Command-Line Dart and Frogc (Wha?)

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Thanks to some pointers from @dartbits, it seems that there may be some hope of using a real editor, namely Emacs, with Dart.

To do so, I need to download the Dart SDK, which can be found amongst the Dart builds. The SDK are the ones without "DartBuild" in the filename. For my Ubuntu system, that means that I need "dart-linux.zip":

➜  Downloads  wget http://gsdview.appspot.com/dart-editor-archive-continuous/latest/dart-linux.zip
...
2011-12-30 16:08:40 (130 KB/s) - `dart-linux.zip' saved [6683485/6683485]

Using the mnemonic suggested in yesterday's comments (unzip -d -- I might actually remember that), I extract the SDK into a temporary directory until I can decide what to do with it:

➜  Downloads  unzip -d ~/tmp/dart dart-linux.zip

Taking a look at the contents, I find:

➜  dart  cd ~/Downloads 
➜  Downloads  cd ~/tmp/dart
➜  dart  ls
dart-sdk
➜  dart  ls dart-sdk/*
dart-sdk/revision

dart-sdk/bin:
dart  frogc  frogc.dart

dart-sdk/lib:
builtin  core  coreimpl  dom  frog  html  htmlimpl  json

dart-sdk/util:
dartdoc

For what it is worth to future readers, the revision that I am using here is 2886:

➜  dart  cat dart-sdk/revision 
2886

Since the dart SDK follows an almost UNIX like directory structure (with bin and lib sub-directories), I am almost tempted to move those sub-directories directly into my $HOME/local. I worry about confusion with the likes of $HOME/local/lib/builtin, so, at least for now, I move the dart SDK directory into $HOME/local and sym-link the executables:

➜  dart  mv dart-sdk ~/local 
➜  dart  cd ~/local/bin/
➜  bin  ln -s ../dart-sdk/bin/dart 
➜  bin  ln -s ../dart-sdk/bin/frogc
➜  bin  ln -s ../dart-sdk/bin/frogc.dart 

First, I think that I will try to replicate yesterday's Dart to Javascript compilation with these tools. If I am successful, I can eschew the Eclipse-based Dart Editor in favor of my beloved Emacs.

Back in the directory containing my simple iterating code, I "frogc" (hunh?) the dart code:

➜  iterator  frogc iterator.dart             
error: File not found: /home/cstrom/local/lib/core/core_frog.dart
error: File not found: /home/cstrom/local/lib/html/html.dart
iterator.dart:6:5: warning: can not resolve "document" on "iterator"
    document.query('#status').innerHTML = '';
    ^^^^^^^^
iterator.dart:6:5: warning: document is not defined anywhere in the world.
    document.query('#status').innerHTML = '';
    ^^^^^^^^
iterator.dart:6:5: warning: can not resolve "noSuchMethod" on "iterator"
    document.query('#status').innerHTML = '';
    ^^^^^^^^
iterator.dart:6:5: warning: noSuchMethod is not defined anywhere in the world.
    document.query('#status').innerHTML = '';
    ^^^^^^^^
compilation failed with 2 errors
Unhandled exception:
Compilation failed
 0. Function: '::main' url: '/home/cstrom/local/dart-sdk/lib/frog/minfrogc.dart' line:32 col:5
 1. Function: '::main' url: '/home/cstrom/local/dart-sdk/bin/frogc.dart' line:11 col:16

Yikes! Well, not too bad I suppose. The reason for the failure is that the compiler cannot find the core libraries. Looks as though I need to sym-link them into my $HOME/local/lib directory after all:

