feat: add Pyodide support

.github/workflows/test.yml

@@ -148,3 +148,37 @@ jobs:
     - name: Run the emulation tests
       run: |
         pytest --run-emulation test/test_emulation.py
+
+  test-pyodide:
+    name: Test cibuildwheel building pyodide wheels
+    needs: lint
+    runs-on: ubuntu-24.04
+    timeout-minutes: 180
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-python@v5
+      name: Install Python 3.12
+      with:
+        python-version: '3.12'
+
+    - name: Install dependencies
+      run: |
+        python -m pip install ".[test]"
+
+    - name: Generate a sample project
+      run: |
+        python -m test.test_projects test.test_0_basic.basic_project sample_proj
+
+    - name: Run a sample build (GitHub Action)
+      uses: ./
+      with:
+        package-dir: sample_proj
+        output-dir: wheelhouse
+      env:
+        CIBW_PLATFORM: pyodide
+
+    - name: Run tests with 'CIBW_PLATFORM' set to 'pyodide'
+      run: |
+        python ./bin/run_tests.py
+      env:
+        CIBW_PLATFORM: pyodide

README.md

@@ -22,24 +22,25 @@ Python wheels are great. Building them across **Mac, Linux, Windows**, on **mult
 What does it do?
 ----------------
 
-|                | macOS Intel | macOS Apple Silicon | Windows 64bit | Windows 32bit | Windows Arm64 | manylinux<br/>musllinux x86_64 | manylinux<br/>musllinux i686 | manylinux<br/>musllinux aarch64 | manylinux<br/>musllinux ppc64le | manylinux<br/>musllinux s390x |
-|----------------|----|-----|-----|-----|-----|----|-----|----|-----|-----|
-| CPython 3.6    | ✅ | N/A | ✅  | ✅  | N/A | ✅  | ✅  | ✅ | ✅  | ✅  |
-| CPython 3.7    | ✅ | N/A | ✅  | ✅  | N/A | ✅ | ✅  | ✅ | ✅  | ✅  |
-| CPython 3.8    | ✅ | ✅  | ✅  | ✅  | N/A | ✅ | ✅  | ✅ | ✅  | ✅  |
-| CPython 3.9    | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅ | ✅ | ✅  | ✅  |
-| CPython 3.10   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  |
-| CPython 3.11   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  |
-| CPython 3.12   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  |
-| CPython 3.13³  | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  |
-| PyPy 3.7 v7.3  | ✅ | N/A | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A |
-| PyPy 3.8 v7.3  | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A |
-| PyPy 3.9 v7.3  | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A |
-| PyPy 3.10 v7.3 | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A |
+|                | macOS Intel | macOS Apple Silicon | Windows 64bit | Windows 32bit | Windows Arm64 | manylinux<br/>musllinux x86_64 | manylinux<br/>musllinux i686 | manylinux<br/>musllinux aarch64 | manylinux<br/>musllinux ppc64le | manylinux<br/>musllinux s390x | Pyodide |
+|----------------|----|-----|-----|-----|-----|----|-----|----|-----|-----|-----|
+| CPython 3.6    | ✅ | N/A | ✅  | ✅  | N/A | ✅  | ✅  | ✅ | ✅  | ✅  | N/A |
+| CPython 3.7    | ✅ | N/A | ✅  | ✅  | N/A | ✅ | ✅  | ✅ | ✅  | ✅  | N/A |
+| CPython 3.8    | ✅ | ✅  | ✅  | ✅  | N/A | ✅ | ✅  | ✅ | ✅  | ✅  | N/A |
+| CPython 3.9    | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅ | ✅ | ✅  | ✅  | N/A |
+| CPython 3.10   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | N/A |
+| CPython 3.11   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | N/A |
+| CPython 3.12   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁴ |
+| CPython 3.13³  | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | N/A |
+| PyPy 3.7 v7.3  | ✅ | N/A | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A |
+| PyPy 3.8 v7.3  | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A |
+| PyPy 3.9 v7.3  | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A |
+| PyPy 3.10 v7.3 | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A |
 
 <sup>¹ PyPy is only supported for manylinux wheels.</sup><br>
 <sup>² Windows arm64 support is experimental.</sup><br>
-<sup>³ CPython 3.13 is available using the [CIBW_PRERELEASE_PYTHONS](https://cibuildwheel.pypa.io/en/stable/options/#prerelease-pythons) option.</sup><br>
+<sup>³ CPython 3.13 is available using the [`CIBW_PRERELEASE_PYTHONS`](https://cibuildwheel.pypa.io/en/stable/options/#prerelease-pythons) option. Free-threaded mode requires opt-in, not yet available on macOS.</sup><br>
+<sup>⁴ Experimental, not yet supported on PyPI, but can be used directly in web deployment. Use `--platform pyodide` to build.</sup><br>
 
