Added special case: empty search string for find_first() func.

Author: springcomp

jmespath/functions.py

@@ -314,6 +314,8 @@ def _func_keys(self, arg):
         {'type': 'number', 'optional': True},
         {'type': 'number', 'optional': True})
     def _func_find_first(self, text, search, start = 0, end = -1):
+        if len(search) == 0:
+            return None
         if end == -1:
             end = len(text)
         pos = text.find(search, start, end)

tests/compliance/string_functions.json

@@ -32,6 +32,7 @@
       { "expression": "find_first(string, 'string', `9`)", "result": null },
       { "expression": "find_first(string, 's')", "result": 0 },
       { "expression": "find_first(string, 's', `1`)", "result": 8 },
+      { "expression": "find_first(string, '')", "result": null },
 
       { "expression": "find_last(string, 'string')", "result": 8 },
       { "expression": "find_last(string, 'string', `8`)", "result": 8 },