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import importlib.util
import os
from collections import namedtuple
from typing import Any, List, Optional
from pip._vendor import tomli
from pip._vendor.packaging.requirements import InvalidRequirement, Requirement
from pip._internal.exceptions import (
InstallationError,
InvalidPyProjectBuildRequires,
MissingPyProjectBuildRequires,
)
def _is_list_of_str(obj: Any) -> bool:
return isinstance(obj, list) and all(isinstance(item, str) for item in obj)
def make_pyproject_path(unpacked_source_directory: str) -> str:
return os.path.join(unpacked_source_directory, "pyproject.toml")
BuildSystemDetails = namedtuple(
"BuildSystemDetails", ["requires", "backend", "check", "backend_path"]
)
def load_pyproject_toml(
use_pep517: Optional[bool], pyproject_toml: str, setup_py: str, req_name: str
) -> Optional[BuildSystemDetails]:
"""Load the pyproject.toml file.
Parameters:
use_pep517 - Has the user requested PEP 517 processing? None
means the user hasn't explicitly specified.
pyproject_toml - Location of the project's pyproject.toml file
setup_py - Location of the project's setup.py file
req_name - The name of the requirement we're processing (for
error reporting)
Returns:
None if we should use the legacy code path, otherwise a tuple
(
requirements from pyproject.toml,
name of PEP 517 backend,
requirements we should check are installed after setting
up the build environment
directory paths to import the backend from (backend-path),
relative to the project root.
)
"""
has_pyproject = os.path.isfile(pyproject_toml)
has_setup = os.path.isfile(setup_py)
if not has_pyproject and not has_setup:
raise InstallationError(
f"{req_name} does not appear to be a Python project: "
f"neither 'setup.py' nor 'pyproject.toml' found."
)
if has_pyproject:
with open(pyproject_toml, encoding="utf-8") as f:
pp_toml = tomli.loads(f.read())
build_system = pp_toml.get("build-system")
else:
build_system = None
# The following cases must use PEP 517
# We check for use_pep517 being non-None and falsey because that means
# the user explicitly requested --no-use-pep517. The value 0 as
# opposed to False can occur when the value is provided via an
# environment variable or config file option (due to the quirk of
# strtobool() returning an integer in pip's configuration code).
if has_pyproject and not has_setup:
if use_pep517 is not None and not use_pep517:
raise InstallationError(
"Disabling PEP 517 processing is invalid: "
"project does not have a setup.py"
)
use_pep517 = True
elif build_system and "build-backend" in build_system:
if use_pep517 is not None and not use_pep517:
raise InstallationError(
"Disabling PEP 517 processing is invalid: "
"project specifies a build backend of {} "
"in pyproject.toml".format(build_system["build-backend"])
)
use_pep517 = True
# If we haven't worked out whether to use PEP 517 yet,
# and the user hasn't explicitly stated a preference,
# we do so if the project has a pyproject.toml file
# or if we cannot import setuptools.
# We fallback to PEP 517 when without setuptools,
# so setuptools can be installed as a default build backend.
# For more info see:
# https://discuss.python.org/t/pip-without-setuptools-could-the-experience-be-improved/11810/9
elif use_pep517 is None:
use_pep517 = has_pyproject or not importlib.util.find_spec("setuptools")
# At this point, we know whether we're going to use PEP 517.
assert use_pep517 is not None
# If we're using the legacy code path, there is nothing further
# for us to do here.
if not use_pep517:
return None
if build_system is None:
# Either the user has a pyproject.toml with no build-system
# section, or the user has no pyproject.toml, but has opted in
# explicitly via --use-pep517.
# In the absence of any explicit backend specification, we
# assume the setuptools backend that most closely emulates the
# traditional direct setup.py execution, and require wheel and
# a version of setuptools that supports that backend.
build_system = {
"requires": ["setuptools>=40.8.0", "wheel"],
"build-backend": "setuptools.build_meta:__legacy__",
}
# If we're using PEP 517, we have build system information (either
# from pyproject.toml, or defaulted by the code above).
# Note that at this point, we do not know if the user has actually
# specified a backend, though.
assert build_system is not None
# Ensure that the build-system section in pyproject.toml conforms
# to PEP 518.
# Specifying the build-system table but not the requires key is invalid
if "requires" not in build_system:
raise MissingPyProjectBuildRequires(package=req_name)
# Error out if requires is not a list of strings
requires = build_system["requires"]
if not _is_list_of_str(requires):
raise InvalidPyProjectBuildRequires(
package=req_name,
reason="It is not a list of strings.",
)
# Each requirement must be valid as per PEP 508
for requirement in requires:
try:
Requirement(requirement)
except InvalidRequirement as error:
raise InvalidPyProjectBuildRequires(
package=req_name,
reason=f"It contains an invalid requirement: {requirement!r}",
) from error
backend = build_system.get("build-backend")
backend_path = build_system.get("backend-path", [])
check: List[str] = []
if backend is None:
# If the user didn't specify a backend, we assume they want to use
# the setuptools backend. But we can't be sure they have included
# a version of setuptools which supplies the backend, or wheel
# (which is needed by the backend) in their requirements. So we
# make a note to check that those requirements are present once
# we have set up the environment.
# This is quite a lot of work to check for a very specific case. But
# the problem is, that case is potentially quite common - projects that
# adopted PEP 518 early for the ability to specify requirements to
# execute setup.py, but never considered needing to mention the build
# tools themselves. The original PEP 518 code had a similar check (but
# implemented in a different way).
backend = "setuptools.build_meta:__legacy__"
check = ["setuptools>=40.8.0", "wheel"]
return BuildSystemDetails(requires, backend, check, backend_path)
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