Mail assignee when issue/pull request is assigned (#8546)

* Send email to assigned user

* Only send mail if enabled

* Mail also when assigned through API

* Need to refactor functions from models to issue service

* Refer to issue index rather than ID

* Disable email notifications completly at initalization if global disable

* Check of user enbled mail shall be in mail notification function only

* Initialize notifications from routers init function.

* Use the assigned comment when sending assigned mail

* Refactor so that assignees always added as separate step when new issue/pr.

* Check error from AddAssignees

* Check if user can be assiged to issue or pull request

* Missing return

* Refactor of CanBeAssigned check.

CanBeAssigned shall have same check as UI.

* Clarify function names (toggle rather than update/change), and clean up.

* Fix review comments.

* Flash error if assignees was not added when creating issue/pr

* Generate error if assignee users doesn't exist

models/issue.go

@@ -896,7 +896,6 @@ type NewIssueOptions struct {
 	Repo        *Repository
 	Issue       *Issue
 	LabelIDs    []int64
-	AssigneeIDs []int64
 	Attachments []string // In UUID format.
 	IsPull      bool
 }
@@ -918,40 +917,7 @@ func newIssue(e *xorm.Session, doer *User, opts NewIssueOptions) (err error) {
 		}
 	}
 
-	// Keep the old assignee id thingy for compatibility reasons
+	// Milestone validation should happen before insert actual object.
-	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 !isAdded {
-			opts.AssigneeIDs = append(opts.AssigneeIDs, opts.Issue.AssigneeID)
-		}
-	}
-
-	// Check for and validate assignees
-	if len(opts.AssigneeIDs) > 0 {
-		for _, assigneeID := range opts.AssigneeIDs {
-			user, err := getUserByID(e, assigneeID)
-			if err != nil {
-				return fmt.Errorf("getUserByID [user_id: %d, repo_id: %d]: %v", assigneeID, opts.Repo.ID, err)
-			}
-			valid, err := canBeAssigned(e, user, opts.Repo)
-			if err != nil {
-				return fmt.Errorf("canBeAssigned [user_id: %d, repo_id: %d]: %v", assigneeID, opts.Repo.ID, err)
-			}
-			if !valid {
-				return ErrUserDoesNotHaveAccessToRepo{UserID: assigneeID, RepoName: opts.Repo.Name}
-			}
-		}
-	}
-
-	// Milestone and assignee validation should happen before insert actual object.
 	if _, err := e.SetExpr("`index`", "coalesce(MAX(`index`),0)+1").
 		Where("repo_id=?", opts.Issue.RepoID).
 		Insert(opts.Issue); err != nil {
@@ -976,14 +942,6 @@ func newIssue(e *xorm.Session, doer *User, opts NewIssueOptions) (err error) {
 		}
 	}
 
-	// Insert the assignees
-	for _, assigneeID := range opts.AssigneeIDs {
-		err = opts.Issue.changeAssignee(e, doer, assigneeID, true)
-		if err != nil {
-			return err
-		}
-	}
-
 	if opts.IsPull {
 		_, err = e.Exec("UPDATE `repository` SET num_pulls = num_pulls + 1 WHERE id = ?", opts.Issue.RepoID)
 	} else {
@@ -1041,11 +999,11 @@ 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, assigneeIDs []int64, uuids []string) (err error) {
+func NewIssue(repo *Repository, issue *Issue, labelIDs []int64, uuids []string) (err error) {
 	// Retry several times in case INSERT fails due to duplicate key for (repo_id, index); see #7887
 	i := 0
 	for {
-		if err = newIssueAttempt(repo, issue, labelIDs, assigneeIDs, uuids); err == nil {
+		if err = newIssueAttempt(repo, issue, labelIDs, uuids); err == nil {
 			return nil
 		}
 		if !IsErrNewIssueInsert(err) {
@@ -1059,7 +1017,7 @@ func NewIssue(repo *Repository, issue *Issue, labelIDs []int64, assigneeIDs []in
 	return fmt.Errorf("NewIssue: too many errors attempting to insert the new issue. Last error was: %v", err)
 }
 
-func newIssueAttempt(repo *Repository, issue *Issue, labelIDs []int64, assigneeIDs []int64, uuids []string) (err error) {
+func newIssueAttempt(repo *Repository, issue *Issue, labelIDs []int64, uuids []string) (err error) {
 	sess := x.NewSession()
 	defer sess.Close()
 	if err = sess.Begin(); err != nil {
@@ -1071,7 +1029,6 @@ func newIssueAttempt(repo *Repository, issue *Issue, labelIDs []int64, assigneeI
 		Issue:       issue,
 		LabelIDs:    labelIDs,
 		Attachments: uuids,
-		AssigneeIDs: assigneeIDs,
 	}); err != nil {
 		if IsErrUserDoesNotHaveAccessToRepo(err) || IsErrNewIssueInsert(err) {
 			return err

models/issue_assignees.go

@@ -58,8 +58,11 @@ func getAssigneesByIssue(e Engine, issue *Issue) (assignees []*User, err error)
 
