refactor: try new design

cibuildwheel/__main__.py

@@ -15,7 +15,7 @@
 import cibuildwheel.windows
 from cibuildwheel.architecture import Architecture, allowed_architectures_check
 from cibuildwheel.environment import EnvironmentParseError, parse_environment
-from cibuildwheel.projectfile import NoProjectFileError, ProjectFile
+from cibuildwheel.projectfiles import ProjectFiles
 from cibuildwheel.typing import PLATFORMS, PlatformName, assert_never
 from cibuildwheel.util import (
     BuildOptions,
@@ -159,19 +159,16 @@ def main() -> None:
     test_extras = get_option_from_environment('CIBW_TEST_EXTRAS', platform=platform, default='')
     build_verbosity_str = get_option_from_environment('CIBW_BUILD_VERBOSITY', platform=platform, default='')
 
-    try:
-        project_file = ProjectFile(package_dir)
-    except NoProjectFileError as err:
-        print("cibuildwheel:", *err.args, file=sys.stderr)
+    project_files = ProjectFiles(package_dir)
+
+    if not project_files.exists():
+        print('cibuildwheel: Could not find setup.py, setup.cfg or pyproject.toml at root of package', file=sys.stderr)
         sys.exit(2)
 
-    # Passing this in as an environment variable will override pyproject.toml or setup.cfg
-    requires_python_str = get_option_from_environment('CIBW_PROJECT_REQUIRES_PYTHON', platform=platform)
+    # Passing this in as an environment variable will override pyproject.toml, setup.cfg, or setup.py
+    requires_python_str: Optional[str] = os.environ.get('CIBW_PROJECT_REQUIRES_PYTHON') or project_files.get_requires_python_str()
     requires_python = None if requires_python_str is None else SpecifierSet(requires_python_str)
 
-    if requires_python is None:
-        requires_python = project_file.get_requires_python()
-
     build_selector = BuildSelector(build_config=build_config, skip_config=skip_config, requires_python=requires_python)
     test_selector = TestSelector(skip_config=test_skip)
 
@@ -347,8 +344,6 @@ def get_build_identifiers(
                                  List[cibuildwheel.windows.PythonConfiguration],
                                  List[cibuildwheel.macos.PythonConfiguration]]
 
-    python_configurations: List[Any] = []
-
     if platform == 'linux':
         python_configurations = cibuildwheel.linux.get_python_configurations(build_selector, architectures)
     elif platform == 'windows':

