Merge branch 'eb/gitrpc_error_handling' of _OKE5H2PQKOUfzFFDuD4FA/default/CODE/gitness (#8)

gitrpc/enum/ref.go

@@ -54,3 +54,22 @@ func RefToRPC(t RefType) rpc.RefType {
 		return rpc.RefType_Undefined
 	}
 }
+
+func (t RefType) String() string {
+	switch t {
+	case RefTypeRaw:
+		return "raw"
+	case RefTypeBranch:
+		return "branch"
+	case RefTypeTag:
+		return "tag"
+	case RefTypePullReqHead:
+		return "head"
+	case RefTypePullReqMerge:
+		return "merge"
+	case RefTypeUndefined:
+		fallthrough
+	default:
+		return ""
+	}
+}

gitrpc/errors.go

@@ -6,11 +6,157 @@ package gitrpc
 
 import (
 	"errors"
+	"fmt"
+
+	"github.com/harness/gitness/gitrpc/rpc"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 )
 
-var ErrNoParamsProvided = errors.New("no params provided")
+var (
-var ErrAlreadyExists = errors.New("already exists")
+	ErrNoParamsProvided = ErrInvalidArgumentf("params not provided")
-var ErrInvalidArgument = errors.New("invalid argument")
+)
-var ErrNotFound = errors.New("not found")
+
-var ErrPreconditionFailed = errors.New("precondition failed")
+type Status string
-var ErrNotMergeable = errors.New("not mergeable")
+
+const (
+	StatusConflict           Status = "conflict"
+	StatusInternal           Status = "internal"
+	StatusInvalidArgument    Status = "invalid"
+	StatusNotFound           Status = "not_found"
+	StatusNotImplemented     Status = "not_implemented"
+	StatusUnauthorized       Status = "unauthorized"
+	StatusFailed             Status = "failed"
+	StatusPreconditionFailed Status = "precondition_failed"
+	StatusNotMergeable       Status = "not_mergeable"
+	StatusAborted            Status = "aborted"
+)
+
+type Error struct {
+	// Machine-readable status code.
+	Status Status
+
+	// Human-readable error message.
+	Message string
+
+	// Details
+	Details map[string]any
+}
+
+// Error implements the error interface.
+func (e *Error) Error() string {
+	return e.Message
+}
+
+// ErrorStatus unwraps an gitrpc error and returns its code.
+// Non-application errors always return StatusInternal.
+func ErrorStatus(err error) Status {
+	var (
+		e *Error
+	)
+	if err == nil {
+		return ""
+	}
+	if errors.As(err, &e) {
+		return e.Status
+	}
+	return StatusInternal
+}
+
+// ErrorMessage unwraps an gitrpc error and returns its message.
+// Non-gitrpc errors always return "Internal error".
+func ErrorMessage(err error) string {
+	var (
+		e *Error
+	)
+	if err == nil {
+		return ""
+	}
+	if errors.As(err, &e) {
+		return e.Message
+	}
+	return "Internal error."
+}
+
+// ErrorDetails unwraps an gitrpc error and returns its details.
+// Non-gitrpc errors always return nil.
+func ErrorDetails(err error) map[string]any {
+	var (
+		e *Error
+	)
+	if err == nil {
+		return nil
+	}
+	if errors.As(err, &e) {
+		return e.Details
+	}
+	return nil
+}
+
+// NewError is a factory function to return an Error with a given status and message.
+func NewError(code Status, message string) *Error {
+	return &Error{
+		Status:  code,
+		Message: message,
+	}
+}
+
+// NewError is a factory function to return an Error with a given status, message and details.
+func NewErrorWithDetails(code Status, message string, details map[string]any) *Error {
+	err := NewError(code, message)
+	err.Details = details
+	return err
+}
+
+// Errorf is a helper function to return an Error with a given status and formatted message.
+func Errorf(code Status, format string, args ...interface{}) *Error {
+	return &Error{
+		Status:  code,
+		Message: fmt.Sprintf(format, args...),
+	}
+}
+
+// ErrInvalidArgumentf is a helper function to return an invalid argument Error.
+func ErrInvalidArgumentf(format string, args ...interface{}) *Error {
+	return Errorf(StatusInvalidArgument, format, args...)
+}
+
+func processRPCErrorf(err error, format string, args ...interface{}) error {
+	// create fallback error returned if we can't map it
+	fallbackErr := fmt.Errorf(format, args...)
+
+	// ensure it's an rpc error
+	st, ok := status.FromError(err)
+	if !ok {
+		return fallbackErr
+	}
+
+	msg := st.Message()
+
+	switch {
+	case st.Code() == codes.AlreadyExists:
+		return NewError(StatusConflict, msg)
+	case st.Code() == codes.NotFound:
+		return NewError(StatusNotFound, msg)
+	case st.Code() == codes.InvalidArgument:
+		return NewError(StatusInvalidArgument, msg)
+	case st.Code() == codes.FailedPrecondition:
+		code := StatusPreconditionFailed
+		details := make(map[string]any)
+		for _, detail := range st.Details() {
+			switch t := detail.(type) {
+			case *rpc.MergeConflictError:
+				details["conflict_files"] = t.ConflictingFiles
+				code = StatusNotMergeable
+			default:
+			}
+		}
+		if len(details) > 0 {
+			return NewErrorWithDetails(code, msg, details)
+		}
+		return NewError(code, msg)
+	default:
+		return fallbackErr
+	}
+}

gitrpc/internal/gitea/merge.go

@@ -206,6 +206,9 @@ func (g Adapter) Merge(
 		// Merge will leave a MERGE_HEAD file in the .git folder if there is a conflict
 		if _, statErr := os.Stat(filepath.Join(tmpBasePath, ".git", "MERGE_HEAD")); statErr == nil {
 			// We have a merge conflict error
+			if err = conflictFiles(ctx, pr, env, tmpBasePath, &outbuf); err != nil {
+				return err
+			}
 			return &types.MergeConflictsError{
 				Method: mergeMethod,
 				StdOut: outbuf.String(),
@@ -228,6 +231,29 @@ func (g Adapter) Merge(
 	return nil
 }
 
