Multiple assignees (#3705)

22 files changed, 699 insertions, 255 deletions

diff --git a/models/error.go b/models/error.go
index d24da2642e..cdb18d23ce 100644
--- a/models/error.go
+++ b/models/error.go
@@ -733,6 +733,22 @@ func (err ErrRepoFileAlreadyExist) Error() string {
 	return fmt.Sprintf("repository file already exists [file_name: %s]", err.FileName)
 }
 
+// ErrUserDoesNotHaveAccessToRepo represets an error where the user doesn't has access to a given repo
+type ErrUserDoesNotHaveAccessToRepo struct {
+	UserID   int64
+	RepoName string
+}
+
+// IsErrUserDoesNotHaveAccessToRepo checks if an error is a ErrRepoFileAlreadyExist.
+func IsErrUserDoesNotHaveAccessToRepo(err error) bool {
+	_, ok := err.(ErrUserDoesNotHaveAccessToRepo)
+	return ok
+}
+
+func (err ErrUserDoesNotHaveAccessToRepo) Error() string {
+	return fmt.Sprintf("user doesn't have acces to repo [user_id: %d, repo_name: %s]", err.UserID, err.RepoName)
+}
+
 // __________                             .__
 // \______   \____________    ____   ____ |  |__
 //  |    |  _/\_  __ \__  \  /    \_/ ___\|  |  \
diff --git a/models/fixtures/issue.yml b/models/fixtures/issue.yml
index ff514e706c..4de8c4fa7e 100644
--- a/models/fixtures/issue.yml
+++ b/models/fixtures/issue.yml
@@ -3,7 +3,6 @@
   repo_id: 1
   index: 1
   poster_id: 1
-  assignee_id: 1
   name: issue1
   content: content for the first issue
   is_closed: false
@@ -67,7 +66,6 @@
   repo_id: 3
   index: 1
   poster_id: 1
-  assignee_id: 1
   name: issue6
   content: content6
   is_closed: false
diff --git a/models/fixtures/issue_assignees.yml b/models/fixtures/issue_assignees.yml
new file mode 100644
index 0000000000..1be07df7d4
--- /dev/null
+++ b/models/fixtures/issue_assignees.yml
@@ -0,0 +1,8 @@
+-
+  id: 1
+  assignee_id: 1
+  issue_id: 1
+-
+  id: 2
+  assignee_id: 1
+  issue_id: 6
diff --git a/models/fixtures/issue_user.yml b/models/fixtures/issue_user.yml
index b3f98a71d3..8039b1e40f 100644
--- a/models/fixtures/issue_user.yml
+++ b/models/fixtures/issue_user.yml
@@ -3,7 +3,6 @@
   uid: 1
   issue_id: 1
   is_read: true
-  is_assigned: true
   is_mentioned: false
 
 -
@@ -11,7 +10,6 @@
   uid: 2
   issue_id: 1
   is_read: true
-  is_assigned: false
   is_mentioned: false
 
 -
@@ -19,5 +17,4 @@
   uid: 4
   issue_id: 1
   is_read: false
-  is_assigned: false
   is_mentioned: false
diff --git a/models/issue.go b/models/issue.go
index 7f83d59842..ad354cc34e 100644
--- a/models/issue.go
+++ b/models/issue.go
@@ -37,7 +37,7 @@ type Issue struct {
 	MilestoneID     int64       `xorm:"INDEX"`
 	Milestone       *Milestone  `xorm:"-"`
 	Priority        int
-	AssigneeID      int64        `xorm:"INDEX"`
+	AssigneeID      int64        `xorm:"-"`
 	Assignee        *User        `xorm:"-"`
 	IsClosed        bool         `xorm:"INDEX"`
 	IsRead          bool         `xorm:"-"`
@@ -56,6 +56,7 @@ type Issue struct {
 	Comments         []*Comment    `xorm:"-"`
 	Reactions        ReactionList  `xorm:"-"`
 	TotalTrackedTime int64         `xorm:"-"`
+	Assignees        []*User       `xorm:"-"`
 }
 
 var (
@@ -140,22 +141,6 @@ func (issue *Issue) loadPoster(e Engine) (err error) {
 	return
 }
 
-func (issue *Issue) loadAssignee(e Engine) (err error) {
-	if issue.Assignee == nil && issue.AssigneeID > 0 {
-		issue.Assignee, err = getUserByID(e, issue.AssigneeID)
-		if err != nil {
-			issue.AssigneeID = -1
-			issue.Assignee = NewGhostUser()
-			if !IsErrUserNotExist(err) {
-				return fmt.Errorf("getUserByID.(assignee) [%d]: %v", issue.AssigneeID, err)
-			}
-			err = nil
-			return
-		}
-	}
-	return
-}
-
 func (issue *Issue) loadPullRequest(e Engine) (err error) {
 	if issue.IsPull && issue.PullRequest == nil {
 		issue.PullRequest, err = getPullRequestByIssueID(e, issue.ID)
@@ -231,7 +216,7 @@ func (issue *Issue) loadAttributes(e Engine) (err error) {
 		}
 	}
 
-	if err = issue.loadAssignee(e); err != nil {
+	if err = issue.loadAssignees(e); err != nil {
 		return
 	}
 
@@ -343,8 +328,11 @@ func (issue *Issue) APIFormat() *api.Issue {
 	if issue.Milestone != nil {
 		apiIssue.Milestone = issue.Milestone.APIFormat()
 	}
-	if issue.Assignee != nil {
-		apiIssue.Assignee = issue.Assignee.APIFormat()
+	if len(issue.Assignees) > 0 {
+		for _, assignee := range issue.Assignees {
+			apiIssue.Assignees = append(apiIssue.Assignees, assignee.APIFormat())
+		}
+		apiIssue.Assignee = issue.Assignees[0].APIFormat() // For compatibility, we're keeping the first assignee as `apiIssue.Assignee`
 	}
 	if issue.IsPull {
 		apiIssue.PullRequest = &api.PullRequestMeta{
@@ -605,19 +593,6 @@ func (issue *Issue) ReplaceLabels(labels []*Label, doer *User) (err error) {
 	return sess.Commit()
 }
 
-// GetAssignee sets the Assignee attribute of this issue.
-func (issue *Issue) GetAssignee() (err error) {
-	if issue.AssigneeID == 0 || issue.Assignee != nil {
-		return nil
-	}
-
-	issue.Assignee, err = GetUserByID(issue.AssigneeID)
-	if IsErrUserNotExist(err) {
-		return nil
-	}
-	return err
-}
-
 // ReadBy sets issue to be read by given user.
 func (issue *Issue) ReadBy(userID int64) error {
 	if err := UpdateIssueUserByRead(userID, issue.ID); err != nil {
@@ -823,55 +798,6 @@ func (issue *Issue) ChangeContent(doer *User, content string) (err error) {
 	return nil
 }
 
