From 51d5881f6b28cb27b8afaca722b7a9134a7da0c8 Mon Sep 17 00:00:00 2001
From: Radek Simko <radek.simko@gmail.com>
Date: Thu, 8 Apr 2021 13:12:50 +0100
Subject: [PATCH] Use custom copiers declared in Config

---
 copystructure.go      |  4 +++-
 copystructure_test.go | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/copystructure.go b/copystructure.go
index f2b925e..89540e4 100644
--- a/copystructure.go
+++ b/copystructure.go
@@ -88,6 +88,7 @@ func (c Config) Copy(v interface{}) (interface{}, error) {
 	if c.Copiers == nil {
 		c.Copiers = Copiers
 	}
+	w.copiers = c.Copiers
 
 	err := reflectwalk.Walk(v, w)
 	if err != nil {
@@ -116,6 +117,7 @@ func ifaceKey(pointers, depth int) uint64 {
 type walker struct {
 	Result interface{}
 
+	copiers     map[reflect.Type]CopierFunc
 	depth       int
 	ignoreDepth int
 	vals        []reflect.Value
@@ -379,7 +381,7 @@ func (w *walker) Struct(s reflect.Value) error {
 	w.lock(s)
 
 	var v reflect.Value
-	if c, ok := Copiers[s.Type()]; ok {
+	if c, ok := w.copiers[s.Type()]; ok {
 		// We have a Copier for this struct, so we use that copier to
 		// get the copy, and we ignore anything deeper than this.
 		w.ignoreDepth = w.depth
diff --git a/copystructure_test.go b/copystructure_test.go
index f661654..c1b77e3 100644
--- a/copystructure_test.go
+++ b/copystructure_test.go
@@ -1153,3 +1153,37 @@ func TestCopy_timeDoublePointer(t *testing.T) {
 		t.Fatalf("\n%#v\n\n%#v", v, result)
 	}
 }
+
+type nestedValue struct {
+	v string
+}
+
+func TestCopy_customCopierConfig(t *testing.T) {
+	type T struct {
+		Val *nestedValue
+	}
+
+	v := &T{
+		Val: &nestedValue{v: "original"},
+	}
+
+	cfg := Config{
+		Copiers: map[reflect.Type]CopierFunc{
+			reflect.TypeOf(nestedValue{}): customCopier,
+		},
+	}
+	result, err := cfg.Copy(v)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	copiedVal := result.(*T)
+
+	if !reflect.DeepEqual(v.Val.v, copiedVal.Val.v) {
+		t.Fatalf("\nexpected: %#v\ngiven: %#v", v.Val.v, copiedVal.Val.v)
+	}
+}
+
+func customCopier(v interface{}) (interface{}, error) {
+	return v.(nestedValue), nil
+}