Add container.FilterSlice function (#30339)

Many places have the following logic:
```go
func (jobs ActionJobList) GetRunIDs() []int64 {
	ids := make(container.Set[int64], len(jobs))
	for _, j := range jobs {
		if j.RunID == 0 {
			continue
		}
		ids.Add(j.RunID)
	}
	return ids.Values()
}
```

this introduces a `container.FilterMapUnique` function, which reduces
the code above to:
```go
func (jobs ActionJobList) GetRunIDs() []int64 {
	return container.FilterMapUnique(jobs, func(j *ActionRunJob) (int64, bool) {
		return j.RunID, j.RunID != 0
	})
}
```

16 files changed, 150 insertions, 184 deletions

diff --git a/models/actions/run_job_list.go b/models/actions/run_job_list.go
index 6ea6cb9d3b..6c5d3b3252 100644
--- a/models/actions/run_job_list.go
+++ b/models/actions/run_job_list.go
@@ -16,14 +16,9 @@ import (
 type ActionJobList []*ActionRunJob
 
 func (jobs ActionJobList) GetRunIDs() []int64 {
-	ids := make(container.Set[int64], len(jobs))
-	for _, j := range jobs {
-		if j.RunID == 0 {
-			continue
-		}
-		ids.Add(j.RunID)
-	}
-	return ids.Values()
+	return container.FilterSlice(jobs, func(j *ActionRunJob) (int64, bool) {
+		return j.RunID, j.RunID != 0
+	})
 }
 
 func (jobs ActionJobList) LoadRuns(ctx context.Context, withRepo bool) error {
diff --git a/models/actions/run_list.go b/models/actions/run_list.go
index 388bfc4f86..4046c7d369 100644
--- a/models/actions/run_list.go
+++ b/models/actions/run_list.go
@@ -19,19 +19,15 @@ type RunList []*ActionRun
 
 // GetUserIDs returns a slice of user's id
 func (runs RunList) GetUserIDs() []int64 {
-	ids := make(container.Set[int64], len(runs))
-	for _, run := range runs {
-		ids.Add(run.TriggerUserID)
-	}
-	return ids.Values()
+	return container.FilterSlice(runs, func(run *ActionRun) (int64, bool) {
+		return run.TriggerUserID, true
+	})
 }
 
 func (runs RunList) GetRepoIDs() []int64 {
-	ids := make(container.Set[int64], len(runs))
-	for _, run := range runs {
-		ids.Add(run.RepoID)
-	}
-	return ids.Values()
+	return container.FilterSlice(runs, func(run *ActionRun) (int64, bool) {
+		return run.RepoID, true
+	})
 }
 
 func (runs RunList) LoadTriggerUser(ctx context.Context) error {
diff --git a/models/actions/runner_list.go b/models/actions/runner_list.go
index 87f0886b47..5ce69e07ac 100644
--- a/models/actions/runner_list.go
+++ b/models/actions/runner_list.go
@@ -16,14 +16,9 @@ type RunnerList []*ActionRunner
 
 // GetUserIDs returns a slice of user's id
 func (runners RunnerList) GetUserIDs() []int64 {
-	ids := make(container.Set[int64], len(runners))
-	for _, runner := range runners {
-		if runner.OwnerID == 0 {
-			continue
-		}
-		ids.Add(runner.OwnerID)
-	}
-	return ids.Values()
+	return container.FilterSlice(runners, func(runner *ActionRunner) (int64, bool) {
+		return runner.OwnerID, runner.OwnerID != 0
+	})
 }
 
 func (runners RunnerList) LoadOwners(ctx context.Context) error {
diff --git a/models/actions/schedule_list.go b/models/actions/schedule_list.go
index b806550b87..1d35adc420 100644
--- a/models/actions/schedule_list.go
+++ b/models/actions/schedule_list.go
@@ -18,19 +18,15 @@ type ScheduleList []*ActionSchedule
 
