Improve validate for buf.lock plugins

This improves validation for buf.lock plugins to ensure duplicates and
invalid digest types are correctly checked.

private/bufpkg/bufconfig/buf_lock_file.go

@@ -205,13 +205,22 @@ func newBufLockFile(
 	if err := validateNoDuplicateModuleKeysByFullName(depModuleKeys); err != nil {
 		return nil, err
 	}
+	if err := validateNoDuplicatePluginKeysByFullName(remotePluginKeys); err != nil {
+		return nil, err
+	}
 	switch fileVersion {
 	case FileVersionV1Beta1, FileVersionV1:
-		if err := validateExpectedDigestType(depModuleKeys, fileVersion, bufmodule.DigestTypeB4); err != nil {
+		if err := validateModuleExpectedDigestType(depModuleKeys, fileVersion, bufmodule.DigestTypeB4); err != nil {
 			return nil, err
 		}
+		if len(remotePluginKeys) > 0 {
+			return nil, errors.New("remote plugins are not supported in v1 or v1beta1 buf.lock files")
+		}
 	case FileVersionV2:
-		if err := validateExpectedDigestType(depModuleKeys, fileVersion, bufmodule.DigestTypeB5); err != nil {
+		if err := validateModuleExpectedDigestType(depModuleKeys, fileVersion, bufmodule.DigestTypeB5); err != nil {
+			return nil, err
+		}
+		if err := validatePluginExpectedDigestType(remotePluginKeys, fileVersion, bufplugin.DigestTypeP1); err != nil {
 			return nil, err
 		}
 	default:
@@ -522,6 +531,18 @@ func validateNoDuplicateModuleKeysByFullName(moduleKeys []bufmodule.ModuleKey) e
 	return nil
 }
 
+func validateNoDuplicatePluginKeysByFullName(pluginKeys []bufplugin.PluginKey) error {
+	pluginFullNameStringMap := make(map[string]struct{})
+	for _, pluginKey := range pluginKeys {
+		pluginFullNameString := pluginKey.FullName().String()
+		if _, ok := pluginFullNameStringMap[pluginFullNameString]; ok {
+			return fmt.Errorf("duplicate plugin %q attempted to be added to lock file", pluginFullNameString)
+		}
+		pluginFullNameStringMap[pluginFullNameString] = struct{}{}
+	}
+	return nil
+}
+
 func validateV1AndV1Beta1DepsHaveCommits(bufLockFile BufLockFile) error {
 	switch fileVersion := bufLockFile.FileVersion(); fileVersion {
 	case FileVersionV1Beta1, FileVersionV1:
@@ -545,7 +566,7 @@ func validateV1AndV1Beta1DepsHaveCommits(bufLockFile BufLockFile) error {
 	}
 }
 
-func validateExpectedDigestType(
+func validateModuleExpectedDigestType(
 	moduleKeys []bufmodule.ModuleKey,
 	fileVersion FileVersion,
 	expectedDigestType bufmodule.DigestType,
@@ -568,6 +589,29 @@ func validateExpectedDigestType(
 	return nil
 }
 
+func validatePluginExpectedDigestType(
+	pluginKeys []bufplugin.PluginKey,
+	fileVersion FileVersion,
+	expectedDigestType bufplugin.DigestType,
+) error {
+	for _, pluginKey := range pluginKeys {
+		digest, err := pluginKey.Digest()
+		if err != nil {
+			return err
+		}
+		if digest.Type() != expectedDigestType {
+			return fmt.Errorf(
+				"%s lock files must use digest type %v, but remote plugin %s had a digest type of %v",
+				fileVersion,
+				expectedDigestType,
+				pluginKey.String(),
+				digest.Type(),
+			)
+		}
+	}
+	return nil
+}
+
 // externalBufLockFileV1Beta1V1 represents the v1 or v1beta1 buf.lock file,
 // which have the same shape.
 type externalBufLockFileV1Beta1V1 struct {