refactor generateString to emit simpler dart code (#49334)

dev/tools/localization/bin/gen_date_localizations.dart

@@ -139,17 +139,17 @@ String _jsonToMap(dynamic json) {
   if (json == null || json is num || json is bool)
     return '$json';
 
-  if (json is String) {
-    if (currentLocale == 'kn')
-      return generateEncodedString(json);
-    else if (json.contains("'"))
-      return 'r"""$json"""';
-    else
-      return "r'''$json'''";
-  }
+  if (json is String)
+    return generateEncodedString(currentLocale, json);
 
-  if (json is Iterable)
-    return '<dynamic>[${json.map<String>(_jsonToMap).join(',')}]';
+  if (json is Iterable) {
+    final StringBuffer buffer = StringBuffer('<dynamic>[');
+    for (final dynamic value in json) {
+      buffer.writeln('${_jsonToMap(value)},');
+    }
+    buffer.write(']');
+    return buffer.toString();
+  }
 
   if (json is Map<String, dynamic>) {
     final StringBuffer buffer = StringBuffer('<String, dynamic>{');

dev/tools/localization/bin/gen_localizations.dart

@@ -464,10 +464,7 @@ String generateValue(String value, Map<String, dynamic> attributes, LocaleInfo l
         return _scriptCategoryToEnum[value];
     }
   }
-  // Localization strings for the Kannada locale ('kn') are encoded because
-  // some of the localized strings contain characters that can crash Emacs on Linux.
-  // See packages/flutter_localizations/lib/src/l10n/README for more information.
-  return locale.languageCode == 'kn' ? generateEncodedString(value) : generateString(value);
+  return  generateEncodedString(locale.languageCode, value);
 }
 
 /// Combines [generateType], [generateKey], and [generateValue] to return

dev/tools/localization/gen_l10n.dart

@@ -225,8 +225,8 @@ String genSimpleMethod(Message message) {
     for (final Placeholder placeholder in message.placeholders) {
         messageValue = messageValue.replaceAll('{${placeholder.name}}', '\${${placeholder.name}}');
     }
-    final String rawMessage = generateString(messageValue); // "r'...'"
-    return rawMessage.substring(1);
+    final String generatedMessage = generateString(messageValue); // "r'...'"
+    return generatedMessage.startsWith('r') ? generatedMessage.substring(1) : generatedMessage;
   }
 
   List<String> genMethodParameters([String type]) {

dev/tools/localization/localizations_utils.dart

@@ -371,46 +371,46 @@ String generateClassDeclaration(
 class $classNamePrefix$camelCaseName extends $superClass {''';
 }
 
-/// Return `s` as a Dart-parseable raw string in single or double quotes.
+/// Return `s` as a Dart-parseable string.
 ///
-/// Double quotes are expanded:
+/// The result tries to avoid character escaping:
 ///
 /// ```
-/// foo => r'foo'
-/// foo "bar" => r'foo "bar"'
-/// foo 'bar' => r'foo ' "'" r'bar' "'"
+/// foo => 'foo'
+/// foo "bar" => 'foo "bar"'
+/// foo 'bar' => "foo 'bar'"
+/// foo 'bar' "baz" => '''foo 'bar' "baz"'''
+/// foo\bar => r'foo\bar'
 /// ```
-String generateString(String s) {
-  if (!s.contains("'"))
-    return "r'$s'";
-
-  final StringBuffer output = StringBuffer();
-  bool started = false; // Have we started writing a raw string.
-  for (int i = 0; i < s.length; i++) {
-    if (s[i] == "'") {
-      if (started)
-        output.write("'");
-      output.write(' "\'" ');
-      started = false;
-    } else if (!started) {
-      output.write("r'${s[i]}");
-      started = true;
-    } else {
-      output.write(s[i]);
-    }
-  }
-  if (started)
-    output.write("'");
-  return output.toString();
+///
+/// Strings with newlines are not supported.
+String generateString(String value) {
+  assert(!value.contains('\n'));
+  final String rawPrefix = value.contains(r'$') || value.contains(r'\') ? 'r' : '';
+  if (!value.contains("'"))
+    return "$rawPrefix'$value'";
+  if (!value.contains('"'))
+    return '$rawPrefix"$value"';
+  if (!value.contains("'''"))
+    return "$rawPrefix'''$value'''";
+  if (!value.contains('"""'))
+    return '$rawPrefix"""$value"""';
+
+  return value.split("'''")
+    .map(generateString)
+    // If value contains more than 6 consecutive single quotes some empty strings may be generated.
+    // The following map removes them.
+    .map((String part) => part == "''" ? '' : part)
+    .join(" \"'''\" ");
 }
 
 /// Only used to generate localization strings for the Kannada locale ('kn') because
 /// some of the localized strings contain characters that can crash Emacs on Linux.
 /// See packages/flutter_localizations/lib/src/l10n/README for more information.
-String generateEncodedString(String s) {
-  if (s.runes.every((int code) => code <= 0xFF))
-    return generateString(s);
+String generateEncodedString(String locale, String value) {
+  if (locale != 'kn' || value.runes.every((int code) => code <= 0xFF))
+    return generateString(value);
 
