Correctly output escapes in directives (#9501)

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

@@ -50,8 +50,35 @@ export function Directive(node: Object) {
   this.semicolon();
 }
 
+// These regexes match an even number of \ followed by a quote
+const unescapedSingleQuoteRE = /(?:^|[^\\])(?:\\\\)*'/;
+const unescapedDoubleQuoteRE = /(?:^|[^\\])(?:\\\\)*"/;
+
+export function DirectiveLiteral(node: Object) {
+  const raw = this.getPossibleRaw(node);
+  if (raw != null) {
+    this.token(raw);
+    return;
+  }
+
+  const { value } = node;
+
+  // NOTE: In directives we can't change escapings,
+  // because they change the behavior.
+  // e.g. "us\x65 string" (\x65 is e) is not a "use strict" directive.
+
+  if (!unescapedDoubleQuoteRE.test(value)) {
+    this.token(`"${value}"`);
+  } else if (!unescapedSingleQuoteRE.test(value)) {
+    this.token(`'${value}'`);
+  } else {
+    throw new Error(
+      "Malformed AST: it is not possible to print a directive containing" +
+        " both unescaped single and double quotes.",
+    );
+  }
+}
+
 export function InterpreterDirective(node: Object) {
   this.token(`#!${node.value}\n`);
 }
-
-export { StringLiteral as DirectiveLiteral } from "./types";

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

@@ -1 +1,2 @@
+0; // Not a directive
 "©";

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

@@ -1 +1,2 @@
+0;// Not a directive
 "\u00A9";

packages/babel-generator/test/index.js

@@ -384,6 +384,48 @@ describe("programmatic generation", function() {
   [key: any]: number
 }`);
   });
+
+  describe("directives", function() {
+    it("preserves escapes", function() {
+      const directive = t.directive(
+        t.directiveLiteral(String.raw`us\x65 strict`),
+      );
+      const output = generate(directive).code;
+
+      expect(output).toBe(String.raw`"us\x65 strict";`);
+    });
+
+    it("preserves escapes in minified output", function() {
+      // https://github.com/babel/babel/issues/4767
+
+      const directive = t.directive(t.directiveLiteral(String.raw`foo\n\t\r`));
+      const output = generate(directive, { minified: true }).code;
+
+      expect(output).toBe(String.raw`"foo\n\t\r";`);
+    });
+
+    it("unescaped single quote", function() {
+      const directive = t.directive(t.directiveLiteral(String.raw`'\'\"`));
+      const output = generate(directive).code;
+
+      expect(output).toBe(String.raw`"'\'\"";`);
+    });
+
+    it("unescaped double quote", function() {
+      const directive = t.directive(t.directiveLiteral(String.raw`"\'\"`));
+      const output = generate(directive).code;
+
+      expect(output).toBe(String.raw`'"\'\"';`);
+    });
+
+    it("unescaped single and double quotes together throw", function() {
+      const directive = t.directive(t.directiveLiteral(String.raw`'"`));
+
+      expect(() => {
+        generate(directive);
+      }).toThrow();
+    });
+  });
 });
 
 describe("CodeGenerator", function() {