 // GetUserIDs returns a slice of user's id
 func (schedules ScheduleList) GetUserIDs() []int64 {
-	ids := make(container.Set[int64], len(schedules))
-	for _, schedule := range schedules {
-		ids.Add(schedule.TriggerUserID)
-	}
-	return ids.Values()
+	return container.FilterSlice(schedules, func(schedule *ActionSchedule) (int64, bool) {
+		return schedule.TriggerUserID, true
+	})
 }
 
 func (schedules ScheduleList) GetRepoIDs() []int64 {
-	ids := make(container.Set[int64], len(schedules))
-	for _, schedule := range schedules {
-		ids.Add(schedule.RepoID)
-	}
-	return ids.Values()
+	return container.FilterSlice(schedules, func(schedule *ActionSchedule) (int64, bool) {
+		return schedule.RepoID, true
+	})
 }
 
 func (schedules ScheduleList) LoadTriggerUser(ctx context.Context) error {
diff --git a/models/actions/schedule_spec_list.go b/models/actions/schedule_spec_list.go
index e9ae268a6e..f7dac72f8b 100644
--- a/models/actions/schedule_spec_list.go
+++ b/models/actions/schedule_spec_list.go
@@ -16,11 +16,9 @@ import (
 type SpecList []*ActionScheduleSpec
 
 func (specs SpecList) GetScheduleIDs() []int64 {
-	ids := make(container.Set[int64], len(specs))
-	for _, spec := range specs {
-		ids.Add(spec.ScheduleID)
-	}
-	return ids.Values()
+	return container.FilterSlice(specs, func(spec *ActionScheduleSpec) (int64, bool) {
+		return spec.ScheduleID, true
+	})
 }
 
 func (specs SpecList) LoadSchedules(ctx context.Context) error {
@@ -46,11 +44,9 @@ func (specs SpecList) LoadSchedules(ctx context.Context) error {
 }
 
 func (specs SpecList) GetRepoIDs() []int64 {
-	ids := make(container.Set[int64], len(specs))
-	for _, spec := range specs {
-		ids.Add(spec.RepoID)
-	}
-	return ids.Values()
+	return container.FilterSlice(specs, func(spec *ActionScheduleSpec) (int64, bool) {
+		return spec.RepoID, true
+	})
 }
 
 func (specs SpecList) LoadRepos(ctx context.Context) error {
diff --git a/models/actions/task_list.go b/models/actions/task_list.go
index b07d00b8db..5e17f91441 100644
--- a/models/actions/task_list.go
+++ b/models/actions/task_list.go
@@ -16,14 +16,9 @@ import (
 type TaskList []*ActionTask
 
 func (tasks TaskList) GetJobIDs() []int64 {
-	ids := make(container.Set[int64], len(tasks))
-	for _, t := range tasks {
-		if t.JobID == 0 {
-			continue
-		}
-		ids.Add(t.JobID)
-	}
-	return ids.Values()
+	return container.FilterSlice(tasks, func(t *ActionTask) (int64, bool) {
+		return t.JobID, t.JobID != 0
+	})
 }
 
 func (tasks TaskList) LoadJobs(ctx context.Context) error {
diff --git a/models/activities/action_list.go b/models/activities/action_list.go
index fdf0f35d4f..6e23b173b5 100644
--- a/models/activities/action_list.go
+++ b/models/activities/action_list.go
@@ -22,11 +22,9 @@ import (
 type ActionList []*Action
 
 func (actions ActionList) getUserIDs() []int64 {
-	userIDs := make(container.Set[int64], len(actions))
-	for _, action := range actions {
-		userIDs.Add(action.ActUserID)
-	}
-	return userIDs.Values()
+	return container.FilterSlice(actions, func(action *Action) (int64, bool) {
+		return action.ActUserID, true
+	})
 }
 
 func (actions ActionList) LoadActUsers(ctx context.Context) (map[int64]*user_model.User, error) {
@@ -50,11 +48,9 @@ func (actions ActionList) LoadActUsers(ctx context.Context) (map[int64]*user_mod
 }
 
 func (actions ActionList) getRepoIDs() []int64 {
-	repoIDs := make(container.Set[int64], len(actions))
-	for _, action := range actions {
-		repoIDs.Add(action.RepoID)
-	}
-	return repoIDs.Values()
+	return container.FilterSlice(actions, func(action *Action) (int64, bool) {
+		return action.RepoID, true
+	})
 }
 
 func (actions ActionList) LoadRepositories(ctx context.Context) error {
@@ -80,18 +76,16 @@ func (actions ActionList) loadRepoOwner(ctx context.Context, userMap map[int64]*
 		userMap = make(map[int64]*user_model.User)
 	}
 