-// ChangeAssignee changes the Assignee field of this issue.
-func (issue *Issue) ChangeAssignee(doer *User, assigneeID int64) (err error) {
-	var oldAssigneeID = issue.AssigneeID
-	issue.AssigneeID = assigneeID
-	if err = UpdateIssueUserByAssignee(issue); err != nil {
-		return fmt.Errorf("UpdateIssueUserByAssignee: %v", err)
-	}
-
-	sess := x.NewSession()
-	defer sess.Close()
-
-	if err = issue.loadRepo(sess); err != nil {
-		return fmt.Errorf("loadRepo: %v", err)
-	}
-
-	if _, err = createAssigneeComment(sess, doer, issue.Repo, issue, oldAssigneeID, assigneeID); err != nil {
-		return fmt.Errorf("createAssigneeComment: %v", err)
-	}
-
-	issue.Assignee, err = GetUserByID(issue.AssigneeID)
-	if err != nil && !IsErrUserNotExist(err) {
-		log.Error(4, "GetUserByID [assignee_id: %v]: %v", issue.AssigneeID, err)
-		return nil
-	}
-
-	// Error not nil here means user does not exist, which is remove assignee.
-	isRemoveAssignee := err != nil
-	if issue.IsPull {
-		issue.PullRequest.Issue = issue
-		apiPullRequest := &api.PullRequestPayload{
-			Index:       issue.Index,
-			PullRequest: issue.PullRequest.APIFormat(),
-			Repository:  issue.Repo.APIFormat(AccessModeNone),
-			Sender:      doer.APIFormat(),
-		}
-		if isRemoveAssignee {
-			apiPullRequest.Action = api.HookIssueUnassigned
-		} else {
-			apiPullRequest.Action = api.HookIssueAssigned
-		}
-		if err := PrepareWebhooks(issue.Repo, HookEventPullRequest, apiPullRequest); err != nil {
-			log.Error(4, "PrepareWebhooks [is_pull: %v, remove_assignee: %v]: %v", issue.IsPull, isRemoveAssignee, err)
-			return nil
-		}
-	}
-	go HookQueue.Add(issue.RepoID)
-	return nil
-}
-
 // GetTasks returns the amount of tasks in the issues content
 func (issue *Issue) GetTasks() int {
 	return len(issueTasksPat.FindAllStringIndex(issue.Content, -1))
@@ -887,6 +813,7 @@ type NewIssueOptions struct {
 	Repo        *Repository
 	Issue       *Issue
 	LabelIDs    []int64
+	AssigneeIDs []int64
 	Attachments []string // In UUID format.
 	IsPull      bool
 }
@@ -909,14 +836,32 @@ func newIssue(e *xorm.Session, doer *User, opts NewIssueOptions) (err error) {
 		}
 	}
 
-	if assigneeID := opts.Issue.AssigneeID; assigneeID > 0 {
-		valid, err := hasAccess(e, assigneeID, opts.Repo, AccessModeWrite)
-		if err != nil {
-			return fmt.Errorf("hasAccess [user_id: %d, repo_id: %d]: %v", assigneeID, opts.Repo.ID, err)
+	// Keep the old assignee id thingy for compatibility reasons
+	if opts.Issue.AssigneeID > 0 {
+		isAdded := false
+		// Check if the user has already been passed to issue.AssigneeIDs, if not, add it
+		for _, aID := range opts.AssigneeIDs {
+			if aID == opts.Issue.AssigneeID {
+				isAdded = true
+				break
+			}
 		}
-		if !valid {
-			opts.Issue.AssigneeID = 0
-			opts.Issue.Assignee = nil
+
+		if !isAdded {
+			opts.AssigneeIDs = append(opts.AssigneeIDs, opts.Issue.AssigneeID)
+		}
+	}
+
+	// Check for and validate assignees
+	if len(opts.AssigneeIDs) > 0 {
+		for _, assigneeID := range opts.AssigneeIDs {
+			valid, err := hasAccess(e, assigneeID, opts.Repo, AccessModeWrite)
+			if err != nil {
+				return fmt.Errorf("hasAccess [user_id: %d, repo_id: %d]: %v", assigneeID, opts.Repo.ID, err)
+			}
+			if !valid {
+				return ErrUserDoesNotHaveAccessToRepo{UserID: assigneeID, RepoName: opts.Repo.Name}
+			}
 		}
 	}
 
@@ -931,11 +876,10 @@ func newIssue(e *xorm.Session, doer *User, opts NewIssueOptions) (err error) {
 		}
 	}
 
-	if opts.Issue.AssigneeID > 0 {
-		if err = opts.Issue.loadRepo(e); err != nil {
-			return err
-		}
-		if _, err = createAssigneeComment(e, doer, opts.Issue.Repo, opts.Issue, -1, opts.Issue.AssigneeID); err != nil {
+	// Insert the assignees
+	for _, assigneeID := range opts.AssigneeIDs {
+		err = opts.Issue.changeAssignee(e, doer, assigneeID)
+		if err != nil {
 			return err
 		}
 	}
@@ -995,7 +939,7 @@ func newIssue(e *xorm.Session, doer *User, opts NewIssueOptions) (err error) {
 }
 
 // NewIssue creates new issue with labels for repository.
-func NewIssue(repo *Repository, issue *Issue, labelIDs []int64, uuids []string) (err error) {
+func NewIssue(repo *Repository, issue *Issue, labelIDs []int64, assigneeIDs []int64, uuids []string) (err error) {
 	sess := x.NewSession()
 	defer sess.Close()
 	if err = sess.Begin(); err != nil {
@@ -1007,7 +951,11 @@ func NewIssue(repo *Repository, issue *Issue, labelIDs []int64, uuids []string)
 		Issue:       issue,
 		LabelIDs:    labelIDs,
 		Attachments: uuids,
+		AssigneeIDs: assigneeIDs,
 	}); err != nil {
+		if IsErrUserDoesNotHaveAccessToRepo(err) {
+			return err
+		}
 		return fmt.Errorf("newIssue: %v", err)
 	}
 
@@ -1150,7 +1098,8 @@ func (opts *IssuesOptions) setupSession(sess *xorm.Session) error {
 	}
 
 	if opts.AssigneeID > 0 {
-		sess.And("issue.assignee_id=?", opts.AssigneeID)
+		sess.Join("INNER", "issue_assignees", "issue.id = issue_assignees.issue_id").
+			And("issue_assignees.assignee_id = ?", opts.AssigneeID)
 	}
 
 	if opts.PosterID > 0 {
@@ -1372,7 +1321,8 @@ func GetIssueStats(opts *IssueStatsOptions) (*IssueStats, error) {
 		}
 
 		if opts.AssigneeID > 0 {
-			sess.And("issue.assignee_id = ?", opts.AssigneeID)
+			sess.Join("INNER", "issue_assignees", "issue.id = issue_assignees.issue_id").
+				And("issue_assignees.assignee_id = ?", opts.AssigneeID)
 		}
 
