Add a merge() function

This allows you to apply a base hash and merge overrides
on top of each successive hash.

Author: jamesls

jmespath/functions.py

@@ -259,6 +259,13 @@ def _func_max(self, arg):
         else:
             return None
 
+    @builtin_function({"types": ["object"], "variadic": True})
+    def _func_merge(self, *arguments):
+        merged = {}
+        for arg in arguments:
+            merged.update(arg)
+        return merged
+
     @builtin_function({"types": ['array-number', 'array-string']})
     def _func_min(self, arg):
         if arg:

tests/compliance/functions.json

@@ -239,6 +239,26 @@
       "expression": "max(empty_list)",
       "result": null
     },
+    {
+      "expression": "merge(`{}`)",
+      "result": {}
+    },
+    {
+      "expression": "merge(`{}`, `{}`)",
+      "result": {}
+    },
+    {
+      "expression": "merge(`{\"a\": 1}`, `{\"b\": 2}`)",
+      "result": {"a": 1, "b": 2}
+    },
+    {
+      "expression": "merge(`{\"a\": 1}`, `{\"a\": 2}`)",
+      "result": {"a": 2}
+    },
+    {
+      "expression": "merge(`{\"a\": 1, \"b\": 2}`, `{\"a\": 2, \"c\": 3}`, `{\"d\": 4}`)",
+      "result": {"a": 2, "b": 2, "c": 3, "d": 4}
+    },
     {
       "expression": "min(numbers)",
       "result": -1