-	userSet := make(container.Set[int64], len(actions))
-	for _, action := range actions {
+	missingUserIDs := container.FilterSlice(actions, func(action *Action) (int64, bool) {
 		if action.Repo == nil {
-			continue
+			return 0, false
 		}
-		if _, ok := userMap[action.Repo.OwnerID]; !ok {
-			userSet.Add(action.Repo.OwnerID)
-		}
-	}
+		_, alreadyLoaded := userMap[action.Repo.OwnerID]
+		return action.Repo.OwnerID, !alreadyLoaded
+	})
 
 	if err := db.GetEngine(ctx).
-		In("id", userSet.Values()).
+		In("id", missingUserIDs).
 		Find(&userMap); err != nil {
 		return fmt.Errorf("find user: %w", err)
 	}
diff --git a/models/git/branch_list.go b/models/git/branch_list.go
index 8319e5ecd0..980bd7b4c9 100644
--- a/models/git/branch_list.go
+++ b/models/git/branch_list.go
@@ -17,15 +17,12 @@ import (
 type BranchList []*Branch
 
 func (branches BranchList) LoadDeletedBy(ctx context.Context) error {
-	ids := container.Set[int64]{}
-	for _, branch := range branches {
-		if !branch.IsDeleted {
-			continue
-		}
-		ids.Add(branch.DeletedByID)
-	}
+	ids := container.FilterSlice(branches, func(branch *Branch) (int64, bool) {
+		return branch.DeletedByID, branch.IsDeleted
+	})
+
 	usersMap := make(map[int64]*user_model.User, len(ids))
-	if err := db.GetEngine(ctx).In("id", ids.Values()).Find(&usersMap); err != nil {
+	if err := db.GetEngine(ctx).In("id", ids).Find(&usersMap); err != nil {
 		return err
 	}
 	for _, branch := range branches {
@@ -41,14 +38,13 @@ func (branches BranchList) LoadDeletedBy(ctx context.Context) error {
 }
 
 func (branches BranchList) LoadPusher(ctx context.Context) error {
-	ids := container.Set[int64]{}
-	for _, branch := range branches {
-		if branch.PusherID > 0 { // pusher_id maybe zero because some branches are sync by backend with no pusher
-			ids.Add(branch.PusherID)
-		}
-	}
+	ids := container.FilterSlice(branches, func(branch *Branch) (int64, bool) {
+		// pusher_id maybe zero because some branches are sync by backend with no pusher
+		return branch.PusherID, branch.PusherID > 0
+	})
+
 	usersMap := make(map[int64]*user_model.User, len(ids))
-	if err := db.GetEngine(ctx).In("id", ids.Values()).Find(&usersMap); err != nil {
+	if err := db.GetEngine(ctx).In("id", ids).Find(&usersMap); err != nil {
 		return err
 	}
 	for _, branch := range branches {
diff --git a/models/issues/comment.go b/models/issues/comment.go
index 6f65a5dbbc..353163ebd6 100644
--- a/models/issues/comment.go
+++ b/models/issues/comment.go
@@ -1272,10 +1272,9 @@ func InsertIssueComments(ctx context.Context, comments []*Comment) error {
 		return nil
 	}
 
-	issueIDs := make(container.Set[int64])
-	for _, comment := range comments {
-		issueIDs.Add(comment.IssueID)
-	}
+	issueIDs := container.FilterSlice(comments, func(comment *Comment) (int64, bool) {
+		return comment.IssueID, true
+	})
 
 	ctx, committer, err := db.TxContext(ctx)
 	if err != nil {
@@ -1298,7 +1297,7 @@ func InsertIssueComments(ctx context.Context, comments []*Comment) error {
 		}
 	}
 