 		if opts.PosterID > 0 {
@@ -1438,13 +1388,15 @@ func GetUserIssueStats(opts UserIssueStatsOptions) (*IssueStats, error) {
 		}
 	case FilterModeAssign:
 		stats.OpenCount, err = x.Where(cond).And("is_closed = ?", false).
-			And("assignee_id = ?", opts.UserID).
+			Join("INNER", "issue_assignees", "issue.id = issue_assignees.issue_id").
+			And("issue_assignees.assignee_id = ?", opts.UserID).
 			Count(new(Issue))
 		if err != nil {
 			return nil, err
 		}
 		stats.ClosedCount, err = x.Where(cond).And("is_closed = ?", true).
-			And("assignee_id = ?", opts.UserID).
+			Join("INNER", "issue_assignees", "issue.id = issue_assignees.issue_id").
+			And("issue_assignees.assignee_id = ?", opts.UserID).
 			Count(new(Issue))
 		if err != nil {
 			return nil, err
@@ -1466,7 +1418,8 @@ func GetUserIssueStats(opts UserIssueStatsOptions) (*IssueStats, error) {
 
 	cond = cond.And(builder.Eq{"issue.is_closed": opts.IsClosed})
 	stats.AssignCount, err = x.Where(cond).
-		And("assignee_id = ?", opts.UserID).
+		Join("INNER", "issue_assignees", "issue.id = issue_assignees.issue_id").
+		And("issue_assignees.assignee_id = ?", opts.UserID).
 		Count(new(Issue))
 	if err != nil {
 		return nil, err
@@ -1505,8 +1458,10 @@ func GetRepoIssueStats(repoID, uid int64, filterMode int, isPull bool) (numOpen
 
