1 files changed, 46 insertions, 37 deletions
diff --git a/setuptools/extension.py b/setuptools/extension.py
index 37b62576..d7892d3d 100644
--- a/setuptools/extension.py
+++ b/setuptools/extension.py
@@ -1,37 +1,46 @@
-from distutils.core import Extension as _Extension
-
-try:
-    from Pyrex.Distutils.build_ext import build_ext
-
-except ImportError:
-
-    # Pyrex isn't around, so fix up the sources
-
-    from dist import _get_unpatched
-    _Extension = _get_unpatched(_Extension)
-
-    class Extension(_Extension):
-
-        """Extension that uses '.c' files in place of '.pyx' files"""
-
-        def __init__(self,*args,**kw):
-            _Extension.__init__(self,*args,**kw)
-            sources = []
-            for s in self.sources:
-                if s.endswith('.pyx'):
-                    sources.append(s[:-3]+'c')
-                else:
-                    sources.append(s)
-            self.sources = sources
-
-    import sys, distutils.core, distutils.extension
-    distutils.core.Extension = Extension
-    distutils.extension.Extension = Extension
-    if 'distutils.command.build_ext' in sys.modules:
-        sys.modules['distutils.command.build_ext'].Extension = Extension
-
-else:
-
-    # Pyrex is here, just use regular extension type
-    Extension = _Extension
-
+import sys
+import distutils.core
+import distutils.extension
+
+from setuptools.dist import _get_unpatched
+
+_Extension = _get_unpatched(distutils.core.Extension)
+
+def have_pyrex():
+    """
+    Return True if Cython or Pyrex can be imported.
+    """
+    pyrex_impls = 'Cython.Distutils.build_ext', 'Pyrex.Distutils.build_ext'
+    for pyrex_impl in pyrex_impls:
+        try:
+            # from (pyrex_impl) import build_ext
+            __import__(pyrex_impl, fromlist=['build_ext']).build_ext
+            return True
+        except Exception:
+            pass
+    return False
+
+
+class Extension(_Extension):
+    """Extension that uses '.c' files in place of '.pyx' files"""
+
+    def __init__(self, *args, **kw):
+        _Extension.__init__(self, *args, **kw)
+        if not have_pyrex():
+            self._convert_pyx_sources_to_c()
+
+    def _convert_pyx_sources_to_c(self):
+        "convert .pyx extensions to .c"
+        def pyx_to_c(source):
+            if source.endswith('.pyx'):
+                source = source[:-4] + '.c'
+            return source
+        self.sources = list(map(pyx_to_c, self.sources))
+
+class Library(Extension):
+    """Just like a regular Extension, but built as a library instead"""
+
+distutils.core.Extension = Extension
+distutils.extension.Extension = Extension
+if 'distutils.command.build_ext' in sys.modules:
+    sys.modules['distutils.command.build_ext'].Extension = Extension