 // 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 isUserAssignedToIssue(x, issue, user)
-	return
+}
+
+func isUserAssignedToIssue(e Engine, issue *Issue, user *User) (isAssigned bool, err error) {
+	return e.Get(&IssueAssignees{IssueID: issue.ID, AssigneeID: user.ID})
 }
 
 // DeleteNotPassedAssignee deletes all assignees who aren't passed via the "assignees" array
@@ -78,7 +81,7 @@ func DeleteNotPassedAssignee(issue *Issue, doer *User, assignees []*User) (err e
 
 		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 {
+			if _, _, err := issue.ToggleAssignee(doer, assignee.ID); err != nil {
 				return err
 			}
 		}
@@ -110,73 +113,56 @@ func clearAssigneeByUserID(sess *xorm.Session, userID int64) (err error) {
 	return
 }
 
-// AddAssigneeIfNotAssigned adds an assignee only if he isn't aleady assigned to the issue
+// ToggleAssignee changes a user between assigned and not assigned for this issue, and make issue comment for it.
-func AddAssigneeIfNotAssigned(issue *Issue, doer *User, assigneeID int64) (err error) {
+func (issue *Issue) ToggleAssignee(doer *User, assigneeID int64) (removed bool, comment *Comment, 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
+		return false, nil, err
 	}
 
-	if err := issue.changeAssignee(sess, doer, assigneeID, false); err != nil {
+	removed, comment, err = issue.toggleAssignee(sess, doer, assigneeID, false)
-		return err
+	if err != nil {
+		return false, nil, err
 	}
 
 	if err := sess.Commit(); err != nil {
-		return err
+		return false, nil, err
 	}
 
 	go HookQueue.Add(issue.RepoID)
-	return nil
+
+	return removed, comment, nil
 }
 
-func (issue *Issue) changeAssignee(sess *xorm.Session, doer *User, assigneeID int64, isCreate bool) (err error) {
+func (issue *Issue) toggleAssignee(sess *xorm.Session, doer *User, assigneeID int64, isCreate bool) (removed bool, comment *Comment, err error) {
-	// Update the assignee
+	removed, err = toggleUserAssignee(sess, issue, assigneeID)
-	removed, err := updateIssueAssignee(sess, issue, assigneeID)
 	if err != nil {
-		return fmt.Errorf("UpdateIssueUserByAssignee: %v", err)
+		return false, nil, fmt.Errorf("UpdateIssueUserByAssignee: %v", err)
 	}
 
 	// Repo infos
 	if err = issue.loadRepo(sess); err != nil {
-		return fmt.Errorf("loadRepo: %v", err)
+		return false, nil, fmt.Errorf("loadRepo: %v", err)
 	}
 
 	// Comment
-	if _, err = createAssigneeComment(sess, doer, issue.Repo, issue, assigneeID, removed); err != nil {
+	comment, err = createAssigneeComment(sess, doer, issue.Repo, issue, assigneeID, removed)
-		return fmt.Errorf("createAssigneeComment: %v", err)
+	if err != nil {
+		return false, nil, fmt.Errorf("createAssigneeComment: %v", err)
 	}
 
 	// if pull request is in the middle of creation - don't call webhook
 	if isCreate {
-		return nil
+		return removed, comment, err
 	}
 
 	if issue.IsPull {
 		mode, _ := accessLevelUnit(sess, doer, issue.Repo, UnitTypePullRequests)
 
 		if err = issue.loadPullRequest(sess); err != nil {
-			return fmt.Errorf("loadPullRequest: %v", err)
+			return false, nil, fmt.Errorf("loadPullRequest: %v", err)
 		}
 		issue.PullRequest.Issue = issue
 		apiPullRequest := &api.PullRequestPayload{
@@ -190,9 +176,10 @@ func (issue *Issue) changeAssignee(sess *xorm.Session, doer *User, assigneeID in
 		} else {
 			apiPullRequest.Action = api.HookIssueAssigned
 		}
+		// Assignee comment triggers a webhook
 		if err := prepareWebhooks(sess, issue.Repo, HookEventPullRequest, apiPullRequest); err != nil {
 			log.Error("PrepareWebhooks [is_pull: %v, remove_assignee: %v]: %v", issue.IsPull, removed, err)
-			return nil
+			return false, nil, err
 		}
 	} else {
 		mode, _ := accessLevelUnit(sess, doer, issue.Repo, UnitTypeIssues)
@@ -208,67 +195,50 @@ func (issue *Issue) changeAssignee(sess *xorm.Session, doer *User, assigneeID in
 		} else {
 			apiIssue.Action = api.HookIssueAssigned
 		}
+		// Assignee comment triggers a webhook
 		if err := prepareWebhooks(sess, issue.Repo, HookEventIssues, apiIssue); err != nil {
 			log.Error("PrepareWebhooks [is_pull: %v, remove_assignee: %v]: %v", issue.IsPull, removed, err)
-			return nil
+			return false, nil, err
 		}
 	}
-	return nil
+	return removed, comment, nil
 }
 
