fix: dont ignore options with nil value (#31)

* Always include optional data

* Clean up control-flow

marshal.go

@@ -165,29 +165,24 @@ func makeDocument(v any, m *Marshaler, isRelationship bool) (*document, error) {
 
 	// at this point we have no errors, so lets make the document
 	d = newDocument()
-	if v == nil {
-		// if v is nil we want `{"data":null}` so return the empty document
-		return d, nil
-	}
-
-	if reflect.ValueOf(v).IsZero() {
-		if reflect.TypeOf(v).Kind() == reflect.Slice {
-			// if v is an empty slice we want `{"data":[]}`
-			d.hasMany = true
-		}
-		return d, nil
-	}
 
 	// the given "v" is the resource object (or a slice of them)
 	//
-	// only a struct or slice of struct are valid here because we'll be parsing
-	// the jsonapi struct tags from the struct to make the resource object
-
+	// besides nil, only a struct or slice of struct are valid here because
+	// we'll be parsing the jsonapi struct tags from the struct to make the
+	// resource object
 	vt := reflect.TypeOf(v)
-	switch derefType(vt).Kind() {
-	case reflect.Slice:
+	switch {
+	case vt == nil:
+		// if v is nil we want `{"data":null}` so continue with an empty document
+		break
+	case derefType(vt).Kind() == reflect.Slice:
 		// if we get a slice we make a resource object for each item
 		d.hasMany = true
+		// if v is an empty slice we want `{"data":[]}`
+		if reflect.ValueOf(v).IsZero() {
+			break
+		}
 		rv := derefValue(reflect.ValueOf(v))
 		for i := 0; i < rv.Len(); i++ {
 			iv := rv.Index(i).Interface()
@@ -199,7 +194,10 @@ func makeDocument(v any, m *Marshaler, isRelationship bool) (*document, error) {
 				d.DataMany = append(d.DataMany, ro)
 			}
 		}
-	case reflect.Struct:
+	case derefType(vt).Kind() == reflect.Struct:
+		if reflect.ValueOf(v).IsZero() {
+			break
+		}
 		// if we get a struct we just make a single resource object
 		ro, err := makeResourceObject(v, vt, m, isRelationship)
 		if err != nil {

marshal_test.go

@@ -36,6 +36,11 @@ func TestMarshal(t *testing.T) {
 			given:       new(Article),
 			expect:      "",
 			expectError: ErrEmptyPrimaryField,
+		}, {
+			description: "[]*Article (nil)",
+			given:       []*Article(nil),
+			expect:      emptyBody,
+			expectError: nil,
 		}, {
 			description: "[]*Article (empty)",
 			given:       make([]*Article, 0),
@@ -295,6 +300,8 @@ func TestMarshalMeta(t *testing.T) {
 	t.Parallel()
 
 	articleAMetaBody := `{"data":{"id":"1","type":"articles","attributes":{"title":"A"}},"meta":{"foo":"bar"}}`
+	articleAMetaNullBody := `{"data": null,"meta":{"foo":"bar"}}`
+	articleAMetaEmptyBody := `{"data":[],"meta":{"foo":"bar"}}`
 	errorsObjectMetaBody := `{"meta":{"foo":"bar"},"errors":[{"title":"T"}]}`
 
 	tests := []struct {
@@ -330,6 +337,24 @@ func TestMarshalMeta(t *testing.T) {
 			givenMeta:   map[string]any{"foo": "bar"},
 			expect:      errorsObjectMetaBody,
 			expectError: nil,
+		}, {
+			description: "map[string]any with nil body",
+			given:       nil,
+			givenMeta:   map[string]any{"foo": "bar"},
+			expect:      articleAMetaNullBody,
+			expectError: nil,
+		}, {
+			description: "map[string]any with Article (empty)",
+			given:       Article{},
+			givenMeta:   map[string]any{"foo": "bar"},
+			expect:      articleAMetaNullBody,
+			expectError: nil,
+		}, {
+			description: "map[string]any with body []*Article (empty)",
+			given:       []*Article(nil),
+			givenMeta:   map[string]any{"foo": "bar"},
+			expect:      articleAMetaEmptyBody,
+			expectError: nil,
 		},
 	}
 
@@ -741,5 +766,4 @@ func TestMarshalMemberNameValidation(t *testing.T) {
 			is.MustNoError(t, err)
 		})
 	}
-
 }