Add must and no panic Options

copier.go

@@ -47,6 +47,11 @@
 	// Custom field name mappings to copy values with different names in `fromValue` and `toValue` types.
 	// Examples can be found in `copier_field_name_mapping_test.go`.
 	FieldNameMapping []FieldNameMapping
+	// When set to true, all fields will be treated as if they have the "must" tag
+	Must bool
+	// When set to true, all fields will be treated as if they have the "nopanic" tag.
+	// This only has an effect when Must is also true
+	NoPanic bool
 }
 
 func (opt Option) converters() map[converterPair]TypeConverter {
@@ -206,7 +211,7 @@
 					to.SetMapIndex(toKey, toValue)
 					break
 				}
 				elemType = reflect.PointerTo(elemType)
 				toValue = toValue.Addr()
 			}
 		}
@@ -312,8 +317,8 @@
 			dest = indirect(reflect.New(toType))
 		}
 
-		// Get tag options
-		flgs, err := getFlags(dest, source, toType, fromType)
+		var flgs flags
+		flgs, err = getFlags(dest, source, toType, fromType, opt)
 		if err != nil {
 			return err
 		}
@@ -732,7 +737,7 @@
 }
 
 // getTagFlags Parses struct tags for bit flags, field name.
-func getFlags(dest, src reflect.Value, toType, fromType reflect.Type) (flags, error) {
+func getFlags(dest, src reflect.Value, toType, fromType reflect.Type, opt Option) (flags, error) {
 	flgs := flags{
 		BitFlags: map[string]uint8{},
 		SrcNames: tagNameMapping{
@@ -745,6 +750,9 @@
 		},
 	}
 
+	mustOpt := opt.Must
+	noPanicOpt := opt.NoPanic
+
 	var toTypeFields, fromTypeFields []reflect.StructField
 	if dest.IsValid() {
 		toTypeFields = deepFields(toType)
@@ -766,6 +774,14 @@
 				flgs.DestNames.TagToFieldName[name] = field.Name
 			}
 		}
+
+		// Apply default flags
+		if mustOpt {
+			flgs.BitFlags[field.Name] = flgs.BitFlags[field.Name] | tagMust
+		}
+		if noPanicOpt {
+			flgs.BitFlags[field.Name] = flgs.BitFlags[field.Name] | tagNoPanic
+		}
 	}
 
 	// Get a list source of tags

copier_tags_test.go

@@ -13,6 +13,20 @@ type EmployeeTags struct {
 	ID      int `copier:"-"`
 }
 
+type EmployeeTags2 struct {
+	Name    string `copier:"must,nopanic"`
+	DOB     string
+	Address string
+	ID      int `copier:"-"`
+}
+
+type EmployeeTags3 struct {
+	Name    string
+	DOB     string
+	Address string
+	ID      int
+}
+
 type User1 struct {
 	Name    string
 	DOB     string
@@ -49,6 +63,46 @@ func TestCopyTagMust(t *testing.T) {
 	copier.Copy(employee, user)
 }
 
+func TestCopyTagMustByOption(t *testing.T) {
+	employee := &EmployeeTags3{}
+	user := &User2{DOB: "1 January 1970"}
+	t.Run("must is true", func(t *testing.T) {
+		defer func() {
+			if r := recover(); r == nil {
+				t.Error("Expected a panic.")
+			}
+		}()
+		copier.CopyWithOption(employee, user, copier.Option{Must: true})
+	})
+
+	t.Run("must is false", func(t *testing.T) {
+		defer func() {
+			if r := recover(); r != nil {
+				t.Error("Expected no panic.")
+			}
+		}()
+		copier.CopyWithOption(employee, user, copier.Option{Must: false})
+	})
+}
+
+func TestCopyTagMustAndNoPanic(t *testing.T) {
+	employee := &EmployeeTags2{}
+	user := &User2{DOB: "1 January 1970"}
+	err := copier.Copy(employee, user)
+	if err == nil {
+		t.Error("expected error")
+	}
+}
+
+func TestCopyTagMustAndNoPanicByOption(t *testing.T) {
+	employee := &EmployeeTags3{}
+	user := &User2{DOB: "1 January 1970"}
+	err := copier.CopyWithOption(employee, user, copier.Option{Must: true, NoPanic: true})
+	if err == nil {
+		t.Error("expected error")
+	}
+}
+
 func TestCopyTagOverrideZeroValue(t *testing.T) {
 	options := copier.Option{IgnoreEmpty: true}
 	employee := EmployeeTags{ID: 100, Address: ""}