fix(bolt): return empty slice for templates list with no rows (#3245)

db/bolt/template.go

@@ -76,6 +76,10 @@ func (d *BoltDb) GetTemplatesWithPermissions(projectID int, userID int, filter d
 		return
 	}
 
+	// Initialize as a non-nil slice so an empty result marshals to `[]` rather than `null`.
+	// The web UI's templates page hangs when the API returns `null` (issue #3245).
+	templates = make([]db.TemplateWithPerms, 0, len(res))
+
 	for _, tpl := range res {
 		var tplWithPerms db.TemplateWithPerms
 		tplWithPerms.Template = tpl

db/bolt/template_test.go

@@ -40,3 +40,31 @@ func Test_SetTemplateDescription(t *testing.T) {
 		t.Fatalf("expected description to be 'New description', got '%s'", *tpl.Description)
 	}
 }
+
+// Regression test for #3245: GetTemplatesWithPermissions used to return a nil
+// slice when no templates matched, which JSON-marshals to `null` and wedges
+// the web UI's templates page. The API contract is an array; an empty result
+// must serialize to `[]`.
+func Test_GetTemplatesWithPermissions_EmptyReturnsNonNilSlice(t *testing.T) {
+	store := CreateTestStore()
+
+	proj, err := store.CreateProject(db.Project{
+		Created: tz.Now(),
+		Name:    "TestProject",
+	})
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+
+	templates, err := store.GetTemplatesWithPermissions(proj.ID, 0, db.TemplateFilter{}, db.RetrieveQueryParams{})
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+
+	if templates == nil {
+		t.Fatal("expected empty (non-nil) slice for project with no templates, got nil")
+	}
+	if len(templates) != 0 {
+		t.Fatalf("expected zero templates, got %d", len(templates))
+	}
+}