implement RPC errors for (#34)

Adds support for returning RPC errors as Go errors. This does it by
always returning a list of RPCErrors (even when there is one) and
supporting the `Unwrap() []error` implicit interface for `errors`
package (Go 1.20 and later)

TODO.md

@@ -4,7 +4,7 @@
 
 - [X] Upgrade transport based on versions (1.0->1.1 upgrade to chunked)
 - [X] Cleanup request/response API (Session.Do, session.Call?)
-- [ ] Convert rpc errors to go errors
+- [X] Convert rpc errors to go errors
 - [X] shutdown / close
 - [ ] all RFC6241 operations (methods + op structs?)
 - [ ] unit tests (>80% coverage?)

go.mod

@@ -4,4 +4,10 @@ go 1.17
 
 require golang.org/x/crypto v0.7.0
 
-require golang.org/x/sys v0.6.0 // indirect
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/testify v1.8.2 // indirect
+	golang.org/x/sys v0.6.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -1,3 +1,15 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
+github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
@@ -36,3 +48,7 @@ golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtn
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
 golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

inttest/ssh_test.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/nemith/netconf"
 	ncssh "github.com/nemith/netconf/transport/ssh"
+	"github.com/stretchr/testify/assert"
 	"golang.org/x/crypto/ssh"
 )
 
@@ -105,3 +106,14 @@ func TestSSHGetConfig(t *testing.T) {
 		t.Fatalf("failed to close session: %v", err)
 	}
 }
+
+func TestBadGetConfig(t *testing.T) {
+	session := setupSSH(t)
+
+	ctx := context.Background()
+	cfg, err := session.GetConfig(ctx, "non-exist")
+	assert.Nil(t, cfg)
+	var rpcErrors netconf.RPCErrors
+	assert.ErrorAs(t, err, &rpcErrors)
+	assert.Len(t, rpcErrors, 1)
+}

msg.go

@@ -2,6 +2,8 @@ package netconf
 
 import (
 	"encoding/xml"
+	"fmt"
+	"strings"
 	"time"
 )
 
@@ -28,8 +30,8 @@ type RPCReplyMsg struct {
 	// RPC call and there were no errors.  This IS NOT set to true if data is
 	// also returned.  To check if a call is ok then look at the Errors field
 
-	Errors []RPCError `xml:"rpc-error,omitempty"`
-	Data   []byte     `xml:",innerxml"`
+	Errors RPCErrors `xml:"rpc-error,omitempty"`
+	Data   []byte    `xml:",innerxml"`
 }
 
 type NotificationMsg struct {
@@ -67,5 +69,26 @@ type RPCError struct {
 }
 
 func (e RPCError) Error() string {
-	return e.Message
+	return fmt.Sprintf("rpc error: %s", e.Message)
+}
+
+type RPCErrors []RPCError
+
+func (errs RPCErrors) Error() string {
+	var sb strings.Builder
+	for i, err := range errs {
+		if i > 0 {
+			sb.WriteRune('\n')
+		}
+		sb.WriteString(err.Error())
+	}
+	return sb.String()
+}
+
+func (errs RPCErrors) Unwrap() []error {
+	boxed := make([]error, len(errs))
+	for i, err := range errs {
+		boxed[i] = err
+	}
+	return boxed
 }

session.go

@@ -302,14 +302,15 @@ func (s *Session) Call(ctx context.Context, op interface{}, resp interface{}) er
 	}
 
 	if resp != nil {
-		if err := xml.Unmarshal(reply.Data, resp); err != nil {
-			return fmt.Errorf("failed to decode response: %w", err)
-		}
+		err = xml.Unmarshal(reply.Data, resp)
 	}
 
-	// XXX: Need to handle RPC errors here.
+	// if we have RPC errors return them
+	if reply.Errors != nil {
+		err = reply.Errors
+	}
 
-	return nil
+	return err
 }
 
 // Close will gracefully close the sessions first by sending a `close-session`