+func conflictFiles(ctx context.Context,
+	pr *types.PullRequest,
+	env []string,
+	repoPath string,
+	buf *strings.Builder,
+) error {
+	stdout, stderr, cferr := git.NewCommand(
+		ctx, "diff", "--name-only", "--diff-filter=U", "--relative",
+	).RunStdString(&git.RunOpts{
+		Env: env,
+		Dir: repoPath,
+	})
+	if cferr != nil {
+		return processGiteaErrorf(cferr, "failed to list conflict files [%s -> %s], stderr: %v, err: %v",
+			pr.HeadBranch, pr.BaseBranch, stderr, cferr)
+	}
+	if len(stdout) > 0 {
+		buf.Reset()
+		buf.WriteString(stdout)
+	}
+	return nil
+}
+
 func (g Adapter) GetDiffTree(ctx context.Context, repoPath, baseBranch, headBranch string) (string, error) {
 	getDiffTreeFromBranch := func(repoPath, baseBranch, headBranch string) (string, error) {
 		var outbuf, errbuf strings.Builder

gitrpc/internal/middleware/error.go

@@ -9,8 +9,7 @@ import (
 	"errors"
 	"reflect"
 
-	"github.com/harness/gitness/gitrpc/internal/types"
+	"github.com/rs/zerolog/log"
-
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
@@ -30,7 +29,7 @@ func (i ErrInterceptor) UnaryInterceptor() grpc.UnaryServerInterceptor {
 		if (value == nil || reflect.ValueOf(value).IsNil()) && err == nil {
 			return nil, status.Error(codes.Internal, "service returned no error and no object")
 		}
-		err = processError(err)
+		err = processError(ctx, err)
 		return value, err
 	}
 }
@@ -39,44 +38,56 @@ func (i ErrInterceptor) StreamInterceptor() grpc.StreamServerInterceptor {
 	return func(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo,
 		handler grpc.StreamHandler) error {
 		err := handler(srv, stream)
-		err = processError(err)
+		err = processError(stream.Context(), err)
 		return err
 	}
 }
 
-func processError(err error) error {
+func processError(ctx context.Context, err error) (rerr error) {
 	if err == nil {
 		return nil
 	}
 
-	// check if error already is grpc error
+	defer func() {
-	// TODO: this should be removed once all error handling has been refactored.
+		statusErr, ok := status.FromError(rerr)
+		if !ok {
+			return
+		}
+		//nolint: exhaustive // log only server side errors, no need to log user based errors
+		switch statusErr.Code() {
+		case codes.Unknown,
+			codes.DeadlineExceeded,
+			codes.ResourceExhausted,
+			codes.FailedPrecondition,
+			codes.Aborted,
+			codes.OutOfRange,
+			codes.Unimplemented,
+			codes.Internal,
+			codes.Unavailable,
+			codes.DataLoss:
+			{
+				logCtx := log.Ctx(ctx)
+				logCtx.Error().Msg(err.Error())
+			}
+		}
+	}()
+
+	// custom errors should implement StatusError
+	var statusError interface {
+		Status() (*status.Status, error)
+	}
+
+	if errors.As(err, &statusError) {
+		st, sterr := statusError.Status()
+		if sterr != nil {
+			return sterr
+		}
+		return st.Err()
+	}
+
 	if status, ok := status.FromError(err); ok {
 		return status.Err()
 	}
 
-	message := err.Error()
+	return status.Errorf(codes.Unknown, err.Error())
-
-	switch {
-	case errors.Is(err, context.DeadlineExceeded):
-		return status.Error(codes.DeadlineExceeded, message)
-	case errors.Is(err, types.ErrNotFound):
-		return status.Error(codes.NotFound, message)
-	case errors.Is(err, types.ErrAlreadyExists):
-		return status.Error(codes.AlreadyExists, message)
-	case errors.Is(err, types.ErrInvalidArgument):
-		return status.Error(codes.InvalidArgument, message)
-	case errors.Is(err, types.ErrInvalidPath):
-		return status.Error(codes.InvalidArgument, message)
-	case errors.Is(err, types.ErrUndefinedAction):
-		return status.Error(codes.InvalidArgument, message)
-	case errors.Is(err, types.ErrHeaderCannotBeEmpty):
-		return status.Error(codes.InvalidArgument, message)
-	case errors.Is(err, types.ErrActionListEmpty):
-		return status.Error(codes.FailedPrecondition, message)
-	case errors.Is(err, types.ErrContentSentBeforeAction):
-		return status.Error(codes.FailedPrecondition, message)
-	default:
-		return status.Errorf(codes.Unknown, message)
-	}
 }

