Add jsonCompatibleStrings option to generator (#4827)

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

@@ -143,10 +143,14 @@ export function StringLiteral(node: Object, parent: Object) {
   }
 
   // ensure the output is ASCII-safe
-  let val = jsesc(node.value, {
+  const opts = {
     quotes: t.isJSX(parent) ? "double" : this.format.quotes,
     wrap: true
-  });
+  };
+  if (this.format.jsonCompatibleStrings) {
+    opts.json = true;
+  }
+  let val = jsesc(node.value, opts);
 
   return this.token(val);
 }

packages/babel-generator/src/index.js

@@ -59,6 +59,7 @@ function normalizeOptions(code, opts, tokens): Format {
     minified: opts.minified,
     concise: opts.concise,
     quotes: opts.quotes || findCommonStringDelimiter(code, tokens),
+    jsonCompatibleStrings: opts.jsonCompatibleStrings,
     indent: {
       adjustMultilineComment: true,
       style: style,

packages/babel-generator/test/fixtures/escapes/jsonEscape/actual.js

@@ -0,0 +1 @@
+"©";

packages/babel-generator/test/fixtures/escapes/jsonEscape/expected.js

@@ -0,0 +1 @@
+"\u00A9";

packages/babel-generator/test/fixtures/escapes/options.json

@@ -0,0 +1,4 @@
+{
+  "minified": true,
+  "jsonCompatibleStrings": true
+}