-// UpdateAPIAssignee is a helper function to add or delete one or multiple issue assignee(s)
+// toggles user assignee state in database
-// Deleting is done the GitHub way (quote from their api documentation):
+func toggleUserAssignee(e *xorm.Session, issue *Issue, assigneeID int64) (removed bool, err error) {
-// 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
+	// Check if the user exists
-	if oneAssignee != "" {
+	assignee, err := getUserByID(e, assigneeID)
-		// Prevent double adding assignees
+	if err != nil {
-		var isDouble bool
+		return false, err
-		for _, assignee := range multipleAssignees {
+	}
-			if assignee == oneAssignee {
+
-				isDouble = true
+	// Check if the submitted user is already assigned, if yes delete him otherwise add him
+	var i int
+	for i = 0; i < len(issue.Assignees); i++ {
+		if issue.Assignees[i].ID == assigneeID {
 			break
 		}
 	}
 
-		if !isDouble {
+	assigneeIn := IssueAssignees{AssigneeID: assigneeID, IssueID: issue.ID}
-			multipleAssignees = append(multipleAssignees, oneAssignee)
-		}
-	}
 
-	// Loop through all assignees to add them
+	toBeDeleted := i < len(issue.Assignees)
-	for _, assigneeName := range multipleAssignees {
+	if toBeDeleted {
-		assignee, err := GetUserByName(assigneeName)
+		issue.Assignees = append(issue.Assignees[:i], issue.Assignees[i:]...)
+		_, err = e.Delete(assigneeIn)
 		if err != nil {
-			return err
+			return toBeDeleted, err
 		}
-
+	} else {
-		allNewAssignees = append(allNewAssignees, assignee)
+		issue.Assignees = append(issue.Assignees, assignee)
-	}
+		_, err = e.Insert(assigneeIn)
-
-	// 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 toBeDeleted, err
 		}
 	}
 
-	return
+	return toBeDeleted, nil
 }
 
 // MakeIDsFromAPIAssigneesToAdd returns an array with all assignee IDs
@@ -292,7 +262,7 @@ func MakeIDsFromAPIAssigneesToAdd(oneAssignee string, multipleAssignees []string
 	}
 
 	// Get the IDs of all assignees
-	assigneeIDs = GetUserIDsByNames(multipleAssignees)
+	assigneeIDs, err = GetUserIDsByNames(multipleAssignees, false)
 
 	return
 }

models/issue_assignees_test.go

@@ -20,17 +20,17 @@ func TestUpdateAssignee(t *testing.T) {
 	// Assign multiple users
 	user2, err := GetUserByID(2)
 	assert.NoError(t, err)
-	err = UpdateAssignee(issue, &User{ID: 1}, user2.ID)
+	_, _, err = issue.ToggleAssignee(&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)
+	_, _, err = issue.ToggleAssignee(&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)
+	_, _, err = issue.ToggleAssignee(&User{ID: 1}, user1.ID)
 	assert.NoError(t, err)
 
 	// Check if he got removed

models/issue_test.go

@@ -297,7 +297,7 @@ func testInsertIssue(t *testing.T, title, content string) {
 		Title:    title,
 		Content:  content,
 	}
-	err := NewIssue(repo, &issue, nil, nil, nil)
+	err := NewIssue(repo, &issue, nil, nil)
 	assert.NoError(t, err)
 
 	var newIssue Issue

models/issue_user.go

@@ -6,8 +6,6 @@ package models
 
 import (
 	"fmt"
-
-	"xorm.io/xorm"
 )
 
 // IssueUser represents an issue-user relation.
@@ -51,42 +49,6 @@ func newIssueUsers(e Engine, repo *Repository, issue *Issue) error {
 	return nil
 }
 
-func updateIssueAssignee(e *xorm.Session, issue *Issue, assigneeID int64) (removed bool, err error) {
-
-	// Check if the user exists
-	assignee, err := getUserByID(e, assigneeID)
-	if err != nil {
-		return false, err
-	}
-
-	// Check if the submitted user is already assigne, if yes delete him otherwise add him
-	var i int
-	for i = 0; i < len(issue.Assignees); i++ {
-		if issue.Assignees[i].ID == assigneeID {
-			break
-		}
-	}
-
-	assigneeIn := IssueAssignees{AssigneeID: assigneeID, IssueID: issue.ID}
-
-	toBeDeleted := i < len(issue.Assignees)
-	if toBeDeleted {
-		issue.Assignees = append(issue.Assignees[:i], issue.Assignees[i:]...)
-		_, err = e.Delete(assigneeIn)
-		if err != nil {
-			return toBeDeleted, err
-		}
-	} else {
-		issue.Assignees = append(issue.Assignees, assignee)
-		_, err = e.Insert(assigneeIn)
-		if err != nil {
-			return toBeDeleted, err
-		}
-	}
-
-	return toBeDeleted, nil
-}
-
 // UpdateIssueUserByRead updates issue-user relation for reading.
 func UpdateIssueUserByRead(uid, issueID int64) error {
 	_, err := x.Exec("UPDATE `issue_user` SET is_read=? WHERE uid=? AND issue_id=?", true, uid, issueID)

