enhance: allow custom watches to bypass on-mention email restriction (#39652)

Users with "Only Email on Mention" can now still receive email for the
events they picked in a custom repository watch, covering issues, pull
requests and releases. The setting is renamed to "Only Email on Mention
and Custom Watches" to make this explicit, matching GitHub's
"Participating, @mentions and custom".

"All activity" watches don't bypass the setting, because they are also
created automatically by `AUTO_WATCH_NEW_REPOS` for repository creators
and team members. To keep picking every event distinct from "All
activity", the custom watch dialog now stores a new `WatchModeCustom`.
Existing custom watches keep working without a migration.

## Screenshots
### Before
<img width="1650" height="675" alt="grafik"
src="https://github.com/user-attachments/assets/ecc56e20-cd05-41e9-a840-607b352c50a8"
/>

### After
<img width="1657" height="671" alt="grafik"
src="https://github.com/user-attachments/assets/a406db94-3ac4-4587-b840-0cd472b135c5"
/>


Addresses https://github.com/openSUSE/openSUSE-git/issues/183
Ref: https://github.com/go-gitea/gitea/issues/35492

---------

Co-authored-by: bircni <bircni@icloud.com>
Co-authored-by: Giteabot <teabot@gitea.io>

services/mailer/mail_comment.go

@@ -54,7 +54,7 @@ func MailMentionsComment(ctx context.Context, pr *issues_model.PullRequest, c *i
 			ActionType: activities_model.ActionCommentPull,
 			Content:    c.Content,
 			Comment:    c,
-		}, mentions, visited, true); err != nil {
+		}, mentions, visited, true, nil); err != nil {
 		log.Error("mailIssueCommentBatch: %v", err)
 	}
 	return nil

services/mailer/mail_issue.go

@@ -66,6 +66,7 @@ func mailIssueCommentToParticipants(ctx context.Context, comment *mailComment, m
 
 	// =========== Repo watchers ===========
 	// Make repo watchers last, since it's likely the list with the most users
+	var customWatchers container.Set[int64]
 	if !(comment.Issue.IsPull && comment.Issue.PullRequest.IsWorkInProgress(ctx) && comment.ActionType != activities_model.ActionCreatePullRequest) {
 		watchType := util.Iif(comment.Issue.IsPull, repo_model.WatchPullRequests, repo_model.WatchIssues)
 		ids, err = repo_model.GetRepoWatchersIDs(ctx, comment.Issue.RepoID, watchType)
@@ -73,6 +74,12 @@ func mailIssueCommentToParticipants(ctx context.Context, comment *mailComment, m
 			return fmt.Errorf("GetRepoWatchersIDs(%d): %w", comment.Issue.RepoID, err)
 		}
 		unfiltered = append(ids, unfiltered...)
+
+		ids, err = repo_model.GetRepoCustomWatchersIDs(ctx, comment.Issue.RepoID, watchType)
+		if err != nil {
+			return fmt.Errorf("GetRepoCustomWatchersIDs(%d): %w", comment.Issue.RepoID, err)
+		}
+		customWatchers = container.SetOf(ids...)
 	}
 
 	visited := make(container.Set[int64], len(unfiltered)+len(mentions)+1)
@@ -90,7 +97,7 @@ func mailIssueCommentToParticipants(ctx context.Context, comment *mailComment, m
 	}
 
 	// =========== Mentions ===========
-	if err = mailIssueCommentBatch(ctx, comment, mentions, visited, true); err != nil {
+	if err = mailIssueCommentBatch(ctx, comment, mentions, visited, true, nil); err != nil {
 		return fmt.Errorf("mailIssueCommentBatch() mentions: %w", err)
 	}
 
@@ -101,18 +108,18 @@ func mailIssueCommentToParticipants(ctx context.Context, comment *mailComment, m
 	}
 	visited.AddMultiple(ids...)
 
-	unfilteredUsers, err := user_model.GetMailableUsersByIDs(ctx, unfiltered, false)
+	unfilteredUsers, err := user_model.GetMailableUsersByIDs(ctx, unfiltered, len(customWatchers) > 0)
 	if err != nil {
 		return err
 	}
-	if err = mailIssueCommentBatch(ctx, comment, unfilteredUsers, visited, false); err != nil {
+	if err = mailIssueCommentBatch(ctx, comment, unfilteredUsers, visited, false, customWatchers); err != nil {
 		return fmt.Errorf("mailIssueCommentBatch(): %w", err)
 	}
 
 	return nil
 }
 
-func mailIssueCommentBatch(ctx context.Context, comment *mailComment, users []*user_model.User, visited container.Set[int64], fromMention bool) error {
+func mailIssueCommentBatch(ctx context.Context, comment *mailComment, users []*user_model.User, visited container.Set[int64], fromMention bool, customWatchers container.Set[int64]) error {
 	checkUnit := unit.TypeIssues
 	if comment.Issue.IsPull {
 		checkUnit = unit.TypePullRequests
@@ -124,10 +131,10 @@ func mailIssueCommentBatch(ctx context.Context, comment *mailComment, users []*u
 			continue
 		}
 		// At this point we exclude:
-		// user that don't have all mails enabled or users only get mail on mention and this is one ...
+		// user that don't have all mails enabled or users only get mail on mention or custom watch and this is neither ...
 		if !(user.EmailNotificationsPreference == user_model.EmailNotificationsEnabled ||
 			user.EmailNotificationsPreference == user_model.EmailNotificationsAndYourOwn ||
-			fromMention && user.EmailNotificationsPreference == user_model.EmailNotificationsOnMention) {
+			user.EmailNotificationsPreference == user_model.EmailNotificationsOnMention && (fromMention || customWatchers.Contains(user.ID))) {
 			continue
 		}
 

services/mailer/mail_release.go

@@ -14,6 +14,7 @@ import (
 	repo_model "gitea.dev/models/repo"
 	"gitea.dev/models/unit"
 	user_model "gitea.dev/models/user"
+	"gitea.dev/modules/container"
 	"gitea.dev/modules/log"
 	"gitea.dev/modules/markup/markdown"
 	"gitea.dev/modules/setting"
@@ -41,7 +42,14 @@ func MailNewRelease(ctx context.Context, rel *repo_model.Release) {
 		return
 	}
 
