Specify packageRoot parameter to Isolate.spawnUri.

sdk/lib/isolate/isolate.dart

Index: sdk/lib/isolate/isolate.dart
diff --git a/sdk/lib/isolate/isolate.dart b/sdk/lib/isolate/isolate.dart
index 96c55b814835208dac713970baf062873c23be16..795940b63f30d2153b7a5bdce735673e5da4fd4a 100644
--- a/sdk/lib/isolate/isolate.dart
+++ b/sdk/lib/isolate/isolate.dart
@@ -106,11 +106,27 @@ class Isolate {
    * When present, the parameter `args` is set to the provided [args] list.
    * When present, the parameter `message` is set to the initial [message].
    *
+   * If the [packageRoot] parameter is passed, it is used as the location
+   * of packages in the spawned isolate.
+   * The `packageRoot` URI must be a "file" or "http"/"https" URI that ends
+   * in a slash.
+   * If it doesn't end in a slash, one will be added before using the URI.

[Anders Johnsen, 2014/08/04 12:54:48]

I don't agree with this. Normally we would use Uri.resolve, and that would just
ignore the last part segment.

[Lasse Reichstein Nielsen, 2014/08/04 13:27:26]

The user will never want to write "file:///foo/bar/baz" and not use the
directory baz as base directory. If we just use resolve blindly, we will use
"bar" as base directory and ignore "baz".
We can also just throw if the URI path doesn't end with a slash.

[Anders Johnsen, 2014/08/05 06:23:29]

If I give it Platform.script, I expect it to work, without me trimming the
basename from the path.

[Lasse Reichstein Nielsen, 2014/08/05 08:01:25]

If we make new Uri.file(directory.path) end in a slash, I think it's ok
(http://dartbug.com/20362).

[Lasse Reichstein Nielsen, 2014/08/05 12:50:37]

The --package-root argument on the VM command line does add a '/' after a
non-slash-terminated URL.

+   * Package URIs (like "package:foo/bar.dart") in the new isolate are

[Anders Johnsen, 2014/08/04 12:54:48]

URIs -> imports

+   * resolved against this location, as by
+   * `packageRoot.resolve(Uri.parse("foo/bar.dart"))`.

[Anders Johnsen, 2014/08/04 12:54:48]

This is contradicting the 'adding slash' as stated above.

[Lasse Reichstein Nielsen, 2014/08/04 13:27:26]

True. It assumes the presence of the trailing slash.

[Lasse Reichstein Nielsen, 2014/08/13 08:06:05]

How about requiring the path to end in a slash, and adding a getter on Uri,
e.g., pathBase, that returns a Uri without any query or fragment, and without
the parts after the last slash of the path? That is, remove everything after the
last slash in the path.

[floitsch, 2014/08/15 18:32:32]

I think the packageRoot should behave similar to how it is handled from the
command-line.

[Lasse Reichstein Nielsen, 2014/08/21 11:14:01]

Agree. The URI must refer to a directory. If the path does not end in a slash,
one will be added before using as base URI for resolving.
Updating documentation to make it clear that the slash is added, not required.

+   * This includes the main entry [uri] if it happens to be a package-URL.
+   * If [packageRoot] is omitted, the spawned isolate will use the same
+   * package root as the spawning isolate.
+   *
    * Returns a future that will complete with an [Isolate] instance if the
    * spawning succeeded. It will complete with an error otherwise.
    */
   external static Future<Isolate> spawnUri(
-      Uri uri, List<String> args, var message, { bool paused: false });
+      Uri uri,
+      List<String> args,
+      var message,
+      { bool paused: false,
+        Uri packageRoot });
 
   /**
    * Requests the isolate to pause.