Make GetPossibleUserByID can handle deleted user (#37430) (#37431)

Backport #37430

models/user/user.go

@@ -7,6 +7,7 @@ package user
 import (
 	"context"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"html/template"
 	"mime"
@@ -1016,17 +1017,22 @@ func GetUserByIDs(ctx context.Context, ids []int64) ([]*User, error) {
 	return users, err
 }
 
-// GetPossibleUserByID returns the user if id > 0 or returns system user if id < 0
-func GetPossibleUserByID(ctx context.Context, id int64) (*User, error) {
+// GetPossibleUserByID returns the possible user and its ID. If the user  doesn't exist, it returns Ghost user
+func GetPossibleUserByID(ctx context.Context, id int64) (_ int64, u *User, err error) {
 	if id < 0 {
 		if newFunc, ok := globalVars().systemUserNewFuncs[id]; ok {
-			return newFunc(), nil
+			u = newFunc()
 		}
-		return nil, ErrUserNotExist{UID: id}
-	} else if id == 0 {
-		return nil, ErrUserNotExist{}
 	}
-	return GetUserByID(ctx, id)
+	if u == nil {
+		u, err = GetUserByID(ctx, id)
+		if errors.Is(err, util.ErrNotExist) {
+			u = NewGhostUser()
+		} else if err != nil {
+			return 0, nil, err
+		}
+	}
+	return u.ID, u, nil
 }
 
 // GetPossibleUserByIDs returns the users if id > 0 or returns system users if id < 0

models/user/user_system_test.go

@@ -11,8 +11,9 @@ import (
 )
 
 func TestSystemUser(t *testing.T) {
-	u, err := GetPossibleUserByID(t.Context(), -1)
+	uid, u, err := GetPossibleUserByID(t.Context(), -1)
 	require.NoError(t, err)
+	assert.Equal(t, int64(-1), uid)
 	assert.Equal(t, "Ghost", u.Name)
 	assert.Equal(t, "ghost", u.LowerName)
 	assert.True(t, u.IsGhost())
@@ -21,8 +22,9 @@ func TestSystemUser(t *testing.T) {
 	require.NotNil(t, u)
 	assert.Equal(t, "Ghost", u.Name)
 
-	u, err = GetPossibleUserByID(t.Context(), -2)
+	uid, u, err = GetPossibleUserByID(t.Context(), -2)
 	require.NoError(t, err)
+	assert.Equal(t, int64(-2), uid)
 	assert.Equal(t, "gitea-actions", u.Name)
 	assert.Equal(t, "gitea-actions", u.LowerName)
 	assert.True(t, u.IsGiteaActions())
@@ -31,6 +33,8 @@ func TestSystemUser(t *testing.T) {
 	require.NotNil(t, u)
 	assert.Equal(t, "Gitea Actions", u.FullName)
 
-	_, err = GetPossibleUserByID(t.Context(), -3)
-	require.Error(t, err)
+	uid, u, err = GetPossibleUserByID(t.Context(), 999999)
+	require.NoError(t, err)
+	assert.Equal(t, int64(-1), uid)
+	assert.Equal(t, "Ghost", u.Name)
 }