models/pull.go

@@ -686,11 +686,11 @@ func (pr *PullRequest) testPatch(e Engine) (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, assigneeIDs []int64) (err error) {
+func NewPullRequest(repo *Repository, pull *Issue, labelIDs []int64, uuids []string, pr *PullRequest, patch []byte) (err error) {
 	// Retry several times in case INSERT fails due to duplicate key for (repo_id, index); see #7887
 	i := 0
 	for {
-		if err = newPullRequestAttempt(repo, pull, labelIDs, uuids, pr, patch, assigneeIDs); err == nil {
+		if err = newPullRequestAttempt(repo, pull, labelIDs, uuids, pr, patch); err == nil {
 			return nil
 		}
 		if !IsErrNewIssueInsert(err) {
@@ -704,7 +704,7 @@ func NewPullRequest(repo *Repository, pull *Issue, labelIDs []int64, uuids []str
 	return fmt.Errorf("NewPullRequest: too many errors attempting to insert the new issue. Last error was: %v", err)
 }
 
-func newPullRequestAttempt(repo *Repository, pull *Issue, labelIDs []int64, uuids []string, pr *PullRequest, patch []byte, assigneeIDs []int64) (err error) {
+func newPullRequestAttempt(repo *Repository, pull *Issue, labelIDs []int64, uuids []string, pr *PullRequest, patch []byte) (err error) {
 	sess := x.NewSession()
 	defer sess.Close()
 	if err = sess.Begin(); err != nil {
@@ -717,7 +717,6 @@ func newPullRequestAttempt(repo *Repository, pull *Issue, labelIDs []int64, uuid
 		LabelIDs:    labelIDs,
 		Attachments: uuids,
 		IsPull:      true,
-		AssigneeIDs: assigneeIDs,
 	}); err != nil {
 		if IsErrUserDoesNotHaveAccessToRepo(err) || IsErrNewIssueInsert(err) {
 			return err

models/repo_permission.go

@@ -329,10 +329,18 @@ func HasAccessUnit(user *User, repo *Repository, unitType UnitType, testMode Acc
 	return hasAccessUnit(x, user, repo, unitType, testMode)
 }
 
-// canBeAssigned return true if user could be assigned to a repo
+// CanBeAssigned return true if user can be assigned to issue or pull requests in repo
+// Currently any write access (code, issues or pr's) is assignable, to match assignee list in user interface.
 // FIXME: user could send PullRequest also could be assigned???
-func canBeAssigned(e Engine, user *User, repo *Repository) (bool, error) {
+func CanBeAssigned(user *User, repo *Repository, isPull bool) (bool, error) {
-	return hasAccessUnit(e, user, repo, UnitTypeCode, AccessModeWrite)
+	if user.IsOrganization() {
+		return false, fmt.Errorf("Organization can't be added as assignee [user_id: %d, repo_id: %d]", user.ID, repo.ID)
+	}
+	perm, err := GetUserRepoPermission(repo, user)
+	if err != nil {
+		return false, err
+	}
+	return perm.CanAccessAny(AccessModeWrite, UnitTypeCode, UnitTypeIssues, UnitTypePullRequests), nil
 }
 
 func hasAccess(e Engine, userID int64, repo *Repository) (bool, error) {

models/user.go

@@ -1320,16 +1320,20 @@ func GetUsersByIDs(ids []int64) ([]*User, error) {
 }
 
 // GetUserIDsByNames returns a slice of ids corresponds to names.
-func GetUserIDsByNames(names []string) []int64 {
+func GetUserIDsByNames(names []string, ignoreNonExistent bool) ([]int64, error) {
 	ids := make([]int64, 0, len(names))
 	for _, name := range names {
 		u, err := GetUserByName(name)
 		if err != nil {
+			if ignoreNonExistent {
 				continue
+			} else {
+				return nil, err
+			}
 		}
 		ids = append(ids, u.ID)
 	}
-	return ids
+	return ids, nil
 }
 
 // UserCommit represents a commit with validation of user.

modules/notification/base/notifier.go

@@ -21,7 +21,7 @@ type Notifier interface {
 	NotifyNewIssue(*models.Issue)
 	NotifyIssueChangeStatus(*models.User, *models.Issue, bool)
 	NotifyIssueChangeMilestone(doer *models.User, issue *models.Issue)
-	NotifyIssueChangeAssignee(doer *models.User, issue *models.Issue, removed bool)
+	NotifyIssueChangeAssignee(doer *models.User, issue *models.Issue, assignee *models.User, removed bool, comment *models.Comment)
 	NotifyIssueChangeContent(doer *models.User, issue *models.Issue, oldContent string)
 	NotifyIssueClearLabels(doer *models.User, issue *models.Issue)
 	NotifyIssueChangeTitle(doer *models.User, issue *models.Issue, oldTitle string)

modules/notification/base/null.go

@@ -83,7 +83,7 @@ func (*NullNotifier) NotifyIssueChangeContent(doer *models.User, issue *models.I
 }
 
 // NotifyIssueChangeAssignee places a place holder function
-func (*NullNotifier) NotifyIssueChangeAssignee(doer *models.User, issue *models.Issue, removed bool) {
+func (*NullNotifier) NotifyIssueChangeAssignee(doer *models.User, issue *models.Issue, assignee *models.User, removed bool, comment *models.Comment) {
 }
 
