Support GraphQL vars in first, offset and after at root.

Author: Pawan Rawal

gql/parser.go

@@ -2186,7 +2186,16 @@ func getRoot(it *lex.ItemIterator) (gq *GraphQuery, rerr error) {
 			}
 			item := it.Item()
 
-			if item.Typ == itemMathOp {
+			if item.Typ == itemDollar {
+				it.Next()
+				item = it.Item()
+				if item.Typ == itemName {
+					val = fmt.Sprintf("$%s", item.Val)
+				} else {
+					return nil, x.Errorf("Expecting a variable name. Got: %v", item)
+				}
+				goto ASSIGN
+			} else if item.Typ == itemMathOp {
 				if item.Val != "+" && item.Val != "-" {
 					return nil,
 						x.Errorf("Only Plus and minus are allowed unary ops. Got: %v",
@@ -2247,6 +2256,7 @@ func getRoot(it *lex.ItemIterator) (gq *GraphQuery, rerr error) {
 				continue
 			}
 
+		ASSIGN:
 			if _, ok := gq.Args[key]; ok {
 				return gq, x.Errorf("Repeated key %q at root", key)
 			}

gql/parser_test.go

@@ -4186,3 +4186,67 @@ func TestParseMissingGraphQLVar(t *testing.T) {
 		require.Error(t, err)
 	}
 }
+
+func TestParseGraphQLVarPaginationRoot(t *testing.T) {
+	for _, q := range []string{
+		"query test($a: int = 2){ q(func: uid(0x1), first: $a) { name }}",
+		"query test($a: int = 2){ q(func: uid(0x1), offset: $a) { name }}",
+		"query test($a: int = 2){ q(func: uid(0x1), orderdesc: name, first: $a) { name }}",
+		"query test($a: int = 2){ q(func: uid(0x1), orderdesc: name, offset: $a) { name }}",
+		"query test($a: int = 2){ q(func: eq(name, \"abc\"), orderdesc: name, first: $a) { name }}",
+		"query test($a: int = 2){ q(func: eq(name, \"abc\"), orderdesc: name, offset: $a) { name }}",
+	} {
+		r := Request{
+			Str:       q,
+			Variables: map[string]string{"$a": "3"},
+		}
+		gq, err := Parse(r)
+		t.Log(q)
+		t.Log(err)
+		require.NoError(t, err)
+		args := gq.Query[0].Args
+		require.True(t, args["first"] == "3" || args["offset"] == "3")
+	}
+}
+
+func TestParseGraphQLVarPaginationChild(t *testing.T) {
+	for _, q := range []string{
+		"query test($a: int = 2){ q(func: uid(0x1)) { friend(first: $a) }}",
+		"query test($a: int = 2){ q(func: uid(0x1)) { friend(offset: $a) }}",
+		"query test($a: int = 2){ q(func: uid(0x1), orderdesc: name) { friend(first: $a) }}",
+		"query test($a: int = 2){ q(func: uid(0x1), orderdesc: name) { friend(offset: $a) }}",
+		"query test($a: int = 2){ q(func: eq(name, \"abc\"), orderdesc: name) { friend(first: $a) }}",
+		"query test($a: int = 2){ q(func: eq(name, \"abc\"), orderdesc: name) { friend(offset: $a) }}",
+	} {
+		r := Request{
+			Str:       q,
+			Variables: map[string]string{"$a": "3"},
+		}
+		gq, err := Parse(r)
+		t.Log(q)
+		t.Log(err)
+		require.NoError(t, err)
+		args := gq.Query[0].Children[0].Args
+		require.True(t, args["first"] == "3" || args["offset"] == "3")
+	}
+}
+
+func TestParseGraphQLVarPaginationRootMultiple(t *testing.T) {
+	q := `query test($a: int, $b: int, $after: string){
+		q(func: uid(0x1), first: $a, offset: $b, after: $after, orderasc: name) {
+			friend
+		}
+	}`
+
+	r := Request{
+		Str:       q,
+		Variables: map[string]string{"$a": "3", "$b": "5", "$after": "0x123"},
+	}
+	gq, err := Parse(r)
+	require.NoError(t, err)
+	args := gq.Query[0].Args
+	require.Equal(t, args["first"], "3")
+	require.Equal(t, args["offset"], "5")
+	require.Equal(t, args["after"], "0x123")
+	require.Equal(t, gq.Query[0].Order[0].Attr, "name")
+}