__main__.py

#!/usr/bin/env python3

import argparse
import contextlib
import functools
import os
import shutil
import subprocess
import sys
import sysconfig
import tempfile
from urllib.request import urlopen
from pathlib import Path
from textwrap import dedent

try:
    from os import process_cpu_count as cpu_count
except ImportError:
    from os import cpu_count


EMSCRIPTEN_DIR = Path(__file__).parent
CHECKOUT = EMSCRIPTEN_DIR.parent.parent.parent

CROSS_BUILD_DIR = CHECKOUT / "cross-build"
NATIVE_BUILD_DIR = CROSS_BUILD_DIR / "build"
HOST_TRIPLE = "wasm32-emscripten"

DOWNLOAD_DIR = CROSS_BUILD_DIR / HOST_TRIPLE / "build"
HOST_BUILD_DIR = CROSS_BUILD_DIR / HOST_TRIPLE / "build"
HOST_DIR = HOST_BUILD_DIR / "python"
PREFIX_DIR = CROSS_BUILD_DIR / HOST_TRIPLE / "prefix"

LOCAL_SETUP = CHECKOUT / "Modules" / "Setup.local"
LOCAL_SETUP_MARKER = "# Generated by Tools/wasm/emscripten.py\n".encode("utf-8")


def updated_env(updates={}):
    """Create a new dict representing the environment to use.

    The changes made to the execution environment are printed out.
    """
    env_defaults = {}
    # https://reproducible-builds.org/docs/source-date-epoch/
    git_epoch_cmd = ["git", "log", "-1", "--pretty=%ct"]
    try:
        epoch = subprocess.check_output(git_epoch_cmd, encoding="utf-8").strip()
        env_defaults["SOURCE_DATE_EPOCH"] = epoch
    except subprocess.CalledProcessError:
        pass  # Might be building from a tarball.
    # This layering lets SOURCE_DATE_EPOCH from os.environ takes precedence.
    environment = env_defaults | os.environ | updates

    env_diff = {}
    for key, value in environment.items():
        if os.environ.get(key) != value:
            env_diff[key] = value

    print("🌎 Environment changes:")
    for key in sorted(env_diff.keys()):
        print(f"  {key}={env_diff[key]}")

    return environment


def subdir(working_dir, *, clean_ok=False):
    """Decorator to change to a working directory."""

    def decorator(func):
        @functools.wraps(func)
        def wrapper(context):
            try:
                tput_output = subprocess.check_output(
                    ["tput", "cols"], encoding="utf-8"
                )
                terminal_width = int(tput_output.strip())
            except subprocess.CalledProcessError:
                terminal_width = 80
            print("⎯" * terminal_width)
            print("📁", working_dir)
            if clean_ok and getattr(context, "clean", False) and working_dir.exists():
                print("🚮 Deleting directory (--clean)...")
                shutil.rmtree(working_dir)

            working_dir.mkdir(parents=True, exist_ok=True)

            with contextlib.chdir(working_dir):
                return func(context, working_dir)

        return wrapper

    return decorator


def call(command, *, quiet, **kwargs):
    """Execute a command.

    If 'quiet' is true, then redirect stdout and stderr to a temporary file.
    """
    print("❯", " ".join(map(str, command)))
    if not quiet:
        stdout = None
        stderr = None
    else:
        stdout = tempfile.NamedTemporaryFile(
            "w",
            encoding="utf-8",
            delete=False,
            prefix="cpython-emscripten-",
            suffix=".log",
        )
        stderr = subprocess.STDOUT
        print(f"📝 Logging output to {stdout.name} (--quiet)...")

    subprocess.check_call(command, **kwargs, stdout=stdout, stderr=stderr)


def build_platform():
    """The name of the build/host platform."""
    # Can also be found via `config.guess`.`
    return sysconfig.get_config_var("BUILD_GNU_TYPE")


def build_python_path():
    """The path to the build Python binary."""
    binary = NATIVE_BUILD_DIR / "python"
    if not binary.is_file():
        binary = binary.with_suffix(".exe")
        if not binary.is_file():
            raise FileNotFoundError("Unable to find `python(.exe)` in " f"{NATIVE_BUILD_DIR}")

    return binary


@subdir(NATIVE_BUILD_DIR, clean_ok=True)
def configure_build_python(context, working_dir):
    """Configure the build/host Python."""
    if LOCAL_SETUP.exists():
        print(f"👍 {LOCAL_SETUP} exists ...")
    else:
        print(f"📝 Touching {LOCAL_SETUP} ...")
        LOCAL_SETUP.write_bytes(LOCAL_SETUP_MARKER)

    configure = [os.path.relpath(CHECKOUT / "configure", working_dir)]
    if context.args:
        configure.extend(context.args)

    call(configure, quiet=context.quiet)


