fix(issues): keep one row per issue when sorting by exclusive label order (#39364) (#39928)

Backport #39364 by @shoemoney

Sorting by an exclusive label scope joined `issue_label`, returning one
row per label. Issues with several labels were listed repeatedly and
pushed others off the page, and `IssueIDs` returned inflated totals.

The sort key now comes from a correlated subquery, so each issue yields
one row.

Fixes https://github.com/go-gitea/gitea/issues/35711

This base-branch update was prepared with AI assistance.

Co-authored-by: Jeremy Schoemaker <jeremy@shoemoney.com>
Co-authored-by: silverwind <me@silverwind.io>

models/issues/issue_search.go

@@ -75,11 +75,11 @@ func applySorts(sess db.Session, sortType string, priorityRepoID int64) {
 	// Since this sortType is dynamically created, it has to be treated specially.
 	if after, ok := strings.CutPrefix(sortType, ScopeSortPrefix); ok {
 		scope := after
-		sess.Join("LEFT", "issue_label", "issue.id = issue_label.issue_id")
-		// "exclusive_order=0" means "no order is set", so exclude it from the JOIN criteria and then "LEFT JOIN" result is also null
-		sess.Join("LEFT", "label", "label.id = issue_label.label_id AND label.exclusive_order <> 0 AND label.name LIKE ?", scope+"/%")
-		// Use COALESCE to make sure we sort NULL last regardless of backend DB (2147483647 == max int)
-		sess.OrderBy("COALESCE(label.exclusive_order, 2147483647) ASC").Desc("issue.id")
+		// a subquery instead of a JOIN keeps one row per issue, "exclusive_order=0" means unset and COALESCE sorts it last on every DB
+		sess.OrderBy("COALESCE((SELECT MIN(label.exclusive_order) FROM issue_label"+
+			" INNER JOIN label ON label.id = issue_label.label_id"+
+			" WHERE issue_label.issue_id = issue.id AND label.exclusive_order <> 0 AND label.name LIKE ?), 2147483647) ASC", scope+"/%").
+			Desc("issue.id")
 		return
 	}
 

tests/integration/issue_test.go

@@ -90,6 +90,27 @@ func TestViewIssuesSortByType(t *testing.T) {
 	})
 }
 
+func TestIssueIDsSortByLabelScope(t *testing.T) {
+	assert.NoError(t, unittest.LoadFixtures())
+	high := &issues_model.Label{RepoID: 1, Name: "priority/high", Exclusive: true, ExclusiveOrder: 1}
+	low := &issues_model.Label{RepoID: 1, Name: "priority/low", Exclusive: true, ExclusiveOrder: 2}
+	assert.NoError(t, db.Insert(t.Context(), high, low))
+	assert.NoError(t, db.Insert(t.Context(),
+		&issues_model.IssueLabel{IssueID: 1, LabelID: low.ID},
+		&issues_model.IssueLabel{IssueID: 2, LabelID: high.ID},
+	))
+	for page, expectedIDs := range [][]int64{{2, 1, 11}, {5, 3}} {
+		issueIDs, total, err := issues_model.IssueIDs(t.Context(), &issues_model.IssuesOptions{
+			RepoIDs:   []int64{1},
+			SortType:  issues_model.ScopeSortPrefix + "priority",
+			Paginator: &db.ListOptions{Page: page + 1, PageSize: 3},
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, expectedIDs, issueIDs)
+		assert.EqualValues(t, 5, total)
+	}
+}
+
 func TestViewIssuesKeyword(t *testing.T) {
 	defer tests.PrepareTestEnv(t)()