Add support for changing default tag name

deepcopy.go

@@ -3,15 +3,20 @@ package deepcopy
 import (
 	"fmt"
 	"reflect"
+	"strings"
 	"sync"
 )
 
 const (
-	// DefaultTagName default tag name for the program to parse input struct tags
-	// to build copier configuration.
 	DefaultTagName = "copy"
 )
 
+var (
+	// defaultTagName default tag name for the program to parse input struct tags
+	// to build copier configuration.
+	defaultTagName = DefaultTagName
+)
+
 // Context copier context
 type Context struct {
 	// CopyBetweenPtrAndValue allow or not copying between pointers and values (default is `true`)
@@ -116,3 +121,12 @@ func ClearCache() {
 	copierCacheMap = map[cacheKey]copier{}
 	mu.Unlock()
 }
+
+// SetDefaultTagName overwrites the default tag name.
+// This function should only be called once at program startup.
+func SetDefaultTagName(tag string) {
+	tagName := strings.TrimSpace(tag)
+	if tagName != "" && tagName == tag {
+		defaultTagName = tagName
+	}
+}

deepcopy_test.go

@@ -232,3 +232,13 @@ func Test_ConfigOption(t *testing.T) {
 	UseGlobalCache(true)(ctx)
 	assert.Equal(t, true, ctx.UseGlobalCache)
 }
+
+func Test_SetDefaultTagName(t *testing.T) {
+	assert.Equal(t, DefaultTagName, defaultTagName)
+	// Invalid one
+	SetDefaultTagName(" abc")
+	assert.Equal(t, DefaultTagName, defaultTagName)
+	// Valid one
+	SetDefaultTagName("abc")
+	assert.Equal(t, "abc", defaultTagName)
+}

struct_tag.go

@@ -27,7 +27,7 @@ func (detail *fieldDetail) markDone() {
 
 // parseTag parses struct tag for getting copying detail and configuration
 func parseTag(detail *fieldDetail) {
-	tagValue, ok := detail.field.Tag.Lookup(DefaultTagName)
+	tagValue, ok := detail.field.Tag.Lookup(defaultTagName)
 	detail.key = detail.field.Name
 	if !ok {
 		return