 // NotifyIssueClearLabels places a place holder function

modules/notification/mail/mail.go

@@ -5,6 +5,8 @@
 package mail
 
 import (
+	"fmt"
+
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/notification/base"
@@ -88,3 +90,11 @@ func (m *mailNotifier) NotifyPullRequestReview(pr *models.PullRequest, r *models
 		log.Error("MailParticipants: %v", err)
 	}
 }
+
+func (m *mailNotifier) NotifyIssueChangeAssignee(doer *models.User, issue *models.Issue, assignee *models.User, removed bool, comment *models.Comment) {
+	// mail only sent to added assignees and not self-assignee
+	if !removed && doer.ID != assignee.ID && assignee.EmailNotifications() == models.EmailNotificationsEnabled {
+		ct := fmt.Sprintf("Assigned #%d.", issue.Index)
+		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []string{assignee.Email})
+	}
+}

modules/notification/notification.go

@@ -12,6 +12,7 @@ import (
 	"code.gitea.io/gitea/modules/notification/mail"
 	"code.gitea.io/gitea/modules/notification/ui"
 	"code.gitea.io/gitea/modules/notification/webhook"
+	"code.gitea.io/gitea/modules/setting"
 )
 
 var (
@@ -24,9 +25,12 @@ func RegisterNotifier(notifier base.Notifier) {
 	notifiers = append(notifiers, notifier)
 }
 
-func init() {
+// NewContext registers notification handlers
+func NewContext() {
 	RegisterNotifier(ui.NewNotifier())
+	if setting.Service.EnableNotifyMail {
 		RegisterNotifier(mail.NewNotifier())
+	}
 	RegisterNotifier(indexer.NewNotifier())
 	RegisterNotifier(webhook.NewNotifier())
 }
@@ -138,9 +142,9 @@ func NotifyIssueChangeContent(doer *models.User, issue *models.Issue, oldContent
 }
 
 // NotifyIssueChangeAssignee notifies change content to notifiers
-func NotifyIssueChangeAssignee(doer *models.User, issue *models.Issue, removed bool) {
+func NotifyIssueChangeAssignee(doer *models.User, issue *models.Issue, assignee *models.User, removed bool, comment *models.Comment) {
 	for _, notifier := range notifiers {
-		notifier.NotifyIssueChangeAssignee(doer, issue, removed)
+		notifier.NotifyIssueChangeAssignee(doer, issue, assignee, removed, comment)
 	}
 }
 

options/locale/locale_en-US.ini

@@ -977,6 +977,7 @@ issues.review.review = Review
 issues.review.reviewers = Reviewers
 issues.review.show_outdated = Show outdated
 issues.review.hide_outdated = Hide outdated
+issues.assignee.error = Not all assignees was added due to an unexpected error.
 
 pulls.desc = Enable pull requests and code reviews.
 pulls.new = New Pull Request

routers/api/v1/repo/issue.go

@@ -213,12 +213,31 @@ func CreateIssue(ctx *context.APIContext, form api.CreateIssueOption) {
 			}
 			return
 		}
+
+		// Check if the passed assignees is assignable
+		for _, aID := range assigneeIDs {
+			assignee, err := models.GetUserByID(aID)
+			if err != nil {
+				ctx.Error(500, "GetUserByID", err)
+				return
+			}
+
+			valid, err := models.CanBeAssigned(assignee, ctx.Repo.Repository, false)
+			if err != nil {
+				ctx.Error(500, "canBeAssigned", err)
+				return
+			}
+			if !valid {
+				ctx.Error(422, "canBeAssigned", models.ErrUserDoesNotHaveAccessToRepo{UserID: aID, RepoName: ctx.Repo.Repository.Name})
+				return
+			}
+		}
 	} else {
 		// setting labels is not allowed if user is not a writer
 		form.Labels = make([]int64, 0)
 	}
 
-	if err := issue_service.NewIssue(ctx.Repo.Repository, issue, form.Labels, assigneeIDs, nil); err != nil {
+	if err := issue_service.NewIssue(ctx.Repo.Repository, issue, form.Labels, nil); err != nil {
 		if models.IsErrUserDoesNotHaveAccessToRepo(err) {
 			ctx.Error(400, "UserDoesNotHaveAccessToRepo", err)
 			return
@@ -227,6 +246,11 @@ func CreateIssue(ctx *context.APIContext, form api.CreateIssueOption) {
 		return
 	}
 
+	if err := issue_service.AddAssignees(issue, ctx.User, assigneeIDs); err != nil {
+		ctx.ServerError("AddAssignees", err)
+		return
+	}
+
 	notification.NotifyNewIssue(issue)
 
 	if form.Closed {
@@ -336,9 +360,9 @@ func EditIssue(ctx *context.APIContext, form api.EditIssueOption) {
 			oneAssignee = *form.Assignee
 		}
 