gitrpc/internal/service/errors.go

@@ -0,0 +1,215 @@
+// Copyright 2022 Harness Inc. All rights reserved.
+// Use of this source code is governed by the Polyform Free Trial License
+// that can be found in the LICENSE.md file for this repository.
+
+package service
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/harness/gitness/gitrpc/internal/types"
+	"github.com/harness/gitness/gitrpc/rpc"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/anypb"
+)
+
+type Error struct {
+	Code    codes.Code
+	Message string
+	Err     error
+	details []proto.Message
+}
+
+func (e *Error) Error() string {
+	return fmt.Sprintf("%s, err: %v", e.Message, e.Err.Error())
+}
+
+func (e *Error) Status() (*status.Status, error) {
+	st := status.New(e.Code, e.Message)
+	if len(e.details) == 0 {
+		return st, nil
+	}
+	// add details
+	proto := st.Proto()
+	for _, detail := range e.details {
+		marshaled, err := anypb.New(detail)
+		if err != nil {
+			return nil, err
+		}
+
+		proto.Details = append(proto.Details, marshaled)
+	}
+	return status.FromProto(proto), nil
+}
+
+func (e *Error) Details() any {
+	return e.details
+}
+
+func (e *Error) Unwrap() error {
+	return e.Err
+}
+
+// Errorf generates new Error with status code and custom arguments.
+// args can contain format args and additional arg like err which will be logged
+// by middleware and details object type of map. Ordering of args element
+// should first process format args and then error or detail.
+func Errorf(code codes.Code, format string, args ...any) (err error) {
+	details := make([]proto.Message, 0, 8)
+	newargs := make([]any, 0, len(args))
+
+	for _, arg := range args {
+		switch t := arg.(type) {
+		case error:
+			err = t
+		case proto.Message:
+			details = append(details, t)
+		default:
+			newargs = append(newargs, arg)
+		}
+	}
+
+	return &Error{
+		Code:    code,
+		Message: fmt.Sprintf(format, newargs...),
+		Err:     err,
+		details: details,
+	}
+}
+
+func wrapError(code codes.Code, err error) error {
+	var e *Error
+	if errors.As(err, &e) {
+		return err
+	}
+	return &Error{
+		Code:    code,
+		Message: err.Error(),
+		Err:     err,
+	}
+}
+
+// ErrCanceled wraps err with codes.Canceled, unless err is already a Error error.
+func ErrCanceled(err error) error { return wrapError(codes.Canceled, err) }
+
+// ErrDeadlineExceeded wraps err with codes.DeadlineExceeded, unless err is already a Error error.
+func ErrDeadlineExceeded(err error) error { return wrapError(codes.DeadlineExceeded, err) }
+
+// ErrInternal wraps err with codes.Internal, unless err is already a Error error.
+func ErrInternal(err error) error { return wrapError(codes.Internal, err) }
+
+// ErrInvalidArgument wraps err with codes.InvalidArgument, unless err is already a Error error.
+func ErrInvalidArgument(err error) error { return wrapError(codes.InvalidArgument, err) }
+
+// ErrNotFound wraps error with codes.NotFound, unless err is already a Error error.
+func ErrNotFound(err error) error { return wrapError(codes.NotFound, err) }
+
+// ErrFailedPrecondition wraps err with codes.FailedPrecondition, unless err is already a Error
+// error.
+func ErrFailedPrecondition(err error) error { return wrapError(codes.FailedPrecondition, err) }
+
+// ErrUnavailable wraps err with codes.Unavailable, unless err is already a gRPC error.
+func ErrUnavailable(err error) error { return wrapError(codes.Unavailable, err) }
+
+// ErrPermissionDenied wraps err with codes.PermissionDenied, unless err is already a Error error.
+func ErrPermissionDenied(err error) error { return wrapError(codes.PermissionDenied, err) }
+
+// ErrAlreadyExists wraps err with codes.AlreadyExists, unless err is already a Error error.
+func ErrAlreadyExists(err error) error { return wrapError(codes.AlreadyExists, err) }
+
+// ErrAborted wraps err with codes.Aborted, unless err is already a Error type.
+func ErrAborted(err error) error { return wrapError(codes.Aborted, err) }
+
+// ErrCanceledf wraps a formatted error with codes.Canceled, unless the formatted error is a
+// wrapped Error error.
+func ErrCanceledf(format string, a ...interface{}) error {
+	return Errorf(codes.Canceled, format, a...)
+}
+
+// ErrDeadlineExceededf wraps a formatted error with codes.DeadlineExceeded, unless the formatted
+// error is a wrapped Error error.
+func ErrDeadlineExceededf(format string, a ...interface{}) error {
+	return Errorf(codes.DeadlineExceeded, format, a...)
+}
+
+// ErrInternalf wraps a formatted error with codes.Internal, unless the formatted error is a
+// wrapped Error error.
+func ErrInternalf(format string, a ...interface{}) error {
+	return Errorf(codes.Internal, format, a...)
+}
+
+// ErrInvalidArgumentf wraps a formatted error with codes.InvalidArgument, unless the formatted
+// error is a wrapped Error error.
+func ErrInvalidArgumentf(format string, a ...interface{}) error {
+	return Errorf(codes.InvalidArgument, format, a...)
+}
+
+// ErrNotFoundf wraps a formatted error with codes.NotFound, unless the
+// formatted error is a wrapped Error error.
+func ErrNotFoundf(format string, a ...interface{}) error {
+	return Errorf(codes.NotFound, format, a...)
+}
+
+// ErrFailedPreconditionf wraps a formatted error with codes.FailedPrecondition, unless the
+// formatted error is a wrapped Error error.
+func ErrFailedPreconditionf(format string, a ...interface{}) error {
+	return Errorf(codes.FailedPrecondition, format, a...)
+}
+
+// ErrUnavailablef wraps a formatted error with codes.Unavailable, unless the
+// formatted error is a wrapped Error error.
+func ErrUnavailablef(format string, a ...interface{}) error {
+	return Errorf(codes.Unavailable, format, a...)
+}
+
+// ErrPermissionDeniedf wraps a formatted error with codes.PermissionDenied, unless the formatted
+// error is a wrapped Error error.
+func ErrPermissionDeniedf(format string, a ...interface{}) error {
+	return Errorf(codes.PermissionDenied, format, a...)
+}
+
+// ErrAlreadyExistsf wraps a formatted error with codes.AlreadyExists, unless the formatted error is
+// a wrapped Error error.
+func ErrAlreadyExistsf(format string, a ...interface{}) error {
+	return Errorf(codes.AlreadyExists, format, a...)
+}
+
+// ErrAbortedf wraps a formatted error with codes.Aborted, unless the formatted error is a wrapped
+// Error error.
+func ErrAbortedf(format string, a ...interface{}) error {
+	return Errorf(codes.Aborted, format, a...)
+}
+
+// processGitErrorf translates error.
+func processGitErrorf(err error, format string, args ...interface{}) error {
+	var (
+		cferr *types.MergeConflictsError
+	)
+	const nl = "\n"
+	// when we add err as argument it will be part of the new error
+	args = append(args, err)
+	switch {
+	case errors.Is(err, types.ErrNotFound):
+		return ErrNotFoundf(format, args...)
+	case errors.Is(err, types.ErrAlreadyExists):
+		return ErrAlreadyExistsf(format, args...)
+	case errors.Is(err, types.ErrInvalidArgument):
+		return ErrInvalidArgumentf(format, args...)
+	case errors.As(err, &cferr):
+		stdout := strings.Trim(cferr.StdOut, nl)
+		conflictingFiles := strings.Split(stdout, nl)
+		files := &rpc.MergeConflictError{
+			ConflictingFiles: conflictingFiles,
+		}
+		return ErrFailedPreconditionf("merging failed! conflict files error", files, err)
+	case types.IsMergeUnrelatedHistoriesError(err):
+		return ErrFailedPreconditionf(format, args...)
+	default:
+		return Errorf(codes.Unknown, format, args...)
+	}
+}