 - Builds manylinux, musllinux, macOS 10.9+, and Windows wheels for CPython and PyPy
 - Works on GitHub Actions, Azure Pipelines, Travis CI, AppVeyor, CircleCI, GitLab CI, and Cirrus CI

bin/generate_schema.py

@@ -280,6 +280,7 @@ def as_object(d: dict[str, Any]) -> dict[str, Any]:
     "linux": as_object(non_global_options),
     "windows": as_object(not_linux),
     "macos": as_object(not_linux),
+    "pyodide": as_object(not_linux),
 }
 
 oses["linux"]["properties"]["repair-wheel-command"] = {

bin/update_nodejs.py

@@ -0,0 +1,148 @@
+#!/usr/bin/env python3
+
+from __future__ import annotations
+
+import difflib
+import logging
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Final
+
+import click
+import packaging.specifiers
+import requests
+import rich
+from packaging.version import InvalidVersion, Version
+from rich.logging import RichHandler
+from rich.syntax import Syntax
+
+from cibuildwheel._compat import tomllib
+
+log = logging.getLogger("cibw")
+
+# Looking up the dir instead of using utils.resources_dir
+# since we want to write to it.
+DIR: Final[Path] = Path(__file__).parent.parent.resolve()
+RESOURCES_DIR: Final[Path] = DIR / "cibuildwheel/resources"
+
+NODEJS_DIST: Final[str] = "https://nodejs.org/dist/"
+NODEJS_INDEX: Final[str] = f"{NODEJS_DIST}index.json"
+
+
+@dataclass(frozen=True, order=True)
+class VersionTuple:
+    version: Version
+    version_string: str
+
+
+def parse_nodejs_index() -> list[VersionTuple]:
+    versions: list[VersionTuple] = []
+    response = requests.get(NODEJS_INDEX)
+    response.raise_for_status()
+    versions_info = response.json()
+    for version_info in versions_info:
+        version_string = version_info.get("version", "???")
+        if not version_info.get("lts", False):
+            log.debug("Ignoring non LTS release %r", version_string)
+            continue
+        if "linux-x64" not in version_info.get("files", []):
+            log.warning(
+                "Ignoring release %r which does not include a linux-x64 binary", version_string
+            )
+            continue
+        try:
+            version = Version(version_string)
+            if version.is_devrelease:
+                log.info("Ignoring development release %r", str(version))
+                continue
+            if version.is_prerelease:
+                log.info("Ignoring pre-release %r", str(version))
+                continue
+            versions.append(VersionTuple(version, version_string))
+        except InvalidVersion:
+            log.warning("Ignoring release %r", version_string)
+    versions.sort(reverse=True)
+    return versions
+
+
+@click.command()
+@click.option("--force", is_flag=True)
+@click.option(
+    "--level", default="INFO", type=click.Choice(["WARNING", "INFO", "DEBUG"], case_sensitive=False)
+)
+def update_nodejs(force: bool, level: str) -> None:
+    logging.basicConfig(
+        level="INFO",
+        format="%(message)s",
+        datefmt="[%X]",
+        handlers=[RichHandler(rich_tracebacks=True, markup=True)],
+    )
+    log.setLevel(level)
+
+    toml_file_path = RESOURCES_DIR / "nodejs.toml"
+
+    original_toml = toml_file_path.read_text()
+    with toml_file_path.open("rb") as f:
+        nodejs_data = tomllib.load(f)
+
+    nodejs_data.pop("url")
+
+    major_versions = [VersionTuple(Version(key), key) for key in nodejs_data]
+    major_versions.sort(reverse=True)
+
+    versions = parse_nodejs_index()
+
+    # update existing versions, 1 per LTS
+    for major_version in major_versions:
+        current = Version(nodejs_data[major_version.version_string])
+        specifier = packaging.specifiers.SpecifierSet(
+            specifiers=f"=={major_version.version.major}.*"
+        )
+        for version in versions:
+            if specifier.contains(version.version) and version.version > current:
+                nodejs_data[major_version.version_string] = version.version_string
+                break
+
+    # check for a new major LTS to insert
+    if versions and versions[0].version.major > major_versions[0].version.major:
+        major_versions.insert(
+            0,
+            VersionTuple(Version(str(versions[0].version.major)), f"v{versions[0].version.major}"),
+        )
+        nodejs_data[major_versions[0].version_string] = versions[0].version_string
+
+    versions_toml = "\n".join(
+        f'{major_version.version_string} = "{nodejs_data[major_version.version_string]}"'
+        for major_version in major_versions
+    )
+    result_toml = f'url = "{NODEJS_DIST}"\n{versions_toml}\n'
+
+    rich.print()  # spacer
+
+    if original_toml == result_toml:
+        rich.print("[green]Check complete, nodejs version unchanged.")
+        return
+
+    rich.print("nodejs version updated.")
+    rich.print("Changes:")
+    rich.print()
+
+    toml_relpath = toml_file_path.relative_to(DIR).as_posix()
+    diff_lines = difflib.unified_diff(
+        original_toml.splitlines(keepends=True),
+        result_toml.splitlines(keepends=True),
+        fromfile=toml_relpath,
+        tofile=toml_relpath,
+    )
+    rich.print(Syntax("".join(diff_lines), "diff", theme="ansi_light"))
+    rich.print()
+
+    if force:
+        toml_file_path.write_text(result_toml)
+        rich.print("[green]TOML file updated.")
+    else:
+        rich.print("[yellow]File left unchanged. Use --force flag to update.")
+
+
+if __name__ == "__main__":
+    update_nodejs()

