Golang 中的错误处理

// The error built-in interface type is the conventional interface for
// representing an error condition, with the nil value representing no error.
type error interface {
	Error() string
}

if err := DoSomething(); err != nil {
    // ...
}

func DoSomethingImportant() (err error){
    defer func() {
        if e := recover(); e != nil {
            err = e.(error)
        }
    }()

	//do your business
	return
}

var (
    Err1   = errors.New("record not exist")
    Err2 = errors.New("connection closed")
)

switch err {
case nil:
	// ...
case Err1:
	// ...
case Err2:
	// ...
default:
	// ...
}

type ErrRecordNotExist errImpl
type ErrPermissionDenined errImpl

type errImpl struct {
    msg string
}

func (e *errImpl) Error() string {
    return e.msg
}

if err == nil {
	// OK
} else if _, ok := err.(*ErrRecordNotExist); ok {
	// 处理记录不存在的错误
} else if _, ok := err.(*ErrPermissionDenined); ok {
	// 处理权限错误
} else {
	// 处理其他类型的错误
}

import (
   "database/sql"
   "fmt"
)

func foo() error {
   return sql.ErrNoRows
}

func bar() error {
   return fmt.Errorf("foo err, %v", sql.ErrNoRows)
}

func zoo() error {
	// 如果不需要增加额外上下文信息，仅附加调用栈后返回，使用 WithStack 方法
   return errors.WithStack(sql.ErrNoRows)
}

func main() {
   err := bar()
   if err == sql.ErrNoRows {
      fmt.Printf("data not found, %+v\n", err)
      return
   }
}

import (
   "github.com/pkg/errors"
)

func foo() error {
   return errors.Wrap(sql.ErrNoRows, "foo failed")
}

func bar() error {
   return errors.WithMessage(foo(), "bar failed")
}

func main() {
   err := bar()
   if errors.Cause(err) == sql.ErrNoRows {
	  // 为 true
      fmt.Printf("data not found, %v\n", err)
      fmt.Printf("%+v\n", err)
      return
   }
}

func (s *HelloServer) SayHelloStrict(ctx context.Context, req *api.HelloReq) (*api.HelloResp, error) {
	if len(req.GetName()) >= 10 {
		return nil, status.Errorf(codes.InvalidArgument,
			"Length of `Name` cannot be more than 10 characters")
	}

	return &api.HelloResp{Result: fmt.Sprintf("Hey, %s!", req.GetName())}, nil
}

resp, err = c.SayHelloStrict(
	context.Background(),
	&api.HelloReq{Name: "Leonhard Euler"},
)

if err != nil {
	// ouch!
	// lets print the gRPC error message
	// which is "Length of `Name` cannot be more than 10 characters"
	errStatus, _ := status.FromError(err)
	fmt.Println(errStatus.Message())
	// lets print the error code which is `INVALID_ARGUMENT`
	fmt.Println(errStatus.Code())
	// Want its int version for some reason?
	// you shouldn't actullay do this, but if you need for debugging,
	// you can do `int(status_code)` which will give you `3`
	//
	// Want to take specific action based on specific error?
	if codes.InvalidArgument == errStatus.Code() {
		// do your stuff here
		log.Fatal()
	}
}

// A Code is an unsigned 32-bit error code as defined in the gRPC spec.
type Code uint32

const (
	// OK is returned on success.
	OK Code = 0

	// Canceled indicates the operation was canceled (typically by the caller).
	//
	// The gRPC framework will generate this error code when cancellation
	// is requested.
	Canceled Code = 1

	// Unknown error. An example of where this error may be returned is
	// if a Status value received from another address space belongs to
	// an error-space that is not known in this address space. Also
	// errors raised by APIs that do not return enough error information
	// may be converted to this error.
	//
	// The gRPC framework will generate this error code in the above two
	// mentioned cases.
	Unknown Code = 2

	// InvalidArgument indicates client specified an invalid argument.
	// Note that this differs from FailedPrecondition. It indicates arguments
	// that are problematic regardless of the state of the system
	// (e.g., a malformed file name).
	//
	// This error code will not be generated by the gRPC framework.
	InvalidArgument Code = 3

