Protect against NPEs in notifications list (#10879) (#10883)

* Protect against NPEs in notifications list (#10879)

Unfortunately there appears to be potential race with notifications
being set before the associated issue has been committed.

This PR adds protection in to the notifications list to log any failures
and remove these notifications from the display.

References #10815 - and prevents the panic but does not completely fix
this.

Signed-off-by: Andrew Thornton <art27@cantab.net>

* add log import

* Update models/notification.go

Co-Authored-By: Lauris BH <lauris@nix.lv>

Co-authored-by: Lauris BH <lauris@nix.lv>

models/notification.go

 import (
 	"fmt"
 
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/timeutil"
 )
 
 }
 
 // LoadRepos loads repositories from database
-func (nl NotificationList) LoadRepos() (RepositoryList, error) {
+func (nl NotificationList) LoadRepos() (RepositoryList, []int, error) {
 	if len(nl) == 0 {
-		return RepositoryList{}, nil
+		return RepositoryList{}, []int{}, nil
 	}
 
 	var repoIDs = nl.getPendingRepoIDs()
 			In("id", repoIDs[:limit]).
 			Rows(new(Repository))
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 
 		for rows.Next() {
 			err = rows.Scan(&repo)
 			if err != nil {
 				rows.Close()
-				return nil, err
+				return nil, nil, err
 			}
 
 			repos[repo.ID] = &repo
 		repoIDs = repoIDs[limit:]
 	}
 
+	failed := []int{}
+
 	var reposList = make(RepositoryList, 0, len(repoIDs))
-	for _, notification := range nl {
+	for i, notification := range nl {
 		if notification.Repository == nil {
 			notification.Repository = repos[notification.RepoID]
 		}
+		if notification.Repository == nil {
+			log.Error("Notification[%d]: RepoID: %d not found", notification.ID, notification.RepoID)
+			failed = append(failed, i)
+			continue
+		}
 		var found bool
 		for _, r := range reposList {
-			if r.ID == notification.Repository.ID {
+			if r.ID == notification.RepoID {
 				found = true
 				break
 			}
 			reposList = append(reposList, notification.Repository)
 		}
 	}
-	return reposList, nil
+	return reposList, failed, nil
 }
 
 func (nl NotificationList) getPendingIssueIDs() []int64 {
 }
 
 // LoadIssues loads issues from database
-func (nl NotificationList) LoadIssues() error {
+func (nl NotificationList) LoadIssues() ([]int, error) {
 	if len(nl) == 0 {
-		return nil
+		return []int{}, nil
 	}
 
 	var issueIDs = nl.getPendingIssueIDs()
 			In("id", issueIDs[:limit]).
 			Rows(new(Issue))
 		if err != nil {
-			return err
+			return nil, err
 		}
 
 		for rows.Next() {
 			err = rows.Scan(&issue)
 			if err != nil {
 				rows.Close()
-				return err
+				return nil, err
 			}
 
 			issues[issue.ID] = &issue
 		issueIDs = issueIDs[limit:]
 	}
 
-	for _, notification := range nl {
+	failures := []int{}
+
+	for i, notification := range nl {
 		if notification.Issue == nil {
 			notification.Issue = issues[notification.IssueID]
+			if notification.Issue == nil {
+				log.Error("Notification[%d]: IssueID: %d Not Found", notification.ID, notification.IssueID)
+				failures = append(failures, i)
+				continue
+			}
 			notification.Issue.Repo = notification.Repository
 		}
 	}
-	return nil
+	return failures, nil
+}
+
+// Without returns the notification list without the failures
+func (nl NotificationList) Without(failures []int) NotificationList {
+	if len(failures) == 0 {
+		return nl
+	}
+	remaining := make([]*Notification, 0, len(nl))
+	last := -1
+	var i int
+	for _, i = range failures {
+		remaining = append(remaining, nl[last+1:i]...)
+		last = i
+	}
+	if len(nl) > i {
+		remaining = append(remaining, nl[i+1:]...)
+	}
+	return remaining
 }
 
 func (nl NotificationList) getPendingCommentIDs() []int64 {
 }
 
 // LoadComments loads comments from database
-func (nl NotificationList) LoadComments() error {
+func (nl NotificationList) LoadComments() ([]int, error) {
 	if len(nl) == 0 {
-		return nil
+		return []int{}, nil
 	}
 
 	var commentIDs = nl.getPendingCommentIDs()
 			In("id", commentIDs[:limit]).
 			Rows(new(Comment))
 		if err != nil {
-			return err
+			return nil, err
 		}
 
 		for rows.Next() {
 			err = rows.Scan(&comment)
 			if err != nil {
 				rows.Close()
-				return err
+				return nil, err
 			}
 
 			comments[comment.ID] = &comment
 		commentIDs = commentIDs[limit:]
 	}
 
-	for _, notification := range nl {
+	failures := []int{}
+	for i, notification := range nl {
 		if notification.CommentID > 0 && notification.Comment == nil && comments[notification.CommentID] != nil {
 			notification.Comment = comments[notification.CommentID]
+			if notification.Comment == nil {
+				log.Error("Notification[%d]: CommentID[%d] failed to load", notification.ID, notification.CommentID)
+				failures = append(failures, i)
+				continue
+			}
 			notification.Comment.Issue = notification.Issue
 		}
 	}
-	return nil
+	return failures, nil
 }
 
 // GetNotificationCount returns the notification count for user

routers/user/notification.go

 		return
 	}
 
-	repos, err := notifications.LoadRepos()
+	failCount := 0
+
+	repos, failures, err := notifications.LoadRepos()
 	if err != nil {
 		c.ServerError("LoadRepos", err)
 		return
 	}
+	notifications = notifications.Without(failures)
 	if err := repos.LoadAttributes(); err != nil {
 		c.ServerError("LoadAttributes", err)
 		return
 	}
+	failCount += len(failures)
 
-	if err := notifications.LoadIssues(); err != nil {
+	failures, err = notifications.LoadIssues()
+	if err != nil {
 		c.ServerError("LoadIssues", err)
 		return
 	}
-	if err := notifications.LoadComments(); err != nil {
+	notifications = notifications.Without(failures)
+	failCount += len(failures)
+
+	failures, err = notifications.LoadComments()
+	if err != nil {
 		c.ServerError("LoadComments", err)
 		return
 	}
+	notifications = notifications.Without(failures)
+	failCount += len(failures)
+
+	if failCount > 0 {
+		c.Flash.Error(fmt.Sprintf("ERROR: %d notifications were removed due to missing parts - check the logs", failCount))
+	}
 
 	total, err := models.GetNotificationCount(c.User, status)
 	if err != nil {