="Don't setup rust environment when building a rust package",
+    ),
 ) -> None:
     """Build packages using yaml recipes but don't try to resolve dependencies"""
     init_environment()
@@ -113,15 +121,25 @@ def build_recipes_no_deps(
         build_dir=build_dir,
         recipe_dir=recipe_dir,
         force_rebuild=force_rebuild,
+        skip_rust_setup=skip_rust_setup,
     )
 
     return build_recipes_no_deps_impl(packages, args, continue_)
 
 
+def _rust_setup(recipe_dir: Path, packages: list[str]):
+    recipes = recipe.load_recipes(recipe_dir, packages, False)
+    if any(recipe.is_rust_package() for recipe in recipes.values()):
+        buildall._ensure_rust_toolchain()
+
+
 def build_recipes_no_deps_impl(
     packages: list[str], args: Args, continue_: bool
 ) -> None:
     # TODO: use multiprocessing?
+    if not args.skip_rust_setup:
+        _rust_setup(args.recipe_dir, packages)
+
     for package in packages:
         package_path = args.recipe_dir / package
         package_build_dir = args.build_dir / package / "build"