	// DeadlineExceeded means operation expired before completion.
	// For operations that change the state of the system, this error may be
	// returned even if the operation has completed successfully. For
	// example, a successful response from a server could have been delayed
	// long enough for the deadline to expire.
	//
	// The gRPC framework will generate this error code when the deadline is
	// exceeded.
	DeadlineExceeded Code = 4

	// NotFound means some requested entity (e.g., file or directory) was
	// not found.
	//
	// This error code will not be generated by the gRPC framework.
	NotFound Code = 5

	// AlreadyExists means an attempt to create an entity failed because one
	// already exists.
	//
	// This error code will not be generated by the gRPC framework.
	AlreadyExists Code = 6

	// PermissionDenied indicates the caller does not have permission to
	// execute the specified operation. It must not be used for rejections
	// caused by exhausting some resource (use ResourceExhausted
	// instead for those errors). It must not be
	// used if the caller cannot be identified (use Unauthenticated
	// instead for those errors).
	//
	// This error code will not be generated by the gRPC core framework,
	// but expect authentication middleware to use it.
	PermissionDenied Code = 7

	// ResourceExhausted indicates some resource has been exhausted, perhaps
	// a per-user quota, or perhaps the entire file system is out of space.
	//
	// This error code will be generated by the gRPC framework in
	// out-of-memory and server overload situations, or when a message is
	// larger than the configured maximum size.
	ResourceExhausted Code = 8

	// FailedPrecondition indicates operation was rejected because the
	// system is not in a state required for the operation's execution.
	// For example, directory to be deleted may be non-empty, an rmdir
	// operation is applied to a non-directory, etc.
	//
	// A litmus test that may help a service implementor in deciding
	// between FailedPrecondition, Aborted, and Unavailable:
	//  (a) Use Unavailable if the client can retry just the failing call.
	//  (b) Use Aborted if the client should retry at a higher-level
	//      (e.g., restarting a read-modify-write sequence).
	//  (c) Use FailedPrecondition if the client should not retry until
	//      the system state has been explicitly fixed. E.g., if an "rmdir"
	//      fails because the directory is non-empty, FailedPrecondition
	//      should be returned since the client should not retry unless
	//      they have first fixed up the directory by deleting files from it.
	//  (d) Use FailedPrecondition if the client performs conditional
	//      REST Get/Update/Delete on a resource and the resource on the
	//      server does not match the condition. E.g., conflicting
	//      read-modify-write on the same resource.
	//
	// This error code will not be generated by the gRPC framework.
	FailedPrecondition Code = 9

	// Aborted indicates the operation was aborted, typically due to a
	// concurrency issue like sequencer check failures, transaction aborts,
	// etc.
	//
	// See litmus test above for deciding between FailedPrecondition,
	// Aborted, and Unavailable.
	//
	// This error code will not be generated by the gRPC framework.
	Aborted Code = 10

	// OutOfRange means operation was attempted past the valid range.
	// E.g., seeking or reading past end of file.
	//
	// Unlike InvalidArgument, this error indicates a problem that may
	// be fixed if the system state changes. For example, a 32-bit file
	// system will generate InvalidArgument if asked to read at an
	// offset that is not in the range [0,2^32-1], but it will generate
	// OutOfRange if asked to read from an offset past the current
	// file size.
	//
	// There is a fair bit of overlap between FailedPrecondition and
	// OutOfRange. We recommend using OutOfRange (the more specific
	// error) when it applies so that callers who are iterating through
	// a space can easily look for an OutOfRange error to detect when
	// they are done.
	//
	// This error code will not be generated by the gRPC framework.
	OutOfRange Code = 11

	// Unimplemented indicates operation is not implemented or not
	// supported/enabled in this service.
	//
	// This error code will be generated by the gRPC framework. Most
	// commonly, you will see this error code when a method implementation
	// is missing on the server. It can also be generated for unknown
	// compression algorithms or a disagreement as to whether an RPC should
	// be streaming.
	Unimplemented Code = 12

	// Internal errors. Means some invariants expected by underlying
	// system has been broken. If you see one of these errors,
	// something is very broken.
	//
	// This error code will be generated by the gRPC framework in several
	// internal error conditions.
	Internal Code = 13