-		err = models.UpdateAPIAssignee(issue, oneAssignee, form.Assignees, ctx.User)
+		err = issue_service.UpdateAssignees(issue, oneAssignee, form.Assignees, ctx.User)
 		if err != nil {
-			ctx.Error(500, "UpdateAPIAssignee", err)
+			ctx.Error(500, "UpdateAssignees", err)
 			return
 		}
 	}

routers/api/v1/repo/pull.go

@@ -17,6 +17,7 @@ import (
 	"code.gitea.io/gitea/modules/notification"
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/timeutil"
+	issue_service "code.gitea.io/gitea/services/issue"
 	milestone_service "code.gitea.io/gitea/services/milestone"
 	pull_service "code.gitea.io/gitea/services/pull"
 )
@@ -285,8 +286,26 @@ func CreatePullRequest(ctx *context.APIContext, form api.CreatePullRequestOption
 		}
 		return
 	}
+	// Check if the passed assignees is assignable
+	for _, aID := range assigneeIDs {
+		assignee, err := models.GetUserByID(aID)
+		if err != nil {
+			ctx.Error(500, "GetUserByID", err)
+			return
+		}
 
-	if err := pull_service.NewPullRequest(repo, prIssue, labelIDs, []string{}, pr, patch, assigneeIDs); err != nil {
+		valid, err := models.CanBeAssigned(assignee, repo, true)
+		if err != nil {
+			ctx.Error(500, "canBeAssigned", err)
+			return
+		}
+		if !valid {
+			ctx.Error(422, "canBeAssigned", models.ErrUserDoesNotHaveAccessToRepo{UserID: aID, RepoName: repo.Name})
+			return
+		}
+	}
+
+	if err := pull_service.NewPullRequest(repo, prIssue, labelIDs, []string{}, pr, patch); err != nil {
 		if models.IsErrUserDoesNotHaveAccessToRepo(err) {
 			ctx.Error(400, "UserDoesNotHaveAccessToRepo", err)
 			return
@@ -298,6 +317,11 @@ func CreatePullRequest(ctx *context.APIContext, form api.CreatePullRequestOption
 		return
 	}
 
+	if err := issue_service.AddAssignees(prIssue, ctx.User, assigneeIDs); err != nil {
+		ctx.ServerError("AddAssignees", err)
+		return
+	}
+
 	notification.NotifyNewPullRequest(pr)
 
 	log.Trace("Pull request created: %d/%d", repo.ID, prIssue.ID)
@@ -387,12 +411,12 @@ func EditPullRequest(ctx *context.APIContext, form api.EditPullRequestOption) {
 	// Send an empty array ([]) to clear all assignees from the Issue.
 
 	if ctx.Repo.CanWrite(models.UnitTypePullRequests) && (form.Assignees != nil || len(form.Assignee) > 0) {
-		err = models.UpdateAPIAssignee(issue, form.Assignee, form.Assignees, ctx.User)
+		err = issue_service.UpdateAssignees(issue, form.Assignee, form.Assignees, ctx.User)
 		if err != nil {
 			if models.IsErrUserNotExist(err) {
 				ctx.Error(422, "", fmt.Sprintf("Assignee does not exist: [name: %s]", err))
 			} else {
-				ctx.Error(500, "UpdateAPIAssignee", err)
+				ctx.Error(500, "UpdateAssignees", err)
 			}
 			return
 		}

routers/init.go

@@ -18,6 +18,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/markup"
 	"code.gitea.io/gitea/modules/markup/external"
+	"code.gitea.io/gitea/modules/notification"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/ssh"
 	"code.gitea.io/gitea/modules/task"
@@ -44,6 +45,7 @@ func NewServices() {
 	setting.NewServices()
 	mailer.NewContext()
 	_ = cache.NewContext()
+	notification.NewContext()
 }
 
 // In case of problems connecting to DB, retry connection. Eg, PGSQL in Docker Container on Synology

routers/repo/issue.go

@@ -503,21 +503,21 @@ func ValidateRepoMetas(ctx *context.Context, form auth.CreateIssueForm, isPull b
 			return nil, nil, 0
 		}
 
-		// Check if the passed assignees actually exists and has write access to the repo
+		// Check if the passed assignees actually exists and is assignable
 		for _, aID := range assigneeIDs {
-			user, err := models.GetUserByID(aID)
+			assignee, err := models.GetUserByID(aID)
 			if err != nil {
 				ctx.ServerError("GetUserByID", err)
 				return nil, nil, 0
 			}
 
-			perm, err := models.GetUserRepoPermission(repo, user)
+			valid, err := models.CanBeAssigned(assignee, repo, isPull)
 			if err != nil {
-				ctx.ServerError("GetUserRepoPermission", err)
+				ctx.ServerError("canBeAssigned", err)
 				return nil, nil, 0
 			}
-			if !perm.CanWriteIssuesOrPulls(isPull) {
+			if !valid {
-				ctx.ServerError("CanWriteIssuesOrPulls", fmt.Errorf("No permission for %s", user.Name))
+				ctx.ServerError("canBeAssigned", models.ErrUserDoesNotHaveAccessToRepo{UserID: aID, RepoName: repo.Name})
 				return nil, nil, 0
 			}
 		}
@@ -574,7 +574,7 @@ func NewIssuePost(ctx *context.Context, form auth.CreateIssueForm) {
 		Content:     form.Content,
 		Ref:         form.Ref,
 	}
-	if err := issue_service.NewIssue(repo, issue, labelIDs, assigneeIDs, attachments); err != nil {
+	if err := issue_service.NewIssue(repo, issue, labelIDs, attachments); err != nil {
 		if models.IsErrUserDoesNotHaveAccessToRepo(err) {
 			ctx.Error(400, "UserDoesNotHaveAccessToRepo", err.Error())
 			return
@@ -583,6 +583,11 @@ func NewIssuePost(ctx *context.Context, form auth.CreateIssueForm) {
 		return
 	}
 