cibuildwheel/__main__.py

@@ -15,6 +15,7 @@
 import cibuildwheel
 import cibuildwheel.linux
 import cibuildwheel.macos
+import cibuildwheel.pyodide
 import cibuildwheel.util
 import cibuildwheel.windows
 from cibuildwheel._compat.typing import assert_never
@@ -45,7 +46,7 @@ def main() -> None:
 
     parser.add_argument(
         "--platform",
-        choices=["auto", "linux", "macos", "windows"],
+        choices=["auto", "linux", "macos", "windows", "pyodide"],
         default=None,
         help="""
             Platform to build for. Use this option to override the
@@ -176,6 +177,8 @@ def _compute_platform_only(only: str) -> PlatformName:
         return "macos"
     if "win_" in only or "win32" in only:
         return "windows"
+    if "pyodide_" in only:
+        return "pyodide"
     print(
         f"Invalid --only='{only}', must be a build selector with a known platform",
         file=sys.stderr,
@@ -246,11 +249,18 @@ def get_platform_module(platform: PlatformName) -> PlatformModule:
         return cibuildwheel.windows
     if platform == "macos":
         return cibuildwheel.macos
+    if platform == "pyodide":
+        return cibuildwheel.pyodide
     assert_never(platform)
 
 
 def build_in_directory(args: CommandLineArguments) -> None:
     platform: PlatformName = _compute_platform(args)
+    if platform == "pyodide" and sys.platform == "win32":
+        msg = "cibuildwheel: Building for pyodide is not supported on Windows"
+        print(msg, file=sys.stderr)
+        sys.exit(2)
+
     options = compute_options(platform=platform, command_line_arguments=args, env=os.environ)
 
     package_dir = options.globals.package_dir

cibuildwheel/architecture.py

@@ -15,6 +15,7 @@
     "linux": "Linux",
     "macos": "macOS",
     "windows": "Windows",
+    "pyodide": "Pyodide",
 }
 
 ARCH_SYNONYMS: Final[list[dict[PlatformName, str | None]]] = [
@@ -46,6 +47,9 @@ class Architecture(Enum):
     AMD64 = "AMD64"
     ARM64 = "ARM64"
 
+    # WebAssembly
+    wasm32 = "wasm32"
+
     # Allow this to be sorted
     def __lt__(self, other: Architecture) -> bool:
         return self.value < other.value
@@ -72,8 +76,9 @@ def parse_config(config: str, platform: PlatformName) -> set[Architecture]:
         return result
 
     @staticmethod
-    def auto_archs(platform: PlatformName) -> set[Architecture]:
-        native_machine = platform_module.machine()
+    def native_arch(platform: PlatformName) -> Architecture | None:
+        if platform == "pyodide":
+            return Architecture.wasm32
 
         # Cross-platform support. Used for --print-build-identifiers or docker builds.
         host_platform: PlatformName = (
@@ -82,6 +87,7 @@ def auto_archs(platform: PlatformName) -> set[Architecture]:
             else ("macos" if sys.platform.startswith("darwin") else "linux")
         )
 
+        native_machine = platform_module.machine()
         native_architecture = Architecture(native_machine)
 
         # we might need to rename the native arch to the machine we're running
@@ -93,11 +99,18 @@ def auto_archs(platform: PlatformName) -> set[Architecture]:
 
                     if synonym is None:
                         # can't build anything on this platform
-                        return set()
+                        return None
 
                     native_architecture = Architecture(synonym)
 
-        result = {native_architecture}
+        return native_architecture
+
+    @staticmethod
+    def auto_archs(platform: PlatformName) -> set[Architecture]:
+        native_arch = Architecture.native_arch(platform)
+        if native_arch is None:
+            return set()  # can't build anything on this platform
+        result = {native_arch}
 
         if platform == "linux" and Architecture.x86_64 in result:
             # x86_64 machines can run i686 containers
@@ -120,6 +133,7 @@ def all_archs(platform: PlatformName) -> set[Architecture]:
             },
             "macos": {Architecture.x86_64, Architecture.arm64, Architecture.universal2},
             "windows": {Architecture.x86, Architecture.AMD64, Architecture.ARM64},
+            "pyodide": {Architecture.wasm32},
         }
         return all_archs_map[platform]
 

cibuildwheel/logger.py

@@ -34,6 +34,7 @@
     "macosx_x86_64": "macOS x86_64",
     "macosx_universal2": "macOS Universal 2 - x86_64 and arm64",
     "macosx_arm64": "macOS arm64 - Apple Silicon",
+    "pyodide_wasm32": "Pyodide",
 }