gitrpc/internal/service/mapping.go

@@ -5,42 +5,13 @@
 package service
 
 import (
-	"errors"
-	"fmt"
-
 	"github.com/harness/gitness/gitrpc/internal/types"
 	"github.com/harness/gitness/gitrpc/rpc"
 
-	"github.com/rs/zerolog/log"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )
 
-// Logs the error and message, returns either the provided message or a rpc equivalent if possible.
-// Always logs the full message with error as warning.
-func processGitErrorf(err error, format string, args ...interface{}) error {
-	// create fallback error returned if we can't map it
-	message := fmt.Sprintf(format, args...)
-
-	// always log internal error together with message.
-	log.Warn().Msgf("%s: [GIT] %v", message, err)
-
-	switch {
-	case errors.Is(err, types.ErrNotFound):
-		return status.Error(codes.NotFound, message)
-	case errors.Is(err, types.ErrAlreadyExists):
-		return status.Errorf(codes.AlreadyExists, message)
-	case errors.Is(err, types.ErrInvalidArgument):
-		return status.Errorf(codes.InvalidArgument, message)
-	case types.IsMergeConflictsError(err):
-		return status.Errorf(codes.Aborted, message)
-	case types.IsMergeUnrelatedHistoriesError(err):
-		return status.Errorf(codes.Aborted, message)
-	default:
-		return status.Errorf(codes.Unknown, message)
-	}
-}
-
 func mapSortOrder(s rpc.SortOrder) types.SortOrder {
 	switch s {
 	case rpc.SortOrder_Asc:

gitrpc/internal/service/tree.go

@@ -71,7 +71,7 @@ func (s RepositoryService) GetTreeNode(ctx context.Context,
 	// TODO: do we need to validate request for nil?
 	gitNode, err := s.adapter.GetTreeNode(ctx, repoPath, request.GetGitRef(), request.GetPath())
 	if err != nil {
-		return nil, processGitErrorf(err, "failed to get tree node")
+		return nil, processGitErrorf(err, "failed to get tree node %s", request.Path)
 	}
 
 	res := &rpc.GetTreeNodeResponse{

gitrpc/mapping.go

@@ -9,44 +9,8 @@ import (
 	"time"
 
 	"github.com/harness/gitness/gitrpc/rpc"
-
-	"github.com/rs/zerolog/log"
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
 )
 
-// Logs the error and message, returns either the provided message or a gitrpc equivalent if possible.
-// Always logs the full message with error as warning.
-func processRPCErrorf(err error, format string, args ...interface{}) error {
-	// create fallback error returned if we can't map it
-	fallbackErr := fmt.Errorf(format, args...)
-
-	// always log internal error together with message.
-	log.Warn().Msgf("%v: [RPC] %v", fallbackErr, err)
-
-	// ensure it's an rpc error
-	rpcErr, ok := status.FromError(err)
-	if !ok {
-		return fallbackErr
-	}
-
-	switch {
-	case rpcErr.Code() == codes.AlreadyExists:
-		return ErrAlreadyExists
-	case rpcErr.Code() == codes.NotFound:
-		return ErrNotFound
-	case rpcErr.Code() == codes.InvalidArgument:
-		return ErrInvalidArgument
-	case rpcErr.Code() == codes.FailedPrecondition:
-		return ErrPreconditionFailed
-	case rpcErr.Code() == codes.Aborted:
-		// TODO: this should not be so generic ...
-		return ErrNotMergeable
-	default:
-		return fallbackErr
-	}
-}
-
 func mapToRPCSortOrder(o SortOrder) rpc.SortOrder {
 	switch o {
 	case SortOrderAsc:

gitrpc/proto/merge.proto

@@ -55,3 +55,10 @@ message MergeResponse {
   // merge_sha is the sha of the commit after merging head_sha with base_sha.
   string merge_sha = 4;
 }
+
+// MergeConflictError is an error returned in the case when merging two commits
+// fails due to a merge conflict.
+message MergeConflictError {
+  // ConflictingFiles is the set of files which have been conflicting.
+  repeated string conflicting_files = 1;
+}

gitrpc/ref.go

@@ -9,9 +9,6 @@ import (
 
 	"github.com/harness/gitness/gitrpc/enum"
 	"github.com/harness/gitness/gitrpc/rpc"
-
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
 )
 
 type GetRefParams struct {
@@ -27,7 +24,7 @@ type GetRefResponse struct {
 func (c *Client) GetRef(ctx context.Context, params GetRefParams) (GetRefResponse, error) {
 	refType := enum.RefToRPC(params.Type)
 	if refType == rpc.RefType_Undefined {
-		return GetRefResponse{}, ErrInvalidArgument
+		return GetRefResponse{}, ErrInvalidArgumentf("invalid argument: '%s'", refType)
 	}
 
 	result, err := c.refService.GetRef(ctx, &rpc.GetRefRequest{
@@ -35,8 +32,8 @@ func (c *Client) GetRef(ctx context.Context, params GetRefParams) (GetRefRespons
 		RefName: params.Name,
 		RefType: refType,
 	})
-	if s, ok := status.FromError(err); err != nil && ok && s.Code() == codes.NotFound {
+	if err != nil {
-		return GetRefResponse{}, ErrNotFound
+		return GetRefResponse{}, processRPCErrorf(err, "failed to get %s ref '%s'", params.Type.String(), params.Name)
 	}
 
 	return GetRefResponse{SHA: result.Sha}, nil
@@ -57,7 +54,7 @@ type UpdateRefParams struct {
 func (c *Client) UpdateRef(ctx context.Context, params UpdateRefParams) error {
 	refType := enum.RefToRPC(params.Type)
 	if refType == rpc.RefType_Undefined {
-		return ErrInvalidArgument
+		return ErrInvalidArgumentf("invalid argument: '%s'", refType)
 	}
 
 	_, err := c.refService.UpdateRef(ctx, &rpc.UpdateRefRequest{
@@ -67,8 +64,8 @@ func (c *Client) UpdateRef(ctx context.Context, params UpdateRefParams) error {
 		NewValue: params.NewValue,
 		OldValue: params.OldValue,
 	})
-	if s, ok := status.FromError(err); err != nil && ok && s.Code() == codes.NotFound {
+	if err != nil {
-		return ErrNotFound
+		return processRPCErrorf(err, "failed to update %s ref '%s'", params.Type.String(), params.Name)
 	}
 
 	return err

gitrpc/rpc/http.pb.go

@@ -151,6 +151,7 @@ type ServicePackRequest struct {
 	// Depending on the service the matching base type has to be passed
 	//
 	// Types that are assignable to Base:
+	//
 	//	*ServicePackRequest_ReadBase
 	//	*ServicePackRequest_WriteBase
 	Base isServicePackRequest_Base `protobuf_oneof:"base"`

gitrpc/rpc/merge.pb.go

@@ -245,6 +245,56 @@ func (x *MergeResponse) GetMergeSha() string {
 	return ""
 }
 
+// MergeConflictError is an error returned in the case when merging two commits
+// fails due to a merge conflict.
+type MergeConflictError struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// ConflictingFiles is the set of files which have been conflicting.
+	ConflictingFiles []string `protobuf:"bytes,1,rep,name=conflicting_files,json=conflictingFiles,proto3" json:"conflicting_files,omitempty"`
+}
+
+func (x *MergeConflictError) Reset() {
+	*x = MergeConflictError{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_merge_proto_msgTypes[2]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *MergeConflictError) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*MergeConflictError) ProtoMessage() {}
+
+func (x *MergeConflictError) ProtoReflect() protoreflect.Message {
+	mi := &file_merge_proto_msgTypes[2]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use MergeConflictError.ProtoReflect.Descriptor instead.
+func (*MergeConflictError) Descriptor() ([]byte, []int) {
+	return file_merge_proto_rawDescGZIP(), []int{2}
+}
+
+func (x *MergeConflictError) GetConflictingFiles() []string {
+	if x != nil {
+		return x.ConflictingFiles
+	}
+	return nil
+}
+
 var File_merge_proto protoreflect.FileDescriptor
 
