Refactor topic Find functions and add more tests for pagination (#30127)

This also fixed #22238

models/repo/topic.go

 	Keyword string
 }
 
-func (opts *FindTopicOptions) toConds() builder.Cond {
+func (opts *FindTopicOptions) ToConds() builder.Cond {
 	cond := builder.NewCond()
 	if opts.RepoID > 0 {
 		cond = cond.And(builder.Eq{"repo_topic.repo_id": opts.RepoID})
 	return cond
 }
 
-// FindTopics retrieves the topics via FindTopicOptions
-func FindTopics(ctx context.Context, opts *FindTopicOptions) ([]*Topic, int64, error) {
-	sess := db.GetEngine(ctx).Select("topic.*").Where(opts.toConds())
+func (opts *FindTopicOptions) ToOrders() string {
 	orderBy := "topic.repo_count DESC"
 	if opts.RepoID > 0 {
-		sess.Join("INNER", "repo_topic", "repo_topic.topic_id = topic.id")
 		orderBy = "topic.name" // when render topics for a repo, it's better to sort them by name, to get consistent result
 	}
-	if opts.PageSize != 0 && opts.Page != 0 {
-		sess = db.SetSessionPagination(sess, opts)
-	}
-	topics := make([]*Topic, 0, 10)
-	total, err := sess.OrderBy(orderBy).FindAndCount(&topics)
-	return topics, total, err
+	return orderBy
 }
 
-// CountTopics counts the number of topics matching the FindTopicOptions
-func CountTopics(ctx context.Context, opts *FindTopicOptions) (int64, error) {
-	sess := db.GetEngine(ctx).Where(opts.toConds())
-	if opts.RepoID > 0 {
-		sess.Join("INNER", "repo_topic", "repo_topic.topic_id = topic.id")
+func (opts *FindTopicOptions) ToJoins() []db.JoinFunc {
+	if opts.RepoID <= 0 {
+		return nil
+	}
+	return []db.JoinFunc{
+		func(e db.Engine) error {
+			e.Join("INNER", "repo_topic", "repo_topic.topic_id = topic.id")
+			return nil
+		},
 	}
-	return sess.Count(new(Topic))
 }
 
 // GetRepoTopicByName retrieves topic from name for a repo if it exist
 
 // SaveTopics save topics to a repository
 func SaveTopics(ctx context.Context, repoID int64, topicNames ...string) error {
-	topics, _, err := FindTopics(ctx, &FindTopicOptions{
+	topics, err := db.Find[Topic](ctx, &FindTopicOptions{
 		RepoID: repoID,
 	})
 	if err != nil {

models/repo/topic_test.go

 
 	assert.NoError(t, unittest.PrepareTestDatabase())
 
-	topics, _, err := repo_model.FindTopics(db.DefaultContext, &repo_model.FindTopicOptions{})
+	topics, err := db.Find[repo_model.Topic](db.DefaultContext, &repo_model.FindTopicOptions{})
 	assert.NoError(t, err)
 	assert.Len(t, topics, totalNrOfTopics)
 
-	topics, total, err := repo_model.FindTopics(db.DefaultContext, &repo_model.FindTopicOptions{
+	topics, total, err := db.FindAndCount[repo_model.Topic](db.DefaultContext, &repo_model.FindTopicOptions{
 		ListOptions: db.ListOptions{Page: 1, PageSize: 2},
 	})
 	assert.NoError(t, err)
 	assert.Len(t, topics, 2)
 	assert.EqualValues(t, 6, total)
 
-	topics, _, err = repo_model.FindTopics(db.DefaultContext, &repo_model.FindTopicOptions{
+	topics, err = db.Find[repo_model.Topic](db.DefaultContext, &repo_model.FindTopicOptions{
 		RepoID: 1,
 	})
 	assert.NoError(t, err)
 
 	assert.NoError(t, repo_model.SaveTopics(db.DefaultContext, 2, "golang"))
 	repo2NrOfTopics := 1
-	topics, _, err = repo_model.FindTopics(db.DefaultContext, &repo_model.FindTopicOptions{})
+	topics, err = db.Find[repo_model.Topic](db.DefaultContext, &repo_model.FindTopicOptions{})
 	assert.NoError(t, err)
 	assert.Len(t, topics, totalNrOfTopics)
 
-	topics, _, err = repo_model.FindTopics(db.DefaultContext, &repo_model.FindTopicOptions{
+	topics, err = db.Find[repo_model.Topic](db.DefaultContext, &repo_model.FindTopicOptions{
 		RepoID: 2,
 	})
 	assert.NoError(t, err)
 	assert.NoError(t, err)
 	assert.EqualValues(t, 1, topic.RepoCount)
 
-	topics, _, err = repo_model.FindTopics(db.DefaultContext, &repo_model.FindTopicOptions{})
+	topics, err = db.Find[repo_model.Topic](db.DefaultContext, &repo_model.FindTopicOptions{})
 	assert.NoError(t, err)
 	assert.Len(t, topics, totalNrOfTopics)
 
