plugin/set: add protocol_version to Description

When a plugin describes its capabilities, it needs to advertise whether
or not protobuf can be used in order for Packer to know which
serialisation protocol to use for communicating with the plugin.

To do so, we add a protocol_version attribute to the returned
structure, which is now set to v2, in order for Packer to know that the
plugin can use that.

plugin/set.go

@@ -42,13 +42,14 @@ type Set struct {
 
 // SetDescription describes a Set.
 type SetDescription struct {
-	Version        string   `json:"version"`
-	SDKVersion     string   `json:"sdk_version"`
-	APIVersion     string   `json:"api_version"`
-	Builders       []string `json:"builders"`
-	PostProcessors []string `json:"post_processors"`
-	Provisioners   []string `json:"provisioners"`
-	Datasources    []string `json:"datasources"`
+	Version         string   `json:"version"`
+	SDKVersion      string   `json:"sdk_version"`
+	APIVersion      string   `json:"api_version"`
+	Builders        []string `json:"builders"`
+	PostProcessors  []string `json:"post_processors"`
+	Provisioners    []string `json:"provisioners"`
+	Datasources     []string `json:"datasources"`
+	ProtocolVersion string   `json:"protocol_version"`
 }
 
 ////
@@ -187,13 +188,14 @@ func (i *Set) start(kind, name string) error {
 
 func (i *Set) description() SetDescription {
 	return SetDescription{
-		Version:        i.version,
-		SDKVersion:     i.sdkVersion,
-		APIVersion:     i.apiVersion,
-		Builders:       i.buildersDescription(),
-		PostProcessors: i.postProcessorsDescription(),
-		Provisioners:   i.provisionersDescription(),
-		Datasources:    i.datasourceDescription(),
+		Version:         i.version,
+		SDKVersion:      i.sdkVersion,
+		APIVersion:      i.apiVersion,
+		Builders:        i.buildersDescription(),
+		PostProcessors:  i.postProcessorsDescription(),
+		Provisioners:    i.provisionersDescription(),
+		Datasources:     i.datasourceDescription(),
+		ProtocolVersion: "v2",
 	}
 }
 

plugin/set_test.go

@@ -52,13 +52,14 @@ func TestSet(t *testing.T) {
 
 	sdkVersion := pluginVersion.NewPluginVersion(pluginVersion.Version, pluginVersion.VersionPrerelease, "")
 	if diff := cmp.Diff(SetDescription{
-		Version:        "1.1.1",
-		SDKVersion:     sdkVersion.String(),
-		APIVersion:     "x" + APIVersionMajor + "." + APIVersionMinor,
-		Builders:       []string{"example", "example-2"},
-		PostProcessors: []string{"example", "example-2"},
-		Provisioners:   []string{"example", "example-2"},
-		Datasources:    []string{"example", "example-2"},
+		Version:         "1.1.1",
+		SDKVersion:      sdkVersion.String(),
+		APIVersion:      "x" + APIVersionMajor + "." + APIVersionMinor,
+		Builders:        []string{"example", "example-2"},
+		PostProcessors:  []string{"example", "example-2"},
+		Provisioners:    []string{"example", "example-2"},
+		Datasources:     []string{"example", "example-2"},
+		ProtocolVersion: "v2",
 	}, outputDesc); diff != "" {
 		t.Fatalf("Unexpected description: %s", diff)
 	}