l10n tool improvements, stocks app i18n refresh (flutter#44473)

* Add check for placeholders being an empty map

* Remove unnecessary properties from en_ES.arb in the stocks example

* Use getter instead of methods in the stocks example

* Fixed "annotating types for function expression parameters" lint issue from generated localizations delegate code

Author: Shi-Hao Hong

dev/tools/localization/gen_l10n.dart

@@ -79,7 +79,7 @@ class @className {
 
   static Future<@className> load(Locale locale) {
     return initializeMessages(locale.toString())
-      .then<@className>((void _) => @className(locale));
+      .then<@className>((_) => @className(locale));
   }
 
   static @className of(BuildContext context) {
@@ -168,8 +168,10 @@ List<String> genIntlMethodArgs(Map<String, dynamic> bundle, String key) {
     }
     if (attributesMap.containsKey('placeholders')) {
       final Map<String, dynamic> placeholders = attributesMap['placeholders'];
-      final String args = placeholders.keys.join(', ');
-      attributes.add('args: <Object>[$args]');
+      if (placeholders.isNotEmpty) {
+        final String args = placeholders.keys.join(', ');
+        attributes.add('args: <Object>[$args]');
+      }
     }
   }
   return attributes;

examples/stocks/lib/i18n/regenerate.md

@@ -16,8 +16,8 @@ for more info.
 
 ```dart
 dart ${FLUTTER_PATH}/dev/tools/localization/gen_l10n.dart --arb-dir=lib/i18n \
-  --template-arb-file=stocks_en_US.arb --output-localization-file=stock_strings.dart \
-  --output-class=StockStrings
+    --template-arb-file=stocks_en_US.arb --output-localization-file=stock_strings.dart \
+    --output-class=StockStrings
 ```
 
 The `StockStrings` class uses the generated `initializeMessages()`function

examples/stocks/lib/i18n/stock_strings.dart

@@ -93,33 +93,30 @@ class StockStrings {
     Locale('en', 'US'),
   ];
 
-  String title() {
+  String get title {
     return Intl.message(
       r'Stocks',
       locale: _localeName,
       name: 'title',
-      desc: r'Title for the Stocks application',
-      args: <Object>[]
+      desc: r'Title for the Stocks application'
     );
   }
 
-  String market() {
+  String get market {
     return Intl.message(
       r'MARKET',
       locale: _localeName,
       name: 'market',
-      desc: r'Label for the Market tab',
-      args: <Object>[]
+      desc: r'Label for the Market tab'
     );
   }
 
-  String portfolio() {
+  String get portfolio {
     return Intl.message(
       r'PORTFOLIO',
       locale: _localeName,
       name: 'portfolio',
-      desc: r'Label for the Portfolio tab',
-      args: <Object>[]
+      desc: r'Label for the Portfolio tab'
     );
   }
 

examples/stocks/lib/i18n/stocks_en_US.arb

@@ -1,22 +1,16 @@
 {
   "title": "Stocks",
   "@title": {
-    "description": "Title for the Stocks application",
-    "type": "text",
-    "placeholders": {}
+    "description": "Title for the Stocks application"
   },
 
   "market": "MARKET",
   "@market": {
-    "description": "Label for the Market tab",
-    "type": "text",
-    "placeholders": {}
+    "description": "Label for the Market tab"
   },
 
   "portfolio": "PORTFOLIO",
   "@portfolio": {
-    "description": "Label for the Portfolio tab",
-    "type": "text",
-    "placeholders": {}
+    "description": "Label for the Portfolio tab"
   }
 }

examples/stocks/lib/i18n/stocks_es_ES.arb

@@ -1,22 +1,5 @@
 {
   "title": "Acciones",
-  "@title": {
-    "description": "Title for the Stocks application",
-    "type": "text",
-    "placeholders": {}
-  },
-
   "market": "MERCADO",
-  "@market": {
-    "description": "Label for the Market tab",
-    "type": "text",
-    "placeholders": {}
-  },
-
-  "portfolio": "CARTERA",
-  "@portfolio": {
-    "description": "Label for the Portfolio tab",
-    "type": "text",
-    "placeholders": {}
-  }
+  "portfolio": "CARTERA"
 }

examples/stocks/lib/stock_home.dart

@@ -191,7 +191,7 @@ class StockHomeState extends State<StockHome> {
   Widget buildAppBar() {
     return AppBar(
       elevation: 0.0,
-      title: Text(StockStrings.of(context).title()),
+      title: Text(StockStrings.of(context).title),
       actions: <Widget>[
         IconButton(
           icon: const Icon(Icons.search),
@@ -223,8 +223,8 @@ class StockHomeState extends State<StockHome> {
       ],
       bottom: TabBar(
         tabs: <Widget>[
-          Tab(text: StockStrings.of(context).market()),
-          Tab(text: StockStrings.of(context).portfolio()),
+          Tab(text: StockStrings.of(context).market),
+          Tab(text: StockStrings.of(context).portfolio),
         ],
       ),
     );