js_ast: Better escaping of strings in preparation for utf8 file encoding

pkg/js_ast/test/string_escape_test.dart

Index: pkg/js_ast/test/string_escape_test.dart
diff --git a/pkg/js_ast/test/string_escape_test.dart b/pkg/js_ast/test/string_escape_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..38116295a6e21d2d60ac192d585e256d67dd4218
--- /dev/null
+++ b/pkg/js_ast/test/string_escape_test.dart
@@ -0,0 +1,149 @@
+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library js_ast.string_escape_test;
+
+import 'package:js_ast/js_ast.dart';
+import 'package:js_ast/src/characters.dart';
+import 'package:unittest/unittest.dart';
+
+const int $LCURLY = $OPEN_CURLY_BRACKET;
+const int $RCURLY = $CLOSE_CURLY_BRACKET;
+
+void main() {
+  check(input, expected, {ascii: false, utf8: false}) {
+    if (input is List) input = new String.fromCharCodes(input);
+    String actual = js.escapedString(input, ascii: ascii, utf8: utf8).value;
+    if (expected is List) {
+      expect(actual.codeUnits, expected);
+    } else {
+      expect(actual, expected);
+    }
+  }
+
+  test('simple', () {
+      check('', [$DQ, $DQ]);
+      check('a', [$DQ, $a, $DQ]);
+    });
+
+  test('simple-escapes', () {
+      check([$BS], [$DQ, $BACKSLASH, $b, $DQ]);
+      check([$BS], [$DQ, $BACKSLASH, $b, $DQ], ascii: true);
+      check([$BS], [$DQ, $BACKSLASH, $b, $DQ], utf8: true);
+
+      check([$LF], [$DQ, $BACKSLASH, $n, $DQ]);
+      check([$LF], [$DQ, $BACKSLASH, $n, $DQ], ascii: true);
+      check([$LF], [$DQ, $BACKSLASH, $n, $DQ], utf8: true);
+
+      check([$FF], [$DQ, $FF, $DQ]);
+      check([$FF], [$DQ, $BACKSLASH, $f, $DQ], ascii: true);
+      check([$FF], [$DQ, $BACKSLASH, $f, $DQ], utf8: true);
+
+      check([$CR], [$DQ, $BACKSLASH, $r, $DQ]);
+      check([$CR], [$DQ, $BACKSLASH, $r, $DQ], ascii: true);
+      check([$CR], [$DQ, $BACKSLASH, $r, $DQ], utf8: true);
+
+      check([$TAB], [$DQ, $BACKSLASH, $t, $DQ]);
+      check([$TAB], [$DQ, $BACKSLASH, $t, $DQ], ascii: true);
+      check([$TAB], [$DQ, $BACKSLASH, $t, $DQ], utf8: true);
+
+      check([$VTAB], [$DQ, $BACKSLASH, $v, $DQ]);
+      check([$VTAB], [$DQ, $BACKSLASH, $v, $DQ], ascii: true);
+      check([$VTAB], [$DQ, $BACKSLASH, $v, $DQ], utf8: true);
+    });
+
+  test('unnamed-control-codes-escapes', () {
+      check([0, 1, 2, 3], [$DQ, 0, 1, 2, 3, $DQ]);
+      check([0, 1, 2, 3], r'''"\x00\x01\x02\x03"''', ascii: true);
+      check([0, 1, 2, 3], [$DQ, 0, 1, 2, 3, $DQ], utf8: true);
+    });
+
+
+  test('line-separator', () {
+      // Legacy escaper is broken.
+      // check([$LS], [$DQ, $BACKSLASH, $u, $2, $0, $2, $8, $DQ]);
+      check([$LS], [$DQ, $BACKSLASH, $u, $2, $0, $2, $8, $DQ], ascii: true);
+      check([$LS], [$DQ, $BACKSLASH, $u, $2, $0, $2, $8, $DQ], utf8: true);
+    });
+
+  test('page-separator', () {
+      // Legacy escaper is broken.