	// Unavailable indicates the service is currently unavailable.
	// This is a most likely a transient condition and may be corrected
	// by retrying with a backoff. Note that it is not always safe to retry
	// non-idempotent operations.
	//
	// See litmus test above for deciding between FailedPrecondition,
	// Aborted, and Unavailable.
	//
	// This error code will be generated by the gRPC framework during
	// abrupt shutdown of a server process or network connection.
	Unavailable Code = 14

	// DataLoss indicates unrecoverable data loss or corruption.
	//
	// This error code will not be generated by the gRPC framework.
	DataLoss Code = 15

	// Unauthenticated indicates the request does not have valid
	// authentication credentials for the operation.
	//
	// The gRPC framework will generate this error code when the
	// authentication metadata is invalid or a Credentials callback fails,
	// but also expect authentication middleware to generate it.
	Unauthenticated Code = 16

	_maxCode = 17
)

// FromError returns a Status representation of err.
//
// - If err was produced by this package or implements the method `GRPCStatus()
//   *Status`, the appropriate Status is returned.
//
// - If err is nil, a Status is returned with codes.OK and no message.
//
// - Otherwise, err is an error not compatible with this package.  In this
//   case, a Status is returned with codes.Unknown and err's Error() message,
//   and ok is false.
func FromError(err error) (s *Status, ok bool) {
	if err == nil {
		return nil, true
	}
	if se, ok := err.(interface {
		GRPCStatus() *Status
	}); ok {
		return se.GRPCStatus(), true
	}
	return New(codes.Unknown, err.Error()), false
}

// Convert is a convenience function which removes the need to handle the
// boolean return value from FromError.
func Convert(err error) *Status {
	s, _ := FromError(err)
	return s
}

// Code returns the Code of the error if it is a Status error, codes.OK if err
// is nil, or codes.Unknown otherwise.
func Code(err error) codes.Code {
	// Don't use FromError to avoid allocation of OK status.
	if err == nil {
		return codes.OK
	}
	if se, ok := err.(interface {
		GRPCStatus() *Status
	}); ok {
		return se.GRPCStatus().Code()
	}
	return codes.Unknown
}

// FromContextError converts a context error or wrapped context error into a
// Status.  It returns a Status with codes.OK if err is nil, or a Status with
// codes.Unknown if err is non-nil and not a context error.
func FromContextError(err error) *Status {
	if err == nil {
		return nil
	}
	if errors.Is(err, context.DeadlineExceeded) {
		return New(codes.DeadlineExceeded, err.Error())
	}
	if errors.Is(err, context.Canceled) {
		return New(codes.Canceled, err.Error())
	}
	return New(codes.Unknown, err.Error())
}

type Status struct {
	// The status code, which should be an enum value of [google.rpc.Code][google.rpc.Code].
	Code int32 `protobuf:"varint,1,opt,name=code,proto3" json:"code,omitempty"`
	// A developer-facing error message, which should be in English. Any
	// user-facing error message should be localized and sent in the
	// [google.rpc.Status.details][google.rpc.Status.details] field, or localized by the client.
	Message string `protobuf:"bytes,2,opt,name=message,proto3" json:"message,omitempty"`
	// A list of messages that carry the error details.  There is a common set of
	// message types for APIs to use.
	Details []*anypb.Any `protobuf:"bytes,3,rep,name=details,proto3" json:"details,omitempty"`
	// contains filtered or unexported fields
}

import (
	"context"
	"errors"
	"io"
	"net/http"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/grpclog"
	"google.golang.org/grpc/status"
)

// HTTPStatusFromCode converts a gRPC error code into the corresponding HTTP response status.
// See: https://github.com/googleapis/googleapis/blob/master/google/rpc/code.proto
func HTTPStatusFromCode(code codes.Code) int {
	switch code {
	case codes.OK:
		return http.StatusOK
	case codes.Canceled:
		return http.StatusRequestTimeout
	case codes.Unknown:
		return http.StatusInternalServerError
	case codes.InvalidArgument:
		return http.StatusBadRequest
	case codes.DeadlineExceeded:
		return http.StatusGatewayTimeout
	case codes.NotFound:
		return http.StatusNotFound
	case codes.AlreadyExists:
		return http.StatusConflict
	case codes.PermissionDenied:
		return http.StatusForbidden
	case codes.Unauthenticated:
		return http.StatusUnauthorized
	case codes.ResourceExhausted:
		return http.StatusTooManyRequests
	case codes.FailedPrecondition:
		// Note, this deliberately doesn't translate to the similarly named'412 Precondition Failed' HTTP response status.
		return http.StatusBadRequest
	case codes.Aborted:
		return http.StatusConflict
	case codes.OutOfRange:
		return http.StatusBadRequest
	case codes.Unimplemented:
		return http.StatusNotImplemented
	case codes.Internal:
		return http.StatusInternalServerError
	case codes.Unavailable:
		return http.StatusServiceUnavailable
	case codes.DataLoss:
		return http.StatusInternalServerError
	}

