Do not search sys.path for .pxd file if no explicit "cimport" is given

CHANGES.rst

@@ -91,6 +91,9 @@ Bugs fixed
 
 * C unions use a saner way to coerce from and to Python dicts.
 
+* When compiling a module ``foo.pyx``, the directories in ``sys.path``
+  are no longer searched when looking for ``foo.pxd``.
+
 Other changes
 -------------
 

Cython/Compiler/Main.py

@@ -187,20 +187,25 @@ class Context(object):
         if not scope.pxd_file_loaded:
             if debug_find_module:
                 print("...pxd not loaded")
-            scope.pxd_file_loaded = 1
             if not pxd_pathname:
                 if debug_find_module:
                     print("...looking for pxd file")
-                pxd_pathname = self.find_pxd_file(qualified_name, pos)
+                # Only look in sys.path if we are explicitly looking
+                # for a .pxd file.
+                pxd_pathname = self.find_pxd_file(qualified_name, pos, sys_path=need_pxd)
                 if debug_find_module:
                     print("......found %s" % pxd_pathname)
                 if not pxd_pathname and need_pxd:
+                    # Set pxd_file_loaded such that we don't need to
+                    # look for the non-existing pxd file next time.
+                    scope.pxd_file_loaded = True
                     package_pathname = self.search_include_directories(qualified_name, ".py", pos)
                     if package_pathname and package_pathname.endswith('__init__.py'):
                         pass
                     else:
                         error(pos, "'%s.pxd' not found" % qualified_name.replace('.', os.sep))
             if pxd_pathname:
+                scope.pxd_file_loaded = True
                 try:
                     if debug_find_module:
                         print("Context.find_module: Parsing %s" % pxd_pathname)
@@ -217,15 +222,16 @@ class Context(object):
                     pass
         return scope
 
-    def find_pxd_file(self, qualified_name, pos):
-        # Search include path for the .pxd file corresponding to the
-        # given fully-qualified module name.
+    def find_pxd_file(self, qualified_name, pos, sys_path=True):
+        # Search include path (and sys.path if sys_path is True) for
+        # the .pxd file corresponding to the given fully-qualified
+        # module name.
         # Will find either a dotted filename or a file in a
         # package directory. If a source file position is given,
         # the directory containing the source file is searched first
         # for a dotted filename, and its containing package root
         # directory is searched first for a non-dotted filename.
-        pxd = self.search_include_directories(qualified_name, ".pxd", pos, sys_path=True)
+        pxd = self.search_include_directories(qualified_name, ".pxd", pos, sys_path=sys_path)
         if pxd is None: # XXX Keep this until Includes/Deprecated is removed
             if (qualified_name.startswith('python') or
                 qualified_name in ('stdlib', 'stdio', 'stl')):

docs/src/userguide/sharing_declarations.rst

@@ -123,12 +123,15 @@ Search paths for definition files
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 When you :keyword:`cimport` a module called ``modulename``, the Cython
-compiler searches for a file called :file:`modulename.pxd` along the search
-path for include files, as specified by ``-I`` command line options.
+compiler searches for a file called :file:`modulename.pxd`.
+It searches for this file along the path for include files
+(as specified by ``-I`` command line options or the ``include_path``
+option to ``cythonize()``), as well as ``sys.path``.
 
 Also, whenever you compile a file :file:`modulename.pyx`, the corresponding
-definition file :file:`modulename.pxd` is first searched for along the same
-path, and if found, it is processed before processing the ``.pyx`` file.  
+definition file :file:`modulename.pxd` is first searched for along the
+include path (but not ``sys.path``), and if found, it is processed before
+processing the ``.pyx`` file.
 
 
 Using cimport to resolve naming conflicts 

tests/compile/find_pxd.srctree

+PYTHON setup.py build_ext --inplace
+
+######## setup.py ########
+
+from Cython.Build import cythonize
+from Cython.Distutils.extension import Extension
+
+import sys
+sys.path.append("path")
+
+ext_modules = [
+    Extension("a", ["a.pyx"]),
+    Extension("b", ["b.pyx"]),
+    Extension("c", ["c.pyx"]),
+]
+
+ext_modules = cythonize(ext_modules, include_path=["include"])
+
+
+######## a.pyx ########
+# Implicit cimport looking in include_path
+cdef my_type foo
+
+######## include/a.pxd ########
+ctypedef int my_type
+
+######## b.pyx ########
+# Explicit cimport looking in sys.path
+from b cimport *
+cdef my_type foo
+
+######## path/b.pxd ########
+ctypedef int my_type
+
+######## c.pyx ########
+# Implicit cimport NOT looking in sys.path
+
+######## path/c.pxd ########
++++syntax error just to show that this file is not actually cimported+++