rust/hgcli/pyoxidizer.bzl

pyoxidizer: produce working Python 3 Windows installers (issue6366)

While we've had code to produce Python 3 Windows installers with
PyOxidizer, we haven't been advertising them on the web site due to
a bug in making TLS connections and issues around resource handling.

This commit upgrades our PyOxidizer install and configuration to
use a recent Git commit of PyOxidizer. This new version of PyOxidizer
contains a *ton* of changes, improvements, and bug fixes. Notably,
Windows shared distributions now mostly "just work" and the TLS bug
and random problems with Python extension modules in the standard
library go away. And Python has been upgraded from 3.7 to 3.8.6.

The price we pay for this upgrade is a ton of backwards incompatible
changes to Starlark.

I applied this commit (the overall series actually) on stable to
produce Windows installers for Mercurial 5.5.2, which I published
shortly before submitting this commit for review.

In order to get the stable branch working, I decided to take a
less aggressive approach to Python resource management. Previously,
we were attempting to load all Python modules from memory and were
performing some hacks to copy Mercurial's non-module resources
into additional directories in Starlark. This commit implements
a resource callback function in Starlark (a new feature since
PyOxidizer 0.7) to dynamically assign standard library resources
to in-memory loading and all other resources to filesystem loading.
This means that Mercurial's files and all the other packages we ship
in the Windows installers (e.g. certifi and pygments) are loaded
from the filesystem instead of from memory. This avoids issues
due to lack of __file__ and enables us to ship a working Python
3 installer on Windows.

The end state of the install layout after this patch is not
ideal for @: we still copy resource files like templates and
help text to directories next to the hg.exe executable. There
is code in @ to use importlib.resources to load these files and
we could likely remove these copies once this lands on @. But for
now, the install layout mimics what we've shipped for seemingly
forever and is backwards compatible. It allows us to achieve the
milestone of working Python 3 Windows installers and gets us a
giant step closer to deleting Python 2.

Differential Revision: https://phab.mercurial-scm.org/D9148

ROOT = CWD + "/../.."

IS_WINDOWS = "windows" in BUILD_TARGET_TRIPLE

# Code to run in Python interpreter.
RUN_CODE = "import hgdemandimport; hgdemandimport.enable(); from mercurial import dispatch; dispatch.run()"

set_build_path(ROOT + "/build/pyoxidizer")

def make_distribution():
    return default_python_distribution()

def make_distribution_windows():
    return default_python_distribution(flavor = "standalone_dynamic")

def resource_callback(policy, resource):
    # We use a custom resource routing policy to influence where things are loaded
    # from.
    #
    # For Python modules and resources, we load from memory if they are in
    # the standard library and from the filesystem if not. This is because
    # parts of Mercurial and some 3rd party packages aren't yet compatible
    # with memory loading.
    #
    # For Python extension modules, we load from the filesystem because
    # this yields greatest compatibility.
    if type(resource) in ("PythonModuleSource", "PythonPackageResource", "PythonPackageDistributionResource"):
        if resource.is_stdlib:
            resource.add_location = "in-memory"
        else:
            resource.add_location = "filesystem-relative:lib"

    elif type(resource) == "PythonExtensionModule":
        resource.add_location = "filesystem-relative:lib"

def make_exe(dist):
    """Builds a Rust-wrapped Mercurial binary."""
    packaging_policy = dist.make_python_packaging_policy()
    # Extension may depend on any Python functionality. Include all
    # extensions.
    packaging_policy.extension_module_filter = "all"
    packaging_policy.resources_policy = "prefer-in-memory-fallback-filesystem-relative:lib"
    packaging_policy.register_resource_callback(resource_callback)

    config = PythonInterpreterConfig(
        raw_allocator = "system",
        run_eval = RUN_CODE,
        # We want to let the user load extensions from the file system
        filesystem_importer = True,
        # We need this to make resourceutil happy, since it looks for sys.frozen.
        sys_frozen = True,
        legacy_windows_stdio = True,
    )

    exe = dist.to_python_executable(
        name = "hg",
        packaging_policy = packaging_policy,
        config = config,
    )

    # Add Mercurial to resources.
    exe.add_python_resources(exe.pip_install(["--verbose", ROOT]))

    # On Windows, we install extra packages for convenience.
    if IS_WINDOWS:
        exe.add_python_resources(
            exe.pip_install(["-r", ROOT + "/contrib/packaging/requirements_win32.txt"]),
        )

    return exe

def make_manifest(dist, exe):
    m = FileManifest()
    m.add_python_resource(".", exe)

    return m

def make_embedded_resources(exe):
    return exe.to_embedded_resources()

register_target("distribution_posix", make_distribution)
register_target("distribution_windows", make_distribution_windows)

register_target("exe_posix", make_exe, depends = ["distribution_posix"])
register_target("exe_windows", make_exe, depends = ["distribution_windows"])

register_target(
    "app_posix",
    make_manifest,
    depends = ["distribution_posix", "exe_posix"],
    default = "windows" not in BUILD_TARGET_TRIPLE,
)
register_target(
    "app_windows",
    make_manifest,
    depends = ["distribution_windows", "exe_windows"],
    default = "windows" in BUILD_TARGET_TRIPLE,
)

resolve_targets()

# END OF COMMON USER-ADJUSTED SETTINGS.
#
# Everything below this is typically managed by PyOxidizer and doesn't need
# to be updated by people.

PYOXIDIZER_VERSION = "0.8.0-pre"
PYOXIDIZER_COMMIT = "4697fb25918dfad6dc73288daeea501063963a08"