-	topics, _, err = repo_model.FindTopics(db.DefaultContext, &repo_model.FindTopicOptions{
+	topics, err = db.Find[repo_model.Topic](db.DefaultContext, &repo_model.FindTopicOptions{
 		RepoID: 2,
 	})
 	assert.NoError(t, err)

routers/api/v1/repo/topic.go

 	"net/http"
 	"strings"
 
+	"code.gitea.io/gitea/models/db"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/modules/log"
 	api "code.gitea.io/gitea/modules/structs"
 		RepoID:      ctx.Repo.Repository.ID,
 	}
 
-	topics, total, err := repo_model.FindTopics(ctx, opts)
+	topics, total, err := db.FindAndCount[repo_model.Topic](ctx, opts)
 	if err != nil {
 		ctx.InternalServerError(err)
 		return
 	}
 
 	// Prevent adding more topics than allowed to repo
-	count, err := repo_model.CountTopics(ctx, &repo_model.FindTopicOptions{
+	count, err := db.Count[repo_model.Topic](ctx, &repo_model.FindTopicOptions{
 		RepoID: ctx.Repo.Repository.ID,
 	})
 	if err != nil {
 		ListOptions: utils.GetListOptions(ctx),
 	}
 
-	topics, total, err := repo_model.FindTopics(ctx, opts)
+	topics, total, err := db.FindAndCount[repo_model.Topic](ctx, opts)
 	if err != nil {
 		ctx.InternalServerError(err)
 		return

routers/web/explore/topic.go

 		},
 	}
 
-	topics, total, err := repo_model.FindTopics(ctx, opts)
+	topics, total, err := db.FindAndCount[repo_model.Topic](ctx, opts)
 	if err != nil {
 		ctx.Error(http.StatusInternalServerError)
 		return

routers/web/repo/view.go

 }
 
 func renderRepoTopics(ctx *context.Context) {
-	topics, _, err := repo_model.FindTopics(ctx, &repo_model.FindTopicOptions{
+	topics, err := db.Find[repo_model.Topic](ctx, &repo_model.FindTopicOptions{
 		RepoID: ctx.Repo.Repository.ID,
 	})
 	if err != nil {

tests/integration/api_repo_topic_test.go

 		TopicNames []*api.TopicResponse `json:"topics"`
 	}
 
+	// search all topics
+	res := MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
+	DecodeJSON(t, res, &topics)
+	assert.Len(t, topics.TopicNames, 6)
+	assert.EqualValues(t, "6", res.Header().Get("x-total-count"))
+
+	// pagination search topics first page
+	topics.TopicNames = nil
 	query := url.Values{"page": []string{"1"}, "limit": []string{"4"}}
 
 	searchURL.RawQuery = query.Encode()
-	res := MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
+	res = MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
 	DecodeJSON(t, res, &topics)
 	assert.Len(t, topics.TopicNames, 4)
 	assert.EqualValues(t, "6", res.Header().Get("x-total-count"))
 
+	// pagination search topics second page
+	topics.TopicNames = nil
+	query = url.Values{"page": []string{"2"}, "limit": []string{"4"}}
+
+	searchURL.RawQuery = query.Encode()
+	res = MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
+	DecodeJSON(t, res, &topics)
+	assert.Len(t, topics.TopicNames, 2)
+	assert.EqualValues(t, "6", res.Header().Get("x-total-count"))
+
+	// add keyword search
+	query = url.Values{"page": []string{"1"}, "limit": []string{"4"}}
 	query.Add("q", "topic")
 	searchURL.RawQuery = query.Encode()
 	res = MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)

tests/integration/repo_topic_test.go

 		TopicNames []*api.TopicResponse `json:"topics"`
 	}
 
+	// search all topics
+	res := MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
+	DecodeJSON(t, res, &topics)
+	assert.Len(t, topics.TopicNames, 6)
+	assert.EqualValues(t, "6", res.Header().Get("x-total-count"))
+
+	// pagination search topics
+	topics.TopicNames = nil
 	query := url.Values{"page": []string{"1"}, "limit": []string{"4"}}
 
 	searchURL.RawQuery = query.Encode()
-	res := MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
+	res = MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
 	DecodeJSON(t, res, &topics)
 	assert.Len(t, topics.TopicNames, 4)
 	assert.EqualValues(t, "6", res.Header().Get("x-total-count"))
 
+	// second page
+	topics.TopicNames = nil
+	query = url.Values{"page": []string{"2"}, "limit": []string{"4"}}
+
+	searchURL.RawQuery = query.Encode()
+	res = MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
+	DecodeJSON(t, res, &topics)
+	assert.Len(t, topics.TopicNames, 2)
+	assert.EqualValues(t, "6", res.Header().Get("x-total-count"))
+
+	// add keyword search
+	topics.TopicNames = nil
+	query = url.Values{"page": []string{"1"}, "limit": []string{"4"}}
 	query.Add("q", "topic")
 	searchURL.RawQuery = query.Encode()
 	res = MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
 	DecodeJSON(t, res, &topics)
 	assert.Len(t, topics.TopicNames, 2)
 
+	topics.TopicNames = nil
 	query.Set("q", "database")
 	searchURL.RawQuery = query.Encode()
 	res = MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)