Wrap command.QueryFailureError in mongo.CommandError

GODRIVER-1141

Change-Id: Iae949cb9ced7bdaa090f84365e34a4547c037ccd

Author: Divjot Arora

mongo/collection_internal_test.go

@@ -1745,6 +1745,20 @@ func TestCollection_Find_Error(t *testing.T) {
 		require.NotNil(t, c.Err())
 		_ = c.Close(context.Background())
 	})
+
+	t.Run("error type", func(t *testing.T) {
+		coll := createTestCollection(t, nil, nil)
+		initCollection(t, coll)
+		c, err := coll.Find(ctx, bson.D{}, options.Find().SetHint("foobar"))
+		if err == nil {
+			_ = c.Close(ctx)
+			t.Fatal("expected bad hint error but got nil")
+		}
+		_, ok := err.(CommandError)
+		if !ok {
+			t.Fatalf("err type mismatch; expected CommandError, got %T", err)
+		}
+	})
 }
 
 func TestCollection_Find_NegativeLimit(t *testing.T) {

mongo/errors.go

@@ -47,6 +47,21 @@ func replaceErrors(err error) error {
 			WriteErrors:       convertBulkWriteErrors(conv.WriteErrors),
 		}
 	}
+	if qe, ok := err.(command.QueryFailureError); ok {
+		// qe.Message is "command failure"
+		ce := CommandError{Name: qe.Message}
+
+		dollarErr, err := qe.Response.LookupErr("$err")
+		if err == nil {
+			ce.Message, _ = dollarErr.StringValueOK()
+		}
+		code, err := qe.Response.LookupErr("code")
+		if err == nil {
+			ce.Code, _ = code.Int32OK()
+		}
+
+		return ce
+	}
 
 	return err
 }