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qemu/python/scripts/mkvenv.py
John Snow 4695a22e9a mkvenv: add --diagnose option to explain "ensure" failures 
This is a routine that is designed to print some usable info for human
beings back out to the terminal if/when "mkvenv ensure" fails to locate
or install a package during configure time, such as meson or sphinx.

Since we are requiring that "meson" and "sphinx" are installed to the
same Python environment as QEMU is configured to build with, this can
produce some surprising failures when things are mismatched. This method
is here to try and ease that sting by offering some actionable
diagnosis.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20230511035435.734312-8-jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2023-05-18 08:53:51 +02:00

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"""
mkvenv - QEMU pyvenv bootstrapping utility
usage: mkvenv [-h] command ...
QEMU pyvenv bootstrapping utility
options:
-h, --help show this help message and exit
Commands:
command Description
create create a venv
ensure Ensure that the specified package is installed.
--------------------------------------------------
usage: mkvenv create [-h] target
positional arguments:
target Target directory to install virtual environment into.
options:
-h, --help show this help message and exit
--------------------------------------------------
usage: mkvenv ensure [-h] [--online] [--dir DIR] dep_spec...
positional arguments:
dep_spec PEP 508 Dependency specification, e.g. 'meson>=0.61.5'
options:
-h, --help show this help message and exit
--online Install packages from PyPI, if necessary.
--dir DIR Path to vendored packages where we may install from.
"""
# Copyright (C) 2022-2023 Red Hat, Inc.
#
# Authors:
# John Snow <jsnow@redhat.com>
# Paolo Bonzini <pbonzini@redhat.com>
#
# This work is licensed under the terms of the GNU GPL, version 2 or
# later. See the COPYING file in the top-level directory.
import argparse
from importlib.util import find_spec
import logging
import os
from pathlib import Path
import re
import shutil
import site
import subprocess
import sys
import sysconfig
from types import SimpleNamespace
from typing import (
Any,
Optional,
Sequence,
Tuple,
Union,
)
import venv
import warnings
import distlib.database
import distlib.version
# Do not add any mandatory dependencies from outside the stdlib:
# This script *must* be usable standalone!
DirType = Union[str, bytes, "os.PathLike[str]", "os.PathLike[bytes]"]
logger = logging.getLogger("mkvenv")
def inside_a_venv() -> bool:
"""Returns True if it is executed inside of a virtual environment."""
return sys.prefix != sys.base_prefix
class Ouch(RuntimeError):
"""An Exception class we can't confuse with a builtin."""
class QemuEnvBuilder(venv.EnvBuilder):
"""
An extension of venv.EnvBuilder for building QEMU's configure-time venv.
The primary difference is that it emulates a "nested" virtual
environment when invoked from inside of an existing virtual
environment by including packages from the parent.
Parameters for base class init:
- system_site_packages: bool = False
- clear: bool = False
- symlinks: bool = False
- upgrade: bool = False
- with_pip: bool = False
- prompt: Optional[str] = None
- upgrade_deps: bool = False (Since 3.9)
"""
def __init__(self, *args: Any, **kwargs: Any) -> None:
logger.debug("QemuEnvBuilder.__init__(...)")
# For nested venv emulation:
self.use_parent_packages = False
if inside_a_venv():
# Include parent packages only if we're in a venv and
# system_site_packages was True.
self.use_parent_packages = kwargs.pop(
"system_site_packages", False
)
# Include system_site_packages only when the parent,
# The venv we are currently in, also does so.
kwargs["system_site_packages"] = sys.base_prefix in site.PREFIXES
if kwargs.get("with_pip", False):
check_ensurepip()
super().__init__(*args, **kwargs)
# Make the context available post-creation:
self._context: Optional[SimpleNamespace] = None
def get_parent_libpath(self) -> Optional[str]:
"""Return the libpath of the parent venv, if applicable."""
if self.use_parent_packages:
return sysconfig.get_path("purelib")
return None
@staticmethod
def compute_venv_libpath(context: SimpleNamespace) -> str:
"""
Compatibility wrapper for context.lib_path for Python < 3.12
"""
# Python 3.12+, not strictly necessary because it's documented
# to be the same as 3.10 code below:
if sys.version_info >= (3, 12):
return context.lib_path
# Python 3.10+
if "venv" in sysconfig.get_scheme_names():
lib_path = sysconfig.get_path(
"purelib", scheme="venv", vars={"base": context.env_dir}
)
assert lib_path is not None
return lib_path
# For Python <= 3.9 we need to hardcode this. Fortunately the
# code below was the same in Python 3.6-3.10, so there is only
# one case.
if sys.platform == "win32":
return os.path.join(context.env_dir, "Lib", "site-packages")
return os.path.join(
context.env_dir,
"lib",
"python%d.%d" % sys.version_info[:2],
"site-packages",
)
def ensure_directories(self, env_dir: DirType) -> SimpleNamespace:
logger.debug("ensure_directories(env_dir=%s)", env_dir)
self._context = super().ensure_directories(env_dir)
return self._context
def create(self, env_dir: DirType) -> None:
logger.debug("create(env_dir=%s)", env_dir)
super().create(env_dir)
assert self._context is not None
self.post_post_setup(self._context)
def post_post_setup(self, context: SimpleNamespace) -> None:
"""
The final, final hook. Enter the venv and run commands inside of it.
