support build script

docs/docs/pyproject.md

@@ -94,3 +94,29 @@ format of `[tool.pdm.cli]` format:
 [tool.pdm.entry_points.pytest11]
 myplugin = "mypackage.plugin:pytest_plugin"
 ```
+
+## Build C extensions
+
+Currently building C extensions still rely on `setuptools`. You should write a python script which contains
+a function named `build` and accepts the arguments dictionary of `setup()` as the only parameter.
+In the function, update the dictionary with your `ext_modules` settings.
+
+Here is an example taken from `MarkupSafe`:
+
+```python
+# build.py
+from setuptools import Extension
+
+ext_modules = [Extension("markupsafe._speedups", ["src/markupsafe/_speedups.c"])]
+
+def build(setup_kwargs):
+    setup_kwargs.update(ext_modules=ext_modules)
+```
+
+Now, specify the build script path via `build` in the `pyproject.toml`:
+
+```toml
+# pyproject.toml
+[tool.pdm]
+build = "build.py"
+```

news/23.feature

+Support specifying build script for C extensions.

pdm/builders/base.py

@@ -195,6 +195,9 @@ class Builder:
         if not include_build:
             return
 
+        if self.meta.build and os.path.isfile(self.meta.build):
+            yield self.meta.build
+
         for pat in ("COPYING", "LICENSE"):
             for path in glob.glob(pat + "*"):
                 if os.path.isfile(path):
@@ -229,6 +232,16 @@ class Builder:
             "url": meta.homepage,
         }
 
+        if meta.build:
+            # The build script must contain a `build(setup_kwargs)`, we just import
+            # and execute it.
+            after.extend(
+                [
+                    "from {} import build\n".format(meta.build.split(".")[0]),
+                    "build(setup_kwargs)\n",
+                ]
+            )
+
         package_paths = meta.convert_package_paths()
         if package_paths["packages"]:
             extra.append("    'packages': {!r},\n".format(package_paths["packages"]))

pdm/builders/wheel.py

@@ -4,6 +4,7 @@ import hashlib
 import os
 import shutil
 import stat
+import subprocess
 import tempfile
 import zipfile
 from base64 import urlsafe_b64encode
@@ -178,7 +179,30 @@ class WheelBuilder(Builder):
         if not self.meta.build:
             return
         self.ensure_setup_py()
-        # TODO: C extension build
+        setup_py = self.ireq.setup_py_path
+        build_args = [
+            self.project.environment.python_executable,
+            setup_py,
+            "build",
+            "-b",
+            str(self.project.root / "build"),
+        ]
+        subprocess.run(
+            build_args, capture_output=stream.verbosity >= stream.DETAIL, check=True
+        )
+        build_dir = self.project.root / "build"
+        lib_dir = next(build_dir.glob("lib.*"), None)
+        if not lib_dir:
+            return
+        for pkg in lib_dir.glob("**/*"):
+            if pkg.is_dir():
+                continue
+
+            rel_path = str(pkg.relative_to(lib_dir))
+
+            if rel_path in wheel.namelist():
+                continue
+            self._add_file(wheel, pkg, rel_path)
 
     def _copy_module(self, wheel):
         for path in self.find_files_to_add():