-  final String unicodeEscapes = s.runes.map((int code) => '\\u{${code.toRadixString(16)}}').join();
+  final String unicodeEscapes = value.runes.map((int code) => '\\u{${code.toRadixString(16)}}').join();
   return "'$unicodeEscapes'";
 }

dev/tools/test/localization/gen_l10n_test.dart

@@ -615,7 +615,7 @@ void main() {
       'Title',
       locale: _localeName,
       name: 'title',
-      desc: r'Title for the application'
+      desc: 'Title for the application'
     );
   }
 ''');
@@ -657,10 +657,10 @@ void main() {
         generator.classMethods.first,
         '''  String itemNumber(Object value) {
     return Intl.message(
-      \'Item \${value}\',
+      'Item \${value}',
       locale: _localeName,
       name: 'itemNumber',
-      desc: r\'Item placement in list.\',
+      desc: 'Item placement in list.',
       args: <Object>[value]
     );
   }
@@ -710,10 +710,10 @@ void main() {
 
     String springBegins(Object springStartDate) {
       return Intl.message(
-        \'Spring begins on \${springStartDate}\',
+        'Spring begins on \${springStartDate}',
         locale: _localeName,
-        name: \'springBegins\',
-        desc: r\'The first day of spring\',
+        name: 'springBegins',
+        desc: 'The first day of spring',
         args: <Object>[springStartDate]
       );
     }
@@ -837,10 +837,10 @@ void main() {
 
     String springGreetings(Object springStartDate, Object helloWorld) {
       return Intl.message(
-        \'Since it\' "\'" r\'s \${springStartDate}, it\' "\'" r\'s finally spring! \${helloWorld}!\',
+        "Since it's \${springStartDate}, it's finally spring! \${helloWorld}!",
         locale: _localeName,
-        name: \'springGreetings\',
-        desc: r\'A realization that it\' "\'" r\'s finally the spring season, followed by a greeting.\',
+        name: 'springGreetings',
+        desc: "A realization that it's finally the spring season, followed by a greeting.",
         args: <Object>[springStartDate, helloWorld]
       );
     }
@@ -897,10 +897,10 @@ void main() {
 
     String springRange(Object springStartDate, Object springEndDate) {
       return Intl.message(
-        \'Spring begins on \${springStartDate} and ends on \${springEndDate}\',
+        'Spring begins on \${springStartDate} and ends on \${springEndDate}',
         locale: _localeName,
-        name: \'springRange\',
-        desc: r\'The range of dates for spring in the year\',
+        name: 'springRange',
+        desc: 'The range of dates for spring in the year',
         args: <Object>[springStartDate, springEndDate]
       );
     }
@@ -1009,10 +1009,10 @@ void main() {
 
     String courseCompletion(Object progress) {
       return Intl.message(
-        \'You have completed \${progress} of the course.\',
+        'You have completed \${progress} of the course.',
         locale: _localeName,
-        name: \'courseCompletion\',
-        desc: r\'The amount of progress the student has made in their class.\',
+        name: 'courseCompletion',
+        desc: 'The amount of progress the student has made in their class.',
         args: <Object>[progress]
       );
     }
@@ -1079,10 +1079,10 @@ void main() {
 
     String courseCompletion(Object progress) {
       return Intl.message(
-        \'You have completed \${progress} of the course.\',
+        'You have completed \${progress} of the course.',
         locale: _localeName,
-        name: \'courseCompletion\',
-        desc: r\'The amount of progress the student has made in their class.\',
+        name: 'courseCompletion',
+        desc: 'The amount of progress the student has made in their class.',
         args: <Object>[progress]
       );
     }
@@ -1139,10 +1139,10 @@ void main() {
 
     String courseCompletion(Object progress) {
       return Intl.message(
-        \'You have completed \${progress} of the course.\',
+        'You have completed \${progress} of the course.',
         locale: _localeName,
-        name: \'courseCompletion\',
-        desc: r\'The amount of progress the student has made in their class.\',
+        name: 'courseCompletion',
+        desc: 'The amount of progress the student has made in their class.',
         args: <Object>[progress]
       );
     }
@@ -1706,4 +1706,37 @@ void main() {
       expect(outputFileString, contains('class _AppLocalizationsDelegate extends LocalizationsDelegate<AppLocalizations>'));
     });
   });
+
+  group('generateString', () {
+    test('handles simple string', () {
+      expect(generateString('abc'), "'abc'");
+    });
+    test('handles string with quote', () {
+      expect(generateString("ab'c"), '''"ab'c"''');
+    });
+    test('handles string with double quote', () {
+      expect(generateString('ab"c'), """'ab"c'""");
+    });
+    test('handles string with both single and double quote', () {
+      expect(generateString('''a'b"c'''), """'''a'b"c'''""");
+    });
+    test('handles string with a triple single quote and a double quote', () {
+      expect(generateString("""a"b'''c"""), '''"""a"b\'''c"""''');
+    });
+    test('handles string with a triple double quote and a single quote', () {
+      expect(generateString('''a'b"""c'''), """'''a'b\"""c'''""");
+    });
+    test('handles string with both triple single and triple double quote', () {
+      expect(generateString('''a\'''\'''\''b"""c'''), """'a' "'''"  "'''" '''''b\"""c'''""");
+    });
+    test('handles dollar', () {
+      expect(generateString(r'ab$c'), r"r'ab$c'");
+    });
+    test('handles back slash', () {
+      expect(generateString(r'ab\c'), r"r'ab\c'");
+    });
+    test("doesn't support multiline strings", () {
+      expect(() => generateString('ab\nc'), throwsA(isA<AssertionError>()));
+    });
+  });
 }