add support for $ in quoted string

gql/parser.go

@@ -474,6 +474,9 @@ func substituteVariablesFilter(f *FilterTree, vmap varMap) error {
 		}
 
 		for idx, v := range f.Func.Args {
+			if !v.IsGraphQLVar {
+				continue
+			}
 			if f.Func.Name == uidFunc {
 				// This is to support GraphQL variables in uid functions.
 				idVal, ok := vmap[v.Value]

gql/parser_test.go

@@ -5136,3 +5136,62 @@ func TestParseExpandFilterErr(t *testing.T) {
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "expand is only compatible with type filters")
 }
+
+func TestFilterWithDollar(t *testing.T) {
+	query := `
+	{
+		q(func: eq(name, "Bob"), first:5) @filter(eq(description, "$yo")) {
+		  name
+		  description
+		}
+	  }
+	`
+	gq, err := Parse(Request{
+		Str: query,
+	})
+	require.NoError(t, err)
+	require.Equal(t, gq.Query[0].Filter.Func.Args[0].Value, "$yo")
+}
+
+func TestFilterWithDollarError(t *testing.T) {
+	query := `
+	{
+		q(func: eq(name, "Bob"), first:5) @filter(eq(description, $yo)) {
+		  name
+		  description
+		}
+	  }
+	`
+	_, err := Parse(Request{
+		Str: query,
+	})
+	require.Error(t, err)
+}
+
+func TestFilterWithVar(t *testing.T) {
+	query := `query data($a: string = "dgraph")
+	{
+		data(func: eq(name, "Bob"), first:5) @filter(eq(description, $a)) {
+			name
+			description
+		  }
+	}`
+	gq, err := Parse(Request{
+		Str: query,
+	})
+	require.NoError(t, err)
+	require.Equal(t, gq.Query[0].Filter.Func.Args[0].Value, "dgraph")
+}
+
+func TestFilterWithEmpty(t *testing.T) {
+	query := `{
+		names(func: has(name)) @filter(eq(name, "")) {
+		  count(uid)
+		}
+	  }`
+	gq, err := Parse(Request{
+		Str: query,
+	})
+	require.NoError(t, err)
+	require.Equal(t, gq.Query[0].Filter.Func.Args[0].Value, "")
+}