fix: Make invalid name error message more similar and move tests

Follow Scott comment\
https://github.com/helm/helm/pull/31491/files#r2524933784

Signed-off-by: Benoit Tigeot <benoit.tigeot@lifen.fr>

internal/plugin/metadata.go

@@ -54,7 +54,7 @@ func (m Metadata) Validate() error {
 	var errs []error
 
 	if !validPluginName.MatchString(m.Name) {
-		errs = append(errs, fmt.Errorf("invalid name"))
+		errs = append(errs, fmt.Errorf("invalid name %q: must contain only a-z, A-Z, 0-9, _ and -", m.Name))
 	}
 
 	if m.APIVersion == "" {

internal/plugin/metadata_legacy.go

@@ -69,7 +69,7 @@ type MetadataLegacy struct {
 
 func (m *MetadataLegacy) Validate() error {
 	if !validPluginName.MatchString(m.Name) {
-		return fmt.Errorf("invalid plugin name %q: must contain only a-z, A-Z, 0-9, _ and -", m.Name)
+		return fmt.Errorf("invalid name %q: must contain only a-z, A-Z, 0-9, _ and -", m.Name)
 	}
 	m.Usage = sanitizeString(m.Usage)
 

internal/plugin/metadata_legacy_test.go

@@ -25,23 +25,8 @@ func TestMetadataLegacyValidate_PluginName(t *testing.T) {
 		pluginName string
 		shouldPass bool
 	}{
-		// Valid names
-		{"lowercase", "myplugin", true},
-		{"uppercase", "MYPLUGIN", true},
-		{"mixed case", "MyPlugin", true},
-		{"with digits", "plugin123", true},
-		{"with hyphen", "my-plugin", true},
-		{"with underscore", "my_plugin", true},
-		{"mixed chars", "my-awesome_plugin_123", true},
-
-		// Invalid names
-		{"empty", "", false},
-		{"space", "my plugin", false},
-		{"colon", "Name:", false},
-		{"period", "my.plugin", false},
-		{"slash", "my/plugin", false},
-		{"dollar", "$plugin", false},
-		{"unicode", "plügîn", false},
+		{"valid name", "my-plugin", true},
+		{"invalid with space", "my plugin", false},
 	}
 
 	for _, tt := range tests {

internal/plugin/metadata_test.go

@@ -66,8 +66,8 @@ func TestValidatePluginData(t *testing.T) {
 		} else if !item.pass && err == nil {
 			t.Errorf("expected case %d to fail", i)
 		}
-		if !item.pass && err.Error() != item.errString {
-			t.Errorf("index [%d]: expected the following error: %s, but got: %s", i, item.errString, err.Error())
+		if !item.pass && !strings.Contains(err.Error(), item.errString) {
+			t.Errorf("index [%d]: expected error to contain: %s, but got: %s", i, item.errString, err.Error())
 		}
 	}
 }

internal/plugin/plugin_test.go

@@ -21,6 +21,44 @@ import (
 	"helm.sh/helm/v4/internal/plugin/schema"
 )
 
+func TestValidPluginName(t *testing.T) {
+	tests := []struct {
+		name       string
+		pluginName string
+		shouldPass bool
+	}{
+		// Valid names
+		{"lowercase", "myplugin", true},
+		{"uppercase", "MYPLUGIN", true},
+		{"mixed case", "MyPlugin", true},
+		{"with digits", "plugin123", true},
+		{"with hyphen", "my-plugin", true},
+		{"with underscore", "my_plugin", true},
+		{"mixed chars", "my-awesome_plugin_123", true},
+
+		// Invalid names
+		{"empty", "", false},
+		{"space", "my plugin", false},
+		{"colon", "plugin:", false},
+		{"period", "my.plugin", false},
+		{"slash", "my/plugin", false},
+		{"dollar", "$plugin", false},
+		{"unicode", "plügîn", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			matches := validPluginName.MatchString(tt.pluginName)
+			if tt.shouldPass && !matches {
+				t.Errorf("expected %q to match validPluginName regex", tt.pluginName)
+			}
+			if !tt.shouldPass && matches {
+				t.Errorf("expected %q to not match validPluginName regex", tt.pluginName)
+			}
+		})
+	}
+}
+
 func mockSubprocessCLIPlugin(t *testing.T, pluginName string) *SubprocessPluginRuntime {
 	t.Helper()