Fix bug in mongoQueryToFilter

lib/mongodb-functions.ts

@@ -522,9 +522,12 @@ export function mongoQueryToFilter(query): Expression {
           }
           exps.push([op, ["PARAM", k], vv]);
         }
-        if (exps.length === 1) return exps[0];
+        if (exps.length === 1) {
-        const and: Expression = ["AND"];
+          expressions.push(exps[0]);
-        expressions.push(and.concat(exps));
+        } else {
+          const and: Expression = ["AND"];
+          expressions.push(and.concat(exps));
+        }
       } else {
         expressions.push(["=", ["PARAM", k], v]);
       }

test/mongodb-functions.ts

@@ -32,6 +32,10 @@ ava("mongoQueryToFilter", t => {
     [
       { test: { $gte: "test1", $ne: "test2" } },
       'test >= "test1" AND test <> "test2"'
+    ],
+    [
+      { test: "test", test2: { $ne: "test2" } },
+      'test = "test" AND test2 <> "test2"'
     ]
   ];