Implement --help option and generalize option parsing.

Implement --help option and generalize option parsing.

Committed: https://code.google.com/p/dart/source/detail?r=7461

[ahe, 2012-05-09 14:09:36]

Kathy, Seth, and Luke: I would like your opinion on the error message.

Here are a few examples:

Example 1. Running the compiler without any arguments:


$ dart2js
dart2js [OPTIONS...] DART-FILE

A Dart to JavaScript compiler.

By default, the compiled JavaScript code is saved to a file named
out.js in the current directory.

Common options:

  --help      Display this message.

  --out=FILE  Save the output to FILE (default is out.js).

  --checked   Turn on checked mode in generated JavaScript code.

Error: no file to compile.
$ 


Example 2. Running the compiler with too many arguments:


$ dart2js foo.dart fisk.dart hest.dart
dart2js [OPTIONS...] DART-FILE

A Dart to JavaScript compiler.

By default, the compiled JavaScript code is saved to a file named
out.js in the current directory.

Common options:

  --help      Display this message.

  --out=FILE  Save the output to FILE (default is out.js).

  --checked   Turn on checked mode in generated JavaScript code.

Error: extra arguments: fisk.dart hest.dart
$ 


Example 3. Using --help:


$ dart2js --help
dart2js [OPTIONS...] DART-FILE

A Dart to JavaScript compiler.

By default, the compiled JavaScript code is saved to a file named
out.js in the current directory.

Common options:

  --help      Display this message.

  --out=FILE  Save the output to FILE (default is out.js).

  --checked   Turn on checked mode in generated JavaScript code.

$

[kasperl, 2012-05-09 14:13:53]

LGTM.

[kathyw, 2012-05-09 18:01:10]

How about:


e 1. Running the compiler without any arguments:

$ dart2js
Usage: dart2js [OPTIONS] DARTFILE

Compiles Dart to JavaScript.

Common options:
 --help      Display this message.
 --out=FILE  Save the output to FILE (default is out.js).
 --checked   Turn on checked mode in generated JavaScript code.

Error: No Dart file specified.
$


Example 2. Running the compiler with too many arguments:

$ dart2js foo.dart fisk.dart hest.dart
Usage: dart2js [OPTIONS] DARTFILE

Compiles Dart to JavaScript.

Common options:
 --help      Display this message.
 --out=FILE  Save the output to FILE (default is out.js).
 --checked   Turn on checked mode in generated JavaScript code.

Error: Extra arguments: fisk.dart hest.dart
$


Example 3. Using --help:

$ dart2js --help
Usage: dart2js [OPTIONS] DARTFILE

Compiles Dart to JavaScript.

Common options:
 --help      Display this message.
 --out=FILE  Save the output to FILE (default is out.js).
 --checked   Turn on checked mode in generated JavaScript code.

[kathyw, 2012-05-09 18:04:11]

The spacing is strange in email (though not in
https://chromiumcodereview.appspot.com/10383086/).

Basically, I tried to reduce redundancy and eliminate some blank lines so that
groupings were clearer. I modeled the format loosely after 'texi2pdf --help' (on
Mac).

-k-

[kathyw, 2012-05-09 18:06:05]

Another thing I just noticed:

default is out.js
->
default: ./out.js

(specify the current directory, and reduce words to make the filename more
noticeable)

[sethladd, 2012-05-09 18:08:12]

https://chromiumcodereview.appspot.com/10383086/diff/2001/dart/lib/compiler/i...
File dart/lib/compiler/implementation/dart2js.dart (right):

https://chromiumcodereview.appspot.com/10383086/diff/2001/dart/lib/compiler/i...
dart/lib/compiler/implementation/dart2js.dart:201: --out=FILE  Save the output
to FILE (default is out.js).
I believe the new dart.js file that Kasper updated expects dart2js output to be
of file.js_  This expectation does not match the default out.js