Implement error interface for Error and move ErrorCode to its own file

error.go

@@ -4,6 +4,8 @@
 
 package jsonrpc2
 
+import "fmt"
+
 // Error represents a JSON-RPC 2.0 Error object, which is used in the Response
 // object.
 type Error struct {
@@ -12,32 +14,6 @@ type Error struct {
 	Data    interface{} `json:"data,omitempty"`
 }
 
-// ErrorCode represent the int JSON RPC 2.0 error code.
-type ErrorCode int
-
-// Official JSON-RPC 2.0 Spec Error Codes and Messages
-const (
-	LowestReservedErrorCode  ErrorCode = -32768
-	ParseErrorCode           ErrorCode = -32700
-	InvalidRequestCode       ErrorCode = -32600
-	MethodNotFoundCode       ErrorCode = -32601
-	InvalidParamsCode        ErrorCode = -32602
-	InternalErrorCode        ErrorCode = -32603
-	HighestReservedErrorCode ErrorCode = -32000
-
-	ParseErrorMessage     = "Parse error"
-	InvalidRequestMessage = "Invalid Request"
-	MethodNotFoundMessage = "Method not found"
-	InvalidParamsMessage  = "Invalid params"
-	InternalErrorMessage  = "Internal error"
-)
-
-// IsReserved returns true if c is within the reserved error code range:
-// [LowestReservedErrorCode, HighestReservedErrorCode].
-func (c ErrorCode) IsReserved() bool {
-	return LowestReservedErrorCode <= c && c <= HighestReservedErrorCode
-}
-
 // Official JSON-RPC 2.0 Errors
 var (
 	// ParseError is returned to the client if a JSON is not well formed.
@@ -68,3 +44,14 @@ func NewInvalidParamsError(data interface{}) Error {
 	err.Data = data
 	return err
 }
+
+// Error implements the error interface.
+func (e Error) Error() string {
+	s := fmt.Sprintf("jsonrpc2.Error{Code:%v, Message:%#v", e.Code, e.Message)
+	if e.Data != nil {
+		s += fmt.Sprintf(", Data:%#v}", e.Data)
+	} else {
+		s += "}"
+	}
+	return s
+}

error_test.go

@@ -15,3 +15,10 @@ func TestErrorCodeIsReserved(t *testing.T) {
 	c = HighestReservedErrorCode
 	assert.True(c.IsReserved())
 }
+
+func TestError(t *testing.T) {
+	assert := assert.New(t)
+	var e error
+	var err Error
+	assert.Implements(&e, err)
+}

errorcode.go

@@ -0,0 +1,27 @@
+package jsonrpc2
+
+// ErrorCode represent the int JSON RPC 2.0 error code.
+type ErrorCode int
+
+// Official JSON-RPC 2.0 Spec Error Codes and Messages
+const (
+	LowestReservedErrorCode  ErrorCode = -32768
+	ParseErrorCode           ErrorCode = -32700
+	InvalidRequestCode       ErrorCode = -32600
+	MethodNotFoundCode       ErrorCode = -32601
+	InvalidParamsCode        ErrorCode = -32602
+	InternalErrorCode        ErrorCode = -32603
+	HighestReservedErrorCode ErrorCode = -32000
+
+	ParseErrorMessage     = "Parse error"
+	InvalidRequestMessage = "Invalid Request"
+	MethodNotFoundMessage = "Method not found"
+	InvalidParamsMessage  = "Invalid params"
+	InternalErrorMessage  = "Internal error"
+)
+
+// IsReserved returns true if c is within the reserved error code range:
+// [LowestReservedErrorCode, HighestReservedErrorCode].
+func (c ErrorCode) IsReserved() bool {
+	return LowestReservedErrorCode <= c && c <= HighestReservedErrorCode
+}