fix functions returning arrays not to emit nil slices

compiler.go

@@ -1196,7 +1196,7 @@ func (c *compiler) funcModulemeta(v any, _ []any) any {
 	if meta == nil {
 		meta = make(map[string]any)
 	}
-	var deps []any
+	deps := []any{}
 	for _, i := range q.Imports {
 		v := i.Meta.ToValue()
 		if v == nil {

execute.go

@@ -436,7 +436,7 @@ func (env *env) pathIntact(v any) bool {
 }
 
 func (env *env) poppaths() []any {
-	var xs []any
+	xs := []any{}
 	for {
 		p := env.paths.pop().(pathValue)
 		if p.path == nil {

func.go

@@ -573,7 +573,7 @@ func funcIndices(v, x any) any {
 }
 
 func indices(vs, xs []any) any {
-	var rs []any
+	rs := []any{}
 	if len(xs) == 0 {
 		return rs
 	}
@@ -1117,7 +1117,7 @@ func funcFlatten(v any, args []any) any {
 			return &flattenDepthError{depth}
 		}
 	}
-	return flatten(nil, vs, depth)
+	return flatten([]any{}, vs, depth)
 }
 
 func flatten(xs, vs []any, depth float64) []any {
@@ -1265,7 +1265,7 @@ func funcGroupBy(v, x any) any {
 	if err != nil {
 		return err
 	}
-	var rs []any
+	rs := []any{}
 	var last any
 	for i, r := range items {
 		if i == 0 || compare(last, r.key) != 0 {
@@ -1290,7 +1290,7 @@ func uniqueBy(name string, v, x any) any {
 	if err != nil {
 		return err
 	}
-	var rs []any
+	rs := []any{}
 	var last any
 	for i, r := range items {
 		if i == 0 || compare(last, r.key) != 0 {

module_loader.go

@@ -84,7 +84,7 @@ func (l *moduleLoader) LoadJSONWithMeta(name string, meta map[string]any) (any,
 		return nil, err
 	}
 	defer f.Close()
-	var vals []any
+	vals := []any{}
 	dec := json.NewDecoder(f)
 	dec.UseNumber()
 	for {

option_test.go

@@ -51,7 +51,7 @@ func TestWithModuleLoaderError(t *testing.T) {
 
 func TestWithModuleLoader_modulemeta(t *testing.T) {
 	query, err := gojq.Parse(`
-		"module1" | modulemeta
+		"module1", "module2" | modulemeta
 	`)
 	if err != nil {
 		t.Fatal(err)
@@ -64,24 +64,34 @@ func TestWithModuleLoader_modulemeta(t *testing.T) {
 		t.Fatal(err)
 	}
 	iter := code.Run(nil)
+	n := 0
 	for {
 		got, ok := iter.Next()
 		if !ok {
 			break
 		}
-		if expected := map[string]any{
-			"deps": []any{
-				map[string]any{
-					"relpath": "module2",
-					"as":      "foo",
-					"is_data": false,
+		if n == 0 {
+			if expected := map[string]any{
+				"deps": []any{
+					map[string]any{
+						"relpath": "module2",
+						"as":      "foo",
+						"is_data": false,
+					},
 				},
-			},
-			"name": "module1",
-			"test": 42,
-		}; !reflect.DeepEqual(got, expected) {
-			t.Errorf("expected: %v, got: %v", expected, got)
+				"name": "module1",
+				"test": 42,
+			}; !reflect.DeepEqual(got, expected) {
+				t.Errorf("expected: %v, got: %v", expected, got)
+			}
+		} else {
+			if expected := map[string]any{
+				"deps": []any{}, // not a nil-slice
+			}; !reflect.DeepEqual(got, expected) {
+				t.Errorf("expected: %v, got: %v", expected, got)
+			}
 		}
+		n++
 	}
 }
 

query_test.go

@@ -250,6 +250,32 @@ func TestQueryRun_Input(t *testing.T) {
 	}
 }
 
+func TestQueryRun_NonNilSlice(t *testing.T) {
+	for _, f := range []string{"keys", "map(.)", "to_entries", "arrays",
+		"reverse", "flatten", "sort", "sort_by(.)", "group_by(.)", "unique",
+		"unique_by(.)", "transpose", "nth(.)", "indices([])", "path(.)"} {
+		t.Run(f, func(t *testing.T) {
+			query, err := gojq.Parse("[] | " + f)
+			if err != nil {
+				t.Fatal(err)
+			}
+			iter := query.Run(nil)
+			for {
+				v, ok := iter.Next()
+				if !ok {
+					break
+				}
+				if err, ok := v.(error); ok {
+					t.Fatal(err)
+				}
+				if expected := []any{}; !reflect.DeepEqual(v, expected) {
+					t.Errorf("expected: %#v, got: %#v", expected, v)
+				}
+			}
+		})
+	}
+}
+
 func TestQueryRun_Race(t *testing.T) {
 	query, err := gojq.Parse("range(10)")
 	if err != nil {