[gen_l10n] Warn users when placeholder types are converted to 'num' when using...

[gen_l10n] Warn users when placeholder types are converted to 'num' when using pluralization (#108036)

* init

* asdf

* fix tests

* change warning slightly

* fix test again

* fix spacing and comment

* fix lint

packages/flutter_tools/lib/src/commands/generate_localizations.dart

@@ -252,9 +252,10 @@ class GenerateLocalizationsCommand extends FlutterCommand {
         areResourceAttributesRequired: areResourceAttributesRequired,
         untranslatedMessagesFile: untranslatedMessagesFile,
         usesNullableGetter: usesNullableGetter,
+        logger: _logger,
       )
         ..loadResources()
-        ..writeOutputFiles(_logger);
+        ..writeOutputFiles();
     } on L10nException catch (e) {
       throwToolExit(e.message);
     }

packages/flutter_tools/lib/src/localizations/gen_l10n.dart

@@ -64,9 +64,10 @@ LocalizationsGenerator generateLocalizations({
       areResourceAttributesRequired: options.areResourceAttributesRequired,
       untranslatedMessagesFile: options.untranslatedMessagesFile?.toFilePath(),
       usesNullableGetter: options.usesNullableGetter,
+      logger: logger,
     )
       ..loadResources()
-      ..writeOutputFiles(logger, isFromYaml: true);
+      ..writeOutputFiles(isFromYaml: true);
   } on L10nException catch (e) {
     throwToolExit(e.message);
   }
@@ -698,6 +699,7 @@ class LocalizationsGenerator {
     bool areResourceAttributesRequired = false,
     String? untranslatedMessagesFile,
     bool usesNullableGetter = true,
+    required Logger logger,
   }) {
     final Directory? projectDirectory = projectDirFromPath(fileSystem, projectPathString);
     final Directory inputDirectory = inputDirectoryFromPath(fileSystem, inputPathString, projectDirectory);
@@ -718,6 +720,7 @@ class LocalizationsGenerator {
       untranslatedMessagesFile: _untranslatedMessagesFileFromPath(fileSystem, untranslatedMessagesFile),
       inputsAndOutputsListFile: _inputsAndOutputsListFileFromPath(fileSystem, inputsAndOutputsListPath),
       areResourceAttributesRequired: areResourceAttributesRequired,
+      logger: logger,
     );
   }
 
@@ -739,6 +742,7 @@ class LocalizationsGenerator {
     this.areResourceAttributesRequired = false,
     this.untranslatedMessagesFile,
     this.usesNullableGetter = true,
+    required this.logger,
   });
 
   final FileSystem _fs;
@@ -859,6 +863,9 @@ class LocalizationsGenerator {
   @visibleForTesting
   final bool areResourceAttributesRequired;
 
+  /// Logger to be used during the execution of the script.
+  Logger logger;
+
   static final RegExp _selectRE = RegExp(r'\{([\w\s,]*),\s*select\s*,\s*([\w\d]+\s*\{.*\})+\s*\}');
 
   static bool _isNotReadable(FileStat fileStat) {
@@ -1141,6 +1148,21 @@ class LocalizationsGenerator {
       );
     });
 
+    for (final Message message in messages) {
+      if (message.isPlural) {
+        if (message.placeholders.isEmpty) {
+          throw L10nException(
+              'Unable to find placeholders for the plural message: ${message.resourceId}.\n'
+              'Check to see if the plural message is in the proper ICU syntax format '
+              'and ensure that placeholders are properly specified.');
+        }
+        final Placeholder countPlaceholder = message.getCountPlaceholder();
+        if (countPlaceholder.type != null && countPlaceholder.type != 'num') {
+          logger.printWarning("Placeholders for plurals are automatically converted to type 'num' for the message: ${message.resourceId}.");
+        }
+      }
+    }
+
     return classFileTemplate
       .replaceAll('@(header)', header.isEmpty ? '' : '$header\n\n')
       .replaceAll('@(language)', describeLocale(locale.toString()))
@@ -1317,7 +1339,7 @@ class LocalizationsGenerator {
         || message.placeholdersRequireFormatting;
   });
 
-  void writeOutputFiles(Logger logger, { bool isFromYaml = false }) {
+  void writeOutputFiles({ bool isFromYaml = false }) {
     // First, generate the string contents of all necessary files.
     final String generatedLocalizationsFile = _generateCode();