+	if err := issue_service.AddAssignees(issue, ctx.User, assigneeIDs); err != nil {
+		log.Error("AddAssignees: %v", err)
+		ctx.Flash.Error(ctx.Tr("issues.assignee.error"))
+	}
+
 	notification.NotifyNewIssue(issue)
 
 	log.Trace("Issue created: %d/%d", repo.ID, issue.ID)
@@ -1112,7 +1117,7 @@ func UpdateIssueMilestone(ctx *context.Context) {
 	})
 }
 
-// UpdateIssueAssignee change issue's assignee
+// UpdateIssueAssignee change issue's or pull's assignee
 func UpdateIssueAssignee(ctx *context.Context) {
 	issues := getActionIssues(ctx)
 	if ctx.Written() {
@@ -1130,10 +1135,29 @@ func UpdateIssueAssignee(ctx *context.Context) {
 				return
 			}
 		default:
-			if err := issue.ChangeAssignee(ctx.User, assigneeID); err != nil {
+			assignee, err := models.GetUserByID(assigneeID)
-				ctx.ServerError("ChangeAssignee", err)
+			if err != nil {
+				ctx.ServerError("GetUserByID", err)
 				return
 			}
+
+			valid, err := models.CanBeAssigned(assignee, issue.Repo, issue.IsPull)
+			if err != nil {
+				ctx.ServerError("canBeAssigned", err)
+				return
+			}
+			if !valid {
+				ctx.ServerError("canBeAssigned", models.ErrUserDoesNotHaveAccessToRepo{UserID: assigneeID, RepoName: issue.Repo.Name})
+				return
+			}
+
+			removed, comment, err := issue.ToggleAssignee(ctx.User, assigneeID)
+			if err != nil {
+				ctx.ServerError("ToggleAssignee", err)
+				return
+			}
+
+			notification.NotifyIssueChangeAssignee(ctx.User, issue, assignee, removed, comment)
 		}
 	}
 	ctx.JSON(200, map[string]interface{}{

routers/repo/pull.go

@@ -24,6 +24,7 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
 	"code.gitea.io/gitea/services/gitdiff"
+	issue_service "code.gitea.io/gitea/services/issue"
 	pull_service "code.gitea.io/gitea/services/pull"
 
 	"github.com/unknwon/com"
@@ -770,7 +771,7 @@ func CompareAndPullRequestPost(ctx *context.Context, form auth.CreateIssueForm)
 	// FIXME: check error in the case two people send pull request at almost same time, give nice error prompt
 	// instead of 500.
 
-	if err := pull_service.NewPullRequest(repo, pullIssue, labelIDs, attachments, pullRequest, patch, assigneeIDs); err != nil {
+	if err := pull_service.NewPullRequest(repo, pullIssue, labelIDs, attachments, pullRequest, patch); err != nil {
 		if models.IsErrUserDoesNotHaveAccessToRepo(err) {
 			ctx.Error(400, "UserDoesNotHaveAccessToRepo", err.Error())
 			return
@@ -782,6 +783,11 @@ func CompareAndPullRequestPost(ctx *context.Context, form auth.CreateIssueForm)
 		return
 	}
 
+	if err := issue_service.AddAssignees(pullIssue, ctx.User, assigneeIDs); err != nil {
+		log.Error("AddAssignees: %v", err)
+		ctx.Flash.Error(ctx.Tr("issues.assignee.error"))
+	}
+
 	notification.NotifyNewPullRequest(pullRequest)
 
 	log.Trace("Pull request created: %d/%d", repo.ID, pullIssue.ID)

services/issue/issue.go

@@ -9,12 +9,13 @@ import (
 
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/notification"
 	api "code.gitea.io/gitea/modules/structs"
 )
 
 // NewIssue creates new issue with labels for repository.
-func NewIssue(repo *models.Repository, issue *models.Issue, labelIDs []int64, assigneeIDs []int64, uuids []string) error {
+func NewIssue(repo *models.Repository, issue *models.Issue, labelIDs []int64, uuids []string) error {
-	if err := models.NewIssue(repo, issue, labelIDs, assigneeIDs, uuids); err != nil {
+	if err := models.NewIssue(repo, issue, labelIDs, uuids); err != nil {
 		return err
 	}
 
