fix(output): emit [] instead of null for empty --json results

README.md

@@ -93,8 +93,9 @@ Filters:
 
 `-p`/`-a`/`-t` combine with any view. The date filters (`--on`, `--from`,
 `--to`) apply to date-filterable views — `today`, `upcoming`, `anytime`,
-`someday`, `deadlines`, and project listings — and `--on` can't be combined
-with `--from`/`--to`. `--include-completed` applies to the `today` view only.
+`deadlines`, and project listings (`someday` items have no start date, so
+they can't be date-filtered) — and `--on` can't be combined with
+`--from`/`--to`. `--include-completed` applies to the `today` view only.
 
 Examples:
 

internal/db/areas.go

@@ -36,7 +36,7 @@ func (d *DB) ListAreas() ([]model.Area, error) {
 	}
 	defer rows.Close()
 
-	var areas []model.Area
+	areas := []model.Area{}
 	for rows.Next() {
 		var a model.Area
 		var visible int

internal/db/db_test.go

@@ -87,3 +87,49 @@ func TestOpenBadPath(t *testing.T) {
 		t.Fatal("expected error for bad path")
 	}
 }
+
+// Empty result sets must be non-nil slices: a nil slice JSON-encodes as
+// `null`, which breaks documented `--json | jq '.[]'` pipelines.
+func TestEmptyResultsAreNonNil(t *testing.T) {
+	d := newTestDB(t)
+
+	tasks, err := d.ListTasks("today", TaskFilter{})
+	if err != nil {
+		t.Fatalf("ListTasks: %v", err)
+	}
+	if tasks == nil || len(tasks) != 0 {
+		t.Errorf("ListTasks: want non-nil empty slice, got %#v", tasks)
+	}
+
+	found, err := d.SearchTasks("no-such-task")
+	if err != nil {
+		t.Fatalf("SearchTasks: %v", err)
+	}
+	if found == nil || len(found) != 0 {
+		t.Errorf("SearchTasks: want non-nil empty slice, got %#v", found)
+	}
+
+	projects, err := d.ListProjects("", false)
+	if err != nil {
+		t.Fatalf("ListProjects: %v", err)
+	}
+	if projects == nil || len(projects) != 0 {
+		t.Errorf("ListProjects: want non-nil empty slice, got %#v", projects)
+	}
+
+	areas, err := d.ListAreas()
+	if err != nil {
+		t.Fatalf("ListAreas: %v", err)
+	}
+	if areas == nil || len(areas) != 0 {
+		t.Errorf("ListAreas: want non-nil empty slice, got %#v", areas)
+	}
+
+	tags, err := d.ListTags()
+	if err != nil {
+		t.Fatalf("ListTags: %v", err)
+	}
+	if tags == nil || len(tags) != 0 {
+		t.Errorf("ListTags: want non-nil empty slice, got %#v", tags)
+	}
+}

internal/db/projects.go

@@ -43,7 +43,7 @@ func (d *DB) ListProjects(areaFilter string, includeCompleted bool) ([]model.Pro
 	}
 	defer rows.Close()
 
-	var projects []model.Project
+	projects := []model.Project{}
 	for rows.Next() {
 		var p model.Project
 		var tagsStr string

internal/db/tags.go

@@ -36,7 +36,7 @@ func (d *DB) ListTags() ([]model.Tag, error) {
 	}
 	defer rows.Close()
 
-	var tags []model.Tag
+	tags := []model.Tag{}
 	for rows.Next() {
 		var t model.Tag
 		if err := rows.Scan(&t.UUID, &t.Title, &t.Shortcut, &t.ParentUUID); err != nil {

internal/db/tasks.go

@@ -25,12 +25,12 @@ type TaskFilter struct {
 
 // dateFilterableViews lists the views where --on/--from/--to make sense.
 // Excluded: inbox tasks have no startDate; trash is trashed-only; logbook
-// items have a stopDate but no meaningful startDate filter.
+// items have a stopDate but no meaningful startDate filter; someday requires
+// startDate IS NULL, so a startDate range could never match anything.
 var dateFilterableViews = map[string]bool{
 	"today":     true,
 	"upcoming":  true,
 	"anytime":   true,
-	"someday":   true,
 	"deadlines": true,
 	"project":   true,
 }
@@ -286,7 +286,7 @@ func (d *DB) collectTasks(query string, args ...any) ([]model.Task, error) {
 	}
 	defer rows.Close()
 
-	var tasks []model.Task
+	tasks := []model.Task{}
 	for rows.Next() {
 		t, err := scanTask(rows)
 		if err != nil {

internal/db/tasks_test.go

@@ -316,8 +316,10 @@ func TestListTasksDeadlinesDateFilters(t *testing.T) {
 }
 
 func TestDateFilterableView(t *testing.T) {
-	allowed := []string{"today", "upcoming", "anytime", "someday", "deadlines", "project"}
-	denied := []string{"inbox", "trash", "logbook", "bogus"}
+	allowed := []string{"today", "upcoming", "anytime", "deadlines", "project"}
+	// someday is denied because its view predicate requires startDate IS NULL —
+	// a startDate range filter could never match anything.
+	denied := []string{"inbox", "trash", "logbook", "someday", "bogus"}
 	for _, v := range allowed {
 		if !DateFilterableView(v) {
 			t.Errorf("%q: expected filterable", v)

internal/output/output_test.go

@@ -82,6 +82,17 @@ func TestPrintEmptyTasks(t *testing.T) {
 	}
 }
 
+// Empty lists must encode as [], not null — jq '.[]' fails on null.
+func TestPrintEmptyTasksJSON(t *testing.T) {
+	var buf bytes.Buffer
+	if err := Print(&buf, []model.Task{}, true); err != nil {
+		t.Fatalf("Print: %v", err)
+	}
+	if got := strings.TrimSpace(buf.String()); got != "[]" {
+		t.Errorf("expected [], got %q", got)
+	}
+}
+
 func TestPrintProjectsPlain(t *testing.T) {
 	projects := []model.Project{
 		{UUID: "p1", Title: "Empty project", TaskCount: 0},

internal/skill/SKILL.md

@@ -25,7 +25,8 @@ things list [view] [--project P] [--area A] [--tag T] [--on D | --from D --to D]
     # shortcut: `things today`, `things inbox`, etc.
     # --on / --from / --to take YYYY-MM-DD (or RFC3339). They filter startDate
     # on most views and `deadline` on the `deadlines` view. Not supported on
-    # inbox/trash/logbook. --on is mutually exclusive with --from/--to.
+    # inbox/trash/logbook/someday (someday items have no start date).
+    # --on is mutually exclusive with --from/--to.
     # today shows only open tasks; --include-completed also lists completed/
     # cancelled items Things hasn't logged out of Today yet (today only).