Detect Cython later in the build process, allowing the library to be specified...

Detect Cython later in the build process, allowing the library to be specified in setup_requires. Fixes #288.

CHANGES.txt

@@ -2,6 +2,30 @@
 CHANGES
 =======
 
+----
+18.0
+----
+
+* Dropped support for builds with Pyrex. Only Cython is supported.
+* Issue #288: Detect Cython later in the build process, after
+  ``setup_requires`` dependencies are resolved.
+  Projects backed by Cython can now be readily built
+  with a ``setup_requires`` dependency. For example::
+
+    ext = setuptools.Extension('mylib', ['src/CythonStuff.pyx', 'src/CStuff.c'])
+    setuptools.setup(
+        ...
+        ext_modules=[ext],
+        setup_requires=['cython'],
+    )
+
+  For compatibility with older versions of setuptools, packagers should
+  still include ``src/CythonMod.c`` in the source distributions or
+  require that Cython be present before building source distributions.
+  However, for systems with this build of setuptools, Cython will be
+  downloaded on demand.
+
+
 ------
 17.1.1
 ------

setuptools/command/build_ext.py

@@ -11,8 +11,8 @@ import itertools
 from setuptools.extension import Library
 
 try:
-    # Attempt to use Pyrex for building extensions, if available
-    from Pyrex.Distutils.build_ext import build_ext as _build_ext
+    # Attempt to use Cython for building extensions, if available
+    from Cython.Distutils.build_ext import build_ext as _build_ext
 except ImportError:
     _build_ext = _du_build_ext
 
@@ -42,7 +42,6 @@ elif os.name != 'nt':
 
 if_dl = lambda s: s if have_rtld else ''
 
-
 class build_ext(_build_ext):
     def run(self):
         """Build extensions in build directory, then copy if --inplace"""
@@ -74,15 +73,6 @@ class build_ext(_build_ext):
             if ext._needs_stub:
                 self.write_stub(package_dir or os.curdir, ext, True)
 
-    if _build_ext is not _du_build_ext and not hasattr(_build_ext,
-                                                       'pyrex_sources'):
-        # Workaround for problems using some Pyrex versions w/SWIG and/or 2.4
-        def swig_sources(self, sources, *otherargs):
-            # first do any Pyrex processing
-            sources = _build_ext.swig_sources(self, sources) or sources
-            # Then do any actual SWIG stuff on the remainder
-            return _du_build_ext.swig_sources(self, sources, *otherargs)
-
     def get_ext_filename(self, fullname):
         filename = _build_ext.get_ext_filename(self, fullname)
         if fullname in self.ext_map:
@@ -176,6 +166,7 @@ class build_ext(_build_ext):
         return _build_ext.get_export_symbols(self, ext)
 
     def build_extension(self, ext):
+        ext._convert_pyx_sources_to_lang()
         _compiler = self.compiler
         try:
             if isinstance(ext, Library):

setuptools/extension.py

@@ -12,35 +12,34 @@ _Extension = _get_unpatched(distutils.core.Extension)
 
 msvc9_support.patch_for_specialized_compiler()
 
-def have_pyrex():
+def _have_cython():
     """
-    Return True if Cython or Pyrex can be imported.
+    Return True if Cython can be imported.
     """
-    pyrex_impls = 'Cython.Distutils.build_ext', 'Pyrex.Distutils.build_ext'
-    for pyrex_impl in pyrex_impls:
+    cython_impls = 'Cython.Distutils.build_ext',
+    for cython_impl in cython_impls:
         try:
-            # from (pyrex_impl) import build_ext
-            __import__(pyrex_impl, fromlist=['build_ext']).build_ext
+            # from (cython_impl) import build_ext
+            __import__(cython_impl, fromlist=['build_ext']).build_ext
             return True
         except Exception:
             pass
     return False
 
+# for compatibility
+have_pyrex = _have_cython
+
 
 class Extension(_Extension):
     """Extension that uses '.c' files in place of '.pyx' files"""
 
-    def __init__(self, *args, **kw):
-        _Extension.__init__(self, *args, **kw)
-        self._convert_pyx_sources_to_lang()
-
     def _convert_pyx_sources_to_lang(self):
         """
         Replace sources with .pyx extensions to sources with the target
         language extension. This mechanism allows language authors to supply
         pre-converted sources but to prefer the .pyx sources.
         """
-        if have_pyrex():
+        if _have_cython():
             # the build has Cython, so allow it to compile the .pyx files
             return
         lang = self.language or ''