Fix problems with default value in order clause

When there's a default value specified on the order clause on a
Keypath that is also part of the return value with a different
default value, then the returned results were wrong. It was sorted
by the return value default, not by the order clause default.

This fixes #53.

Author: vmx

repl-tests/order.noise

@@ -0,0 +1,74 @@
+# order expressions.
+
+drop target/tests/querytestorder;
+create target/tests/querytestorder;
+
+add {"_id":"1", "bar": false};
+"1"
+add {"_id":"2", "bar": true};
+"2"
+add {"_id":"3", "bar": "string"};
+"3"
+add {"_id":"4"};
+"4"
+
+find {}
+order .bar asc
+return .bar;
+[
+null,
+false,
+true,
+"string"
+]
+
+find {}
+order .bar default=1 asc
+return .bar default=1;
+[
+false,
+true,
+1,
+"string"
+]
+
+find {}
+order .bar default=1 asc
+return .bar;
+[
+false,
+true,
+null,
+"string"
+]
+
+
+find {}
+order .bar asc
+return ._id;
+[
+"4",
+"1",
+"2",
+"3"
+]
+
+find {}
+order .bar default=1 asc
+return ._id;
+[
+"1",
+"2",
+"4",
+"3"
+]
+
+find {}
+order .bar asc
+return .bar default=1;
+[
+1,
+false,
+true,
+"string"
+]

src/returnable.rs

@@ -312,7 +312,19 @@ impl Returnable for RetValue {
     }
 
     fn take_order_for_matching_fields(&mut self, map: &mut HashMap<String, OrderInfo>) {
-        self.order_info = map.remove(&self.rp.to_key());
+        // Compare the default values of the to be removed order info with the default value for
+        // the return value. If they are equal, the order can be safely removed, as the ordering
+        // of the result will be the same.
+        // If they are not equal, then we need to keep the order else the final result would be
+        // sorted by the values of the result and not of the orde clause.
+        let keypath = &self.rp.to_key();
+        let remove_order = match map.get(keypath) {
+            Some(order_info) => order_info.default == self.default,
+            None => false,
+        };
+        if remove_order {
+            self.order_info = map.remove(keypath);
+        }
     }
 
     fn get_ordering(&mut self, orders: &mut Vec<Option<OrderInfo>>) {