-	recipients, err := user_model.GetMailableUsersByIDs(ctx, watcherIDList, false)
+	customWatcherIDs, err := repo_model.GetRepoCustomWatchersIDs(ctx, rel.RepoID, repo_model.WatchReleases)
+	if err != nil {
+		log.Error("GetRepoCustomWatchersIDs(%d): %v", rel.RepoID, err)
+		return
+	}
+	customWatchers := container.SetOf(customWatcherIDs...)
+
+	recipients, err := user_model.GetMailableUsersByIDs(ctx, watcherIDList, len(customWatchers) > 0)
 	if err != nil {
 		log.Error("user_model.GetMailableUsersByIDs: %v", err)
 		return
@@ -52,9 +60,11 @@ func MailNewRelease(ctx context.Context, rel *repo_model.Release) {
 		return
 	}
 
-	// delete publisher or any users with no permission
+	// delete publisher, on-mention users without a custom watch or any users with no permission
 	recipients = slices.DeleteFunc(recipients, func(u *user_model.User) bool {
-		return u.ID == rel.PublisherID || !access_model.CheckRepoUnitUser(ctx, rel.Repo, u, unit.TypeReleases)
+		return u.ID == rel.PublisherID ||
+			u.EmailNotificationsPreference == user_model.EmailNotificationsOnMention && !customWatchers.Contains(u.ID) ||
+			!access_model.CheckRepoUnitUser(ctx, rel.Repo, u, unit.TypeReleases)
 	})
 
 	langMap := make(map[string][]*user_model.User)

services/mailer/mail_release_test.go

@@ -61,3 +61,29 @@ func TestMailNewReleaseFiltersUnauthorizedWatchers(t *testing.T) {
 	assert.Equal(t, admin.EmailTo(), sent[0].To)
 	assert.NotEqual(t, unauthorized.EmailTo(), sent[0].To)
 }
+
+func TestMailNewReleaseOnMentionCustomWatch(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	defer test.MockVariableValue(&setting.MailService, &setting.Mailer{FromEmail: "noreply@example.com"})()
+	defer mockMailTemplates(string(tplNewReleaseMail), "{{.Subject}}", "<p>{{.Release.TagName}}</p>")()
+
+	// users 4 and 9 only get mail on mention and watch repo 1 with all activity
+	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 1})
+	customWatcher := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 4})
+	allWatcher := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 9})
+	require.NoError(t, repo_model.WatchRepoWithOptions(t.Context(), customWatcher, repo, repo_model.WatchOptions{Mode: repo_model.WatchModeCustom, WatchReleases: true}))
+
+	rel := unittest.AssertExistsAndLoadBean(t, &repo_model.Release{ID: 1, RepoID: repo.ID})
+	rel.Publisher = unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: rel.PublisherID})
+
+	var recipients []string
+	defer test.MockVariableValue(&SendAsync, func(msgs ...*sender_service.Message) {
+		for _, msg := range msgs {
+			recipients = append(recipients, msg.To)
+		}
+	})()
+
+	MailNewRelease(t.Context(), rel)
+	assert.Contains(t, recipients, customWatcher.EmailTo())
+	assert.NotContains(t, recipients, allWatcher.EmailTo())
+}

services/mailer/mail_test.go

@@ -167,6 +167,28 @@ func TestMailMentionsComment(t *testing.T) {
 	assert.Equal(t, 3, mails)
 }
 
+func TestMailParticipantsOnMentionCustomWatch(t *testing.T) {
+	doer, repo, issue, comment := prepareMailerTest(t)
+	comment.Poster = doer
+	defer mockMailTemplates("mail/repo/issue/comment", subjectTpl, bodyTpl)()
+
+	// users 4 and 9 only get mail on mention and watch repo 1 with all activity
+	customWatcher := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 4})
+	allWatcher := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 9})
+	require.NoError(t, repo_model.WatchRepoWithOptions(t.Context(), customWatcher, repo, repo_model.WatchOptions{Mode: repo_model.WatchModeCustom, WatchPullRequests: true, WatchIssues: true, WatchReleases: true}))
+
+	var recipients []string
+	defer test.MockVariableValue(&SendAsync, func(msgs ...*sender_service.Message) {
+		for _, msg := range msgs {
+			recipients = append(recipients, msg.To)
+		}
+	})()
+
+	require.NoError(t, MailParticipantsComment(t.Context(), comment, activities_model.ActionCommentIssue, issue, nil))
+	assert.Contains(t, recipients, customWatcher.Email)
+	assert.NotContains(t, recipients, allWatcher.Email)
+}
+
 func TestMailsSkipBots(t *testing.T) {
 	doer, repo, issue, comment := prepareMailerTest(t)
 	comment.Poster = doer