[#114] client: Add `WithNeoFSErrorParsing` option

This option make client parse all NeoFS error statuses and return them as
errors from method calls (not as part of result structure). This is done
for applications that want to handle errors as it is customary in golang.
Default behaviour (construction client without new option) has not been
changed.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

client/common.go

@@ -58,7 +58,8 @@ type processResponseV2Res struct {
 //
 // Actions:
 //  * verify signature (internal);
-//  * call response callback (internal).
+//  * call response callback (internal);
+//  * unwrap status error (optional).
 func (c *Client) processResponseV2(res *processResponseV2Res, prm processResponseV2Prm) bool {
 	// verify response structure
 	if isInvalidSignatureV2(res, prm.resp) {
@@ -71,10 +72,18 @@ func (c *Client) processResponseV2(res *processResponseV2Res, prm processRespons
 		return true
 	}
 
-	// set result status
+	// get result status
 	st := apistatus.FromStatusV2(prm.resp.GetMetaHeader().GetStatus())
 
+	// unwrap unsuccessful status and return it
+	// as error if client has been configured so
+	unsuccessfulStatus := !apistatus.IsSuccessful(st)
+	if unsuccessfulStatus && c.opts.parseNeoFSErrors {
+		res.cliErr = apistatus.ErrFromStatus(st)
+		return true
+	}
+
 	res.statusRes.setStatus(st)
 
-	return !apistatus.IsSuccessful(st)
+	return unsuccessfulStatus
 }

client/opts.go

@@ -35,6 +35,12 @@ type (
 		rawOpts []client.Option
 
 		cbRespInfo func(ResponseMetaInfo) error
+
+		// defines if client parses erroneous NeoFS
+		// statuses and returns them as `error`
+		//
+		// default is false
+		parseNeoFSErrors bool
 	}
 
 	v2SessionReqInfo struct {
@@ -195,3 +201,12 @@ func WithGRPCConnection(grpcConn *grpc.ClientConn) Option {
 		opts.rawOpts = append(opts.rawOpts, client.WithGRPCConn(grpcConn))
 	}
 }
+
+// WithNeoFSErrorParsing returns option that makes client parse
+// erroneous NeoFS statuses and return them as `error` of the method
+// call.
+func WithNeoFSErrorParsing() Option {
+	return func(opts *clientOptions) {
+		opts.parseNeoFSErrors = true
+	}
+}