 var file_merge_proto_rawDesc = []byte{
@@ -285,14 +335,19 @@ var file_merge_proto_rawDesc = []byte{
 	0x72, 0x67, 0x65, 0x5f, 0x62, 0x61, 0x73, 0x65, 0x5f, 0x73, 0x68, 0x61, 0x18, 0x03, 0x20, 0x01,
 	0x28, 0x09, 0x52, 0x0c, 0x6d, 0x65, 0x72, 0x67, 0x65, 0x42, 0x61, 0x73, 0x65, 0x53, 0x68, 0x61,
 	0x12, 0x1b, 0x0a, 0x09, 0x6d, 0x65, 0x72, 0x67, 0x65, 0x5f, 0x73, 0x68, 0x61, 0x18, 0x04, 0x20,
-	0x01, 0x28, 0x09, 0x52, 0x08, 0x6d, 0x65, 0x72, 0x67, 0x65, 0x53, 0x68, 0x61, 0x32, 0x40, 0x0a,
+	0x01, 0x28, 0x09, 0x52, 0x08, 0x6d, 0x65, 0x72, 0x67, 0x65, 0x53, 0x68, 0x61, 0x22, 0x41, 0x0a,
-	0x0c, 0x4d, 0x65, 0x72, 0x67, 0x65, 0x53, 0x65, 0x72, 0x76, 0x69, 0x63, 0x65, 0x12, 0x30, 0x0a,
+	0x12, 0x4d, 0x65, 0x72, 0x67, 0x65, 0x43, 0x6f, 0x6e, 0x66, 0x6c, 0x69, 0x63, 0x74, 0x45, 0x72,
-	0x05, 0x4d, 0x65, 0x72, 0x67, 0x65, 0x12, 0x11, 0x2e, 0x72, 0x70, 0x63, 0x2e, 0x4d, 0x65, 0x72,
+	0x72, 0x6f, 0x72, 0x12, 0x2b, 0x0a, 0x11, 0x63, 0x6f, 0x6e, 0x66, 0x6c, 0x69, 0x63, 0x74, 0x69,
-	0x67, 0x65, 0x52, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x1a, 0x12, 0x2e, 0x72, 0x70, 0x63, 0x2e,
+	0x6e, 0x67, 0x5f, 0x66, 0x69, 0x6c, 0x65, 0x73, 0x18, 0x01, 0x20, 0x03, 0x28, 0x09, 0x52, 0x10,
-	0x4d, 0x65, 0x72, 0x67, 0x65, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x22, 0x00, 0x42,
+	0x63, 0x6f, 0x6e, 0x66, 0x6c, 0x69, 0x63, 0x74, 0x69, 0x6e, 0x67, 0x46, 0x69, 0x6c, 0x65, 0x73,
-	0x27, 0x5a, 0x25, 0x67, 0x69, 0x74, 0x68, 0x75, 0x62, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x68, 0x61,
+	0x32, 0x40, 0x0a, 0x0c, 0x4d, 0x65, 0x72, 0x67, 0x65, 0x53, 0x65, 0x72, 0x76, 0x69, 0x63, 0x65,
-	0x72, 0x6e, 0x65, 0x73, 0x73, 0x2f, 0x67, 0x69, 0x74, 0x6e, 0x65, 0x73, 0x73, 0x2f, 0x67, 0x69,
+	0x12, 0x30, 0x0a, 0x05, 0x4d, 0x65, 0x72, 0x67, 0x65, 0x12, 0x11, 0x2e, 0x72, 0x70, 0x63, 0x2e,
-	0x74, 0x72, 0x70, 0x63, 0x2f, 0x72, 0x70, 0x63, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
+	0x4d, 0x65, 0x72, 0x67, 0x65, 0x52, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x1a, 0x12, 0x2e, 0x72,
+	0x70, 0x63, 0x2e, 0x4d, 0x65, 0x72, 0x67, 0x65, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65,
+	0x22, 0x00, 0x42, 0x27, 0x5a, 0x25, 0x67, 0x69, 0x74, 0x68, 0x75, 0x62, 0x2e, 0x63, 0x6f, 0x6d,
+	0x2f, 0x68, 0x61, 0x72, 0x6e, 0x65, 0x73, 0x73, 0x2f, 0x67, 0x69, 0x74, 0x6e, 0x65, 0x73, 0x73,
+	0x2f, 0x67, 0x69, 0x74, 0x72, 0x70, 0x63, 0x2f, 0x72, 0x70, 0x63, 0x62, 0x06, 0x70, 0x72, 0x6f,
+	0x74, 0x6f, 0x33,
 }
 
 var (
@@ -307,19 +362,20 @@ func file_merge_proto_rawDescGZIP() []byte {
 	return file_merge_proto_rawDescData
 }
 
-var file_merge_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
+var file_merge_proto_msgTypes = make([]protoimpl.MessageInfo, 3)
 var file_merge_proto_goTypes = []interface{}{
 	(*MergeRequest)(nil),       // 0: rpc.MergeRequest
 	(*MergeResponse)(nil),      // 1: rpc.MergeResponse
-	(*WriteRequest)(nil),  // 2: rpc.WriteRequest
+	(*MergeConflictError)(nil), // 2: rpc.MergeConflictError
-	(*Identity)(nil),      // 3: rpc.Identity
+	(*WriteRequest)(nil),       // 3: rpc.WriteRequest
-	(RefType)(0),          // 4: rpc.RefType
+	(*Identity)(nil),           // 4: rpc.Identity
+	(RefType)(0),               // 5: rpc.RefType
 }
 var file_merge_proto_depIdxs = []int32{
-	2, // 0: rpc.MergeRequest.base:type_name -> rpc.WriteRequest
+	3, // 0: rpc.MergeRequest.base:type_name -> rpc.WriteRequest
-	3, // 1: rpc.MergeRequest.author:type_name -> rpc.Identity
+	4, // 1: rpc.MergeRequest.author:type_name -> rpc.Identity
-	3, // 2: rpc.MergeRequest.committer:type_name -> rpc.Identity
+	4, // 2: rpc.MergeRequest.committer:type_name -> rpc.Identity
-	4, // 3: rpc.MergeRequest.ref_type:type_name -> rpc.RefType
+	5, // 3: rpc.MergeRequest.ref_type:type_name -> rpc.RefType
 	0, // 4: rpc.MergeService.Merge:input_type -> rpc.MergeRequest
 	1, // 5: rpc.MergeService.Merge:output_type -> rpc.MergeResponse
 	5, // [5:6] is the sub-list for method output_type
@@ -360,6 +416,18 @@ func file_merge_proto_init() {
 				return nil
 			}
 		}
+		file_merge_proto_msgTypes[2].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*MergeConflictError); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
 	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
@@ -367,7 +435,7 @@ func file_merge_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: file_merge_proto_rawDesc,
 			NumEnums:      0,
-			NumMessages:   2,
+			NumMessages:   3,
 			NumExtensions: 0,
 			NumServices:   1,
 		},