"""
if self.use_parent_packages:
# We're inside of a venv and we want to include the parent
# venv's packages.
parent_libpath = self.get_parent_libpath()
assert parent_libpath is not None
logger.debug("parent_libpath: %s", parent_libpath)
our_libpath = self.compute_venv_libpath(context)
logger.debug("our_libpath: %s", our_libpath)
pth_file = os.path.join(our_libpath, "nested.pth")
with open(pth_file, "w", encoding="UTF-8") as file:
file.write(parent_libpath + os.linesep)
def get_value(self, field: str) -> str:
"""
Get a string value from the context namespace after a call to build.
For valid field names, see:
https://docs.python.org/3/library/venv.html#venv.EnvBuilder.ensure_directories
"""
ret = getattr(self._context, field)
assert isinstance(ret, str)
return ret
def check_ensurepip() -> None:
"""
Check that we have ensurepip.
Raise a fatal exception with a helpful hint if it isn't available.
"""
if not find_spec("ensurepip"):
msg = (
"Python's ensurepip module is not found.\n"
"It's normally part of the Python standard library, "
"maybe your distribution packages it separately?\n"
"Either install ensurepip, or alleviate the need for it in the "
"first place by installing pip and setuptools for "
f"'{sys.executable}'.\n"
"(Hint: Debian puts ensurepip in its python3-venv package.)"
)
raise Ouch(msg)
# ensurepip uses pyexpat, which can also go missing on us:
if not find_spec("pyexpat"):
msg = (
"Python's pyexpat module is not found.\n"
"It's normally part of the Python standard library, "
"maybe your distribution packages it separately?\n"
"Either install pyexpat, or alleviate the need for it in the "
"first place by installing pip and setuptools for "
f"'{sys.executable}'.\n\n"
"(Hint: NetBSD's pkgsrc debundles this to e.g. 'py310-expat'.)"
)
raise Ouch(msg)
def make_venv( # pylint: disable=too-many-arguments
env_dir: Union[str, Path],
system_site_packages: bool = False,
clear: bool = True,
symlinks: Optional[bool] = None,
with_pip: bool = True,
) -> None:
"""
Create a venv using `QemuEnvBuilder`.
This is analogous to the `venv.create` module-level convenience
function that is part of the Python stdblib, except it uses
`QemuEnvBuilder` instead.
:param env_dir: The directory to create/install to.
:param system_site_packages:
Allow inheriting packages from the system installation.
:param clear: When True, fully remove any prior venv and files.
:param symlinks:
Whether to use symlinks to the target interpreter or not. If
left unspecified, it will use symlinks except on Windows to
match behavior with the "venv" CLI tool.
:param with_pip:
Whether to install "pip" binaries or not.
"""
logger.debug(
"%s: make_venv(env_dir=%s, system_site_packages=%s, "
"clear=%s, symlinks=%s, with_pip=%s)",
__file__,
str(env_dir),
system_site_packages,
clear,
symlinks,
with_pip,
)
if symlinks is None:
# Default behavior of standard venv CLI
symlinks = os.name != "nt"
builder = QemuEnvBuilder(
system_site_packages=system_site_packages,
clear=clear,
symlinks=symlinks,
with_pip=with_pip,
)
style = "non-isolated" if builder.system_site_packages else "isolated"
nested = ""
if builder.use_parent_packages:
nested = f"(with packages from '{builder.get_parent_libpath()}') "
print(
f"mkvenv: Creating {style} virtual environment"
f" {nested}at '{str(env_dir)}'",
file=sys.stderr,
)
try:
logger.debug("Invoking builder.create()")
try:
builder.create(str(env_dir))
except SystemExit as exc:
