Add label/author/assignee filters to the user/org home issue list (#32779)

Replace #26661, fix #25979

Not perfect, but usable and much better than before. Since it is quite
complex, I am not quite sure whether there would be any regression, if
any, I will fix in first time.

I have tested the related pages many times: issue list, milestone issue
list, project view, user issue list, org issue list.

4 files changed, 34 insertions, 30 deletions

diff --git a/models/db/search.go b/models/db/search.go
index 37565f45e1..e0a1b6bde9 100644
--- a/models/db/search.go
+++ b/models/db/search.go
@@ -26,8 +26,10 @@ const (
 	SearchOrderByForksReverse          SearchOrderBy = "num_forks DESC"
 )
 
-const (
-	// Which means a condition to filter the records which don't match any id.
-	// It's different from zero which means the condition could be ignored.
-	NoConditionID = -1
-)
+// NoConditionID means a condition to filter the records which don't match any id.
+// eg: "milestone_id=-1" means "find the items without any milestone.
+const NoConditionID int64 = -1
+
+// NonExistingID means a condition to match no result (eg: a non-existing user)
+// It doesn't use -1 or -2 because they are used as builtin users.
+const NonExistingID int64 = -1000000
diff --git a/models/issues/issue_search.go b/models/issues/issue_search.go
index 5948a67d4e..f1cd125d49 100644
--- a/models/issues/issue_search.go
+++ b/models/issues/issue_search.go
@@ -27,8 +27,8 @@ type IssuesOptions struct { //nolint
 	RepoIDs            []int64 // overwrites RepoCond if the length is not 0
 	AllPublic          bool    // include also all public repositories
 	RepoCond           builder.Cond
-	AssigneeID         int64
-	PosterID           int64
+	AssigneeID         optional.Option[int64]
+	PosterID           optional.Option[int64]
 	MentionedID        int64
 	ReviewRequestedID  int64
 	ReviewedID         int64
@@ -231,15 +231,8 @@ func applyConditions(sess *xorm.Session, opts *IssuesOptions) {
 		sess.And("issue.is_closed=?", opts.IsClosed.Value())
 	}
 
-	if opts.AssigneeID > 0 {
-		applyAssigneeCondition(sess, opts.AssigneeID)
-	} else if opts.AssigneeID == db.NoConditionID {
-		sess.Where("issue.id NOT IN (SELECT issue_id FROM issue_assignees)")
-	}
-
-	if opts.PosterID > 0 {
-		applyPosterCondition(sess, opts.PosterID)
-	}
+	applyAssigneeCondition(sess, opts.AssigneeID)
+	applyPosterCondition(sess, opts.PosterID)
 
 	if opts.MentionedID > 0 {
 		applyMentionedCondition(sess, opts.MentionedID)
@@ -359,13 +352,27 @@ func issuePullAccessibleRepoCond(repoIDstr string, userID int64, org *organizati
 	return cond
 }
 
-func applyAssigneeCondition(sess *xorm.Session, assigneeID int64) {
-	sess.Join("INNER", "issue_assignees", "issue.id = issue_assignees.issue_id").
-		And("issue_assignees.assignee_id = ?", assigneeID)
+func applyAssigneeCondition(sess *xorm.Session, assigneeID optional.Option[int64]) {
+	// old logic: 0 is also treated as "not filtering assignee", because the "assignee" was read as FormInt64
+	if !assigneeID.Has() || assigneeID.Value() == 0 {
+		return
+	}
+	if assigneeID.Value() == db.NoConditionID {
+		sess.Where("issue.id NOT IN (SELECT issue_id FROM issue_assignees)")
+	} else {
+		sess.Join("INNER", "issue_assignees", "issue.id = issue_assignees.issue_id").
+			And("issue_assignees.assignee_id = ?", assigneeID.Value())
+	}
 }
 
-func applyPosterCondition(sess *xorm.Session, posterID int64) {
-	sess.And("issue.poster_id=?", posterID)
+func applyPosterCondition(sess *xorm.Session, posterID optional.Option[int64]) {
+	if !posterID.Has() {
+		return
+	}
+	// poster doesn't need to support db.NoConditionID(-1), so just use the value as-is
+	if posterID.Has() {
+		sess.And("issue.poster_id=?", posterID.Value())
+	}
 }
 
 func applyMentionedCondition(sess *xorm.Session, mentionedID int64) {
diff --git a/models/issues/issue_stats.go b/models/issues/issue_stats.go
index 39326616f8..9ef9347a16 100644
--- a/models/issues/issue_stats.go
+++ b/models/issues/issue_stats.go
@@ -151,15 +151,9 @@ func applyIssuesOptions(sess *xorm.Session, opts *IssuesOptions, issueIDs []int6
 
 	applyProjectCondition(sess, opts)
 
-	if opts.AssigneeID > 0 {
-		applyAssigneeCondition(sess, opts.AssigneeID)
-	} else if opts.AssigneeID == db.NoConditionID {
-		sess.Where("issue.id NOT IN (SELECT issue_id FROM issue_assignees)")
-	}
+	applyAssigneeCondition(sess, opts.AssigneeID)
 
-	if opts.PosterID > 0 {
-		applyPosterCondition(sess, opts.PosterID)
-	}
+	applyPosterCondition(sess, opts.PosterID)
 
 	if opts.MentionedID > 0 {
 		applyMentionedCondition(sess, opts.MentionedID)
diff --git a/models/issues/issue_test.go b/models/issues/issue_test.go
index 1bbc0eee56..548f137f39 100644
--- a/models/issues/issue_test.go
+++ b/models/issues/issue_test.go
@@ -16,6 +16,7 @@ import (
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/setting"
 
 	"github.com/stretchr/testify/assert"
@@ -155,7 +156,7 @@ func TestIssues(t *testing.T) {
 	}{
 		{
 			issues_model.IssuesOptions{
-				AssigneeID: 1,
+				AssigneeID: optional.Some(int64(1)),
 				SortType:   "oldest",
 			},
 			[]int64{1, 6},