accounts/abi: add ErrorById

accounts/abi/abi.go

@@ -222,6 +222,17 @@ func (abi *ABI) EventByID(topic common.Hash) (*Event, error) {
 	return nil, fmt.Errorf("no event with id: %#x", topic.Hex())
 }
 
+// ErrorByID looks up an error by the 4-byte id,
+// returns nil if none found.
+func (abi *ABI) ErrorByID(sigdata [4]byte) (*Error, error) {
+	for _, errABI := range abi.Errors {
+		if bytes.Equal(errABI.ID[:4], sigdata[:]) {
+			return &errABI, nil
+		}
+	}
+	return nil, fmt.Errorf("no error with id: %#x", sigdata[:])
+}
+
 // HasFallback returns an indicator whether a fallback function is included.
 func (abi *ABI) HasFallback() bool {
 	return abi.Fallback.Type == Fallback

accounts/abi/abi_test.go

@@ -1057,6 +1057,33 @@ func TestABI_EventById(t *testing.T) {
 	}
 }
 
+func TestABI_ErrorByID(t *testing.T) {
+	abi, err := JSON(strings.NewReader(`[
+		{"inputs":[{"internalType":"uint256","name":"x","type":"uint256"}],"name":"MyError1","type":"error"},
+		{"inputs":[{"components":[{"internalType":"uint256","name":"a","type":"uint256"},{"internalType":"string","name":"b","type":"string"},{"internalType":"address","name":"c","type":"address"}],"internalType":"struct MyError.MyStruct","name":"x","type":"tuple"},{"internalType":"address","name":"y","type":"address"},{"components":[{"internalType":"uint256","name":"a","type":"uint256"},{"internalType":"string","name":"b","type":"string"},{"internalType":"address","name":"c","type":"address"}],"internalType":"struct MyError.MyStruct","name":"z","type":"tuple"}],"name":"MyError2","type":"error"},
+		{"inputs":[{"internalType":"uint256[]","name":"x","type":"uint256[]"}],"name":"MyError3","type":"error"}
+	]`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	for name, m := range abi.Errors {
+		a := fmt.Sprintf("%v", &m)
+		id := *(*[4]byte)(m.ID[:4])
+		m2, err := abi.ErrorByID(id)
+		if err != nil {
+			t.Fatalf("Failed to look up ABI error: %v", err)
+		}
+		b := fmt.Sprintf("%v", m2)
+		if a != b {
+			t.Errorf("Error %v (id %x) not 'findable' by id in ABI", name, id)
+		}
+	}
+	// test unsuccessful lookups
+	if _, err = abi.ErrorByID([4]byte{}); err == nil {
+		t.Error("Expected error: no error with this id")
+	}
+}
+
 // TestDoubleDuplicateMethodNames checks that if transfer0 already exists, there won't be a name
 // conflict and that the second transfer method will be renamed transfer1.
 func TestDoubleDuplicateMethodNames(t *testing.T) {

accounts/abi/error.go

@@ -78,7 +78,7 @@ func NewError(name string, inputs Arguments) Error {
 	}
 }
 
-func (e *Error) String() string {
+func (e Error) String() string {
 	return e.str
 }