 	switch filterMode {
 	case FilterModeAssign:
-		openCountSession.And("assignee_id = ?", uid)
-		closedCountSession.And("assignee_id = ?", uid)
+		openCountSession.Join("INNER", "issue_assignees", "issue.id = issue_assignees.issue_id").
+			And("issue_assignees.assignee_id = ?", uid)
+		closedCountSession.Join("INNER", "issue_assignees", "issue.id = issue_assignees.issue_id").
+			And("issue_assignees.assignee_id = ?", uid)
 	case FilterModeCreate:
 		openCountSession.And("poster_id = ?", uid)
 		closedCountSession.And("poster_id = ?", uid)
diff --git a/models/issue_assignees.go b/models/issue_assignees.go
new file mode 100644
index 0000000000..3e68126a6c
--- /dev/null
+++ b/models/issue_assignees.go
@@ -0,0 +1,263 @@
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package models
+
+import (
+	"fmt"
+
+	"code.gitea.io/gitea/modules/log"
+
+	api "code.gitea.io/sdk/gitea"
+	"github.com/go-xorm/xorm"
+)
+
+// IssueAssignees saves all issue assignees
+type IssueAssignees struct {
+	ID         int64 `xorm:"pk autoincr"`
+	AssigneeID int64 `xorm:"INDEX"`
+	IssueID    int64 `xorm:"INDEX"`
+}
+
+// This loads all assignees of an issue
+func (issue *Issue) loadAssignees(e Engine) (err error) {
+	// Reset maybe preexisting assignees
+	issue.Assignees = []*User{}
+
+	err = e.Table("`user`").
+		Join("INNER", "issue_assignees", "assignee_id = `user`.id").
+		Where("issue_assignees.issue_id = ?", issue.ID).
+		Find(&issue.Assignees)
+
+	if err != nil {
+		return err
+	}
+
+	// Check if we have at least one assignee and if yes put it in as `Assignee`
+	if len(issue.Assignees) > 0 {
+		issue.Assignee = issue.Assignees[0]
+	}
+
+	return
+}
+
+// GetAssigneesByIssue returns everyone assigned to that issue
+func GetAssigneesByIssue(issue *Issue) (assignees []*User, err error) {
+	err = issue.loadAssignees(x)
+	if err != nil {
+		return assignees, err
+	}
+
+	return issue.Assignees, nil
+}
+
+// IsUserAssignedToIssue returns true when the user is assigned to the issue
+func IsUserAssignedToIssue(issue *Issue, user *User) (isAssigned bool, err error) {
+	isAssigned, err = x.Exist(&IssueAssignees{IssueID: issue.ID, AssigneeID: user.ID})
+	return
+}
+
+// DeleteNotPassedAssignee deletes all assignees who aren't passed via the "assignees" array
+func DeleteNotPassedAssignee(issue *Issue, doer *User, assignees []*User) (err error) {
+	var found bool
+
+	for _, assignee := range issue.Assignees {
+
+		found = false
+		for _, alreadyAssignee := range assignees {
+			if assignee.ID == alreadyAssignee.ID {
+				found = true
+				break
+			}
+		}
+
+		if !found {
+			// This function also does comments and hooks, which is why we call it seperatly instead of directly removing the assignees here
+			if err := UpdateAssignee(issue, doer, assignee.ID); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+// MakeAssigneeList concats a string with all names of the assignees. Useful for logs.
+func MakeAssigneeList(issue *Issue) (assigneeList string, err error) {
+	err = issue.loadAssignees(x)
+	if err != nil {
+		return "", err
+	}
+
+	for in, assignee := range issue.Assignees {
+		assigneeList += assignee.Name
+
+		if len(issue.Assignees) > (in + 1) {
+			assigneeList += ", "
+		}
+	}
+	return
+}
+
+// ClearAssigneeByUserID deletes all assignments of an user
+func clearAssigneeByUserID(sess *xorm.Session, userID int64) (err error) {
+	_, err = sess.Delete(&IssueAssignees{AssigneeID: userID})
+	return
+}
+
+// AddAssigneeIfNotAssigned adds an assignee only if he isn't aleady assigned to the issue
+func AddAssigneeIfNotAssigned(issue *Issue, doer *User, assigneeID int64) (err error) {
+	// Check if the user is already assigned
+	isAssigned, err := IsUserAssignedToIssue(issue, &User{ID: assigneeID})
+	if err != nil {
+		return err
+	}
+
+	if !isAssigned {
+		return issue.ChangeAssignee(doer, assigneeID)
+	}
+	return nil
+}
+
+// UpdateAssignee deletes or adds an assignee to an issue
+func UpdateAssignee(issue *Issue, doer *User, assigneeID int64) (err error) {
+	return issue.ChangeAssignee(doer, assigneeID)
+}
+
+// ChangeAssignee changes the Assignee of this issue.
+func (issue *Issue) ChangeAssignee(doer *User, assigneeID int64) (err error) {
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	if err := issue.changeAssignee(sess, doer, assigneeID); err != nil {
+		return err
+	}
+
+	return sess.Commit()
+}
+
+func (issue *Issue) changeAssignee(sess *xorm.Session, doer *User, assigneeID int64) (err error) {
+
+	// Update the assignee
+	removed, err := updateIssueAssignee(sess, issue, assigneeID)
+	if err != nil {
+		return fmt.Errorf("UpdateIssueUserByAssignee: %v", err)
+	}
+
+	// Repo infos
+	if err = issue.loadRepo(sess); err != nil {
+		return fmt.Errorf("loadRepo: %v", err)
+	}
+
+	// Comment
+	if _, err = createAssigneeComment(sess, doer, issue.Repo, issue, assigneeID, removed); err != nil {
+		return fmt.Errorf("createAssigneeComment: %v", err)
+	}
+
+	if issue.IsPull {
+		issue.PullRequest = &PullRequest{Issue: issue}
+		apiPullRequest := &api.PullRequestPayload{
+			Index:       issue.Index,
+			PullRequest: issue.PullRequest.APIFormat(),
+			Repository:  issue.Repo.APIFormat(AccessModeNone),
+			Sender:      doer.APIFormat(),
+		}
+		if removed {
+			apiPullRequest.Action = api.HookIssueUnassigned
+		} else {
+			apiPullRequest.Action = api.HookIssueAssigned
+		}
+		if err := PrepareWebhooks(issue.Repo, HookEventPullRequest, apiPullRequest); err != nil {
+			log.Error(4, "PrepareWebhooks [is_pull: %v, remove_assignee: %v]: %v", issue.IsPull, removed, err)
+			return nil
+		}
+	}
+	go HookQueue.Add(issue.RepoID)
+	return nil
+}
+
+// UpdateAPIAssignee is a helper function to add or delete one or multiple issue assignee(s)
+// Deleting is done the Github way (quote from their api documentation):
+// https://developer.github.com/v3/issues/#edit-an-issue
+// "assignees" (array): Logins for Users to assign to this issue.
+// Pass one or more user logins to replace the set of assignees on this Issue.
+// Send an empty array ([]) to clear all assignees from the Issue.
+func UpdateAPIAssignee(issue *Issue, oneAssignee string, multipleAssignees []string, doer *User) (err error) {
+	var allNewAssignees []*User
+
+	// Keep the old assignee thingy for compatibility reasons
+	if oneAssignee != "" {
+		// Prevent double adding assignees
+		var isDouble bool
+		for _, assignee := range multipleAssignees {
+			if assignee == oneAssignee {
+				isDouble = true
+				break
+			}
+		}
+
+		if !isDouble {
+			multipleAssignees = append(multipleAssignees, oneAssignee)
+		}
+	}
+
+	// Loop through all assignees to add them
+	for _, assigneeName := range multipleAssignees {
+		assignee, err := GetUserByName(assigneeName)
+		if err != nil {
+			return err
+		}
+
+		allNewAssignees = append(allNewAssignees, assignee)
+	}
+
+	// Delete all old assignees not passed
+	if err = DeleteNotPassedAssignee(issue, doer, allNewAssignees); err != nil {
+		return err
+	}
+
+	// Add all new assignees
+	// Update the assignee. The function will check if the user exists, is already
+	// assigned (which he shouldn't as we deleted all assignees before) and
+	// has access to the repo.
+	for _, assignee := range allNewAssignees {
+		// Extra method to prevent double adding (which would result in removing)
+		err = AddAssigneeIfNotAssigned(issue, doer, assignee.ID)
+		if err != nil {
+			return err
+		}
+	}
+
+	return
+}
+
+// MakeIDsFromAPIAssigneesToAdd returns an array with all assignee IDs
+func MakeIDsFromAPIAssigneesToAdd(oneAssignee string, multipleAssignees []string) (assigneeIDs []int64, err error) {
+
+	// Keeping the old assigning method for compatibility reasons
+	if oneAssignee != "" {
+
+		// Prevent double adding assignees
+		var isDouble bool
+		for _, assignee := range multipleAssignees {
+			if assignee == oneAssignee {
+				isDouble = true
+				break
+			}
+		}
+
+		if !isDouble {
+			multipleAssignees = append(multipleAssignees, oneAssignee)
+		}
+	}
+
+	// Get the IDs of all assignees
+	assigneeIDs = GetUserIDsByNames(multipleAssignees)
+
+	return
+}
diff --git a/models/issue_assignees_test.go b/models/issue_assignees_test.go
new file mode 100644
index 0000000000..3247812198
--- /dev/null
+++ b/models/issue_assignees_test.go
@@ -0,0 +1,71 @@
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package models
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUpdateAssignee(t *testing.T) {
+	assert.NoError(t, PrepareTestDatabase())
+
+	// Fake issue with assignees
+	issue, err := GetIssueByID(1)
+	assert.NoError(t, err)
+
+	// Assign multiple users
+	user2, err := GetUserByID(2)
+	assert.NoError(t, err)
+	err = UpdateAssignee(issue, &User{ID: 1}, user2.ID)
+	assert.NoError(t, err)
+
+	user3, err := GetUserByID(3)
+	assert.NoError(t, err)
+	err = UpdateAssignee(issue, &User{ID: 1}, user3.ID)
+	assert.NoError(t, err)
+
+	user1, err := GetUserByID(1) // This user is already assigned (see the definition in fixtures), so running  UpdateAssignee should unassign him
+	assert.NoError(t, err)
+	err = UpdateAssignee(issue, &User{ID: 1}, user1.ID)
+	assert.NoError(t, err)
+
+	// Check if he got removed
+	isAssigned, err := IsUserAssignedToIssue(issue, user1)
+	assert.NoError(t, err)
+	assert.False(t, isAssigned)
+
+	// Check if they're all there
+	assignees, err := GetAssigneesByIssue(issue)
+	assert.NoError(t, err)
+
+	var expectedAssignees []*User
+	expectedAssignees = append(expectedAssignees, user2)
+	expectedAssignees = append(expectedAssignees, user3)
+
+	for in, assignee := range assignees {
+		assert.Equal(t, assignee.ID, expectedAssignees[in].ID)
+	}
+
+	// Check if the user is assigned
+	isAssigned, err = IsUserAssignedToIssue(issue, user2)
+	assert.NoError(t, err)
+	assert.True(t, isAssigned)
+
+	// This user should not be assigned
+	isAssigned, err = IsUserAssignedToIssue(issue, &User{ID: 4})
+	assert.NoError(t, err)
+	assert.False(t, isAssigned)
+
+	// Clean everyone
+	err = DeleteNotPassedAssignee(issue, user1, []*User{})
+	assert.NoError(t, err)
+
+	// Check they're gone
+	assignees, err = GetAssigneesByIssue(issue)
+	assert.NoError(t, err)
+	assert.Equal(t, 0, len(assignees))
+}
diff --git a/models/issue_comment.go b/models/issue_comment.go
index aedb124863..2c5875c29c 100644
--- a/models/issue_comment.go
+++ b/models/issue_comment.go
@@ -81,23 +81,22 @@ const (
 
