Create a TokenStreamRewriter class.

pkg/front_end/test/fasta/parser/token_stream_rewriter_test.dart

+// Copyright (c) 2017, 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.
+
+import 'package:front_end/src/fasta/parser/token_stream_rewriter.dart';
+import 'package:front_end/src/fasta/scanner/precedence.dart';
+import 'package:front_end/src/fasta/scanner/token.dart';
+import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';

[ahe, 2017/03/09 13:47:08]

At some point we should talk about test frameworks.

+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(TokenStreamRewriterTest_NoPrevious);
+    defineReflectiveTests(TokenStreamRewriterTest_UsingPrevious);
+  });
+}
+
+/// Abstract base class for tests of [TokenStreamRewriter].
+abstract class TokenStreamRewriterTest {
+  /// Indicates whether the tests should set up [Token.previousToken].
+  bool get setPrevious;
+
+  void test_insert_at_end() {
+    var a = _makeToken(0, 'a');
+    var b = _makeToken(1, 'b');
+    var eof = _link([a]);
+    var rewriter = new TokenStreamRewriter(a);
+    rewriter.insertTokenBefore(b, eof);
+    expect(rewriter.firstToken, same(a));
+    expect(a.next, same(b));
+    expect(b.next, same(eof));
+    expect(eof.previousToken, same(b));
+    expect(b.previousToken, same(a));
+  }
+
+  void test_insert_at_start() {
+    var a = _makeToken(0, 'a');
+    var b = _makeToken(1, 'b');
+    _link([b]);
+    var rewriter = new TokenStreamRewriter(b);
+    rewriter.insertTokenBefore(a, b);
+    expect(rewriter.firstToken, same(a));
+    expect(a.next, same(b));
+    expect(a.previousToken.next, same(a));
+    expect(b.previousToken, same(a));
+  }
+
+  void test_resume_at_previous_insertion_point() {
+    var a = _makeToken(0, 'a');
+    var b = _makeToken(1, 'b');
+    var c = _makeToken(2, 'c');
+    var d = _makeToken(3, 'd');
+    var e = _makeToken(4, 'e');
+    _link([a, b, e]);
+    var rewriter = new TokenStreamRewriter(a);
+    rewriter.insertTokenBefore(d, e);
+    expect(b.next, same(d));
+    expect(d.next, same(e));
+    a.next = null;
+    // The next call to rewriter should be able to find the insertion point
+    // without using a.next.
+    rewriter.insertTokenBefore(c, d);
+    expect(b.next, same(c));
+    expect(c.next, same(d));
+  }
+
+  void test_second_insertion_earlier_in_stream() {
+    var a = _makeToken(0, 'a');
+    var b = _makeToken(1, 'b');
+    var c = _makeToken(2, 'c');
+    var d = _makeToken(3, 'd');
+    var e = _makeToken(4, 'e');
+    _link([a, c, e]);
+    var rewriter = new TokenStreamRewriter(a);
+    rewriter.insertTokenBefore(d, e);
+    expect(c.next, same(d));
+    expect(d.next, same(e));
+    // The next call to rewriter should be able to find the insertion point
+    // even though it is before the insertion point used above.
+    rewriter.insertTokenBefore(b, c);
+    expect(a.next, same(b));
+    expect(b.next, same(c));
+  }
+
+  void test_skip_group() {
+    var a = _makeBeginGroupToken(0);
+    var b = _makeToken(1, 'b');
+    var c = _makeToken(2, 'c');
+    var d = _makeToken(3, 'd');
+    var e = _makeToken(4, 'e');
+    a.endGroup = c;
+    _link([a, b, c, e]);
+    // The rewriter should skip from a to c when finding the insertion position;
+    // we test this by corrupting b's next pointer.
+    b.next = null;
+    var rewriter = new TokenStreamRewriter(a);
+    rewriter.insertTokenBefore(d, e);
+    expect(c.next, same(d));
+    expect(d.next, same(e));
+  }
+
+  /// Links together the given [tokens] and adds an EOF token to the end of the
+  /// token stream.
+  ///
+  /// The EOF token is returned.
+  Token _link(Iterable<Token> tokens) {
+    Token head = new SymbolToken(EOF_INFO, -1);
+    for (var token in tokens) {
+      head.next = token;
+      if (setPrevious) token.previousToken = head;
+      head = token;
+    }
+    int eofOffset = head.charOffset + head.value.length;
+    if (eofOffset < 0) eofOffset = 0;
+    Token eof = new SymbolToken(EOF_INFO, eofOffset);
+    head.next = eof;
+    if (setPrevious) eof.previousToken = head;
+    return eof;
+  }
+
+  BeginGroupToken _makeBeginGroupToken(int charOffset) {
+    return new BeginGroupToken(OPEN_PAREN_INFO, charOffset);
+  }
+
+  StringToken _makeToken(int charOffset, String text) {
+    return new StringToken.fromString(null, text, charOffset);
+  }
+}
+
+/// Concrete implementation of [TokenStreamRewriterTest] in which
+/// [Token.previousToken] values are set to null.
+///
+/// This forces [TokenStreamRewriter] to use its more complex heursitc for
+/// finding previous tokens.
+@reflectiveTest
+class TokenStreamRewriterTest_NoPrevious extends TokenStreamRewriterTest {
+  bool get setPrevious => false;
+}
+
+/// Concrete implementation of [TokenStreamRewriterTest] in which
+/// [Token.previousToken] values are set to non-null.
+///
+/// Since [TokenStreamRewriter] makes use of [Token.previousToken] when it can,
+/// these tests do not exercise the more complex heuristics for finding previous
+/// tokens.
+@reflectiveTest
+class TokenStreamRewriterTest_UsingPrevious extends TokenStreamRewriterTest {
+  bool get setPrevious => true;
+}