Mango $allMatch return false for empty list (#511)

The $allMatch selector returns false for a document with an empty list

2 files changed, 16 insertions, 4 deletions

diff --git a/src/mango/src/mango_selector.erl b/src/mango/src/mango_selector.erl
index 691aac7ed..13e7d883b 100644
--- a/src/mango/src/mango_selector.erl
+++ b/src/mango/src/mango_selector.erl
@@ -461,7 +461,7 @@ match({[{<<"$elemMatch">>, _Arg}]}, _Value, _Cmp) ->
 
 % Matches when all elements in values match the
 % sub-selector Arg.
-match({[{<<"$allMatch">>, Arg}]}, Values, Cmp) when is_list(Values) ->
+match({[{<<"$allMatch">>, Arg}]}, Values, Cmp) when is_list(Values), length(Values) > 0 ->
     try
         lists:foreach(fun(V) ->
             case match(Arg, V, Cmp) of
diff --git a/src/mango/test/03-operator-test.py b/src/mango/test/03-operator-test.py
index 56c286227..edfd95f4d 100644
--- a/src/mango/test/03-operator-test.py
+++ b/src/mango/test/03-operator-test.py
@@ -20,7 +20,6 @@ class OperatorTests(mango.UserDocsTests):
                 "manager": True,
                 "favorites": {"$all": ["Lisp", "Python"]}
             })
-        print docs
         assert len(docs) == 4
         assert docs[0]["user_id"] == 2
         assert docs[1]["user_id"] == 12
@@ -59,7 +58,6 @@ class OperatorTests(mango.UserDocsTests):
                 "bam": True
             }}
         })
-        print docs
         assert len(docs) == 1
         assert docs[0]["user_id"] == "b"
 
@@ -94,7 +92,6 @@ class OperatorTests(mango.UserDocsTests):
         ]
         self.db.save_docs(amdocs, w=3)
         docs = self.db.find({
-            "_id": {"$gt": None},
             "bang": {"$allMatch": {
                 "foo": {"$mod": [2,1]},
                 "bar": {"$mod": [2,0]}
@@ -102,6 +99,21 @@ class OperatorTests(mango.UserDocsTests):
         })
         assert len(docs) == 1
         assert docs[0]["user_id"] == "a"
+    
+    def test_empty_all_match(self):
+        amdocs = [
+            {
+                "bad_doc": "a",
+                "emptybang": []
+            }
+        ]
+        self.db.save_docs(amdocs, w=3)
+        docs = self.db.find({
+            "emptybang": {"$allMatch": {
+                "foo": {"$eq": 2}
+            }}
+        })
+        assert len(docs) == 0
 
     def test_in_operator_array(self):
         docs = self.db.find({