[gen_l10n] Escape special JSON characters in generateString utility function (#53605)

dev/tools/localization/localizations_utils.dart

@@ -373,36 +373,36 @@ class $classNamePrefix$camelCaseName extends $superClass {''';
 /// foo "bar" => 'foo "bar"'
 /// foo 'bar' => "foo 'bar'"
 /// foo 'bar' "baz" => '''foo 'bar' "baz"'''
-/// foo\bar => 'foo\\bar'
-/// foo\nbar => 'foo\\\\nbar'
 /// ```
 ///
-/// When [shouldEscapeDollar] is set to true, the
-/// result avoids character escaping, with the
-/// exception of the dollar sign:
+/// This function is used by tools that take in a JSON-formatted file to
+/// generate Dart code. For this reason, characters with special meaning
+/// in JSON files. For example, the backspace character (\b) have to be
+/// properly escaped by this function so that the generated Dart code
+/// correctly represents this character:
+/// ```
+/// foo\bar => 'foo\\bar'
+/// foo\nbar => 'foo\\nbar'
+/// foo\\nbar => 'foo\\\\nbar'
+/// foo\\bar => 'foo\\\\bar'
+/// foo\ bar => 'foo\\ bar'
+/// ```
 ///
+/// When [shouldEscapeDollar] is set to true, the '$' characters in the
+/// input will be replaced by '$' in the returned string:
 /// ```
 /// foo$bar = 'foo\$bar'
 /// ```
 ///
-/// When [shouldEscapeDollar] is set to false, the
-/// result tries to avoid character escaping:
-///
+/// When [shouldEscapeDollar] is set to false, '$' will be replaced
+/// by '\$' in the returned string:
 /// ```
 /// foo$bar => 'foo\\\$bar'
 /// ```
 ///
 /// [shouldEscapeDollar] is true by default.
-///
-/// Strings with newlines are not supported.
 String generateString(String value, { bool escapeDollar = true }) {
   assert(escapeDollar != null);
-  assert(
-    !value.contains('\n'),
-    'Since it is assumed that the input string comes '
-    'from a json/arb file source, messages cannot '
-    'contain newlines.'
-  );
 
   const String backslash = '__BACKSLASH__';
   assert(
@@ -419,6 +419,11 @@ String generateString(String value, { bool escapeDollar = true }) {
   value = value
     .replaceAll("'", "\\'")
     .replaceAll('"', '\\"')
+    .replaceAll('\n', '\\n')
+    .replaceAll('\f', '\\f')
+    .replaceAll('\t', '\\t')
+    .replaceAll('\r', '\\r')
+    .replaceAll('\b', '\\b')
     .replaceAll(backslash, '\\\\');
 
   return "'$value'";

dev/tools/test/localization/localizations_utils_test.dart

@@ -45,15 +45,31 @@ void main() {
     });
 
     test('handles backslash', () {
-      expect(generateString(r'ab\c'), "'ab\\\\c'");
+      expect(generateString(r'ab\c'), r"'ab\\c'");
     });
 
     test('handles backslash followed by "n" character', () {
-      expect(generateString(r'ab\nc'), "'ab\\\\nc'");
+      expect(generateString(r'ab\nc'), r"'ab\\nc'");
     });
 
-    test('does not support multiline strings', () {
-      expect(() => generateString('ab\nc'), throwsA(isA<AssertionError>()));
+    test('supports newline escaping', () {
+      expect(generateString('ab\nc'), "'ab\\nc'");
+    });
+
+    test('supports form feed escaping', () {
+      expect(generateString('ab\fc'), "'ab\\fc'");
+    });
+
+    test('supports tab escaping', () {
+      expect(generateString('ab\tc'), "'ab\\tc'");
+    });
+
+    test('supports carriage return escaping', () {
+      expect(generateString('ab\rc'), "'ab\\rc'");
+    });
+
+    test('supports backspace escaping', () {
+      expect(generateString('ab\bc'), "'ab\\bc'");
     });
   });
 }