@subdir(NATIVE_BUILD_DIR)
def make_build_python(context, working_dir):
    """Make/build the build Python."""
    call(["make", "--jobs", str(cpu_count()), "all"], quiet=context.quiet)

    binary = build_python_path()
    cmd = [
        binary,
        "-c",
        "import sys; " "print(f'{sys.version_info.major}.{sys.version_info.minor}')",
    ]
    version = subprocess.check_output(cmd, encoding="utf-8").strip()

    print(f"🎉 {binary} {version}")


@subdir(HOST_BUILD_DIR, clean_ok=True)
def make_emscripten_libffi(context, working_dir):
    shutil.rmtree(working_dir / "libffi-3.4.6", ignore_errors=True)
    with tempfile.NamedTemporaryFile(suffix=".tar.gz") as tmp_file:
        with urlopen(
            "https://github.com/libffi/libffi/releases/download/v3.4.6/libffi-3.4.6.tar.gz"
        ) as response:
            shutil.copyfileobj(response, tmp_file)
        shutil.unpack_archive(tmp_file.name, working_dir)
    call(
        [EMSCRIPTEN_DIR / "make_libffi.sh"],
        env=updated_env({"PREFIX": PREFIX_DIR}),
        cwd=working_dir / "libffi-3.4.6",
        quiet=context.quiet,
    )


@subdir(HOST_DIR, clean_ok=True)
def configure_emscripten_python(context, working_dir):
    """Configure the emscripten/host build."""
    config_site = os.fsdecode(
        CHECKOUT / "Tools" / "wasm" / "config.site-wasm32-emscripten"
    )

    emscripten_build_dir = working_dir.relative_to(CHECKOUT)

    python_build_dir = NATIVE_BUILD_DIR / "build"
    lib_dirs = list(python_build_dir.glob("lib.*"))
    assert (
        len(lib_dirs) == 1
    ), f"Expected a single lib.* directory in {python_build_dir}"
    _, python_version, abiflags = os.fsdecode(lib_dirs[0]).rsplit('-', maxsplit=2)
    sysconfig_data = (
        f"{emscripten_build_dir}/build/"
        f"lib.emscripten-wasm32-emscripten-{python_version}-{abiflags}"
    )
    if pydebug:
        sysconfig_data += "-pydebug"

    host_runner = context.host_runner
    pkg_config_path_dir = (PREFIX_DIR / "lib/pkgconfig/").resolve()
    env_additions = {
        "CONFIG_SITE": config_site,
        "HOSTRUNNER": host_runner,
        "EM_PKG_CONFIG_PATH": str(pkg_config_path_dir),
    }
    build_python = os.fsdecode(build_python_path())
    configure = [
        "emconfigure",
        os.path.relpath(CHECKOUT / "configure", working_dir),
        "CFLAGS=-DPY_CALL_TRAMPOLINE -sUSE_BZIP2",
        "PKG_CONFIG=pkg-config",
        f"--host={HOST_TRIPLE}",
        f"--build={build_platform()}",
        f"--with-build-python={build_python}",
        "--without-pymalloc",
        "--disable-shared",
        "--disable-ipv6",
        "--enable-big-digits=30",
        "--enable-wasm-dynamic-linking",
        f"--prefix={PREFIX_DIR}",
    ]
    for flag in abiflags:
        if flag == 'd':
            configure.append("--with-pydebug")
        elif flag == 't':
            configure.append("--disable-gil")
        else:
            raise ValueError(f"Unknown ABI flag: {flag}")
    if context.args:
        configure.extend(context.args)
    call(
        configure,
        env=updated_env(env_additions),
        quiet=context.quiet,
    )

    shutil.copy(EMSCRIPTEN_DIR / "node_entry.mjs", working_dir / "node_entry.mjs")

    node_entry = working_dir / "node_entry.mjs"
    exec_script = working_dir / "python.sh"
    exec_script.write_text(
        dedent(
            f"""\
            #!/bin/sh

