Dart Pub for Local Development

‹prev | My Chain | next›

I got a nice taste of the pub packager for Dart (it's so new, it has a commit, not a landing page). Like just about everything else in Dart, pub is starting small, with just enough to get an idea how it might work, but not so much that it is at all encumbered by previous implementation.

Tonight, I'd like to see how far I can push the current implementation. Specifically, I would like to see if I can make it manually emulate npm's very excellent npm link. The "link" in that command instructs npm to link a local copy of a package instead of installing it from the npm registry. It is more than installing it from a local copy—it creates a symbolic link to the local package instead of installing it. The invaluable benefit of this approach is that any changes made to the linked package can be immediately committed without the intermediate step of copying them into a separate repository.

I do this constantly as I am developing Hipster MVC. Try something new in Dart Comics / tweak the code in Hipster MVC. Struggle with an implementation aspect in Dart Comics / update the documentation in Hipster MVC.

But until now, this has been a pain. I either need to update the code on GitHub to see the change locally:

...
#import('https://raw.github.com/eee-c/hipster-mvc/master/HipsterSync.dart');
...

Or I have to manually sym-link the Hipster MVC libraries for local development only to remove them (and the updated #import() statements) before I commit to the Dart Comics repository.

So I get started by replacing the remaining references to GitHub-hosted code in Dart Comics with the pub package equivalent:

...
#import('package:hipster-mvc/HipsterSync.dart');
...

Next, in the scripts directory of Dart Comics, I replace the pub installed Hipster MVC with a symbolic link to my local copy of the repository:

➜  scripts git:(pub-packages) cd packages
➜  packages git:(pub-packages) mv hipster-mvc hipster-mvc.orig
➜  packages git:(pub-packages) ln -s ../../../../hipster-mvc
➜  packages git:(pub-packages) ls -l
total 4
lrwxrwxrwx 1 chris chris   23 May 28 22:02 hipster-mvc -> ../../../../hipster-mvc
drwxr-xr-x 3 chris chris 4096 May 27 23:06 hipster-mvc.orig

And, indeed, it all still works. I can view, delete, and add comic books to my collection just as before:

Best of all, if I make a change to my local copy of Hipster MVC, such as breaking forEach():

class HipsterCollection implements Collection {
  // ...
  void forEach(fn) {
    //models.forEach(fn);
  }
  // ...
}

Then the change is immediately visible in my Dart Comics application:

And if I fix the change in the local Hipster MVC repository:

class HipsterCollection implements Collection {
  // ...
  void forEach(fn) {
    models.forEach(fn);
  }
  // ...
}

Then Dart Comics is fixed:

That is pretty freaking amazing. If there is anything even close in client-side Javascript land, I am unaware. But even is a pre-release / proof-of-concept, the pub packager already makes life oh-so-sweet for the Dart developer.

Am I overstating? This seems huge.


Day #400