Fix: plugin list throwing Nil Pointer exception when plugin with empty .yaml file was loaded

Signed-off-by: Zethan <zetHannes@outlook.com>

pkg/plugin/plugin.go

@@ -172,7 +172,13 @@ func (p *Plugin) PrepareCommand(extraArgs []string) (string, []string, error) {
 var validPluginName = regexp.MustCompile("^[A-Za-z0-9_-]+$")
 
 // validatePluginData validates a plugin's YAML data.
+// IF the plugin metadata is non-existent(the YAML data does not
+//		exist -> empty plugin YAML file), the plugin cannot be loaded
+// 		because of missing metadata.
 func validatePluginData(plug *Plugin, filepath string) error {
+	if plug.Metadata == nil {
+		return fmt.Errorf("plugin metadata is missing at %q", filepath)
+	}
 	if !validPluginName.MatchString(plug.Metadata.Name) {
 		return fmt.Errorf("invalid plugin name at %q", filepath)
 	}
@@ -225,7 +231,14 @@ func LoadDir(dirname string) (*Plugin, error) {
 	if err := yaml.UnmarshalStrict(data, &plug.Metadata); err != nil {
 		return nil, errors.Wrapf(err, "failed to load plugin at %q", pluginfile)
 	}
-	return plug, validatePluginData(plug, pluginfile)
+	if plug.Metadata == nil {
+		return plug, errors.New(fmt.Sprintf("configuration data missing at %q", pluginfile))
+	}
+	validationError := validatePluginData(plug, pluginfile)
+	if validationError != nil {
+		plug = nil
+	}
+	return plug, validationError
 }
 
 // LoadAll loads all plugins found beneath the base directory.
@@ -247,7 +260,10 @@ func LoadAll(basedir string) ([]*Plugin, error) {
 	for _, yaml := range matches {
 		dir := filepath.Dir(yaml)
 		p, err := LoadDir(dir)
-		if err != nil {
+		if p != nil && err != nil {
+			// Plugin was found but could not be loaded due to missing configuration
+			continue
+		} else if err != nil {
 			return plugins, err
 		}
 		plugins = append(plugins, p)

pkg/plugin/plugin_test.go

@@ -212,6 +212,13 @@ func TestLoadDirDuplicateEntries(t *testing.T) {
 	}
 }
 
+func TestLoadDirNoMetadata(t *testing.T) {
+	dirname := "testdata/plugdir/bad/empty-config"
+	if plug, err := LoadDir(dirname); err == nil || plug == nil {
+		t.Errorf("successfully loaded empty plugin")
+	}
+}
+
 func TestDownloader(t *testing.T) {
 	dirname := "testdata/plugdir/good/downloader"
 	plug, err := LoadDir(dirname)
@@ -272,6 +279,36 @@ func TestLoadAll(t *testing.T) {
 	}
 }
 
+func TestLoadAllAndSkipEmptyOnes(t *testing.T) {
+
+	// Verify that empty dir loads:
+	if plugs, err := LoadAll("testdata"); err != nil {
+		t.Fatalf("error loading dir with no plugins: %s", err)
+	} else if len(plugs) > 0 {
+		t.Fatalf("expected empty dir to have 0 plugins")
+	}
+
+	basedir := "testdata/plugdir/bad/skip-some"
+	plugs, err := LoadAll(basedir)
+	if err != nil {
+		t.Fatalf("Could not load %q: %s", basedir, err)
+	}
+
+	if l := len(plugs); l != 3 {
+		t.Fatalf("expected 3 plugins, found %d", l)
+	}
+
+	if plugs[0].Metadata.Name != "downloader" {
+		t.Errorf("Expected first plugin to be echo, got %q", plugs[0].Metadata.Name)
+	}
+	if plugs[1].Metadata.Name != "echo" {
+		t.Errorf("Expected first plugin to be echo, got %q", plugs[0].Metadata.Name)
+	}
+	if plugs[2].Metadata.Name != "hello" {
+		t.Errorf("Expected second plugin to be hello, got %q", plugs[1].Metadata.Name)
+	}
+}
+
 func TestFindPlugins(t *testing.T) {
 	cases := []struct {
 		name     string

pkg/plugin/testdata/plugdir/bad/skip-some/downloader/plugin.yaml

@@ -0,0 +1,11 @@
+name: "downloader"
+version: "1.2.3"
+usage: "usage"
+description: |-
+  download something
+command: "echo Hello"
+downloaders:
+  - protocols:
+    - "myprotocol"
+    - "myprotocols"
+    command: "echo Download"

pkg/plugin/testdata/plugdir/bad/skip-some/echo/plugin.yaml

@@ -0,0 +1,8 @@
+name: "echo"
+version: "1.2.3"
+usage: "echo something"
+description: |-
+  This is a testing fixture.
+command: "echo Hello"
+hooks:
+  install: "echo Installing"

pkg/plugin/testdata/plugdir/bad/skip-some/hello/hello.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+echo "Hello from a Helm plugin"
+
+echo "PARAMS"
+echo $*
+
+$HELM_BIN ls --all
+

pkg/plugin/testdata/plugdir/bad/skip-some/hello/plugin.yaml

@@ -0,0 +1,9 @@
+name: "hello"
+version: "0.1.0"
+usage: "usage"
+description: |-
+  description
+command: "$HELM_PLUGIN_DIR/hello.sh"
+ignoreFlags: true
+hooks:
+  install: "echo installing..."