feat: add an option to hide empty sections (#3029)

internal/core/view.go

@@ -21,8 +21,9 @@ type ViewField struct {
 }
 
 type ViewSection struct {
-	Title     string
-	FieldName string
+	Title       string
+	FieldName   string
+	HideIfEmpty bool
 }
 
 func (v *View) getHumanMarshalerOpt() *human.MarshalOpt {
@@ -38,8 +39,9 @@ func (v *View) getHumanMarshalerOpt() *human.MarshalOpt {
 	}
 	for _, section := range v.Sections {
 		opt.Sections = append(opt.Sections, &human.MarshalSection{
-			Title:     section.Title,
-			FieldName: section.FieldName,
+			Title:       section.Title,
+			FieldName:   section.FieldName,
+			HideIfEmpty: section.HideIfEmpty,
 		})
 	}
 	opt.Title = v.Title

internal/gofields/gofields.go

@@ -7,6 +7,18 @@ import (
 	"strings"
 )
 
+type NilValueError struct {
+	Path string
+}
+
+func NewNilValueError(path string) *NilValueError {
+	return &NilValueError{Path: path}
+}
+
+func (e *NilValueError) Error() string {
+	return fmt.Sprintf("field %s is nil", e.Path)
+}
+
 // GetValue will extract the value at the given path from the data Go struct
 // E.g data = { Friends: []Friend{ { Name: "John" } }, path = "Friends.0.Name"  will return "John"
 func GetValue(data interface{}, path string) (interface{}, error) {
@@ -23,8 +35,8 @@ func getValue(value reflect.Value, parents []string, path []string) (reflect.Val
 		return value, nil
 	}
 
-	if !value.IsValid() || isNil(value) {
-		return reflect.Value{}, fmt.Errorf("field %s is nil", strings.Join(parents, "."))
+	if !value.IsValid() || IsNil(value) {
+		return reflect.Value{}, NewNilValueError(strings.Join(parents, "."))
 	}
 
 	if value.Type().Kind() == reflect.Ptr {
@@ -148,8 +160,8 @@ func listFields(t reflect.Type, parents []string, filter ListFieldFilter) []stri
 	}
 }
 
-// isNil test if a given value is nil. It is saf to call the mthod with non nillable value like scalar types
-func isNil(value reflect.Value) bool {
+// IsNil test if a given value is nil. It is saf to call the mthod with non nillable value like scalar types
+func IsNil(value reflect.Value) bool {
 	return (value.Kind() == reflect.Ptr || value.Kind() == reflect.Slice || value.Kind() == reflect.Map) && value.IsNil()
 }
 

internal/human/marshal.go

@@ -102,8 +102,12 @@ func marshalStruct(value reflect.Value, opt *MarshalOpt) (string, error) {
 		if err != nil {
 			return "", err
 		}
-		sectionsStrs = append(sectionsStrs, sectionStr)
+
 		sectionFieldNames[section.FieldName] = true
+
+		if sectionStr != "" {
+			sectionsStrs = append(sectionsStrs, sectionStr)
+		}
 	}
 
 	var marshal func(reflect.Value, []string) ([][]string, error)
@@ -379,8 +383,19 @@ func marshalSection(section *MarshalSection, value reflect.Value, opt *MarshalOp
 
 	field, err := gofields.GetValue(value.Interface(), section.FieldName)
 	if err != nil {
+		if section.HideIfEmpty {
+			if _, ok := err.(*gofields.NilValueError); ok {
+				return "", nil
+			}
+		}
+
 		return "", err
 	}
+
+	if section.HideIfEmpty && reflect.ValueOf(field).IsZero() {
+		return "", nil
+	}
+
 	return Marshal(field, &subOpt)
 }
 

internal/human/marshal_test.go

@@ -175,6 +175,97 @@ func TestMarshal(t *testing.T) {
 		`,
 	}))
 
+	t.Run("hide if empty pointer 1", run(&testCase{
+		data: &Human{
+			Name:    "Sherlock Holmes",
+			Age:     42,
+			Address: nil,
+			Acquaintances: []*Acquaintance{
+				{Name: "Dr watson", Link: "Assistant"},
+				{Name: "Mrs. Hudson", Link: "Landlady"},
+			},
+		},
+		opt: &MarshalOpt{
+			Title: "Personal Information",
+			Sections: []*MarshalSection{
+				{FieldName: "Address", HideIfEmpty: true},
+				{Title: "Relationship", FieldName: "Acquaintances"},
+			},
+		},
+		result: `
+			Personal Information:
+			Name  Sherlock Holmes
+			Age   42
+			
+			Relationship:
+			NAME         LINK
+			Dr watson    Assistant
+			Mrs. Hudson  Landlady
+		`,
+	}))
+
+	t.Run("hide if empty pointer 2", run(&testCase{
+		data: &Human{
+			Name:    "Sherlock Holmes",
+			Age:     42,
+			Address: nil,
+			Acquaintances: []*Acquaintance{
+				{Name: "Dr watson", Link: "Assistant"},
+				{Name: "Mrs. Hudson", Link: "Landlady"},
+			},
+		},
+		opt: &MarshalOpt{
+			Title: "Personal Information",
+			Sections: []*MarshalSection{
+				{FieldName: "Address.Street", HideIfEmpty: true},
+				{Title: "Relationship", FieldName: "Acquaintances"},
+			},
+		},
+		result: `
+			Personal Information:
+			Name  Sherlock Holmes
+			Age   42
+			
+			Relationship:
+			NAME         LINK
+			Dr watson    Assistant
+			Mrs. Hudson  Landlady
+		`,
+	}))
+
+	t.Run("hide if empty string", run(&testCase{
+		data: &Human{
+			Name:    "",
+			Age:     42,
+			Address: &Address{Street: "221b Baker St", City: "London"},
+			Acquaintances: []*Acquaintance{
+				{Name: "Dr watson", Link: "Assistant"},
+				{Name: "Mrs. Hudson", Link: "Landlady"},
+			},
+		},
+		opt: &MarshalOpt{
+			Title: "Personal Information",
+			Sections: []*MarshalSection{
+				{FieldName: "Name", HideIfEmpty: true},
+				{FieldName: "Address"},
+				{Title: "Relationship", FieldName: "Acquaintances"},
+			},
+		},
+		result: `
+			Personal Information:
+			Age  42
+			
+			Address:
+			Street  221b Baker St
+			City    London
+			
+			Relationship:
+			NAME         LINK
+			Dr watson    Assistant
+			Mrs. Hudson  Landlady
+		`,
+	}))
+
 	t.Run("empty string", run(&testCase{
 		data:   "",
 		result: `-`,

internal/human/specs.go

@@ -27,8 +27,9 @@ type MarshalFieldOpt struct {
 // MarshalSection describes a section to build from a given struct.
 // When marshalling, this section is shown under the main struct section.
 type MarshalSection struct {
-	FieldName string
-	Title     string
+	FieldName   string
+	Title       string
+	HideIfEmpty bool
 }
 
 func (s *MarshalFieldOpt) getLabel() string {