Move plugin client to separate interface

This makes it a bit simpler to remove this interface for v2 plugins
and not break external projects (libnetwork and swarmkit).

Note that before we remove the `Client()` interface from `CompatPlugin`
libnetwork and swarmkit must be updated to explicitly check for the v1
client interface as is done int his PR.

This is just a minor tweak that I realized is needed after trying to
implement the needed changes on libnetwork.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/volume/drivers/extpoint.go b/volume/drivers/extpoint.go
index f7d3617caa..5a3c4ce95a 100644
--- a/volume/drivers/extpoint.go
+++ b/volume/drivers/extpoint.go
@@ -212,9 +212,13 @@ func (s *Store) GetAllDrivers() ([]volume.Driver, error) {
 }
 
 func makePluginAdapter(p getter.CompatPlugin) (*volumeDriverAdapter, error) {
+	if pc, ok := p.(getter.PluginWithV1Client); ok {
+		return &volumeDriverAdapter{name: p.Name(), scopePath: p.ScopedPath, proxy: &volumeDriverProxy{pc.Client()}}, nil
+	}
+
 	pa, ok := p.(getter.PluginAddr)
 	if !ok {
-		return &volumeDriverAdapter{name: p.Name(), scopePath: p.ScopedPath, proxy: &volumeDriverProxy{p.Client()}}, nil
+		return nil, errdefs.System(errors.Errorf("got unknown plugin instance %T", p))
 	}
 
 	if pa.Protocol() != plugins.ProtocolSchemeHTTPV1 {