ErrorHandler turns a Go error into an HTTP response. It should be placed in the middleware chain below the logger middleware so the logger properly logs the HTTP response. ErrorHandler understands instances of goa.ServiceError and returns the status and response body embodied in them, it turns other Go error types into a 500 internal error response. If verbose is false the details of internal errors is not included in HTTP responses.


// If verbose is false the details of internal errors is not included in HTTP responses.
// If you use then wrapping the error will allow a trace to be printed to the logs
func ErrorHandler(service *goa.Service, verbose bool) goa.Middleware {
	return func(h goa.Handler) goa.Handler {
		return func(ctx context.Context, rw http.ResponseWriter, req *http.Request) error {
			e := h(ctx, rw, req)
			if e == nil {
				return nil
			cause := errors.Cause(e)
			status := http.StatusInternalServerError
			var respBody interface{}
			if err, ok := cause.(goa.ServiceError); ok {
				status = err.ResponseStatus()
				respBody = err
				goa.ContextResponse(ctx).ErrorCode = err.Token()
				rw.Header().Set("Content-Type", goa.ErrorMediaIdentifier)
			} else {
				respBody = e.Error()
				rw.Header().Set("Content-Type", "text/plain")
			if status >= 500 && status < 600 {
				reqID := ctx.Value(reqIDKey)
				if reqID == nil {
					reqID = shortID()
					ctx = context.WithValue(ctx, reqIDKey, reqID)
				goa.LogError(ctx, "uncaught error", "err", fmt.Sprintf("%+v", e), "id", reqID, "msg", respBody)
				if !verbose {
					rw.Header().Set("Content-Type", goa.ErrorMediaIdentifier)
					msg := fmt.Sprintf("%s [%s]", http.StatusText(http.StatusInternalServerError), reqID)
					respBody = goa.ErrInternal(msg)
					// Preserve the ID of the original error as that's what gets logged, the client
					// received error ID must match the original
					if origErrID := goa.ContextResponse(ctx).ErrorCode; origErrID != "" {
						respBody.(*goa.ErrorResponse).ID = origErrID
			return service.Send(ctx, status, respBody)