From feac4226b1473a3ff4a3f55f9ade66a7ce116637 Mon Sep 17 00:00:00 2001
From: Minh Vu <vuhoangminh97@gmail.com>
Date: Fri, 10 Jul 2026 00:02:39 +0200
Subject: [PATCH] abigen: use original names for custom errors

---
 accounts/abi/abigen/bindv2_test.go | 22 ++++++++++++++++++++++
 accounts/abi/abigen/source2.go.tpl |  4 ++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/accounts/abi/abigen/bindv2_test.go b/accounts/abi/abigen/bindv2_test.go
index ee943f1c3f..9c917a120d 100644
--- a/accounts/abi/abigen/bindv2_test.go
+++ b/accounts/abi/abigen/bindv2_test.go
@@ -297,6 +297,28 @@ func TestBindingV2ConvertedV1Tests(t *testing.T) {
 	}
 }
 
+func TestBindingV2ErrorUsesOriginalName(t *testing.T) {
+	const errorABI = `[{
+		"inputs":[{"internalType":"uint256","name":"value","type":"uint256"}],
+		"name":"bad_thing",
+		"type":"error"
+	}]`
+
+	code, err := BindV2([]string{"C"}, []string{errorABI}, []string{""}, "bindings", nil, nil)
+	if err != nil {
+		t.Fatalf("failed to generate binding: %v", err)
+	}
+	for _, want := range []string{
+		`abi.Errors["bad_thing"]`,
+		`UnpackIntoInterface(out, "bad_thing", raw)`,
+		`UnpackBadThingError(raw[4:])`,
+	} {
+		if !strings.Contains(code, want) {
+			t.Fatalf("generated binding does not contain %q:\n%s", want, code)
+		}
+	}
+}
+
 func TestNormalizeArgs(t *testing.T) {
 	type normalizeArgsTc struct {
 		inp      []string
diff --git a/accounts/abi/abigen/source2.go.tpl b/accounts/abi/abigen/source2.go.tpl
index 9285497511..1730fe25a0 100644
--- a/accounts/abi/abigen/source2.go.tpl
+++ b/accounts/abi/abigen/source2.go.tpl
@@ -219,7 +219,7 @@ var (
 	// error definitions.
 	func ({{ decapitalise $contract.Type}} *{{$contract.Type}}) UnpackError(raw []byte) (any, error) {
 		{{- range $k, $v := .Errors}}
-		if bytes.Equal(raw[:4], {{ decapitalise $contract.Type}}.abi.Errors["{{.Normalized.Name}}"].ID.Bytes()[:4]) {
+		if bytes.Equal(raw[:4], {{ decapitalise $contract.Type}}.abi.Errors["{{.Original.Name}}"].ID.Bytes()[:4]) {
 			return {{ decapitalise $contract.Type}}.Unpack{{.Normalized.Name}}Error(raw[4:])
 		}
 		{{- end }}
@@ -246,7 +246,7 @@ var (
 		// Solidity: {{.Original.String}}
 		func ({{ decapitalise $contract.Type}} *{{$contract.Type}}) Unpack{{.Normalized.Name}}Error(raw []byte) (*{{$contract.Type}}{{.Normalized.Name}}, error) {
 			out := new({{$contract.Type}}{{.Normalized.Name}})
-			if err := {{ decapitalise $contract.Type}}.abi.UnpackIntoInterface(out, "{{.Normalized.Name}}", raw); err != nil {
+			if err := {{ decapitalise $contract.Type}}.abi.UnpackIntoInterface(out, "{{.Original.Name}}", raw); err != nil {
 				return nil, err
 			}
 			return out, nil