+      // check([$PS], [$DQ, $BACKSLASH, $u, $2, $0, $2, $9, $DQ]);
+      check([$PS], [$DQ, $BACKSLASH, $u, $2, $0, $2, $9, $DQ], ascii: true);
+      check([$PS], [$DQ, $BACKSLASH, $u, $2, $0, $2, $9, $DQ], utf8: true);
+    });
+
+  test('legacy-escaper-is-broken', () {
+      check([$LS], [$DQ, 0x2028, $DQ]);
+      check([$PS], [$DQ, 0x2029, $DQ]);
+    });
+
+  test('choose-quotes', () {
+      check('\'', [$DQ, $SQ, $DQ]);
+      check('"', [$SQ, $DQ, $SQ], ascii: true);
+      check("'", [$DQ, $SQ, $DQ], ascii: true);
+      // Legacy always double-quotes
+      check([$DQ, $DQ, $SQ],
+            [$DQ, $BACKSLASH, $DQ, $BACKSLASH, $DQ, $SQ, $DQ]);
+      // Using single quotes saves us one backslash:
+      check([$DQ, $DQ, $SQ],
+            [$SQ, $DQ, $DQ, $BACKSLASH, $SQ, $SQ],
+            ascii: true);
+      check([$DQ, $SQ, $SQ],
+            [$DQ, $BACKSLASH, $DQ, $SQ, $SQ, $DQ],
+            ascii: true);
+    });
+
+  test('u1234', () {
+      check('\u1234', [$DQ, 0x1234, $DQ]);
+      check('\u1234', [$DQ, $BACKSLASH, $u, $1, $2, $3, $4, $DQ], ascii: true);
+      check('\u1234', [$DQ, 0x1234, $DQ], utf8: true);
+    });
+
+  test('u12345', () {
+      check([0x12345], [$DQ, 55304, 57157, $DQ]);
+      // TODO: ES6 option:
+      //check([0x12345],
+      //      [$DQ, $BACKSLASH, $u, $LCURLY, $1, $2, $3, $4, $5, $RCURLY, $DQ],
+      //      ascii: true);
+      check([0x12345], r'''"\ud808\udf45"''', ascii: true);
+      check([0x12345],
+            [$DQ, $BACKSLASH, $u, $d, $8, $0, $8,
+                  $BACKSLASH, $u, $d, $f, $4, $5, $DQ],
+            ascii: true);
+      check([0x12345], [$DQ, 55304, 57157, $DQ], utf8: true);
+    });
+
+  test('unpaired-surrogate', () {
+      // (0xD834, 0xDD1E) = 0x1D11E
+      // Strings containing unpaired surrogates must be encoded to prevent
+      // problems with the utf8 file-level encoding.
+      check([0xD834], [$DQ, 0xD834, $DQ]);  // Legacy escapedString broken.
+      check([0xD834], [$DQ, $BACKSLASH, $u, $d, $8, $3, $4, $DQ], ascii: true);
+      check([0xD834], [$DQ, $BACKSLASH, $u, $d, $8, $3, $4, $DQ], utf8: true);
+
+      check([0xDD1E], [$DQ, 0xDD1E, $DQ]);  // Legacy escapedString broken.
+      check([0xDD1E], [$DQ, $BACKSLASH, $u, $d, $d, $1, $e, $DQ], ascii: true);
+      check([0xDD1E], [$DQ, $BACKSLASH, $u, $d, $d, $1, $e, $DQ], utf8: true);
+
+      check([0xD834, $A],
+            [$DQ, 0xD834, $A, $DQ]);  // Legacy escapedString broken.
+      check([0xD834, $A],
+            [$DQ, $BACKSLASH, $u, $d, $8, $3, $4, $A, $DQ],
+            ascii: true);
+      check([0xD834, $A],
+            [$DQ, $BACKSLASH, $u, $d, $8, $3, $4, $A, $DQ],
+            utf8: true);
+
+      check([0xD834, 0xDD1E], [$DQ, 0xD834, 0xDD1E, $DQ]);  // Legacy ok.
+      check([0xD834, 0xDD1E],
+            [$DQ,
+              $BACKSLASH, $u, $d, $8, $3, $4,
+              $BACKSLASH, $u, $d, $d, $1, $e,
+              $DQ],
+            ascii: true);
+      check([0xD834, 0xDD1E], r'''"\ud834\udd1e"''', ascii: true);
+      check([0xD834, 0xDD1E], [$DQ, 0xD834, 0xDD1E, $DQ], utf8: true);
+    });
+}