babel-generator: Ensure ASCII-safe output for string literals (#4478)

Ref. #4477.

packages/babel-generator/package.json

@@ -15,6 +15,7 @@
     "babel-runtime": "^6.9.0",
     "babel-types": "^6.14.0",
     "detect-indent": "^3.0.1",
+    "jsesc": "^1.3.0",
     "lodash": "^4.2.0",
     "source-map": "^0.5.0"
   },

packages/babel-generator/src/generators/types.js

@@ -2,6 +2,7 @@
 /* eslint quotes: 0 */
 
 import * as t from "babel-types";
+import jsesc from "jsesc";
 
 export function Identifier(node: Object) {
   // FIXME: We hang variance off Identifer to support Flow's def-site variance.
@@ -135,26 +136,11 @@ export function StringLiteral(node: Object, parent: Object) {
     return;
   }
 
-  let val = JSON.stringify(node.value);
-
-  // escape illegal js but valid json unicode characters
-  val = val.replace(/[\u000A\u000D\u2028\u2029]/g, function (c) {
-    return "\\u" + ("0000" + c.charCodeAt(0).toString(16)).slice(-4);
+  // ensure the output is ASCII-safe
+  let val = jsesc(node.value, {
+    quotes: t.isJSX(parent) ? "double" : this.format.quotes,
+    wrap: true
   });
 
-  if (this.format.quotes === "single" && !t.isJSX(parent)) {
-    // remove double quotes
-    val = val.slice(1, -1);
-
-    // unescape double quotes
-    val = val.replace(/\\"/g, '"');
-
-    // escape single quotes
-    val = val.replace(/'/g, "\\'");
-
-    // add single quotes
-    val = `'${val}'`;
-  }
-
   return this.token(val);
 }

packages/babel-generator/test/fixtures/minified/literals/actual.js

@@ -4,6 +4,7 @@
 '\x20';
 "\n\r";
 "😂";
+`😂`;
 /foobar/g;
 null;
 true;

packages/babel-generator/test/fixtures/minified/literals/expected.js

@@ -1 +1 @@
-5;5;"foobar";" ";"\n\r";"😂";/foobar/g;null;true;false;5;2;56;31;
+5;5;"foobar";" ";"\n\r";"\uD83D\uDE02";`😂`;/foobar/g;null;true;false;5;2;56;31;