@@ -96,3 +97,104 @@ func ChangeTitle(issue *models.Issue, doer *models.User, title string) (err erro
 
 	return nil
 }
+
+// UpdateAssignees 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 UpdateAssignees(issue *models.Issue, oneAssignee string, multipleAssignees []string, doer *models.User) (err error) {
+	var allNewAssignees []*models.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 := models.GetUserByName(assigneeName)
+		if err != nil {
+			return err
+		}
+
+		allNewAssignees = append(allNewAssignees, assignee)
+	}
+
+	// Delete all old assignees not passed
+	if err = models.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
+}
+
+// AddAssigneeIfNotAssigned adds an assignee only if he isn't already assigned to the issue.
+// Also checks for access of assigned user
+func AddAssigneeIfNotAssigned(issue *models.Issue, doer *models.User, assigneeID int64) (err error) {
+	assignee, err := models.GetUserByID(assigneeID)
+	if err != nil {
+		return err
+	}
+
+	// Check if the user is already assigned
+	isAssigned, err := models.IsUserAssignedToIssue(issue, assignee)
+	if err != nil {
+		return err
+	}
+	if isAssigned {
+		// nothing to to
+		return nil
+	}
+
+	valid, err := models.CanBeAssigned(assignee, issue.Repo, issue.IsPull)
+	if err != nil {
+		return err
+	}
+	if !valid {
+		return models.ErrUserDoesNotHaveAccessToRepo{UserID: assigneeID, RepoName: issue.Repo.Name}
+	}
+
+	removed, comment, err := issue.ToggleAssignee(doer, assigneeID)
+	if err != nil {
+		return err
+	}
+
+	notification.NotifyIssueChangeAssignee(doer, issue, assignee, removed, comment)
+
+	return nil
+}
+
+// AddAssignees adds a list of assignes (from IDs) to an issue
+func AddAssignees(issue *models.Issue, doer *models.User, assigneeIDs []int64) (err error) {
+	for _, assigneeID := range assigneeIDs {
+		if err = AddAssigneeIfNotAssigned(issue, doer, assigneeID); err != nil {
+			return err
+		}
+	}
+	return nil
+}

services/mailer/mail.go

@@ -30,6 +30,7 @@ const (
 
 	mailIssueComment  base.TplName = "issue/comment"
 	mailIssueMention  base.TplName = "issue/mention"
+	mailIssueAssigned base.TplName = "issue/assigned"
 
 	mailNotifyCollaborator base.TplName = "notify/collaborator"
 )
@@ -183,6 +184,7 @@ func composeIssueCommentMessage(issue *models.Issue, doer *models.User, content
 		data = composeTplData(subject, body, issue.HTMLURL())
 	}
 	data["Doer"] = doer
+	data["Issue"] = issue
 
 	var mailBody bytes.Buffer
 
@@ -220,3 +222,8 @@ func SendIssueMentionMail(issue *models.Issue, doer *models.User, content string
 	}
 	SendAsync(composeIssueCommentMessage(issue, doer, content, comment, mailIssueMention, tos, "issue mention"))
 }
+
+// SendIssueAssignedMail composes and sends issue assigned email
+func SendIssueAssignedMail(issue *models.Issue, doer *models.User, content string, comment *models.Comment, tos []string) {
+	SendAsync(composeIssueCommentMessage(issue, doer, content, comment, mailIssueAssigned, tos, "issue assigned"))
+}

services/mailer/mail_issue.go

@@ -10,7 +10,6 @@ import (
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/references"
-	"code.gitea.io/gitea/modules/setting"
 
 	"github.com/unknwon/com"
 )
@@ -24,9 +23,6 @@ func mailSubject(issue *models.Issue) string {
 // 1. Repository watchers and users who are participated in comments.
 // 2. Users who are not in 1. but get mentioned in current issue/comment.
 func mailIssueCommentToParticipants(issue *models.Issue, doer *models.User, content string, comment *models.Comment, mentions []string) error {
-	if !setting.Service.EnableNotifyMail {
-		return nil
-	}
 
 	watchers, err := models.GetWatchers(issue.RepoID)
 	if err != nil {

services/pull/pull.go

@@ -14,8 +14,8 @@ import (
 )
 
 // NewPullRequest creates new pull request with labels for repository.
-func NewPullRequest(repo *models.Repository, pull *models.Issue, labelIDs []int64, uuids []string, pr *models.PullRequest, patch []byte, assigneeIDs []int64) error {
+func NewPullRequest(repo *models.Repository, pull *models.Issue, labelIDs []int64, uuids []string, pr *models.PullRequest, patch []byte) error {
-	if err := models.NewPullRequest(repo, pull, labelIDs, uuids, pr, patch, assigneeIDs); err != nil {
+	if err := models.NewPullRequest(repo, pull, labelIDs, uuids, pr, patch); err != nil {
 		return err
 	}
 

templates/mail/issue/assigned.tmpl

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+<head>
+	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+	<title>{{.Subject}}</title>
+</head>
+
+<body>
+	<p>@{{.Doer.Name}} assigned you to the {{if eq .Issue.IsPull true}}pull request{{else}}issue{{end}} <a href="{{.Link}}">#{{.Issue.Index}}</a> in repository {{.Issue.Repo.FullName}}.</p>
+    <p>
+        ---
+        <br>
+        <a href="{{.Link}}">View it on Gitea</a>.
+    </p>
+
+</body>
+</html>