gitrpc/rpc/operations.pb.go

@@ -247,6 +247,7 @@ type CommitFilesAction struct {
 	unknownFields protoimpl.UnknownFields
 
 	// Types that are assignable to Payload:
+	//
 	//	*CommitFilesAction_Header
 	//	*CommitFilesAction_Content
 	Payload isCommitFilesAction_Payload `protobuf_oneof:"payload"`
@@ -330,6 +331,7 @@ type CommitFilesRequest struct {
 	unknownFields protoimpl.UnknownFields
 
 	// Types that are assignable to Payload:
+	//
 	//	*CommitFilesRequest_Header
 	//	*CommitFilesRequest_Action
 	Payload isCommitFilesRequest_Payload `protobuf_oneof:"payload"`

gitrpc/rpc/repo.pb.go

@@ -130,6 +130,7 @@ type CreateRepositoryRequest struct {
 	unknownFields protoimpl.UnknownFields
 
 	// Types that are assignable to Data:
+	//
 	//	*CreateRepositoryRequest_Header
 	//	*CreateRepositoryRequest_File
 	Data isCreateRepositoryRequest_Data `protobuf_oneof:"data"`

gitrpc/rpc/shared.pb.go

@@ -298,6 +298,7 @@ type FileUpload struct {
 	unknownFields protoimpl.UnknownFields
 
 	// Types that are assignable to Data:
+	//
 	//	*FileUpload_Header
 	//	*FileUpload_Chunk
 	Data isFileUpload_Data `protobuf_oneof:"data"`

internal/api/controller/pullreq/controller.go

@@ -6,7 +6,6 @@ package pullreq
 
 import (
 	"context"
-	"errors"
 	"fmt"
 
 	"github.com/harness/gitness/gitrpc"
@@ -83,7 +82,7 @@ func (c *Controller) verifyBranchExistence(ctx context.Context,
 			Name:       branch,
 			Type:       gitrpcenum.RefTypeBranch,
 		})
-	if errors.Is(err, gitrpc.ErrNotFound) {
+	if gitrpc.ErrorStatus(err) == gitrpc.StatusNotFound {
 		return "", usererror.BadRequest(
 			fmt.Sprintf("branch %s does not exist in the repository %s", branch, repo.UID))
 	}

internal/api/controller/repo/merge_check.go

@@ -6,7 +6,6 @@ package repo
 
 import (
 	"context"
-	"errors"
 	"fmt"
 
 	"github.com/harness/gitness/gitrpc"
@@ -24,24 +23,24 @@ func (c *Controller) MergeCheck(
 	session *auth.Session,
 	repoRef string,
 	diffPath string,
-) (MergeCheck, error) {
+) error {
 	repo, err := c.repoStore.FindByRef(ctx, repoRef)
 	if err != nil {
-		return MergeCheck{}, err
+		return err
 	}
 
 	if err = apiauth.CheckRepo(ctx, c.authorizer, session, repo, enum.PermissionRepoView, false); err != nil {
-		return MergeCheck{}, fmt.Errorf("access check failed: %w", err)
+		return fmt.Errorf("access check failed: %w", err)
 	}
 
 	info, err := parseDiffPath(diffPath)
 	if err != nil {
-		return MergeCheck{}, err
+		return err
 	}
 
 	writeParams, err := CreateRPCWriteParams(ctx, c.urlProvider, session, repo)
 	if err != nil {
-		return MergeCheck{}, fmt.Errorf("failed to create rpc write params: %w", err)
+		return fmt.Errorf("failed to create rpc write params: %w", err)
 	}
 
 	_, err = c.gitRPCClient.Merge(ctx, &gitrpc.MergeParams{
@@ -50,16 +49,9 @@ func (c *Controller) MergeCheck(
 		HeadRepoUID: writeParams.RepoUID, // forks are not supported for now
 		HeadBranch:  info.HeadRef,
 	})
-	if errors.Is(err, gitrpc.ErrNotMergeable) {
-		return MergeCheck{
-			Mergeable: false,
-		}, nil
-	}
 	if err != nil {
-		return MergeCheck{}, fmt.Errorf("merge execution failed: %w", err)
+		return fmt.Errorf("merge execution failed: %w", err)
 	}
 
-	return MergeCheck{
+	return nil
-		Mergeable: true,
-	}, nil
 }

internal/api/handler/repo/merge_check.go

@@ -25,12 +25,12 @@ func HandleMergeCheck(repoCtrl *repo.Controller) http.HandlerFunc {
 
 		path := request.GetOptionalRemainderFromPath(r)
 
-		output, err := repoCtrl.MergeCheck(ctx, session, repoRef, path)
+		err = repoCtrl.MergeCheck(ctx, session, repoRef, path)
 		if err != nil {
 			render.TranslatedUserError(w, err)
 			return
 		}
 
