Fix deleted milestone bug (#1942) (#2300)

* Fix deleted milestone bug

* Use locale for ghost milestone name

* Fix pointer bug

models/issue_comment.go

@@ -231,12 +231,9 @@ func (c *Comment) LoadMilestone() error {
 		has, err := x.ID(c.OldMilestoneID).Get(&oldMilestone)
 		if err != nil {
 			return err
-		} else if !has {
-			return ErrMilestoneNotExist{
-				ID: c.OldMilestoneID,
-			}
+		} else if has {
+			c.OldMilestone = &oldMilestone
 		}
-		c.OldMilestone = &oldMilestone
 	}
 
 	if c.MilestoneID > 0 {
@@ -244,12 +241,9 @@ func (c *Comment) LoadMilestone() error {
 		has, err := x.ID(c.MilestoneID).Get(&milestone)
 		if err != nil {
 			return err
-		} else if !has {
-			return ErrMilestoneNotExist{
-				ID: c.MilestoneID,
-			}
+		} else if has {
+			c.Milestone = &milestone
 		}
-		c.Milestone = &milestone
 	}
 	return nil
 }

options/locale/locale_en-US.ini

@@ -558,6 +558,7 @@ issues.remove_label_at = `removed the <div class="ui label" style="color: %s; ba
 issues.add_milestone_at = `added this to the <b>%s</b> milestone %s`
 issues.change_milestone_at = `modified the milestone from <b>%s</b> to <b>%s</b> %s`
 issues.remove_milestone_at = `removed this from the <b>%s</b> milestone %s`
+issues.deleted_milestone = `(deleted)`
 issues.self_assign_at = `self-assigned this %s`
 issues.add_assignee_at = `was assigned by <b>%s</b> %s`
 issues.remove_assignee_at = `removed their assignment %s`

routers/repo/issue.go

@@ -596,6 +596,16 @@ func ViewIssue(ctx *context.Context) {
 				ctx.Handle(500, "LoadMilestone", err)
 				return
 			}
+			ghostMilestone := &models.Milestone{
+				ID:   -1,
+				Name: ctx.Tr("repo.issues.deleted_milestone"),
+			}
+			if comment.OldMilestoneID > 0 && comment.OldMilestone == nil {
+				comment.OldMilestone = ghostMilestone
+			}
+			if comment.MilestoneID > 0 && comment.Milestone == nil {
+				comment.Milestone = ghostMilestone
+			}
 		} else if comment.Type == models.CommentTypeAssignees {
 			if err = comment.LoadAssignees(); err != nil {
 				ctx.Handle(500, "LoadAssignees", err)