Add support for pub install.

utils/pub/utils.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.
 
 /**
  * Generic utility functions. Stuff that should possibly be in core.
  */
 #library('pub_utils');
 
 // TODO(rnystrom): Move into String?
 /** Pads [source] to [length] by adding spaces at the end. */
 String padRight(String source, int length) {
   final result = new StringBuffer();
   result.add(source);
 
   while (result.length < length) {
     result.add(' ');
   }
 
   return result.toString();
-}
+}
+
+/**
+ * Runs [fn] after [future] completes, whether it completes successfully or not.
+ * Essentially an asynchronous `finally` block.
+ */
+always(Future future, fn()) {

[Bob Nystrom, 2012/05/03 00:15:49]

I sketched out something like this once but didn't end up keeping it. It might
be nice to have it take (optional) arguments for the then and exception cases
too so you don't have to capture the future in a variable at all in the calling
code.

[nweiz, 2012/05/04 01:03:43]

I don't follow... what would these arguments do?

[Bob Nystrom, 2012/05/04 17:02:06]

I don't know if this is a good idea, but for example, here's some (simplified
code using always:


Future<Package> install(PackageId id) {
  var future = ensureDir(dirname(packageDir)).chain((_) {
    return exists(packageDir);
  }).chain((exists) {
    ...
  }).chain((_) => Package.load(packageDir));

  future.then((pkg) => _loadedPackages[id] = pkg);
  always(future, () => _pendingInstalls.remove(id));
  return future;
}

Instead of "always" imagine you replace that with "foo" (need some real name),
like:

Future<Package> install(PackageId id) {
  return foo(ensureDir(dirname(packageDir)).chain((_) {
      return exists(packageDir);
    }).chain((exists) {
      ...
    }).chain((_) => Package.load(packageDir)),
    then: (pkg) => _loadedPackages[id] = pkg,
    always: () => _pendingInstalls.remove(id));
  return future;
}

[nweiz, 2012/05/07 18:28:35]

I don't think that really adds any clarity.

+  var completer = new Completer();
+  future.then((_) => fn());
+  future.handleException((_) {
+    fn();
+    return false;
+  });
+}
+
+/**
+ * Flattens nested lists into a single list containing only non-list elements.
+ */
+List flatten(List nested) {
+  var result = [];
+  helper(list) {
+    for (var e in list) {

[Bob Nystrom, 2012/05/03 00:15:49]

e -> element or item

[Bob Nystrom, 2012/05/03 00:15:49]

"e" -> element or item

[nweiz, 2012/05/04 01:03:43]

Done.

+      if (e is List) {

[Bob Nystrom, 2012/05/03 00:15:49]

Iterable?

[nweiz, 2012/05/04 01:03:43]

That's how I had it originally, but I changed it to list because I wanted it to
be very clear which objects would get flattened and which wouldn't. Imagine if
you were flattening [[{"foo": "bar"}, 12]] and then Josh changes Map to
implement Iterable and the behavior changes. Ick.

[Bob Nystrom, 2012/05/04 17:02:06]

I was thinking the same thing. Type tests are always a little risky. :(

+        helper(e);
+      } else {
+        result.add(e);
+      }
+    }
+  }
+  helper(nested);
+  return result;
+}