 // Comment represents a comment in commit and issue page.
 type Comment struct {
-	ID             int64 `xorm:"pk autoincr"`
-	Type           CommentType
-	PosterID       int64 `xorm:"INDEX"`
-	Poster         *User `xorm:"-"`
-	IssueID        int64 `xorm:"INDEX"`
-	LabelID        int64
-	Label          *Label `xorm:"-"`
-	OldMilestoneID int64
-	MilestoneID    int64
-	OldMilestone   *Milestone `xorm:"-"`
-	Milestone      *Milestone `xorm:"-"`
-	OldAssigneeID  int64
-	AssigneeID     int64
-	Assignee       *User `xorm:"-"`
-	OldAssignee    *User `xorm:"-"`
-	OldTitle       string
-	NewTitle       string
+	ID              int64 `xorm:"pk autoincr"`
+	Type            CommentType
+	PosterID        int64 `xorm:"INDEX"`
+	Poster          *User `xorm:"-"`
+	IssueID         int64 `xorm:"INDEX"`
+	LabelID         int64
+	Label           *Label `xorm:"-"`
+	OldMilestoneID  int64
+	MilestoneID     int64
+	OldMilestone    *Milestone `xorm:"-"`
+	Milestone       *Milestone `xorm:"-"`
+	AssigneeID      int64
+	RemovedAssignee bool
+	Assignee        *User `xorm:"-"`
+	OldTitle        string
+	NewTitle        string
 
 	CommitID        int64
 	Line            int64
@@ -247,18 +246,9 @@ func (c *Comment) LoadMilestone() error {
 	return nil
 }
 
-// LoadAssignees if comment.Type is CommentTypeAssignees, then load assignees
-func (c *Comment) LoadAssignees() error {
+// LoadAssigneeUser if comment.Type is CommentTypeAssignees, then load assignees
+func (c *Comment) LoadAssigneeUser() error {
 	var err error
-	if c.OldAssigneeID > 0 {
-		c.OldAssignee, err = getUserByID(x, c.OldAssigneeID)
-		if err != nil {
-			if !IsErrUserNotExist(err) {
-				return err
-			}
-			c.OldAssignee = NewGhostUser()
-		}
-	}
 
 	if c.AssigneeID > 0 {
 		c.Assignee, err = getUserByID(x, c.AssigneeID)
@@ -324,21 +314,21 @@ func createComment(e *xorm.Session, opts *CreateCommentOptions) (_ *Comment, err
 		LabelID = opts.Label.ID
 	}
 	comment := &Comment{
-		Type:           opts.Type,
-		PosterID:       opts.Doer.ID,
-		Poster:         opts.Doer,
-		IssueID:        opts.Issue.ID,
-		LabelID:        LabelID,
-		OldMilestoneID: opts.OldMilestoneID,
-		MilestoneID:    opts.MilestoneID,
-		OldAssigneeID:  opts.OldAssigneeID,
-		AssigneeID:     opts.AssigneeID,
-		CommitID:       opts.CommitID,
-		CommitSHA:      opts.CommitSHA,
-		Line:           opts.LineNum,
-		Content:        opts.Content,
-		OldTitle:       opts.OldTitle,
-		NewTitle:       opts.NewTitle,
+		Type:            opts.Type,
+		PosterID:        opts.Doer.ID,
+		Poster:          opts.Doer,
+		IssueID:         opts.Issue.ID,
+		LabelID:         LabelID,
+		OldMilestoneID:  opts.OldMilestoneID,
+		MilestoneID:     opts.MilestoneID,
+		RemovedAssignee: opts.RemovedAssignee,
+		AssigneeID:      opts.AssigneeID,
+		CommitID:        opts.CommitID,
+		CommitSHA:       opts.CommitSHA,
+		Line:            opts.LineNum,
+		Content:         opts.Content,
+		OldTitle:        opts.OldTitle,
+		NewTitle:        opts.NewTitle,
 	}
 	if _, err = e.Insert(comment); err != nil {
 		return nil, err
@@ -480,14 +470,14 @@ func createMilestoneComment(e *xorm.Session, doer *User, repo *Repository, issue
 	})
 }
 
-func createAssigneeComment(e *xorm.Session, doer *User, repo *Repository, issue *Issue, oldAssigneeID, assigneeID int64) (*Comment, error) {
+func createAssigneeComment(e *xorm.Session, doer *User, repo *Repository, issue *Issue, assigneeID int64, removedAssignee bool) (*Comment, error) {
 	return createComment(e, &CreateCommentOptions{
-		Type:          CommentTypeAssignees,
-		Doer:          doer,
-		Repo:          repo,
-		Issue:         issue,
-		OldAssigneeID: oldAssigneeID,
-		AssigneeID:    assigneeID,
+		Type:            CommentTypeAssignees,
+		Doer:            doer,
+		Repo:            repo,
+		Issue:           issue,
+		RemovedAssignee: removedAssignee,
+		AssigneeID:      assigneeID,
 	})
 }
 
@@ -548,17 +538,17 @@ type CreateCommentOptions struct {
 	Issue *Issue
 	Label *Label
 
-	OldMilestoneID int64
-	MilestoneID    int64
-	OldAssigneeID  int64
-	AssigneeID     int64
-	OldTitle       string
-	NewTitle       string
-	CommitID       int64
-	CommitSHA      string
-	LineNum        int64
-	Content        string
-	Attachments    []string // UUIDs of attachments
+	OldMilestoneID  int64
+	MilestoneID     int64
+	AssigneeID      int64
+	RemovedAssignee bool
+	OldTitle        string
+	NewTitle        string
+	CommitID        int64
+	CommitSHA       string
+	LineNum         int64
+	Content         string
+	Attachments     []string // UUIDs of attachments
 }
 
 // CreateComment creates comment of issue or commit.
diff --git a/models/issue_list.go b/models/issue_list.go
index 01a1a15f44..05130a6eef 100644
--- a/models/issue_list.go
+++ b/models/issue_list.go
@@ -154,38 +154,38 @@ func (issues IssueList) loadMilestones(e Engine) error {
 	return nil
 }
 
-func (issues IssueList) getAssigneeIDs() []int64 {
-	var ids = make(map[int64]struct{}, len(issues))
-	for _, issue := range issues {
-		if _, ok := ids[issue.AssigneeID]; !ok {
-			ids[issue.AssigneeID] = struct{}{}
-		}
-	}
-	return keysInt64(ids)
-}
-
 func (issues IssueList) loadAssignees(e Engine) error {
-	assigneeIDs := issues.getAssigneeIDs()
-	if len(assigneeIDs) == 0 {
+	if len(issues) == 0 {
 		return nil
 	}
 
-	assigneeMaps := make(map[int64]*User, len(assigneeIDs))
-	err := e.
-		In("id", assigneeIDs).
-		Find(&assigneeMaps)
+	type AssigneeIssue struct {
+		IssueAssignee *IssueAssignees `xorm:"extends"`
+		Assignee      *User           `xorm:"extends"`
+	}
+
+	var assignees = make(map[int64][]*User, len(issues))
+	rows, err := e.Table("issue_assignees").
+		Join("INNER", "user", "`user`.id = `issue_assignees`.assignee_id").
+		In("`issue_assignees`.issue_id", issues.getIssueIDs()).
+		Rows(new(AssigneeIssue))
 	if err != nil {
 		return err
 	}
+	defer rows.Close()
 
