Add Path class to dart:io, and add unit tests for it.

runtime/bin/path_impl.dart

+// Copyright (c) 2012, 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.
+
+class _PathImpl implements Path {
+  final String path;
+  _PathImpl(String source) : path = _clean(source);
+  const _PathImpl.c(String source) : path = source;

[Mads Ager (google), 2012/05/29 07:36:02]

const _PathImpl.c(String this.path);
?

Where do you use this?

[Bill Hesse, 2012/05/31 15:55:10]

Done.

+
+  static String _clean(String source) {
+    switch (Platform.operatingSystem) {
+      case 'windows':
+        return _cleanWindows(source);
+      default:
+        return _cleanPosix(source);
+    }
+  }
+
+  static String _cleanWindows(source) {
+    // Change \ to /.
+    var clean = source.replaceAll('\\', '/');
+    // Add / before intial [Drive letter]:
+    if (const RegExp(@'^[a-zA-Z]:').hasMatch(clean)) {

[Søren Gjesse, 2012/05/29 07:18:01]

Just

  if (clean.length > 1 && clean[1] = ":")

instead of the RegExp.

[Bill Hesse, 2012/05/31 15:55:10]

Done.

+      clean = '/$clean';
+    }
+    return _cleanPosix(clean);
+  }
+
+  static String _cleanPosix(source) {
+    // Change //+ to / (remove all consecutive / marks).
+    var clean = source.replaceAll(const RegExp('//+'), '/');
+    return clean;
+  }
+
+  bool isEmpty() => path == '';

[Mads Ager (google), 2012/05/29 07:36:02]

Add 'get' and either remove the blank line below or have a blank between the two
other getters.

[Bill Hesse, 2012/05/31 15:55:10]

Done.

+
+  bool get isAbsolute() => path.startsWith('/');
+  bool get isDirectory() => path.endsWith('/') || isEmpty();

[Bob Nystrom, 2012/05/30 17:58:37]

When you make isEmpty a getter, don't forget to remove the () here. :)

[Bill Hesse, 2012/05/31 15:55:10]

Removed this case from hasTrailingSlash.

+
+  String toString() => path;
+
+  Path relativeTo(Path base) {
+    // Throws exception if not doable.
+    // Unimplemented
+    if (base.isAbsolute && path.startsWith(base.path)) {
+      if (path == base.path) return new Path('.');
+      if (path[base.path.length] == '/') {
+        return new Path(path.substring(base.path.length + 1));
+      }
+    }
+    throw "Unimplemented case ofPath.relativeTo(base):"

[Bill Hesse, 2012/05/25 13:14:38]

Switch to throw PathException (or UnimplementedException?)

[Mads Ager (google), 2012/05/29 07:36:02]

I would throw a PathException and be very clear about the rules in the
documentation.

[Bill Hesse, 2012/05/31 15:55:10]

The PathException class is removed.  Throwing an UnimplementedException.

On 2012/05/29 07:36:02, Mads Ager wrote:

+          "Path $path relative to ${base.path}";
+  }
+
+  Path join(Path further) {
+    if (further.isAbsolute) {

[Bill Hesse, 2012/05/25 13:14:38]

PathException.

[Bob Nystrom, 2012/05/30 17:58:37]

Better: IllegalArgumentException.

[Bill Hesse, 2012/05/31 15:55:10]

Done.

+      throw "Make a path exception class, and throw it: join with absolute";
+    }
+    return new Path('$path/${further.path}');
+    // Canonicalize?

[Mads Ager (google), 2012/05/29 07:36:02]

Add TODO(whesse): 

[Bill Hesse, 2012/05/31 15:55:10]

Done.

+  }
+
+  Path safeJoin(Path further) => join(further);

[Mads Ager (google), 2012/05/29 07:36:02]

This is not in the interface. What is it used for? Delete?

[Bill Hesse, 2012/05/31 15:55:10]

Added to the interface.  It joins two paths, checking that the second does not
include an upward traversal into the first.

