setup.py: run cython if core.c is out of date

setup.py

@@ -46,13 +46,31 @@ libraries = []
 extra_objects = []
 
 
-# hack: create a symlink from build/../core.so to gevent/core.so to prevent "ImportError: cannot import name core" failures
 cmdclass = {}
-try:
-    from distutils.command import build_ext
-    class my_build_ext(build_ext.build_ext):
+class my_build_ext(build_ext.build_ext):
+
+    def compile_cython(self):
+        sources = glob.glob('gevent/*.pyx') + sorted(glob.glob('gevent/*.pxi'))
+        if not sources:
+            print >> sys.stderr, 'Could not find gevent.core sources'
+            return
+        core_c_mtime = os.stat('gevent/core.c').st_mtime
+        changed = [filename for filename in sources if os.stat(filename).st_mtime >= core_c_mtime]
+        if changed:
+            print >> sys.stderr, 'Running cython (changed: %s)' % ', '.join(changed)
+            cython_result = os.system('cython gevent/core.pyx')
+            if cython_result:
+                if os.system('cython -V 2> %s' % os.devnull):
+                    # there's no cython in the system
+                    print >> sys.stderr, 'No cython found, cannot rebuild core.c'
+                    return
+                sys.exit(1)
+
     def build_extension(self, ext):
+        self.compile_cython()
         result = build_ext.build_ext.build_extension(self, ext)
+        # hack: create a symlink from build/../core.so to gevent/core.so
+        # to prevent "ImportError: cannot import name core" failures
         try:
             fullname = self.get_ext_fullname(ext.name)
             modpath = fullname.split('.')
@@ -63,22 +81,22 @@ try:
                 path_to_build_core_so = abspath(os.path.join(self.build_lib, filename))
                 path_to_core_so = abspath(join('gevent', basename(path_to_build_core_so)))
                 if path_to_build_core_so != path_to_core_so:
-                        print 'Linking %s to %s' % (path_to_build_core_so, path_to_core_so)
                     try:
                         os.unlink(path_to_core_so)
                     except OSError:
                         pass
                     if hasattr(os, 'symlink'):
+                        print 'Linking %s to %s' % (path_to_build_core_so, path_to_core_so)
                         os.symlink(path_to_build_core_so, path_to_core_so)
                     else:
+                        print 'Copying %s to %s' % (path_to_build_core_so, path_to_core_so)
                         import shutil
                         shutil.copyfile(path_to_build_core_so, path_to_core_so)
         except Exception:
             traceback.print_exc()
         return result
-    cmdclass = {'build_ext': my_build_ext}
-except Exception:
-    traceback.print_exc()
+
+cmdclass = {'build_ext': my_build_ext}
 
 
 def check_dir(path, must_exist):