From a20dc8ddfdec5e1de233f3c9c63e1dd85cdcc19d Mon Sep 17 00:00:00 2001
From: imtbkcat <songlingyu@pingcap.com>
Date: Fri, 20 Mar 2020 21:19:47 +0800
Subject: [PATCH] fix select current_role error

---
 executor/simple_test.go       | 16 ++++++++++++++++
 privilege/privileges/cache.go |  9 ++++-----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/executor/simple_test.go b/executor/simple_test.go
index 548b36d94042f..2e365de48053d 100644
--- a/executor/simple_test.go
+++ b/executor/simple_test.go
@@ -59,6 +59,22 @@ func (s *testSuite3) TestDo(c *C) {
 	tk.MustQuery("select @a").Check(testkit.Rows("1"))
 }
 
+func (s *testSuite3) TestSetRoleAllCorner(c *C) {
+	// For user with no role, `SET ROLE ALL` should active
+	// a empty slice, rather than nil.
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("create user set_role_all")
+	se, err := session.CreateSession4Test(s.store)
+	c.Check(err, IsNil)
+	defer se.Close()
+	c.Assert(se.Auth(&auth.UserIdentity{Username: "set_role_all", Hostname: "localhost"}, nil, nil), IsTrue)
+	ctx := context.Background()
+	_, err = se.Execute(ctx, `set role all`)
+	c.Assert(err, IsNil)
+	_, err = se.Execute(ctx, `select current_role`)
+	c.Assert(err, IsNil)
+}
+
 func (s *testSuite3) TestCreateRole(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("create user testCreateRole;")
diff --git a/privilege/privileges/cache.go b/privilege/privileges/cache.go
index f1110edfc5490..0d3af938f9e4a 100644
--- a/privilege/privileges/cache.go
+++ b/privilege/privileges/cache.go
@@ -1253,11 +1253,10 @@ func (p *MySQLPrivilege) getAllRoles(user, host string) []*auth.RoleIdentity {
 	key := user + "@" + host
 	edgeTable, ok := p.RoleGraph[key]
 	ret := make([]*auth.RoleIdentity, 0, len(edgeTable.roleList))
-	if !ok {
-		return nil
-	}
-	for _, r := range edgeTable.roleList {
-		ret = append(ret, r)
+	if ok {
+		for _, r := range edgeTable.roleList {
+			ret = append(ret, r)
+		}
 	}
 	return ret
 }