-	for issueID := range issueIDs {
+	for _, issueID := range issueIDs {
 		if _, err := db.Exec(ctx, "UPDATE issue set num_comments = (SELECT count(*) FROM comment WHERE issue_id = ? AND `type`=?) WHERE id = ?",
 			issueID, CommentTypeComment, issueID); err != nil {
 			return err
diff --git a/models/issues/comment_list.go b/models/issues/comment_list.go
index 0047b054ba..370b5396e0 100644
--- a/models/issues/comment_list.go
+++ b/models/issues/comment_list.go
@@ -17,13 +17,9 @@ import (
 type CommentList []*Comment
 
 func (comments CommentList) getPosterIDs() []int64 {
-	posterIDs := make(container.Set[int64], len(comments))
-	for _, comment := range comments {
-		if comment.PosterID > 0 {
-			posterIDs.Add(comment.PosterID)
-		}
-	}
-	return posterIDs.Values()
+	return container.FilterSlice(comments, func(c *Comment) (int64, bool) {
+		return c.PosterID, c.PosterID > 0
+	})
 }
 
 // LoadPosters loads posters
@@ -44,13 +40,9 @@ func (comments CommentList) LoadPosters(ctx context.Context) error {
 }
 
 func (comments CommentList) getLabelIDs() []int64 {
-	ids := make(container.Set[int64], len(comments))
-	for _, comment := range comments {
-		if comment.LabelID > 0 {
-			ids.Add(comment.LabelID)
-		}
-	}
-	return ids.Values()
+	return container.FilterSlice(comments, func(comment *Comment) (int64, bool) {
+		return comment.LabelID, comment.LabelID > 0
+	})
 }
 
 func (comments CommentList) loadLabels(ctx context.Context) error {
@@ -94,13 +86,9 @@ func (comments CommentList) loadLabels(ctx context.Context) error {
 }
 
 func (comments CommentList) getMilestoneIDs() []int64 {
-	ids := make(container.Set[int64], len(comments))
-	for _, comment := range comments {
-		if comment.MilestoneID > 0 {
-			ids.Add(comment.MilestoneID)
-		}
-	}
-	return ids.Values()
+	return container.FilterSlice(comments, func(comment *Comment) (int64, bool) {
+		return comment.MilestoneID, comment.MilestoneID > 0
+	})
 }
 
 func (comments CommentList) loadMilestones(ctx context.Context) error {
@@ -137,13 +125,9 @@ func (comments CommentList) loadMilestones(ctx context.Context) error {
 }
 
 func (comments CommentList) getOldMilestoneIDs() []int64 {
-	ids := make(container.Set[int64], len(comments))
-	for _, comment := range comments {
-		if comment.OldMilestoneID > 0 {
-			ids.Add(comment.OldMilestoneID)
-		}
-	}
-	return ids.Values()
+	return container.FilterSlice(comments, func(comment *Comment) (int64, bool) {
+		return comment.OldMilestoneID, comment.OldMilestoneID > 0
+	})
 }
 
 func (comments CommentList) loadOldMilestones(ctx context.Context) error {
@@ -180,13 +164,9 @@ func (comments CommentList) loadOldMilestones(ctx context.Context) error {
 }
 
 func (comments CommentList) getAssigneeIDs() []int64 {
-	ids := make(container.Set[int64], len(comments))
-	for _, comment := range comments {
-		if comment.AssigneeID > 0 {
-			ids.Add(comment.AssigneeID)
-		}
-	}
-	return ids.Values()
+	return container.FilterSlice(comments, func(comment *Comment) (int64, bool) {
+		return comment.AssigneeID, comment.AssigneeID > 0
+	})
 }
 
 func (comments CommentList) loadAssignees(ctx context.Context) error {
@@ -237,14 +217,9 @@ func (comments CommentList) loadAssignees(ctx context.Context) error {
 
 // getIssueIDs returns all the issue ids on this comment list which issue hasn't been loaded
 func (comments CommentList) getIssueIDs() []int64 {
-	ids := make(container.Set[int64], len(comments))
-	for _, comment := range comments {
-		if comment.Issue != nil {
-			continue
-		}
-		ids.Add(comment.IssueID)
-	}
-	return ids.Values()
+	return container.FilterSlice(comments, func(comment *Comment) (int64, bool) {
+		return comment.IssueID, comment.Issue == nil
+	})
 }
 