➜  iterator  cd ~/local/lib
➜  lib  ln -s ../dart-sdk/lib/* .
➜  lib  ls -l
total 14068
lrwxrwxrwx  1 cstrom cstrom      23 2011-12-30 21:51 builtin -> ../dart-sdk/lib/builtin
lrwxrwxrwx  1 cstrom cstrom      20 2011-12-30 21:51 core -> ../dart-sdk/lib/core
lrwxrwxrwx  1 cstrom cstrom      24 2011-12-30 21:51 coreimpl -> ../dart-sdk/lib/coreimpl
lrwxrwxrwx  1 cstrom cstrom      19 2011-12-30 21:51 dom -> ../dart-sdk/lib/dom
drwxr-xr-x  2 cstrom cstrom    4096 2011-05-14 21:39 engines
lrwxrwxrwx  1 cstrom cstrom      20 2011-12-30 21:51 frog -> ../dart-sdk/lib/frog
lrwxrwxrwx  1 cstrom cstrom      20 2011-12-30 21:51 html -> ../dart-sdk/lib/html
lrwxrwxrwx  1 cstrom cstrom      24 2011-12-30 21:51 htmlimpl -> ../dart-sdk/lib/htmlimpl
drwxr-xr-x  3 cstrom cstrom    4096 2011-03-06 12:00 io
lrwxrwxrwx  1 cstrom cstrom      20 2011-12-30 21:51 json -> ../dart-sdk/lib/json
...

At least that is a little better than moving those Dart sub-directories directly into $HOME/local/lib—the sym-links describe the source of what might otherwise be mysterious entries 6 months hence.

Back in my simple iterator directory, I try again:

➜  iterator  frogc iterator.dart
/home/cstrom/local/lib/htmlimpl/htmlimpl.dart:23094:21: warning: a map literal takes one type argument specifying the value type
    _listenerMap = <String, EventListenerList>{};
                    ^^^^^^

Er... What?

That is not an error from my code. That is from Dart itself. Ugh. Checking line 23,094 of htmlimpl.dart, I see:

EventsImplementation._wrap(this._ptr) {
    // TODO(sigmund): the key type (String) yields a warning in frog and the vm,
    // but it is currently necessary to compile with dartc.
    _listenerMap = {};
  }

Ah, so it is an expected warning. But why then did the expected Javascript version of the app not compile?

➜  iterator  ls -l
total 2272
-rw-rw-r-- 1 cstrom cstrom     416 2011-12-30 21:58 iterator.dart
-rw-rw-r-- 1 cstrom cstrom 2125072 2011-12-30 00:05 iterator.dart.app.js.bak
-rw-rw-r-- 1 cstrom cstrom  182516 2011-12-30 21:58 iterator.dart.js
-rw-rw-r-- 1 cstrom cstrom     220 2011-12-29 23:07 iterator.html
drwxrwxr-x 4 cstrom cstrom    4096 2011-12-30 00:04 workspace

It turns out that it did compile. I had expected it to be named iterator.dart.app.js like it was when the Dart Editor generated it. Instead it is just iterator.dart.js. And wow, it is an order of magnitude smaller than the Editor generated version.

Of course, it does not mean squat unless the smaller version actually works. So I point the HTML to the new Javascript file and load the page in the browser to find:

Awesome. That is a huge win for me. Not only was the Dart Editor not Emacs, it was also a bit slow with the code auto-completion (which I detest anyway) and took up much memory.

In addition to compiled Dart into Javascript, I expect to want to execute pure Dart from the command line as well. That should be what the dart command is for:

➜  iterator  dart iterator.dart
'/home/cstrom/dart/iterator/iterator.dart': Error: line 1 pos 1: library handler failed: Do not know how to load 'dart:html'
#import('dart:html');
^

Hrm... One the one hand, why would I want to load dart:html when I am working on the command line? On the other hand, if I want to load it, why can't I?

I can kinda-sorta get it working by changing the #import statement to:

#import('./lib/html/html.dart');
// #import('dart:html');

And sym-linking the html library:

$ ln -s ~/local/dart-sdk/lib .

does the trick. Sort of:

➜  iterator  dart iterator.dart
'/home/cstrom/dart/iterator/iterator.dart': Error: line 1 pos 1: library handler failed: '/home/cstrom/local/dart-sdk/lib/html/html.dart': Error: line 3 pos 1: library handler failed: Do not know how to load 'dart:dom'
#import('dart:dom', prefix:'dom');
^

#import('./lib/html/html.dart');
^

Of course dart:html references dart:dom so now that does no resolve. I am not going to worry about that too much. Not yet at least. For now, it is good to be able to call and compile Dart code.

I call it a night here. Tomorrow, I plan to get a little more familiar with this dart executable. As well as Dart itself.



Day #250