work around inability to detect existing Python globals (e.g. from imports)...

work around inability to detect existing Python globals (e.g. from imports) when cpdef-ing global functions

Cython/Compiler/ParseTreeTransforms.py

@@ -1997,6 +1997,7 @@ class AdjustDefByDirectives(CythonTransform, SkipDeclarations):
         self.in_py_class = old_in_pyclass
         return node
 
+
 class AlignFunctionDefinitions(CythonTransform):
     """
     This class takes the signatures from a .pxd file and applies them to
@@ -2006,6 +2007,7 @@ class AlignFunctionDefinitions(CythonTransform):
     def visit_ModuleNode(self, node):
         self.scope = node.scope
         self.directives = node.directives
+        self.imported_names = set()  # hack, see visit_FromImportStatNode()
         self.visitchildren(node)
         return node
 
@@ -2042,12 +2044,23 @@ class AlignFunctionDefinitions(CythonTransform):
                 return None
             node = node.as_cfunction(pxd_def)
         elif (self.scope.is_module_scope and self.directives['auto_cpdef']
+              and not node.name in self.imported_names
               and node.is_cdef_func_compatible()):
+            # FIXME: cpdef-ing should be done in analyse_declarations()
             node = node.as_cfunction(scope=self.scope)
         # Enable this when nested cdef functions are allowed.
         # self.visitchildren(node)
         return node
 
+    def visit_FromImportStatNode(self, node):
+        # hack to prevent conditional import fallback functions from
+        # being cdpef-ed (global Python variables currently conflict
+        # with imports)
+        if self.scope.is_module_scope:
+            for name, _ in node.items:
+                self.imported_names.add(name)
+        return node
+
     def visit_ExprNode(self, node):
         # ignore lambdas and everything else that appears in expressions
         return node

tests/run/auto_cpdef.py

@@ -45,3 +45,32 @@ def test_lambda():
     >>> l(1)
     1
     """
+
+
+# test classical import fallbacks
+try:
+    from math import fabs
+except ImportError:
+    def fabs(x):
+        if x < 0:
+            return -x
+        else:
+            return x
+
+try:
+    from math import no_such_function
+except ImportError:
+    def no_such_function(x):
+        return x + 1.0
+
+
+def test_import_fallback():
+    """
+    >>> fabs(1.0)
+    1.0
+    >>> no_such_function(1.0)
+    2.0
+    >>> test_import_fallback()
+    (1.0, 2.0)
+    """
+    return fabs(1.0), no_such_function(1.0)