 // Issues returns all the issues of comments
@@ -311,16 +286,12 @@ func (comments CommentList) LoadIssues(ctx context.Context) error {
 }
 
 func (comments CommentList) getDependentIssueIDs() []int64 {
-	ids := make(container.Set[int64], len(comments))
-	for _, comment := range comments {
+	return container.FilterSlice(comments, func(comment *Comment) (int64, bool) {
 		if comment.DependentIssue != nil {
-			continue
-		}
-		if comment.DependentIssueID > 0 {
-			ids.Add(comment.DependentIssueID)
+			return 0, false
 		}
-	}
-	return ids.Values()
+		return comment.DependentIssueID, comment.DependentIssueID > 0
+	})
 }
 
 func (comments CommentList) loadDependentIssues(ctx context.Context) error {
@@ -375,15 +346,9 @@ func (comments CommentList) loadDependentIssues(ctx context.Context) error {
 
 // getAttachmentCommentIDs only return the comment ids which possibly has attachments
 func (comments CommentList) getAttachmentCommentIDs() []int64 {
-	ids := make(container.Set[int64], len(comments))
-	for _, comment := range comments {
-		if comment.Type == CommentTypeComment ||
-			comment.Type == CommentTypeReview ||
-			comment.Type == CommentTypeCode {
-			ids.Add(comment.ID)
-		}
-	}
-	return ids.Values()
+	return container.FilterSlice(comments, func(comment *Comment) (int64, bool) {
+		return comment.ID, comment.Type.HasAttachmentSupport()
+	})
 }
 
 // LoadAttachmentsByIssue loads attachments by issue id
@@ -451,13 +416,9 @@ func (comments CommentList) LoadAttachments(ctx context.Context) (err error) {
 }
 
 func (comments CommentList) getReviewIDs() []int64 {
-	ids := make(container.Set[int64], len(comments))
-	for _, comment := range comments {
-		if comment.ReviewID > 0 {
-			ids.Add(comment.ReviewID)
-		}
-	}
-	return ids.Values()
+	return container.FilterSlice(comments, func(comment *Comment) (int64, bool) {
+		return comment.ReviewID, comment.ReviewID > 0
+	})
 }
 
 func (comments CommentList) loadReviews(ctx context.Context) error {
diff --git a/models/issues/issue_list.go b/models/issues/issue_list.go
index 218891ad35..1b05f0aa35 100644
--- a/models/issues/issue_list.go
+++ b/models/issues/issue_list.go
@@ -74,11 +74,9 @@ func (issues IssueList) LoadRepositories(ctx context.Context) (repo_model.Reposi
 }
 
 func (issues IssueList) getPosterIDs() []int64 {
-	posterIDs := make(container.Set[int64], len(issues))
-	for _, issue := range issues {
-		posterIDs.Add(issue.PosterID)
-	}
-	return posterIDs.Values()
+	return container.FilterSlice(issues, func(issue *Issue) (int64, bool) {
+		return issue.PosterID, true
+	})
 }
 
 func (issues IssueList) loadPosters(ctx context.Context) error {
@@ -193,11 +191,9 @@ func (issues IssueList) loadLabels(ctx context.Context) error {
 }
 
 func (issues IssueList) getMilestoneIDs() []int64 {
-	ids := make(container.Set[int64], len(issues))
-	for _, issue := range issues {
-		ids.Add(issue.MilestoneID)
-	}
-	return ids.Values()
+	return container.FilterSlice(issues, func(issue *Issue) (int64, bool) {
+		return issue.MilestoneID, true
+	})
 }
 
 func (issues IssueList) loadMilestones(ctx context.Context) error {
diff --git a/models/issues/reaction.go b/models/issues/reaction.go
index d5448636fe..eb7faefc79 100644
--- a/models/issues/reaction.go
+++ b/models/issues/reaction.go
@@ -305,14 +305,12 @@ func (list ReactionList) GroupByType() map[string]ReactionList {
 }
 