            # Macs come with FreeBSD coreutils which doesn't have the -s option
            # so feature detect and work around it.
            if which grealpath > /dev/null; then
                # It has brew installed gnu core utils, use that
                REALPATH="grealpath -s"
            elif which realpath > /dev/null && realpath --version > /dev/null 2> /dev/null && realpath --version | grep GNU > /dev/null; then
                # realpath points to GNU realpath so use it.
                REALPATH="realpath -s"
            else
                # Shim for macs without GNU coreutils
                abs_path () {{
                    echo "$(cd "$(dirname "$1")" || exit; pwd)/$(basename "$1")"
                }}
                REALPATH=abs_path
            fi

            # We compute our own path, not following symlinks and pass it in so that
            # node_entry.mjs can set sys.executable correctly.
            # Intentionally allow word splitting on NODEFLAGS.
            exec {host_runner} $NODEFLAGS {node_entry} --this-program="$($REALPATH "$0")" "$@"
            """
        )
    )
    exec_script.chmod(0o755)
    print(f"🏃‍♀️ Created {exec_script} ... ")
    sys.stdout.flush()


@subdir(HOST_DIR)
def make_emscripten_python(context, working_dir):
    """Run `make` for the emscripten/host build."""
    call(
        ["make", "--jobs", str(cpu_count()), "all"],
        env=updated_env(),
        quiet=context.quiet,
    )

    exec_script = working_dir / "python.sh"
    subprocess.check_call([exec_script, "--version"])


def build_all(context):
    """Build everything."""
    steps = [
        configure_build_python,
        make_build_python,
        make_emscripten_libffi,
        configure_emscripten_python,
        make_emscripten_python,
    ]
    for step in steps:
        step(context)


def clean_contents(context):
    """Delete all files created by this script."""
    if CROSS_BUILD_DIR.exists():
        print(f"🧹 Deleting {CROSS_BUILD_DIR} ...")
        shutil.rmtree(CROSS_BUILD_DIR)

    if LOCAL_SETUP.exists():
        with LOCAL_SETUP.open("rb") as file:
            if file.read(len(LOCAL_SETUP_MARKER)) == LOCAL_SETUP_MARKER:
                print(f"🧹 Deleting generated {LOCAL_SETUP} ...")


def main():
    default_host_runner = "node"

    parser = argparse.ArgumentParser()
    subcommands = parser.add_subparsers(dest="subcommand")
    build = subcommands.add_parser("build", help="Build everything")
    configure_build = subcommands.add_parser(
        "configure-build-python", help="Run `configure` for the " "build Python"
    )
    make_libffi_cmd = subcommands.add_parser(
        "make-libffi", help="Clone libffi repo, configure and build it for emscripten"
    )
    make_build = subcommands.add_parser(
        "make-build-python", help="Run `make` for the build Python"
    )
    configure_host = subcommands.add_parser(
        "configure-host",
        help="Run `configure` for the host/emscripten (pydebug builds are inferred from the build Python)",
    )
    make_host = subcommands.add_parser(
        "make-host", help="Run `make` for the host/emscripten"
    )
    clean = subcommands.add_parser(
        "clean", help="Delete files and directories created by this script"
    )
    for subcommand in (
        build,
        configure_build,
        make_libffi_cmd,
        make_build,
        configure_host,
        make_host,
    ):
        subcommand.add_argument(
            "--quiet",
            action="store_true",
            default=False,
            dest="quiet",
            help="Redirect output from subprocesses to a log file",
        )
    for subcommand in configure_build, configure_host:
        subcommand.add_argument(
            "--clean",
            action="store_true",
            default=False,
            dest="clean",
            help="Delete any relevant directories before building",
        )
    for subcommand in build, configure_build, configure_host:
        subcommand.add_argument(
            "args", nargs="*", help="Extra arguments to pass to `configure`"
        )
    for subcommand in build, configure_host:
        subcommand.add_argument(
            "--host-runner",
            action="store",
            default=default_host_runner,
            dest="host_runner",
            help="Command template for running the emscripten host"
            f"`{default_host_runner}`)",
        )

    context = parser.parse_args()

    dispatch = {
        "make-libffi": make_emscripten_libffi,
        "configure-build-python": configure_build_python,
        "make-build-python": make_build_python,
        "configure-host": configure_emscripten_python,
        "make-host": make_emscripten_python,
        "build": build_all,
        "clean": clean_contents,
    }

    if not context.subcommand:
        # No command provided, display help and exit
        print("Expected one of", ", ".join(sorted(dispatch.keys())), file=sys.stderr)
        parser.print_help(sys.stderr)
        sys.exit(1)
    dispatch[context.subcommand](context)


if __name__ == "__main__":
    main()