	grpclog.Infof("Unknown gRPC error code: %v", code)
	return http.StatusInternalServerError
}


// DefaultRoutingErrorHandler is our default handler for routing errors.
// By default http error codes mapped on the following error codes:
//   NotFound -> grpc.NotFound
//   StatusBadRequest -> grpc.InvalidArgument
//   MethodNotAllowed -> grpc.Unimplemented
//   Other -> grpc.Internal, method is not expecting to be called for anything else
func DefaultRoutingErrorHandler(ctx context.Context, mux *ServeMux, marshaler Marshaler, w http.ResponseWriter, r *http.Request, httpStatus int) {
	sterr := status.Error(codes.Internal, "Unexpected routing error")
	switch httpStatus {
	case http.StatusBadRequest:
		sterr = status.Error(codes.InvalidArgument, http.StatusText(httpStatus))
	case http.StatusMethodNotAllowed:
		sterr = status.Error(codes.Unimplemented, http.StatusText(httpStatus))
	case http.StatusNotFound:
		sterr = status.Error(codes.NotFound, http.StatusText(httpStatus))
	}
	mux.errorHandler(ctx, mux, marshaler, w, r, sterr)
}

func (s *server) RpcMethod(ctx context.Context, orderReq *pb.Order) (*wrappers.StringValue, error) {
	if orderReq.Id == "-1" {
		log.Printf("Order ID is vaild : %s", orderReq.Id)

		errorStatus := status.New(codes.InvalidArgument, "Order ID is not valid")
		//附加业务错误
		ds, err := errorStatus.WithDetails(
			&epb.BadRequest_FieldViolation{
				Field:       "ID",
				Description: fmt.Sprintf("Order ID received is not valid %s : %s", orderReq.Id, orderReq.Description),
			},
		)
		if err != nil {
			return nil, errorStatus.Err()
		}

		//返回details错误
		return nil, ds.Err()
	}
	orderMap[orderReq.Id] = *orderReq
	log.Println("Order : ", orderReq.Id, " -> Added")
	return &wrapper.StringValue{Value: "Order Added: " + orderReq.Id}, nil
}

func main(){
	//...
	order1 := pb.Order{Id: "-1",
					   Items:[]string{"iPhone XS", "Mac Book Pro"},
						Destination:"San Jose, CA",
						 Price:2300.00}
	res, addOrderError := client.AddOrder(ctx, &order1)
	if addOrderError != nil {
		errorCode := status.Code(addOrderError)
		if errorCode == codes.InvalidArgument {
			log.Printf("Invalid Argument Error : %s", errorCode)
			errorStatus := status.Convert(addOrderError)
			for _, d := range errorStatus.Details() {
				switch info := d.(type) {
				case *epb.BadRequest_FieldViolation:
					log.Printf("Request Field Invalid: %s", info)
				default:
					log.Printf("Unexpected error type: %s", info)
				}
			}
		} else {
			log.Printf("Unhandled error : %s ", errorCode)
		}
	} else {
		log.Print("AddOrder Response -> ", res.Value)
	}
}

func (a A) Dosomethink(c context.Context, sessionRequest *model.MyModel) (*model.Model, error) {
	return &model.Model{}, status.New(400,"Default error message for 400")
}

func (a A) Dosomethink(c context.Context, sessionRequest *model.MyModel) (*model.Model, error) {
	err := status.Errorf(codes.Code(resp.ErrNum),  errcode.GetCodeDesc(int(resp.ErrNum)))
	return &model.Model{}, err
}    

message BizErr {
    int32 ret = 1;  //错误码
    string msg = 2; //错误信息
    string ext = 3; //扩展错误信息（按照错误码和客户端约定信息格式）
}