PSA - Breaking Change in Dart main signature

[Florian Loitsch]

Hi all,

starting with commit 2738f1b76f9edf11de0dea5d6caef6e9beec0707, Dart Mojo applications have to change their `main` function.

What changed?:

Before, the Mojo parameters were given in the `arguments` object:

main(arguments) {

  arguments[0] => Mojo handle

  arguments[1] => URI

  arguments[2] => original arguments array.

}

After the change the additional parameters are in the extra message parameter slot, and in Uri.base:

main(arguments, Object mojoHandle) {

  var uri = Uri.base;

}

Sidenote: I recommend not to type the mojo-handle as integer.

Why?:

This aligns the main signature of Mojo applications with the standard main signature. In particular, the `List<String> arguments` parameter is not actually a list of Strings, and represents the arguments that were given to the application.

When:

this change has been committed to the repository: #2738f1b76f9edf11de0dea5d6caef6e9beec0707

// florian

[James Robinson]

On Mon, Feb 29, 2016 at 7:47 AM, 'Florian Loitsch' via mojo-dev <mojo...@chromium.org> wrote:

Sidenote: I recommend not to type the mojo-handle as integer.

Could you explain the reason behind this sidenote?

- James

[Florian Loitsch]

Two reasons:

- in the Dart-standalone (not Mojo shell) version, the handle is not an integer.

- unless you need to do integer operations with the handle, there is no need to type it as int. Ideally it should be a typedef, but we don't have those in Dart (yet). Typing it as 'int' makes it harder to do changes in the future. It could be interesting to track handles differently (and if it's just to be able to use them in Expandos), but that wouldn't be possible if users typed the handles as 'int's.

- James