-	for _, issue := range issues {
-		if issue.AssigneeID <= 0 {
-			continue
-		}
-		var ok bool
-		if issue.Assignee, ok = assigneeMaps[issue.AssigneeID]; !ok {
-			issue.Assignee = NewGhostUser()
+	for rows.Next() {
+		var assigneeIssue AssigneeIssue
+		err = rows.Scan(&assigneeIssue)
+		if err != nil {
+			return err
 		}
+
+		assignees[assigneeIssue.IssueAssignee.IssueID] = append(assignees[assigneeIssue.IssueAssignee.IssueID], assigneeIssue.Assignee)
+	}
+
+	for _, issue := range issues {
+		issue.Assignees = assignees[issue.ID]
 	}
 	return nil
 }
diff --git a/models/issue_mail.go b/models/issue_mail.go
index 08e4eed584..179bb6527b 100644
--- a/models/issue_mail.go
+++ b/models/issue_mail.go
@@ -46,9 +46,16 @@ func mailIssueCommentToParticipants(e Engine, issue *Issue, doer *User, content
 		participants = append(participants, issue.Poster)
 	}
 
-	// Assignee must receive any communications
-	if issue.Assignee != nil && issue.AssigneeID > 0 && issue.AssigneeID != doer.ID {
-		participants = append(participants, issue.Assignee)
+	// Assignees must receive any communications
+	assignees, err := GetAssigneesByIssue(issue)
+	if err != nil {
+		return err
+	}
+
+	for _, assignee := range assignees {
+		if assignee.ID != doer.ID {
+			participants = append(participants, assignee)
+		}
 	}
 
 	tos := make([]string, 0, len(watchers)) // List of email addresses.
diff --git a/models/issue_user.go b/models/issue_user.go
index 1aded0b440..de5a185aec 100644
--- a/models/issue_user.go
+++ b/models/issue_user.go
@@ -6,6 +6,8 @@ package models
 
 import (
 	"fmt"
+
+	"github.com/go-xorm/xorm"
 )
 
 // IssueUser represents an issue-user relation.
@@ -14,7 +16,6 @@ type IssueUser struct {
 	UID         int64 `xorm:"INDEX"` // User ID.
 	IssueID     int64
 	IsRead      bool
-	IsAssigned  bool
 	IsMentioned bool
 }
 
@@ -32,9 +33,8 @@ func newIssueUsers(e Engine, repo *Repository, issue *Issue) error {
 	issueUsers := make([]*IssueUser, 0, len(assignees)+1)
 	for _, assignee := range assignees {
 		issueUsers = append(issueUsers, &IssueUser{
-			IssueID:    issue.ID,
-			UID:        assignee.ID,
-			IsAssigned: assignee.ID == issue.AssigneeID,
+			IssueID: issue.ID,
+			UID:     assignee.ID,
 		})
 		isPosterAssignee = isPosterAssignee || assignee.ID == issue.PosterID
 	}
@@ -51,34 +51,38 @@ func newIssueUsers(e Engine, repo *Repository, issue *Issue) error {
 	return nil
 }
 
-func updateIssueUserByAssignee(e Engine, issue *Issue) (err error) {
-	if _, err = e.Exec("UPDATE `issue_user` SET is_assigned = ? WHERE issue_id = ?", false, issue.ID); err != nil {
-		return err
+func updateIssueAssignee(e *xorm.Session, issue *Issue, assigneeID int64) (removed bool, err error) {
+
+	// Check if the user exists
+	_, err = GetUserByID(assigneeID)
+	if err != nil {
+		return false, err
 	}
 
-	// Assignee ID equals to 0 means clear assignee.
-	if issue.AssigneeID > 0 {
-		if _, err = e.Exec("UPDATE `issue_user` SET is_assigned = ? WHERE uid = ? AND issue_id = ?", true, issue.AssigneeID, issue.ID); err != nil {
-			return err
+	// Check if the submitted user is already assigne, if yes delete him otherwise add him
+	var toBeDeleted bool
+	for _, assignee := range issue.Assignees {
+		if assignee.ID == assigneeID {
+			toBeDeleted = true
+			break
 		}
 	}
 
-	return updateIssue(e, issue)
-}
+	assigneeIn := IssueAssignees{AssigneeID: assigneeID, IssueID: issue.ID}
 
-// UpdateIssueUserByAssignee updates issue-user relation for assignee.
-func UpdateIssueUserByAssignee(issue *Issue) (err error) {
-	sess := x.NewSession()
-	defer sess.Close()
-	if err = sess.Begin(); err != nil {
-		return err
-	}
-
-	if err = updateIssueUserByAssignee(sess, issue); err != nil {
-		return err
+	if toBeDeleted {
+		_, err = e.Delete(assigneeIn)
+		if err != nil {
+			return toBeDeleted, err
+		}
+	} else {
+		_, err = e.Insert(assigneeIn)
+		if err != nil {
+			return toBeDeleted, err
+		}
 	}
 
-	return sess.Commit()
+	return toBeDeleted, nil
 }
 
 // UpdateIssueUserByRead updates issue-user relation for reading.
diff --git a/models/issue_user_test.go b/models/issue_user_test.go
index e3ebfa8fa2..a333bc8619 100644
--- a/models/issue_user_test.go
+++ b/models/issue_user_test.go
@@ -32,23 +32,6 @@ func Test_newIssueUsers(t *testing.T) {
 	AssertExistsAndLoadBean(t, &IssueUser{IssueID: newIssue.ID, UID: repo.OwnerID})
 }
 
-func TestUpdateIssueUserByAssignee(t *testing.T) {
-	assert.NoError(t, PrepareTestDatabase())
-	issue := AssertExistsAndLoadBean(t, &Issue{ID: 1}).(*Issue)
-
-	// artificially change assignee in issue_user table
-	AssertSuccessfulInsert(t, &IssueUser{IssueID: issue.ID, UID: 5, IsAssigned: true})
-	_, err := x.Cols("is_assigned").
-		Update(&IssueUser{IsAssigned: false}, &IssueUser{IssueID: issue.ID, UID: issue.AssigneeID})
-	assert.NoError(t, err)
-
-	assert.NoError(t, UpdateIssueUserByAssignee(issue))
-
-	// issue_user table should now be correct again
-	AssertExistsAndLoadBean(t, &IssueUser{IssueID: issue.ID, UID: issue.AssigneeID}, "is_assigned=1")
-	AssertExistsAndLoadBean(t, &IssueUser{IssueID: issue.ID, UID: 5}, "is_assigned=0")
-}
-
 func TestUpdateIssueUserByRead(t *testing.T) {
 	assert.NoError(t, PrepareTestDatabase())
 	issue := AssertExistsAndLoadBean(t, &Issue{ID: 1}).(*Issue)
diff --git a/models/migrations/migrations.go b/models/migrations/migrations.go
index aa9dd13107..e85da8de79 100644
--- a/models/migrations/migrations.go
+++ b/models/migrations/migrations.go
@@ -180,6 +180,8 @@ var migrations = []Migration{
 	NewMigration("add last used passcode column for TOTP", addLastUsedPasscodeTOTP),
 	// v63 -> v64
 	NewMigration("add language column for user setting", addLanguageSetting),
+	// v64 -> v65
+	NewMigration("add multiple assignees", addMultipleAssignees),
 }
 