cibuildwheel/projectfiles.py

@@ -0,0 +1,107 @@
+import ast
+from configparser import ConfigParser
+from pathlib import Path
+from typing import Any, Dict, Mapping, Optional
+
+import toml
+
+
+class Analyzer(ast.NodeVisitor):
+    def __init__(self) -> None:
+        self.requires_python: Optional[str] = None
+        self.constants: Dict[str, str] = {}
+
+    def visit_Assign(self, node: ast.Assign) -> None:
+        for target in node.targets:
+            if (
+                isinstance(target, ast.Name)
+                and isinstance(node.value, ast.Constant)
+                and isinstance(node.value.value, str)
+            ):
+                self.constants[target.id] = node.value.value
+
+    def visit_keyword(self, node: ast.keyword) -> None:
+        self.generic_visit(node)
+        if node.arg == "python_requires":
+            if isinstance(node.value, ast.Constant):
+                self.requires_python = node.value.value
+            elif isinstance(node.value, ast.Name):
+                self.requires_python = self.constants.get(node.value.id)
+
+
+def dig(d: Mapping[str, Any], *keys: str) -> Any:
+    """
+    Access a nested dictionary, returns None if any access is empty. Equivalent
+    to #dig in Ruby.
+    """
+
+    try:
+        for key in keys:
+            d = d[key]
+        return d
+    except (KeyError, IndexError, TypeError):
+        return None
+
+
+class ProjectFiles:
+    def __init__(self, package_dir: Path) -> None:
+        self.package_dir = package_dir
+
+    def __repr__(self) -> str:
+        return f'{self.__class__.__name__}({self.package_dir!r})'
+
+    @property
+    def setup_py_path(self) -> Path:
+        return self.package_dir / 'setup.py'
+
+    @property
+    def setup_cfg_path(self) -> Path:
+        return self.package_dir / 'setup.cfg'
+
+    @property
+    def pyproject_toml_path(self) -> Path:
+        return self.package_dir / 'pyproject.toml'
+
+    # Can cache eventually if needed more than once
+    # or just leave stateless.
+
+    @property
+    def pyproject_toml(self) -> Mapping[str, Any]:
+        try:
+            return toml.load(self.pyproject_toml_path)
+        except FileNotFoundError:
+            return {}
+
+    @property
+    def setup_cfg(self) -> Mapping[str, Any]:
+        try:
+            config = ConfigParser()
+            config.read(self.setup_cfg_path)
+            return config
+        except FileNotFoundError:
+            return {}
+
+    def _setup_py_python_requires(self) -> Optional[str]:
+        try:
+            with open(self.setup_py_path) as f:
+                tree = ast.parse(f.read())
+
+            analyzer = Analyzer()
+            analyzer.visit(tree)
+
+            return analyzer.requires_python or None
+        except Exception:
+            return None
+
+    def exists(self) -> bool:
+        "Returns True if any project file exists"
+
+        return self.pyproject_toml_path.exists() or self.setup_cfg_path.exists() or self.setup_py_path.exists()
+
+    def get_requires_python_str(self) -> Optional[str]:
+        "Return the python requires string from the most cannonical source available, or None"
+        return (
+            dig(self.pyproject_toml, 'project', 'requires-python')
+            or dig(self.setup_cfg, 'options', 'python_requires')
+            or self._setup_py_python_requires()
+        )

docs/options.md

@@ -186,7 +186,7 @@ CIBW_ARCHS_LINUX: "auto aarch64"
 
 
 ###  `CIBW_PROJECT_REQUIRES_PYTHON` {: #requires-python}
-> Limit the Python versions to build
+> Manually set the Python compatibility of your project
 
 By default, cibuildwheel reads your package's Python compatibility from
 `pyproject.toml` following [PEP621](https://www.python.org/dev/peps/pep-0621/)
@@ -213,7 +213,7 @@ Platform-specific variants also available:<br/>
 
     Example `pyproject.toml`:
 
-    ```toml
+    ~~~toml
     [project]
     requires-python = ">=3.6"
 
@@ -223,15 +223,15 @@ Platform-specific variants also available:<br/>
     [build-system]
     requires = ["setuptools>=42", "wheel"]
     build-backend = "setuptools.build_meta"
-    ```
+    ~~~
 
     If you don't want to use this yet, you can also use the currently
     recommended location for setuptools in `setup.cfg`. Example `setup.cfg`:
 
-    ```ini
+    ~~~ini
     [options]
     python_requires = ">=3.6"
-    ```
+    ~~~
 
 #### Examples
 

unit_test/main_tests/main_requires_python_test.py

@@ -80,3 +80,24 @@ def test_override_pyproject_toml(platform, monkeypatch, intercepted_build_args,
 
     assert intercepted_build_selector('cp39-win32')
     assert not intercepted_build_selector('cp36-win32')
+
+
+def test_override_setup_py_simple(platform, monkeypatch, intercepted_build_args, fake_package_dir):
+
+    fake_package_dir.joinpath("setup.py").write_text(textwrap.dedent("""
+        from setuptools import setup
+
+        setup(
+            name = "other",
+            python_requires = ">=3.7",
+        )
+    """))
+
+    main()
+
+    intercepted_build_selector = intercepted_build_args.args[0].build_selector
+
+    assert intercepted_build_selector.requires_python == SpecifierSet(">=3.7")
+
+    assert intercepted_build_selector('cp39-win32')
+    assert not intercepted_build_selector('cp36-win32')