Add a filesystem descriptor library to scheduled_test.

pkg/scheduled_test/lib/src/descriptor/file.dart

+// Copyright (c) 2013, 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 descriptor.file;
+
+import 'dart:async';
+import 'dart:io' as io;
+import 'dart:math' as math;
+import 'dart:utf';
+
+import 'package:pathos/path.dart' as path;
+
+import '../../descriptor.dart' as descriptor;
+import '../../scheduled_test.dart';
+import '../utils.dart';
+import 'utils.dart';
+
+/// A descriptor describing a single file.
+class File extends descriptor.Entry {
+  /// Whether this descriptor describes a binary file. This is only used when
+  /// displaying error messages.
+  final bool isBinary;
+
+  /// The contents of the file, in bytes.
+  final List<int> contents;
+
+  /// The contents of the file as a String. Assumes UTF-8 encoding.
+  String get textContents => new String.fromCharCodes(contents);
+
+  File.binary(Pattern name, List<int> contents)
+      : this._(name, contents, true);
+
+  File(Pattern name, String contents)
+      : this._(name, encodeUtf8(contents), false);
+
+  File._(Pattern name, this.contents, this.isBinary)
+      : super(name);
+
+  Future create([String parent]) => schedule(() {
+    if (parent == null) parent = descriptor.defaultRoot;
+    return new io.File(path.join(parent, stringName)).writeAsBytes(contents);
+  }, 'creating file $nameDescription');
+
+  Future validate([String parent]) => schedule(() {
+    if (parent == null) parent = descriptor.defaultRoot;
+    var fullPath = entryMatchingPattern('File', parent, name);
+    return new io.File(fullPath).readAsBytes()
+        .then((actualContents) {
+      if (orderedIterableEquals(contents, actualContents)) return;
+      if (isBinary) {
+        // TODO(nweiz): show a hex dump here if the data is small enough.
+        throw "File $nameDescription didn't contain the expected binary "
+            "data.";
+      }
+      var description = nameDescription;
+      if (name is! String) {
+        description = "'${path.basename(fullPath)}' (matching $description)";
+      }
+      throw _textMismatchMessage(description, textContents,
+          new String.fromCharCodes(actualContents));;
+    });
+  }, 'validating file $nameDescription');
+
+  Stream<List<int>> read() => new Future.immediate(contents).asStream();
+
+  String describe() {
+    if (name is String) return name;
+    return 'file matching $nameDescription';
+  }
+}
+
+String _textMismatchMessage(String description, String expected,
+    String actual) {
+  final expectedLines = expected.split('\n');
+  final actualLines = actual.split('\n');
+
+  var results = [];
+
+  // Compare them line by line to see which ones match.
+  var length = math.max(expectedLines.length, actualLines.length);
+  for (var i = 0; i < length; i++) {
+    if (i >= actualLines.length) {
+      // Missing output.
+      results.add('? ${expectedLines[i]}');
+    } else if (i >= expectedLines.length) {
+      // Unexpected extra output.
+      results.add('X ${actualLines[i]}');
+    } else {
+      var expectedLine = expectedLines[i];
+      var actualLine = actualLines[i];
+
+      if (expectedLine != actualLine) {
+        // Mismatched lines.
+        results.add('X $actualLine');
+      } else {
+        // Matched lines.
+        results.add('| $actualLine');
+      }
+    }
+  }
+
+  return "File $description should contain:\n"
+    "${prefixLines(expected)}\n"
+    "but actually contained:\n"
+    "${results.join('\n')}";
+}