validate packer connection type data

Author: mschuchard

provisioner/communication.go

@@ -17,13 +17,18 @@ func (provisioner *Provisioner) determineCommunication(ui packer.Ui) ([]string,
 	// declare communication args
 	var args []string
 
-	// determine communication type enum by packer data
-	connectionType, err := connectionType(provisioner.generatedData["ConnType"].(string)).New()
-	if err != nil {
-		// do not log the enum returned error because it is only a symptom of the packer data issue
-		ui.Error("packer is unable to resolve the communicator connection type")
+	// determine communication type string by packer data
+	connectionString, ok := provisioner.generatedData["ConnType"].(string)
+	if !ok || len(connectionString) == 0 {
+		ui.Error("packer is unable to determine the communicator connection type from available data")
 		return nil, errors.New("unknown communicator connection type")
 	}
+	// convert to enum
+	connectionType, err := connectionType(connectionString).New()
+	if err != nil {
+		ui.Error("packer is using an unsupported connection type")
+		return nil, err
+	}
 
 	ui.Sayf("testinfra communicating via %s connection type", connectionType)
 

provisioner/communication_test.go

@@ -156,9 +156,15 @@ func TestProvisionerDetermineCommunication(test *testing.T) {
 	}
 
 	_, err = provisioner.determineCommunication(ui)
-	if err == nil || err.Error() != "unknown communicator connection type" {
+	if err == nil || err.Error() != "invalid connection enum" {
 		test.Error("determineCommunication function did not fail on unsupported connection type")
 	}
+
+	delete(provisioner.generatedData, "ConnType")
+	_, err = provisioner.determineCommunication(ui)
+	if err == nil || err.Error() != "unknown communicator connection type" {
+		test.Error("determineCommunication function did not fail on missing connection type")
+	}
 }
 
 // test provisioner determineUserAddr properly determines user and instance address