-		render.JSON(w, http.StatusOK, output)
+		w.WriteHeader(http.StatusNoContent)
 	}
 }

internal/api/openapi/repo.go

@@ -550,7 +550,8 @@ func repoOperations(reflector *openapi3.Reflector) {
 	opMergeCheck.WithTags("repository")
 	opMergeCheck.WithMapOfAnything(map[string]interface{}{"operationId": "mergeCheck"})
 	_ = reflector.SetRequest(&opMergeCheck, new(getRawDiffRequest), http.MethodPost)
-	_ = reflector.SetJSONResponse(&opMergeCheck, new(repo.MergeCheck), http.StatusOK)
+	_ = reflector.SetJSONResponse(&opMergeCheck, nil, http.StatusNoContent)
+	_ = reflector.SetJSONResponse(&opMergeCheck, new(usererror.Error), http.StatusPreconditionFailed)
 	_ = reflector.SetJSONResponse(&opMergeCheck, new(usererror.Error), http.StatusInternalServerError)
 	_ = reflector.SetJSONResponse(&opMergeCheck, new(usererror.Error), http.StatusUnauthorized)
 	_ = reflector.SetJSONResponse(&opMergeCheck, new(usererror.Error), http.StatusForbidden)

internal/api/usererror/translate.go

@@ -18,8 +18,12 @@ import (
 )
 
 func Translate(err error) *Error {
-	var rError *Error
+	var (
-	var checkError *check.ValidationError
+		rError      *Error
+		checkError  *check.ValidationError
+		gitrpcError *gitrpc.Error
+	)
+
 	switch {
 	// api errors
 	case errors.As(err, &rError):
@@ -52,16 +56,12 @@ func Translate(err error) *Error {
 		return ErrSpaceWithChildsCantBeDeleted
 
 	// gitrpc errors
-	case errors.Is(err, gitrpc.ErrAlreadyExists):
+	case errors.As(err, &gitrpcError):
-		return ErrDuplicate
+		return NewWithPayload(httpStatusCode(
-	case errors.Is(err, gitrpc.ErrInvalidArgument):
+			gitrpcError.Status),
-		return ErrBadRequest
+			gitrpcError.Message,
-	case errors.Is(err, gitrpc.ErrNotFound):
+			gitrpcError.Details,
-		return ErrNotFound
+		)
-	case errors.Is(err, gitrpc.ErrPreconditionFailed):
-		return ErrPreconditionFailed
-	case errors.Is(err, gitrpc.ErrNotMergeable):
-		return ErrNotMergeable
 
 	// webhook errors
 	case errors.Is(err, webhook.ErrWebhookNotRetriggerable):
@@ -73,3 +73,23 @@ func Translate(err error) *Error {
 		return ErrInternal
 	}
 }
+
+// lookup of gitrpc error codes to HTTP status codes.
+var codes = map[gitrpc.Status]int{
+	gitrpc.StatusConflict:           http.StatusConflict,
+	gitrpc.StatusInvalidArgument:    http.StatusBadRequest,
+	gitrpc.StatusNotFound:           http.StatusNotFound,
+	gitrpc.StatusNotImplemented:     http.StatusNotImplemented,
+	gitrpc.StatusPreconditionFailed: http.StatusPreconditionFailed,
+	gitrpc.StatusUnauthorized:       http.StatusUnauthorized,
+	gitrpc.StatusInternal:           http.StatusInternalServerError,
+	gitrpc.StatusNotMergeable:       http.StatusPreconditionFailed,
+}
+
+// httpStatusCode returns the associated HTTP status code for a gitrpc error code.
+func httpStatusCode(code gitrpc.Status) int {
+	if v, ok := codes[code]; ok {
+		return v
+	}
+	return http.StatusInternalServerError
+}

internal/services/pullreq/handlers_mergeable.go

@@ -6,7 +6,6 @@ package pullreq
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"strconv"
 
@@ -206,12 +205,12 @@ func (s *Service) updateMergeData(
 		HeadExpectedSHA: newSHA,
 		Force:           true,
 	})
-	if errors.Is(err, gitrpc.ErrPreconditionFailed) {
+	if gitrpc.ErrorStatus(err) == gitrpc.StatusPreconditionFailed {
 		return events.NewDiscardEventErrorf("Source branch '%s' is not on SHA '%s' anymore.",
 			pr.SourceBranch, newSHA)
 	}
 
-	isNotMergeableError := errors.Is(err, gitrpc.ErrNotMergeable)
+	isNotMergeableError := gitrpc.ErrorStatus(err) == gitrpc.StatusNotMergeable
 	if err != nil && !isNotMergeableError {
 		return fmt.Errorf("merge check failed for %s and %s with err: %w",
 			targetRepo.UID+":"+pr.TargetBranch, sourceRepo.UID+":"+pr.SourceBranch, err)

internal/services/webhook/branch.go

@@ -6,7 +6,6 @@ package webhook
 
 import (
 	"context"
-	"errors"
 	"fmt"
 
 	"github.com/harness/gitness/events"
@@ -140,7 +139,7 @@ func (s *Service) fetchCommitInfoForEvent(ctx context.Context, repoUID string, s
 		SHA: sha,
 	})
 
-	if errors.Is(err, gitrpc.ErrNotFound) {
+	if gitrpc.ErrorStatus(err) == gitrpc.StatusNotFound {
 		// this could happen if the commit has been deleted and garbage collected by now
 		// or if the sha doesn't point to an event - either way discard the event.
 		return CommitInfo{}, events.NewDiscardEventErrorf("commit with sha '%s' doesn't exist", sha)