Prepare setup.py/.cfg for additional import-time dependencies

Reading the version number using attr: rsrcfork.__version__ will no
longer work properly if rsrcfork has non-stdlib dependencies at import
time, because setuptools needs to be able to import rsrcfork and read
the version number before the dependencies are installed.

As a workaround, our setup.py now manually parses the version number
from rsrcfork/__init__.py using the ast module.
This commit is contained in:
dgelessus 2020-04-03 22:31:23 +02:00
parent f7b6080c0e
commit 7c77c4ef20
2 changed files with 42 additions and 2 deletions

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@ -1,6 +1,12 @@
[metadata] [metadata]
name = rsrcfork name = rsrcfork
version = attr: rsrcfork.__version__ # The version is defined in setup.py,
# which extracts the value of the __version__ attribute from rsrcfork/__init__.py,
# so that the version number/string is only explicitly written in a single place.
# We cannot use "version = attr: rsrcfork.__version__" here,
# because the attr directive needs to import the module to read its attributes,
# which won't work if any of the module's import-time dependencies are not installed yet
# (as is usually the case when setup.cfg is first evaluated before installation).
url = https://github.com/dgelessus/python-rsrcfork url = https://github.com/dgelessus/python-rsrcfork
author = dgelessus author = dgelessus
classifiers = classifiers =

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@ -1,5 +1,39 @@
#!/usr/bin/env python3 #!/usr/bin/env python3
import ast
import setuptools import setuptools
setuptools.setup()
def attr(file, name):
"""Read the constant value of a global variable from a Python file without importing/executing it.
The variable in question must be assigned a constant literal
(as understood by :func:`ast.literal_eval`)
in a simple assignment.
The variable *should* only be assigned once
(later assignments are silently ignored).
Based on https://github.com/pypa/setuptools/issues/1960#issue-547330414.
"""
with open(file, "rb") as f:
module = ast.parse(f.read())
for node in ast.iter_child_nodes(module):
if (
isinstance(node, ast.Assign)
and len(node.targets) == 1
and isinstance(node.targets[0], ast.Name)
and node.targets[0].id == name
):
return ast.literal_eval(node.value)
else:
raise ValueError(f"No simple assignment of variable {name!r} found in {file!r}")
setuptools.setup(
# Read the version number from the module source code without importing or executing it.
# This is necessary because at the time that setup.py is executed,
# the dependencies necessary to import rsrcfork may not be installed yet.
version=attr("rsrcfork/__init__.py", "__version__"),
)