 func (list ReactionList) getUserIDs() []int64 {
-	userIDs := make(container.Set[int64], len(list))
-	for _, reaction := range list {
+	return container.FilterSlice(list, func(reaction *Reaction) (int64, bool) {
 		if reaction.OriginalAuthor != "" {
-			continue
+			return 0, false
 		}
-		userIDs.Add(reaction.UserID)
-	}
-	return userIDs.Values()
+		return reaction.UserID, true
+	})
 }
 
 func valuesUser(m map[int64]*user_model.User) []*user_model.User {
diff --git a/models/issues/review_list.go b/models/issues/review_list.go
index ec6cb07988..7b8c3d319c 100644
--- a/models/issues/review_list.go
+++ b/models/issues/review_list.go
@@ -38,12 +38,11 @@ func (reviews ReviewList) LoadReviewers(ctx context.Context) error {
 }
 
 func (reviews ReviewList) LoadIssues(ctx context.Context) error {
-	issueIDs := container.Set[int64]{}
-	for i := 0; i < len(reviews); i++ {
-		issueIDs.Add(reviews[i].IssueID)
-	}
+	issueIDs := container.FilterSlice(reviews, func(review *Review) (int64, bool) {
+		return review.IssueID, true
+	})
 
-	issues, err := GetIssuesByIDs(ctx, issueIDs.Values())
+	issues, err := GetIssuesByIDs(ctx, issueIDs)
 	if err != nil {
 		return err
 	}
diff --git a/models/repo/repo_list.go b/models/repo/repo_list.go
index cb7cd47a8d..987c7df9b0 100644
--- a/models/repo/repo_list.go
+++ b/models/repo/repo_list.go
@@ -104,18 +104,19 @@ func (repos RepositoryList) LoadAttributes(ctx context.Context) error {
 		return nil
 	}
 
-	set := make(container.Set[int64])
+	userIDs := container.FilterSlice(repos, func(repo *Repository) (int64, bool) {
+		return repo.OwnerID, true
+	})
 	repoIDs := make([]int64, len(repos))
 	for i := range repos {
-		set.Add(repos[i].OwnerID)
 		repoIDs[i] = repos[i].ID
 	}
 
 	// Load owners.
-	users := make(map[int64]*user_model.User, len(set))
+	users := make(map[int64]*user_model.User, len(userIDs))
 	if err := db.GetEngine(ctx).
 		Where("id > 0").
-		In("id", set.Values()).
+		In("id", userIDs).
 		Find(&users); err != nil {
 		return fmt.Errorf("find users: %w", err)
 	}
diff --git a/modules/container/filter.go b/modules/container/filter.go
new file mode 100644
index 0000000000..37ec7c3d56
--- /dev/null
+++ b/modules/container/filter.go
@@ -0,0 +1,21 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package container
+
+import "slices"
+
+// FilterSlice ranges over the slice and calls include() for each element.
+// If the second returned value is true, the first returned value will be included in the resulting
+// slice (after deduplication).
+func FilterSlice[E any, T comparable](s []E, include func(E) (T, bool)) []T {
+	filtered := make([]T, 0, len(s)) // slice will be clipped before returning
+	seen := make(map[T]bool, len(s))
+	for i := range s {
+		if v, ok := include(s[i]); ok && !seen[v] {
+			filtered = append(filtered, v)
+			seen[v] = true
+		}
+	}
+	return slices.Clip(filtered)
+}
diff --git a/modules/container/filter_test.go b/modules/container/filter_test.go
new file mode 100644
index 0000000000..ad304e5abb
--- /dev/null
+++ b/modules/container/filter_test.go
@@ -0,0 +1,28 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package container
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFilterMapUnique(t *testing.T) {
+	result := FilterSlice([]int{
+		0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
+	}, func(i int) (int, bool) {
+		switch i {
+		case 0:
+			return 0, true // included later
+		case 1:
+			return 0, true // duplicate of previous (should be ignored)
+		case 2:
+			return 2, false // not included
+		default:
+			return i, true
+		}
+	})
+	assert.Equal(t, []int{0, 3, 4, 5, 6, 7, 8, 9}, result)
+}