# Some versions of the venv module raise SystemExit; *nasty*!
# We want the exception that prompted it. It might be a subprocess
# error that has output we *really* want to see.
logger.debug("Intercepted SystemExit from EnvBuilder.create()")
raise exc.__cause__ or exc.__context__ or exc
logger.debug("builder.create() finished")
except subprocess.CalledProcessError as exc:
logger.error("mkvenv subprocess failed:")
logger.error("cmd: %s", exc.cmd)
logger.error("returncode: %d", exc.returncode)
def _stringify(data: Union[str, bytes]) -> str:
if isinstance(data, bytes):
return data.decode()
return data
lines = []
if exc.stdout:
lines.append("========== stdout ==========")
lines.append(_stringify(exc.stdout))
lines.append("============================")
if exc.stderr:
lines.append("========== stderr ==========")
lines.append(_stringify(exc.stderr))
lines.append("============================")
if lines:
logger.error(os.linesep.join(lines))
raise Ouch("VENV creation subprocess failed.") from exc
# print the python executable to stdout for configure.
print(builder.get_value("env_exe"))
def pkgname_from_depspec(dep_spec: str) -> str:
"""
Parse package name out of a PEP-508 depspec.
See https://peps.python.org/pep-0508/#names
"""
match = re.match(
r"^([A-Z0-9]([A-Z0-9._-]*[A-Z0-9])?)", dep_spec, re.IGNORECASE
)
if not match:
raise ValueError(
f"dep_spec '{dep_spec}'"
" does not appear to contain a valid package name"
)
return match.group(0)
def diagnose(
dep_spec: str,
online: bool,
wheels_dir: Optional[Union[str, Path]],
prog: Optional[str],
) -> Tuple[str, bool]:
"""
Offer a summary to the user as to why a package failed to be installed.
:param dep_spec: The package we tried to ensure, e.g. 'meson>=0.61.5'
:param online: Did we allow PyPI access?
:param prog:
Optionally, a shell program name that can be used as a
bellwether to detect if this program is installed elsewhere on
the system. This is used to offer advice when a program is
detected for a different python version.
:param wheels_dir:
Optionally, a directory that was searched for vendored packages.
"""
# pylint: disable=too-many-branches
# Some errors are not particularly serious
bad = False
pkg_name = pkgname_from_depspec(dep_spec)
pkg_version = None
has_importlib = False
try:
# Python 3.8+ stdlib
# pylint: disable=import-outside-toplevel
# pylint: disable=no-name-in-module
# pylint: disable=import-error
from importlib.metadata import ( # type: ignore
PackageNotFoundError,
version,
)
has_importlib = True
try:
pkg_version = version(pkg_name)
except PackageNotFoundError:
pass
except ModuleNotFoundError:
pass
lines = []
if pkg_version:
lines.append(
f"Python package '{pkg_name}' version '{pkg_version}' was found,"
" but isn't suitable."
)
elif has_importlib:
lines.append(
f"Python package '{pkg_name}' was not found nor installed."
)
else:
lines.append(
f"Python package '{pkg_name}' is either not found or"
" not a suitable version."
)
if wheels_dir:
lines.append(
"No suitable version found in, or failed to install from"
f" '{wheels_dir}'."
)
bad = True
if online:
lines.append("A suitable version could not be obtained from PyPI.")
bad = True
else:
lines.append(
"mkvenv was configured to operate offline and did not check PyPI."
)
if prog and not pkg_version:
which = shutil.which(prog)
if which:
if sys.base_prefix in site.PREFIXES:
pypath = Path(sys.executable).resolve()
lines.append(
f"'{prog}' was detected on your system at '{which}', "
f"but the Python package '{pkg_name}' was not found by "
f"this Python interpreter ('{pypath}'). "
f"Typically this means that '{prog}' has been installed "
"against a different Python interpreter on your system."
)
else:
lines.append(
f"'{prog}' was detected on your system at '{which}', "
"but the build is using an isolated virtual environment."
)
bad = True
lines = [f" • {line}" for line in lines]
if bad:
lines.insert(0, f"Could not provide build dependency '{dep_spec}':")
else:
lines.insert(0, f"'{dep_spec}' not found:")
return os.linesep.join(lines), bad
def pip_install(
args: Sequence[str],
online: bool = False,
wheels_dir: Optional[Union[str, Path]] = None,
) -> None:
"""
Use pip to install a package or package(s) as specified in @args.
"""
loud = bool(
os.environ.get("DEBUG")
or os.environ.get("GITLAB_CI")
or os.environ.get("V")
)
full_args = [
sys.executable,
"-m",
"pip",
"install",
"--disable-pip-version-check",
"-v" if loud else "-q",
]
if not online:
full_args += ["--no-index"]
if wheels_dir:
full_args += ["--find-links", f"file://{str(wheels_dir)}"]
full_args += list(args)
subprocess.run(
full_args,
check=True,
)
def _do_ensure(
dep_specs: Sequence[str],
online: bool = False,
wheels_dir: Optional[Union[str, Path]] = None,
) -> None:
"""
Use pip to ensure we have the package specified by @dep_specs.
