Merge branch 'fix-custom-functions' into develop

* fix-custom-functions:
  Always create a new copy of the function table

Author: jamesls

CHANGELOG.rst

@@ -6,6 +6,9 @@ Next Release (TBD)
   (`issue 125 <https://github.com/jmespath/jmespath.py/issues/125>`__)
 * Handle numbers in scientific notation in ``to_number()`` function
   (`issue 120 <https://github.com/jmespath/jmespath.py/issues/120>`__)
+* Fix issue where custom functions would override the function table
+  of the builtin function class
+  (`issue 133 <https://github.com/jmespath/jmespath.py/issues/133>`__)
 
 
 0.9.2

jmespath/functions.py

@@ -47,7 +47,7 @@ def __init__(cls, name, bases, attrs):
         super(FunctionRegistry, cls).__init__(name, bases, attrs)
 
     def _populate_function_table(cls):
-        function_table = getattr(cls, 'FUNCTION_TABLE', {})
+        function_table = {}
         # Any method with a @signature decorator that also
         # starts with "_func_" is registered as a function.
         # _func_max_by -> max_by function.

tests/test_search.py

@@ -38,6 +38,12 @@ def _func_my_subtract(self, x, y):
             jmespath.search('my_subtract(`10`, `3`)', {}, options=options),
             7
         )
+        # Should still be able to use the original functions without
+        # any interference from the CustomFunctions class.
+        self.assertEqual(
+            jmespath.search('length(`[1, 2]`)', {}), 2
+        )
+
 
 
 class TestPythonSpecificCases(unittest.TestCase):