add standard error library (pkg#24)

Author: Lingyu Song

.gitignore

@@ -6,6 +6,7 @@
 # Folders
 _obj
 _test
+.idea
 
 # Architecture specific extensions/prefixes
 *.[568vq]

terror_dsl.go

@@ -21,6 +21,16 @@ import (
 	"strings"
 )
 
+// ErrCode represents a specific error type in a error class.
+// Same error code can be used in different error classes.
+type ErrCode int
+
+// ErrCodeText is a textual error code that represents a specific error type in a error class.
+type ErrCodeText string
+
+type ErrorID string
+type RFCErrorCode string
+
 // Error is the 'prototype' of a type of errors.
 // Use DefineError to make a *Error:
 // var ErrUnavailable = ClassRegion.DefineError().
@@ -46,29 +56,25 @@ import (
 //     // handle this error.
 // }
 type Error struct {
-	class *ErrClass
-	code  ErrCode
+	code ErrCode
 	// codeText is the textual describe of the error code
 	codeText ErrCodeText
 	// message is a template of the description of this error.
 	// printf-style formatting is enabled.
 	message string
 	// The workaround field: how to work around this error.
 	// It's used to teach the users how to solve the error if occurring in the real environment.
-	Workaround string
+	workaround string
 	// Description is the expanded detail of why this error occurred.
 	// This could be written by developer at a static env,
 	// and the more detail this field explaining the better,
 	// even some guess of the cause could be included.
-	Description string
-	args        []interface{}
-	file        string
-	line        int
-}
-
-// Class returns ErrClass
-func (e *Error) Class() *ErrClass {
-	return e.class
+	description string
+	// Cause is used to warp some third party error.
+	cause error
+	args  []interface{}
+	file  string
+	line  int
 }
 
 // Code returns the numeric code of this error.
@@ -84,23 +90,7 @@ func (e *Error) Code() ErrCode {
 // The error code is a 3-tuple of abbreviated component name, error class and error code,
 // joined by a colon like {Component}:{ErrorClass}:{InnerErrorCode}.
 func (e *Error) RFCCode() RFCErrorCode {
-	ec := e.Class()
-	if ec == nil {
-		return RFCErrorCode(e.ID())
-	}
-	reg := ec.registry
-	// Maybe top-level errors.
-	if reg.Name == "" {
-		return RFCErrorCode(fmt.Sprintf("%s:%s",
-			ec.Description,
-			e.ID(),
-		))
-	}
-	return RFCErrorCode(fmt.Sprintf("%s:%s:%s",
-		reg.Name,
-		ec.Description,
-		e.ID(),
-	))
+	return RFCErrorCode(e.ID())
 }
 
 // ID returns the ID of this error.
@@ -124,14 +114,17 @@ func (e *Error) MessageTemplate() string {
 
 // Error implements error interface.
 func (e *Error) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
 	describe := e.codeText
 	if len(describe) == 0 {
 		describe = ErrCodeText(strconv.Itoa(int(e.code)))
 	}
-	return fmt.Sprintf("[%s] %s", e.RFCCode(), e.getMsg())
+	return fmt.Sprintf("[%s]%s", e.RFCCode(), e.GetMsg())
 }
 
-func (e *Error) getMsg() string {
+func (e *Error) GetMsg() string {
 	if len(e.args) > 0 {
 		return fmt.Sprintf(e.message, e.args...)
 	}
@@ -197,9 +190,8 @@ func (e *Error) Equal(err error) bool {
 	if !ok {
 		return false
 	}
-	classEquals := e.class.Equal(inErr.class)
 	idEquals := e.ID() == inErr.ID()
-	return classEquals && idEquals
+	return idEquals
 }
 
 // NotEqual checks if err is not equal to e.
@@ -239,7 +231,6 @@ type jsonError struct {
 	Error       string       `json:"message"`
 	Description string       `json:"description,omitempty"`
 	Workaround  string       `json:"workaround,omitempty"`
-	Class       ErrClassID   `json:"classID"`
 	File        string       `json:"file"`
 	Line        int          `json:"line"`
 }
@@ -251,11 +242,10 @@ type jsonError struct {
 // This function is reserved for compatibility.
 func (e *Error) MarshalJSON() ([]byte, error) {
 	return json.Marshal(&jsonError{
-		Error:       e.getMsg(),
-		Description: e.Description,
-		Workaround:  e.Workaround,
+		Error:       e.GetMsg(),
+		Description: e.description,
+		Workaround:  e.workaround,
 		RFCCode:     e.RFCCode(),
-		Class:       e.class.ID,
 		Line:        e.line,
 		File:        e.file,
 	})
@@ -273,21 +263,90 @@ func (e *Error) UnmarshalJSON(data []byte) error {
 		return Trace(err)
 	}
 	codes := strings.Split(string(err.RFCCode), ":")
-	regName := codes[0]
-	className := codes[1]
-	innerCode := codes[2]
+	innerCode := codes[len(codes)-1]
 	if i, errAtoi := strconv.Atoi(innerCode); errAtoi == nil {
 		e.code = ErrCode(i)
-	} else {
-		e.codeText = ErrCodeText(innerCode)
 	}
+	e.codeText = ErrCodeText(err.RFCCode)
 	e.line = err.Line
 	e.file = err.File
 	e.message = err.Error
-	e.class = &ErrClass{
-		Description: className,
-		ID:          err.Class,
-		registry:    &Registry{Name: regName},
-	}
 	return nil
 }
+
+func (e *Error) Wrap(err error) *Error {
+	if err != nil {
+		newErr := *e
+		newErr.cause = err
+		return &newErr
+	}
+	return e
+}
+
+func (e *Error) Cause() error {
+	root := Unwrap(e.cause)
+	if root == nil {
+		return e.cause
+	}
+	return root
+}
+
+func (e *Error) FastGenWithCause(args ...interface{}) error {
+	err := *e
+	if e.cause != nil {
+		err.message = e.cause.Error()
+	}
+	err.args = args
+	return SuspendStack(&err)
+}
+
+func (e *Error) GenWithStackByCause(args ...interface{}) error {
+	err := *e
+	if e.cause != nil {
+		err.message = e.cause.Error()
+	}
+	err.args = args
+	err.fillLineAndFile(1)
+	return AddStack(&err)
+}
+
+type NormalizeOption func(*Error)
+
+// Description returns a NormalizeOption to set description.
+func Description(desc string) NormalizeOption {
+	return func(e *Error) {
+		e.description = desc
+	}
+}
+
+// Workaround returns a NormalizeOption to set workaround.
+func Workaround(wr string) NormalizeOption {
+	return func(e *Error) {
+		e.workaround = wr
+	}
+}
+
+// RFCCodeText returns a NormalizeOption to set RFC error code.
+func RFCCodeText(codeText string) NormalizeOption {
+	return func(e *Error) {
+		e.codeText = ErrCodeText(codeText)
+	}
+}
+
+// MySQLErrorCode returns a NormalizeOption to set error code.
+func MySQLErrorCode(code int) NormalizeOption {
+	return func(e *Error) {
+		e.code = ErrCode(code)
+	}
+}
+
+// Normalize creates a new Error object.
+func Normalize(message string, opts ...NormalizeOption) *Error {
+	e := &Error{
+		message: message,
+	}
+	for _, opt := range opts {
+		opt(e)
+	}
+	return e
+}