gh-71052: Add Android build script and instructions (#116426)

Android/android.py

@@ -0,0 +1,202 @@
+#!/usr/bin/env python3
+
+import argparse
+import os
+import re
+import shutil
+import subprocess
+import sys
+import sysconfig
+from os.path import relpath
+from pathlib import Path
+
+SCRIPT_NAME = Path(__file__).name
+CHECKOUT = Path(__file__).resolve().parent.parent
+CROSS_BUILD_DIR = CHECKOUT / "cross-build"
+
+
+def delete_if_exists(path):
+    if path.exists():
+        print(f"Deleting {path} ...")
+        shutil.rmtree(path)
+
+
+def subdir(name, *, clean=None):
+    path = CROSS_BUILD_DIR / name
+    if clean:
+        delete_if_exists(path)
+    if not path.exists():
+        if clean is None:
+            sys.exit(
+                f"{path} does not exist. Create it by running the appropriate "
+                f"`configure` subcommand of {SCRIPT_NAME}.")
+        else:
+            path.mkdir(parents=True)
+    return path
+
+
+def run(command, *, host=None, **kwargs):
+    env = os.environ.copy()
+    if host:
+        env_script = CHECKOUT / "Android/android-env.sh"
+        env_output = subprocess.run(
+            f"set -eu; "
+            f"HOST={host}; "
+            f"PREFIX={subdir(host)}/prefix; "
+            f". {env_script}; "
+            f"export",
+            check=True, shell=True, text=True, stdout=subprocess.PIPE
+        ).stdout
+
+        for line in env_output.splitlines():
+            # We don't require every line to match, as there may be some other
+            # output from installing the NDK.
+            if match := re.search(
+                "^(declare -x |export )?(\\w+)=['\"]?(.*?)['\"]?$", line
+            ):
+                key, value = match[2], match[3]
+                if env.get(key) != value:
+                    print(line)
+                    env[key] = value
+
+        if env == os.environ:
+            raise ValueError(f"Found no variables in {env_script.name} output:\n"
+                             + env_output)
+
+    print(">", " ".join(map(str, command)))
+    try:
+        subprocess.run(command, check=True, env=env, **kwargs)
+    except subprocess.CalledProcessError as e:
+        sys.exit(e)
+
+
+def build_python_path():
+    """The path to the build Python binary."""
+    build_dir = subdir("build")
+    binary = 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"{build_dir}")
+
+    return binary
+
+
+def configure_build_python(context):
+    os.chdir(subdir("build", clean=context.clean))
+
+    command = [relpath(CHECKOUT / "configure")]
+    if context.args:
+        command.extend(context.args)
+    run(command)
+
+
+def make_build_python(context):
+    os.chdir(subdir("build"))
+    run(["make", "-j", str(os.cpu_count())])
+
+
+def unpack_deps(host):
+    deps_url = "https://github.com/beeware/cpython-android-source-deps/releases/download"
+    for name_ver in ["bzip2-1.0.8-1", "libffi-3.4.4-2", "openssl-3.0.13-1",
+                     "sqlite-3.45.1-0", "xz-5.4.6-0"]:
+        filename = f"{name_ver}-{host}.tar.gz"
+        run(["wget", f"{deps_url}/{name_ver}/{filename}"])
+        run(["tar", "-xf", filename])
+        os.remove(filename)
+
+
+def configure_host_python(context):
+    host_dir = subdir(context.host, clean=context.clean)
+
+    prefix_dir = host_dir / "prefix"
+    if not prefix_dir.exists():
+        prefix_dir.mkdir()
+        os.chdir(prefix_dir)
+        unpack_deps(context.host)
+
+    build_dir = host_dir / "build"
+    build_dir.mkdir(exist_ok=True)
+    os.chdir(build_dir)
+
+    command = [
+        # Basic cross-compiling configuration
+        relpath(CHECKOUT / "configure"),
+        f"--host={context.host}",
+        f"--build={sysconfig.get_config_var('BUILD_GNU_TYPE')}",
+        f"--with-build-python={build_python_path()}",
+        "--without-ensurepip",
+
+        # Android always uses a shared libpython.
+        "--enable-shared",
+        "--without-static-libpython",
+
+        # Dependent libraries. The others are found using pkg-config: see
+        # android-env.sh.
+        f"--with-openssl={prefix_dir}",
+    ]
+
+    if context.args:
+        command.extend(context.args)
+    run(command, host=context.host)
+
+
+def make_host_python(context):
+    host_dir = subdir(context.host)
+    os.chdir(host_dir / "build")
+    run(["make", "-j", str(os.cpu_count())], host=context.host)
+    run(["make", "install", f"prefix={host_dir}/prefix"], host=context.host)
+
+
+def build_all(context):
+    steps = [configure_build_python, make_build_python, configure_host_python,
+             make_host_python]
+    for step in steps:
+        step(context)
+
+
+def clean_all(context):
+    delete_if_exists(CROSS_BUILD_DIR)
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    subcommands = parser.add_subparsers(dest="subcommand")
+    build = subcommands.add_parser("build", help="Build everything")
+    configure_build = subcommands.add_parser("configure-build",
+                                             help="Run `configure` for the "
+                                             "build Python")
+    make_build = subcommands.add_parser("make-build",
+                                        help="Run `make` for the build Python")
+    configure_host = subcommands.add_parser("configure-host",
+                                            help="Run `configure` for Android")
+    make_host = subcommands.add_parser("make-host",
+                                       help="Run `make` for Android")
+    clean = subcommands.add_parser("clean", help="Delete files and directories "
+                                                 "created by this script")
+    for subcommand in build, 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_host, make_host:
+        subcommand.add_argument(
+            "host", metavar="HOST",
+            choices=["aarch64-linux-android", "x86_64-linux-android"],
+            help="Host triplet: choices=[%(choices)s]")
+    for subcommand in build, configure_build, configure_host:
+        subcommand.add_argument("args", nargs="*",
+                                help="Extra arguments to pass to `configure`")
+
+    context = parser.parse_args()
+    dispatch = {"configure-build": configure_build_python,
+                "make-build": make_build_python,
+                "configure-host": configure_host_python,
+                "make-host": make_host_python,
+                "build": build_all,
+                "clean": clean_all}
+    dispatch[context.subcommand](context)
+
+
+if __name__ == "__main__":
+    main()