 // Migrate database to current version
@@ -229,7 +231,7 @@ Please try to upgrade to a lower version (>= v0.6.0) first, then upgrade to curr
 	return nil
 }
 
-func dropTableColumns(x *xorm.Engine, tableName string, columnNames ...string) (err error) {
+func dropTableColumns(sess *xorm.Session, tableName string, columnNames ...string) (err error) {
 	if tableName == "" || len(columnNames) == 0 {
 		return nil
 	}
@@ -245,17 +247,10 @@ func dropTableColumns(x *xorm.Engine, tableName string, columnNames ...string) (
 			}
 			cols += "DROP COLUMN `" + col + "`"
 		}
-		if _, err := x.Exec(fmt.Sprintf("ALTER TABLE `%s` %s", tableName, cols)); err != nil {
+		if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `%s` %s", tableName, cols)); err != nil {
 			return fmt.Errorf("Drop table `%s` columns %v: %v", tableName, columnNames, err)
 		}
 	case setting.UseMSSQL:
-		sess := x.NewSession()
-		defer sess.Close()
-
-		if err = sess.Begin(); err != nil {
-			return err
-		}
-
 		cols := ""
 		for _, col := range columnNames {
 			if cols != "" {
diff --git a/models/migrations/v56.go b/models/migrations/v56.go
index 1f96cc543e..79f8ce0ba5 100644
--- a/models/migrations/v56.go
+++ b/models/migrations/v56.go
@@ -9,5 +9,15 @@ import (
 )
 
 func removeIsOwnerColumnFromOrgUser(x *xorm.Engine) (err error) {
-	return dropTableColumns(x, "org_user", "is_owner", "num_teams")
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err = sess.Begin(); err != nil {
+		return err
+	}
+
+	if err := dropTableColumns(sess, "org_user", "is_owner", "num_teams"); err != nil {
+		return err
+	}
+	return sess.Commit()
 }
diff --git a/models/migrations/v64.go b/models/migrations/v64.go
new file mode 100644
index 0000000000..a281ac67e4
--- /dev/null
+++ b/models/migrations/v64.go
@@ -0,0 +1,129 @@
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"code.gitea.io/gitea/modules/util"
+
+	"github.com/go-xorm/xorm"
+)
+
+func addMultipleAssignees(x *xorm.Engine) error {
+
+	// Redeclare issue struct
+	type Issue struct {
+		ID          int64  `xorm:"pk autoincr"`
+		RepoID      int64  `xorm:"INDEX UNIQUE(repo_index)"`
+		Index       int64  `xorm:"UNIQUE(repo_index)"` // Index in one repository.
+		PosterID    int64  `xorm:"INDEX"`
+		Title       string `xorm:"name"`
+		Content     string `xorm:"TEXT"`
+		MilestoneID int64  `xorm:"INDEX"`
+		Priority    int
+		AssigneeID  int64 `xorm:"INDEX"`
+		IsClosed    bool  `xorm:"INDEX"`
+		IsPull      bool  `xorm:"INDEX"` // Indicates whether is a pull request or not.
+		NumComments int
+		Ref         string
+
+		DeadlineUnix util.TimeStamp `xorm:"INDEX"`
+		CreatedUnix  util.TimeStamp `xorm:"INDEX created"`
+		UpdatedUnix  util.TimeStamp `xorm:"INDEX updated"`
+		ClosedUnix   util.TimeStamp `xorm:"INDEX"`
+	}
+
+	allIssues := []Issue{}
+	err := x.Find(&allIssues)
+	if err != nil {
+		return err
+	}
+
+	// Create the table
+	type IssueAssignees struct {
+		ID         int64 `xorm:"pk autoincr"`
+		AssigneeID int64 `xorm:"INDEX"`
+		IssueID    int64 `xorm:"INDEX"`
+	}
+	err = x.Sync2(IssueAssignees{})
+	if err != nil {
+		return err
+	}
+
+	// Range over all issues and insert a new entry for each issue/assignee
+	sess := x.NewSession()
+	defer sess.Close()
+
+	err = sess.Begin()
+	if err != nil {
+		return err
+	}
+
+	for _, issue := range allIssues {
+		if issue.AssigneeID != 0 {
+			_, err := sess.Insert(IssueAssignees{IssueID: issue.ID, AssigneeID: issue.AssigneeID})
+			if err != nil {
+				sess.Rollback()
+				return err
+			}
+		}
+	}
+
+	// Updated the comment table
+	type Comment struct {
+		ID              int64 `xorm:"pk autoincr"`
+		Type            int
+		PosterID        int64 `xorm:"INDEX"`
+		IssueID         int64 `xorm:"INDEX"`
+		LabelID         int64
+		OldMilestoneID  int64
+		MilestoneID     int64
+		OldAssigneeID   int64
+		AssigneeID      int64
+		RemovedAssignee bool
+		OldTitle        string
+		NewTitle        string
+
+		CommitID        int64
+		Line            int64
+		Content         string `xorm:"TEXT"`
+		RenderedContent string `xorm:"-"`
+
+		CreatedUnix util.TimeStamp `xorm:"INDEX created"`
+		UpdatedUnix util.TimeStamp `xorm:"INDEX updated"`
+
+		// Reference issue in commit message
+		CommitSHA string `xorm:"VARCHAR(40)"`
+	}
+	if err := x.Sync2(Comment{}); err != nil {
+		return err
+	}
+
+	// Migrate comments
+	// First update everything to not have nulls in db
+	if _, err := sess.Where("type = ?", 9).Cols("removed_assignee").Update(Comment{RemovedAssignee: false}); err != nil {
+		return err
+	}
+
+	allAssignementComments := []Comment{}
+	if err := sess.Where("type = ?", 9).Find(&allAssignementComments); err != nil {
+		return err
+	}
+
+	for _, comment := range allAssignementComments {
+		// Everytime where OldAssigneeID is > 0, the assignement was removed.
+		if comment.OldAssigneeID > 0 {
+			_, err = sess.ID(comment.ID).Update(Comment{RemovedAssignee: true})
+		}
+	}
+
+	if err := dropTableColumns(sess, "issue", "assignee_id"); err != nil {
+		return err
+	}
+
+	if err := dropTableColumns(sess, "issue_user", "is_assigned"); err != nil {
+		return err
+	}
+	return sess.Commit()
+}
diff --git a/models/models.go b/models/models.go
index 549d2eadc9..9213cd3b79 100644
--- a/models/models.go
+++ b/models/models.go
@@ -119,6 +119,7 @@ func init() {
 		new(RepoIndexerStatus),
 		new(LFSLock),
 		new(Reaction),
+		new(IssueAssignees),
 	)
 
 	gonicNames := []string{"SSL", "UID"}
diff --git a/models/pull.go b/models/pull.go
index 5f4a6e2054..d23d885b6c 100644
--- a/models/pull.go
+++ b/models/pull.go
@@ -198,6 +198,7 @@ func (pr *PullRequest) APIFormat() *api.PullRequest {
 		Labels:    apiIssue.Labels,
 		Milestone: apiIssue.Milestone,
 		Assignee:  apiIssue.Assignee,
+		Assignees: apiIssue.Assignees,
 		State:     apiIssue.State,
 		Comments:  apiIssue.Comments,
 		HTMLURL:   pr.Issue.HTMLURL(),
@@ -719,7 +720,7 @@ func (pr *PullRequest) testPatch() (err error) {
 }
 