packages/flutter_tools/test/integration.shard/gen_l10n_test.dart

@@ -88,28 +88,29 @@ void main() {
       '#l10n 9 (Hello GB fallback World)\n'
       '#l10n 10 (--- General formatting tests ---)\n'
       '#l10n 11 (Hello World)\n'
-      '#l10n 12 (Hello World)\n'
+      '#l10n 12 (Hello _NEWLINE_ World)\n'
       '#l10n 13 (Hello World)\n'
-      '#l10n 14 (Hello World on Friday, January 1, 1960)\n'
-      '#l10n 15 (Hello world argument on 1/1/1960 at 00:00)\n'
-      '#l10n 16 (Hello World from 1960 to 2020)\n'
-      '#l10n 17 (Hello for 123)\n'
-      '#l10n 18 (Hello for price USD123.00)\n'
-      '#l10n 19 (Hello)\n'
-      '#l10n 20 (Hello World)\n'
-      '#l10n 21 (Hello two worlds)\n'
-      '#l10n 22 (Hello)\n'
-      '#l10n 23 (Hello new World)\n'
-      '#l10n 24 (Hello two new worlds)\n'
-      '#l10n 25 (Hello on Friday, January 1, 1960)\n'
-      '#l10n 26 (Hello World, on Friday, January 1, 1960)\n'
-      '#l10n 27 (Hello two worlds, on Friday, January 1, 1960)\n'
-      '#l10n 28 (Hello other 0 worlds, with a total of 100 citizens)\n'
-      '#l10n 29 (Hello World of 101 citizens)\n'
-      '#l10n 30 (Hello two worlds with 102 total citizens)\n'
-      '#l10n 31 ([Hello] -World- #123#)\n'
-      '#l10n 32 (Flutter\'s amazing!)\n'
-      '#l10n 33 (Flutter is "amazing"!)\n'
+      '#l10n 14 (Hello World)\n'
+      '#l10n 15 (Hello World on Friday, January 1, 1960)\n'
+      '#l10n 16 (Hello world argument on 1/1/1960 at 00:00)\n'
+      '#l10n 17 (Hello World from 1960 to 2020)\n'
+      '#l10n 18 (Hello for 123)\n'
+      '#l10n 19 (Hello for price USD123.00)\n'
+      '#l10n 20 (Hello)\n'
+      '#l10n 21 (Hello World)\n'
+      '#l10n 22 (Hello two worlds)\n'
+      '#l10n 23 (Hello)\n'
+      '#l10n 24 (Hello new World)\n'
+      '#l10n 25 (Hello two new worlds)\n'
+      '#l10n 26 (Hello on Friday, January 1, 1960)\n'
+      '#l10n 27 (Hello World, on Friday, January 1, 1960)\n'
+      '#l10n 28 (Hello two worlds, on Friday, January 1, 1960)\n'
+      '#l10n 29 (Hello other 0 worlds, with a total of 100 citizens)\n'
+      '#l10n 30 (Hello World of 101 citizens)\n'
+      '#l10n 31 (Hello two worlds with 102 total citizens)\n'
+      '#l10n 32 ([Hello] -World- #123#)\n'
+      '#l10n 33 (Flutter\'s amazing!)\n'
+      '#l10n 34 (Flutter is "amazing"!)\n'
       '#l10n END\n'
     );
   });

packages/flutter_tools/test/integration.shard/test_data/gen_l10n_project.dart

@@ -124,6 +124,7 @@ class Home extends StatelessWidget {
             final AppLocalizations localizations = AppLocalizations.of(context);
             results.addAll(<String>[
               '${localizations.helloWorld}',
+              '${localizations.helloNewlineWorld}',
               '${localizations.hello("World")}',
               '${localizations.greeting("Hello", "World")}',
               '${localizations.helloWorldOn(DateTime(1960))}',
@@ -154,7 +155,9 @@ class Home extends StatelessWidget {
             try {
               int n = 0;
               for (final String result in results) {
-                print('#l10n $n ($result)');
+                // Newline character replacement is necessary because
+                // the stream breaks up stdout by new lines.
+                print('#l10n $n (${result.replaceAll('\n', '_NEWLINE_')})');
                 n += 1;
               }
             }
@@ -188,6 +191,11 @@ void main() {
     "description": "The conventional newborn programmer greeting"
   },
 
+  "helloNewlineWorld": "Hello \n World",
+  "@helloNewlineWorld": {
+    "description": "The JSON decoder should convert backslash-n to a newline character in the generated Dart string."
+  },
+
   "hello": "Hello {world}",
   "@hello": {
     "description": "A message with a single parameter",