+
+  Path canonicalize() {
+    if (isCanonical) return this;
+    return makeCanonical();
+  }
+
+  bool get isCanonical() {
+    // Contains no consecutive /s.
+    // Contains no . components.
+    // Absolute paths have no .. components.
+    // All .. components of a relative path are initial.
+    List components = path.split('/');
+    if (components[0] == '') {  // Absolute path
+      components.removeRange(0, 1);

[Mads Ager (google), 2012/05/29 07:36:02]

I would use indices instead of copying 'components' repeatedly.

[Bill Hesse, 2012/05/31 15:55:10]

Yes, that would be better.

[Bill Hesse, 2012/05/31 15:55:10]

Fixed using indices, but keeping the components.some check at the end.

+    } else {  // Relative path starting with .. components.
+      while (!components.isEmpty() && components[0] == '..') {
+        components.removeRange(0, 1);
+      }
+    }
+    if (components.isEmpty()) return true;
+    if (components.last() == '') components.removeLast();  // Path ends with /.
+    // No remaining components can be ., .., or empty.
+    return !components.some((c) => c == '..' || c == '.' || c == '');
+  }
+
+  Path makeCanonical() {
+    bool absolute = isAbsolute;
+    // Unimplemented.
+    throw "Unimplemented Path.makeCanonical()";

[Mads Ager (google), 2012/05/29 07:36:02]

NotImplementedException, but it doesn't really matter since we should implement
before landing. :-)

[Bill Hesse, 2012/05/31 15:55:10]

Done.

+    return this;
+  }
+
+  String toNativePath() {
+    if (Platform.operatingSystem == 'windows') {
+      String nativePath = path;
+      if (const RegExp(@'^/[a-zA-z]:').hasMatch(nativePath)) {

[Mads Ager (google), 2012/05/29 07:36:02]

I guess you could just check for '/' and maybe ':' here instead of using
regexps.

[Bill Hesse, 2012/05/31 15:55:10]

Done.

[Bill Hesse, 2012/05/31 15:55:10]

Done.

+        nativePath = nativePath = substring(1);
+      }
+      nativePath = nativePath.replace('/', '\\');
+      return nativePath;
+    }
+    return path;
+  }
+
+  String last() {

[Mads Ager (google), 2012/05/29 07:36:02]

Make this private since it is not part of the interface.

[Bill Hesse, 2012/05/31 15:55:10]

removed.

+    int pos = path.lastIndexOf('/');
+    return path.substring(pos+1);

[Søren Gjesse, 2012/05/29 07:18:01]

Spaces on both sides of +.

[Bill Hesse, 2012/05/31 15:55:10]

Done.

[Bill Hesse, 2012/05/31 15:55:10]

Done.

+  }
+
+  Path dropLast() {

[Mads Ager (google), 2012/05/29 07:36:02]

Move the code to dirname which is the only user. If you don't want to do that,
make dropLast private. It is not part of the interface and therefore should not
be callable by others.

[Bill Hesse, 2012/05/31 15:55:10]

Done.

[Bill Hesse, 2012/05/31 15:55:10]

Done.

+    int pos = path.lastIndexOf('/');
+    if (pos < 0) return new Path('');
+    // while (pos > 0 && path[pos - 1] == '/') --pos;

[Mads Ager (google), 2012/05/29 07:36:02]

Code in comments.

[Bill Hesse, 2012/05/31 15:55:10]

Uncommented, because we don't always clean consecutive / marks now.

+    return new Path((pos > 0) ? path.substring(0, pos) : '/');
+  }
+
+  String basename() {
+    var name = last();
+    int pos = name.lastIndexOf('.');
+    return (pos < 0) ? name : name.substring(0, pos);
+  }
+
+  String extension() {
+    var name = last();
+    int pos = name.lastIndexOf('.');
+    return (pos < 0) ? '' : name.substring(pos + 1);
+  }
+
+  Path dirname() {
+    return dropLast();
+  }
+
+  String filename() {
+    return last();
+  }
+}