 // NewPullRequest creates new pull request with labels for repository.
-func NewPullRequest(repo *Repository, pull *Issue, labelIDs []int64, uuids []string, pr *PullRequest, patch []byte) (err error) {
+func NewPullRequest(repo *Repository, pull *Issue, labelIDs []int64, uuids []string, pr *PullRequest, patch []byte, assigneeIDs []int64) (err error) {
 	sess := x.NewSession()
 	defer sess.Close()
 	if err = sess.Begin(); err != nil {
@@ -732,7 +733,11 @@ func NewPullRequest(repo *Repository, pull *Issue, labelIDs []int64, uuids []str
 		LabelIDs:    labelIDs,
 		Attachments: uuids,
 		IsPull:      true,
+		AssigneeIDs: assigneeIDs,
 	}); err != nil {
+		if IsErrUserDoesNotHaveAccessToRepo(err) {
+			return err
+		}
 		return fmt.Errorf("newIssue: %v", err)
 	}
 
diff --git a/models/repo.go b/models/repo.go
index 43fb1e0c73..4a7eb859c4 100644
--- a/models/repo.go
+++ b/models/repo.go
@@ -600,9 +600,9 @@ func (repo *Repository) GetAssignees() (_ []*User, err error) {
 	return repo.getAssignees(x)
 }
 
-// GetAssigneeByID returns the user that has write access of repository by given ID.
-func (repo *Repository) GetAssigneeByID(userID int64) (*User, error) {
-	return GetAssigneeByID(repo, userID)
+// GetUserIfHasWriteAccess returns the user that has write access of repository by given ID.
+func (repo *Repository) GetUserIfHasWriteAccess(userID int64) (*User, error) {
+	return GetUserIfHasWriteAccess(repo, userID)
 }
 
 // GetMilestoneByID returns the milestone belongs to repository by given ID.
diff --git a/models/user.go b/models/user.go
index 106d79ffcc..8f5ee6e5a7 100644
--- a/models/user.go
+++ b/models/user.go
@@ -993,7 +993,7 @@ func deleteUser(e *xorm.Session, u *User) error {
 	// ***** END: PublicKey *****
 
 	// Clear assignee.
-	if _, err = e.Exec("UPDATE `issue` SET assignee_id=0 WHERE assignee_id=?", u.ID); err != nil {
+	if err = clearAssigneeByUserID(e, u.ID); err != nil {
 		return fmt.Errorf("clear assignee: %v", err)
 	}
 
@@ -1110,8 +1110,8 @@ func GetUserByID(id int64) (*User, error) {
 	return getUserByID(x, id)
 }
 
-// GetAssigneeByID returns the user with write access of repository by given ID.
-func GetAssigneeByID(repo *Repository, userID int64) (*User, error) {
+// GetUserIfHasWriteAccess returns the user with write access of repository by given ID.
+func GetUserIfHasWriteAccess(repo *Repository, userID int64) (*User, error) {
 	has, err := HasAccess(userID, repo, AccessModeWrite)
 	if err != nil {
 		return nil, err
diff --git a/models/webhook_dingtalk.go b/models/webhook_dingtalk.go
index e25e989084..719ffcae73 100644
--- a/models/webhook_dingtalk.go
+++ b/models/webhook_dingtalk.go
@@ -118,8 +118,12 @@ func getDingtalkPullRequestPayload(p *api.PullRequestPayload) (*DingtalkPayload,
 		title = fmt.Sprintf("[%s] Pull request edited: #%d %s", p.Repository.FullName, p.Index, p.PullRequest.Title)
 		text = p.PullRequest.Body
 	case api.HookIssueAssigned:
+		list, err := MakeAssigneeList(&Issue{ID: p.PullRequest.ID})
+		if err != nil {
+			return &DingtalkPayload{}, err
+		}
 		title = fmt.Sprintf("[%s] Pull request assigned to %s: #%d %s", p.Repository.FullName,
-			p.PullRequest.Assignee.UserName, p.Index, p.PullRequest.Title)
+			list, p.Index, p.PullRequest.Title)
 		text = p.PullRequest.Body
 	case api.HookIssueUnassigned:
 		title = fmt.Sprintf("[%s] Pull request unassigned: #%d %s", p.Repository.FullName, p.Index, p.PullRequest.Title)
diff --git a/models/webhook_discord.go b/models/webhook_discord.go
index 6d39d8b993..40d9d58992 100644
--- a/models/webhook_discord.go
+++ b/models/webhook_discord.go
@@ -191,8 +191,12 @@ func getDiscordPullRequestPayload(p *api.PullRequestPayload, meta *DiscordMeta)
 		text = p.PullRequest.Body
 		color = warnColor
 	case api.HookIssueAssigned:
+		list, err := MakeAssigneeList(&Issue{ID: p.PullRequest.ID})
+		if err != nil {
+			return &DiscordPayload{}, err
+		}
 		title = fmt.Sprintf("[%s] Pull request assigned to %s: #%d %s", p.Repository.FullName,
-			p.PullRequest.Assignee.UserName, p.Index, p.PullRequest.Title)
+			list, p.Index, p.PullRequest.Title)
 		text = p.PullRequest.Body
 		color = successColor
 	case api.HookIssueUnassigned:
diff --git a/models/webhook_slack.go b/models/webhook_slack.go
index dd25a8d7df..256819adc5 100644
--- a/models/webhook_slack.go
+++ b/models/webhook_slack.go
@@ -172,8 +172,12 @@ func getSlackPullRequestPayload(p *api.PullRequestPayload, slack *SlackMeta) (*S
 		text = fmt.Sprintf("[%s] Pull request edited: %s by %s", p.Repository.FullName, titleLink, senderLink)
 		attachmentText = SlackTextFormatter(p.PullRequest.Body)
 	case api.HookIssueAssigned:
+		list, err := MakeAssigneeList(&Issue{ID: p.PullRequest.ID})
+		if err != nil {
+			return &SlackPayload{}, err
+		}
 		text = fmt.Sprintf("[%s] Pull request assigned to %s: %s by %s", p.Repository.FullName,
-			SlackLinkFormatter(setting.AppURL+p.PullRequest.Assignee.UserName, p.PullRequest.Assignee.UserName),
+			SlackLinkFormatter(setting.AppURL+list, list),
 			titleLink, senderLink)
 	case api.HookIssueUnassigned:
 		text = fmt.Sprintf("[%s] Pull request unassigned: %s by %s", p.Repository.FullName, titleLink, senderLink)