If the package is already installed, do nothing. If online and
wheels_dir are both provided, prefer packages found in wheels_dir
first before connecting to PyPI.
:param dep_specs:
PEP 508 dependency specifications. e.g. ['meson>=0.61.5'].
:param online: If True, fall back to PyPI.
:param wheels_dir: If specified, search this path for packages.
"""
with warnings.catch_warnings():
warnings.filterwarnings(
"ignore", category=UserWarning, module="distlib"
)
dist_path = distlib.database.DistributionPath(include_egg=True)
absent = []
for spec in dep_specs:
matcher = distlib.version.LegacyMatcher(spec)
dist = dist_path.get_distribution(matcher.name)
if dist is None or not matcher.match(dist.version):
absent.append(spec)
else:
logger.info("found %s", dist)
if absent:
# Some packages are missing or aren't a suitable version,
# install a suitable (possibly vendored) package.
print(f"mkvenv: installing {', '.join(absent)}", file=sys.stderr)
pip_install(args=absent, online=online, wheels_dir=wheels_dir)
def ensure(
dep_specs: Sequence[str],
online: bool = False,
wheels_dir: Optional[Union[str, Path]] = None,
prog: Optional[str] = None,
) -> None:
"""
Use pip to ensure we have the package specified by @dep_specs.
If the package is already installed, do nothing. If online and
wheels_dir are both provided, prefer packages found in wheels_dir
first before connecting to PyPI.
:param dep_specs:
PEP 508 dependency specifications. e.g. ['meson>=0.61.5'].
:param online: If True, fall back to PyPI.
:param wheels_dir: If specified, search this path for packages.
:param prog:
If specified, use this program name for error diagnostics that will
be presented to the user. e.g., 'sphinx-build' can be used as a
bellwether for the presence of 'sphinx'.
"""
print(f"mkvenv: checking for {', '.join(dep_specs)}", file=sys.stderr)
try:
_do_ensure(dep_specs, online, wheels_dir)
except subprocess.CalledProcessError as exc:
# Well, that's not good.
msg, bad = diagnose(dep_specs[0], online, wheels_dir, prog)
if bad:
raise Ouch(msg) from exc
raise SystemExit(f"\n{msg}\n\n") from exc
def _add_create_subcommand(subparsers: Any) -> None:
subparser = subparsers.add_parser("create", help="create a venv")
subparser.add_argument(
"target",
type=str,
action="store",
help="Target directory to install virtual environment into.",
)
def _add_ensure_subcommand(subparsers: Any) -> None:
subparser = subparsers.add_parser(
"ensure", help="Ensure that the specified package is installed."
)
subparser.add_argument(
"--online",
action="store_true",
help="Install packages from PyPI, if necessary.",
)
subparser.add_argument(
"--dir",
type=str,
action="store",
help="Path to vendored packages where we may install from.",
)
subparser.add_argument(
"--diagnose",
type=str,
action="store",
help=(
"Name of a shell utility to use for "
"diagnostics if this command fails."
),
)
subparser.add_argument(
"dep_specs",
type=str,
action="store",
help="PEP 508 Dependency specification, e.g. 'meson>=0.61.5'",
nargs="+",
)
def main() -> int:
"""CLI interface to make_qemu_venv. See module docstring."""
if os.environ.get("DEBUG") or os.environ.get("GITLAB_CI"):
# You're welcome.
logging.basicConfig(level=logging.DEBUG)
else:
if os.environ.get("V"):
logging.basicConfig(level=logging.INFO)
# These are incredibly noisy even for V=1
logging.getLogger("distlib.metadata").addFilter(lambda record: False)
logging.getLogger("distlib.database").addFilter(lambda record: False)
parser = argparse.ArgumentParser(
prog="mkvenv",
description="QEMU pyvenv bootstrapping utility",
)
subparsers = parser.add_subparsers(
title="Commands",
dest="command",
metavar="command",
help="Description",
)
_add_create_subcommand(subparsers)
_add_ensure_subcommand(subparsers)
args = parser.parse_args()
try:
if args.command == "create":
make_venv(
args.target,
system_site_packages=True,
clear=True,
)
if args.command == "ensure":
ensure(
dep_specs=args.dep_specs,
online=args.online,
wheels_dir=args.dir,
prog=args.diagnose,
)
logger.debug("mkvenv.py %s: exiting", args.command)
except Ouch as exc:
print("\n*** Ouch! ***\n", file=sys.stderr)
print(str(exc), "\n\n", file=sys.stderr)
return 1
except SystemExit:
raise
except: # pylint: disable=bare-except
logger.exception("mkvenv did not complete successfully:")
return 2
return 0
if __name__ == "__main__":
sys.exit(main())
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