From 45c283f2a704d6179dae7ae385966f8dc92c6f0d Mon Sep 17 00:00:00 2001
From: Vikram Rangnekar <vicram@gmail.com>
Date: Sun, 16 Jun 2019 15:41:28 -0400
Subject: [PATCH] Fix bug #676 found by fuzzer

---
 qcode/parse_test.go | 11 ++++++++++-
 qcode/qcode.go      | 11 +++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/qcode/parse_test.go b/qcode/parse_test.go
index 3fef81c..6edd9ca 100644
--- a/qcode/parse_test.go
+++ b/qcode/parse_test.go
@@ -59,7 +59,7 @@ func TestCompile(t *testing.T) {
 	}
 }
 
-func TestInvalidCompile(t *testing.T) {
+func TestInvalidCompile1(t *testing.T) {
 	qcompile, _ := NewCompiler(Config{})
 	_, err := qcompile.CompileQuery([]byte(`#`))
 
@@ -68,6 +68,15 @@ func TestInvalidCompile(t *testing.T) {
 	}
 }
 
+func TestInvalidCompile2(t *testing.T) {
+	qcompile, _ := NewCompiler(Config{})
+	_, err := qcompile.CompileQuery([]byte(`{u(where:{not:0})}`))
+
+	if err == nil {
+		t.Fatal(errors.New("expecting an error"))
+	}
+}
+
 func TestEmptyCompile(t *testing.T) {
 	qcompile, _ := NewCompiler(Config{})
 	_, err := qcompile.CompileQuery([]byte(``))
diff --git a/qcode/qcode.go b/qcode/qcode.go
index 731c0aa..d61519d 100644
--- a/qcode/qcode.go
+++ b/qcode/qcode.go
@@ -419,6 +419,7 @@ func (com *Compiler) compileArgNode(node *Node, usePool bool) (*Exp, error) {
 			return nil, fmt.Errorf("16: unexpected value %v (%t)", intf, intf)
 		}
 
+		// Objects inside a list
 		if len(node.Name) == 0 {
 			pushChildren(st, node.exp, node)
 			continue
@@ -686,12 +687,21 @@ func newExp(st *util.Stack, node *Node, usePool bool) (*Exp, error) {
 
 	switch name {
 	case "and":
+		if len(node.Children) == 0 {
+			return nil, errors.New("missing expression after 'AND' operator")
+		}
 		ex.Op = OpAnd
 		pushChildren(st, ex, node)
 	case "or":
+		if len(node.Children) == 0 {
+			return nil, errors.New("missing expression after 'OR' operator")
+		}
 		ex.Op = OpOr
 		pushChildren(st, ex, node)
 	case "not":
+		if len(node.Children) == 0 {
+			return nil, errors.New("missing expression after 'NOT' operator")
+		}
 		ex.Op = OpNot
 		pushChild(st, ex, node)
 	case "eq", "equals":
@@ -848,6 +858,7 @@ func pushChildren(st *util.Stack, exp *Exp, node *Node) {
 func pushChild(st *util.Stack, exp *Exp, node *Node) {
 	node.Children[0].exp = exp
 	st.Push(node.Children[0])
+
 }
 
 func compileFilter(filter []string) (*Exp, error) {