Centralize and improve String literal handling (#125)

* Share code for escape String literals
* Add support for escaping strings w/ new line characters

Author: kevmoo

json_serializable/lib/src/generator_helper.dart

@@ -322,8 +322,7 @@ void $toJsonMapHelperName(String key, dynamic value) {
 
 String _safeNameAccess(FieldElement field) {
   var name = jsonKeyFor(field).name ?? field.name;
-  // TODO(kevmoo): JsonKey.name could also have quotes and other silly.
-  return name.contains(r'$') ? "r'$name'" : "'$name'";
+  return escapeDartString(name);
 }
 
 JsonSerializable _valueForAnnotation(ConstantReader annotation) =>

json_serializable/lib/src/json_literal_generator.dart

@@ -12,6 +12,8 @@ import 'package:source_gen/source_gen.dart';
 
 import 'package:json_annotation/json_annotation.dart';
 
+import 'utils.dart';
+
 class JsonLiteralGenerator extends GeneratorForAnnotation<JsonLiteral> {
   const JsonLiteralGenerator();
 
@@ -44,7 +46,7 @@ class JsonLiteralGenerator extends GeneratorForAnnotation<JsonLiteral> {
 String _jsonLiteralAsDart(dynamic value, bool asConst) {
   if (value == null) return 'null';
 
-  if (value is String) return _jsonStringAsDart(value);
+  if (value is String) return escapeDartString(value);
 
   if (value is bool || value is num) return value.toString();
 
@@ -74,7 +76,7 @@ String _jsonMapAsDart(Map<String, dynamic> value, bool asConst) {
     } else {
       buffer.writeln(',');
     }
-    buffer.write(_jsonStringAsDart(k));
+    buffer.write(escapeDartString(k));
     buffer.write(':');
     buffer.write(_jsonLiteralAsDart(v, asConst));
   });
@@ -83,34 +85,3 @@ String _jsonMapAsDart(Map<String, dynamic> value, bool asConst) {
 
   return buffer.toString();
 }
-
-String _jsonStringAsDart(String value) {
-  var containsSingleQuote = value.contains("'");
-  var contains$ = value.contains(r'$');
-
-  if (containsSingleQuote) {
-    if (value.contains('"')) {
-      // `value` contains both single and double quotes as well as `$`.
-      // The only safe way to wrap the content is to escape all of the
-      // problematic characters.
-      var string = value
-          .replaceAll('\$', '\\\$')
-          .replaceAll('"', '\\"')
-          .replaceAll("'", "\\'");
-      return "'$string'";
-    } else if (contains$) {
-      // `value` contains "'" and "$", but not '"'.
-      // Safely wrap it in a raw string within double-quotes.
-      return 'r"$value"';
-    }
-    return '"$value"';
-  } else if (contains$) {
-    // `value` contains "$", but no "'"
-    // wrap it in a raw string using single quotes
-    return "r'$value'";
-  }
-
-  // `value` contains no problematic characters - except for '"' maybe.
-  // Wrap it in standard single-quotes.
-  return "'$value'";
-}

json_serializable/lib/src/utils.dart

@@ -11,6 +11,43 @@ import 'package:analyzer/src/dart/resolver/inheritance_manager.dart'
 
 import 'package:source_gen/source_gen.dart';
 
+/// Returns a quoted String literal for [value] that can be used in generated
+/// Dart code.
+// TODO: still need handle triple singe/double quotes within `value`
+String escapeDartString(String value) {
+  if (value.contains('\n')) {
+    return "r'''\n$value'''";
+  }
+
+  var containsDollar = value.contains(r'$');
+
+  if (value.contains("'")) {
+    if (value.contains('"')) {
+      // `value` contains both single and double quotes.
+      // The only safe way to wrap the content is to escape all of the
+      // problematic characters.
+      var string = value
+          .replaceAll(r'$', r'\$')
+          .replaceAll('"', r'\"')
+          .replaceAll("'", r"\'");
+      return "'$string'";
+    } else if (containsDollar) {
+      // `value` contains "'" and "$", but not '"'.
+      // Safely wrap it in a raw string within double-quotes.
+      return 'r"$value"';
+    }
+    return '"$value"';
+  } else if (containsDollar) {
+    // `value` contains "$", but no "'"
+    // wrap it in a raw string using single quotes
+    return "r'$value'";
+  }
+
+  // `value` contains no problematic characters - except for '"' maybe.
+  // Wrap it in standard single-quotes.
+  return "'$value'";
+}
+
 String commonNullPrefix(
         bool nullable, String expression, String unsafeExpression) =>
     nullable

json_serializable/test/test_files/data.json

@@ -1,4 +1,5 @@
 [
+ "\nnew lines are fun!\n",
  "simple string",
  "'string with single quotes'",
  "\"string with double quotes\"",

json_serializable/test/test_files/json_literal.g.dart

@@ -11,6 +11,10 @@ part of 'json_literal.dart';
 // **************************************************************************
 
 final _$dataJsonLiteral = [
+  r'''
+
+new lines are fun!
+''',
   'simple string',
   "'string with single quotes'",
   '"string with double quotes"',
@@ -38,6 +42,10 @@ final _$dataJsonLiteral = [
   }
 ];
 const _$asConstJsonLiteral = const [
+  r'''
+
+new lines are fun!
+''',
   'simple string',
   "'string with single quotes'",
   '"string with double quotes"',