Add the "arguments" global to the shell sample. The "arguments"...

Add the "arguments" global to the shell sample.

The "arguments" global is commonly used by Javascript shells to pass command line arguments to
the Javascript script. Rhino does this, as does v8's own "d8" shell.

This change works by adding a new public API to v8, GetJSAttributes(), which
returns a Javascript array of the arguments. While it might seem scary to add a
new API, this API is already implicit in the way that arguments are parsed by
the existing SetFlagsFromString and SetFlagsFromCommandLine APIs. Those APIs
already recognize the "--" flag and saves away any arguments after the "--"
flag. All this change does is prove a way of getting
at the saved arguments.

The implementation of GetJSAttributes() was extracted from the d8 shell.

[jackpal, 2009-04-30 23:24:39]

My first patch to v8, please help me correct any mistakes.

Mr. Gjesse, I just guessed that you are the reviewer, because you've been a
reviewer on past changes to the shell sample. Please let me know if someone else
is more appropriate to review this change.

Here's a little history behind the patch:

I was using the V8 sample shell to run benchmarks from
http://shootout.alioth.debian.org/, and I noticed that many of the JavaScript
benchmarks assumed that command-line-shell arguments would be available to the
JavaScript script in the "arguments" global variable. This is apparently a
standard among JavaScript shells.

I also notice the topic was raised a few months ago on the v8-users mailing
list, but the suggested work-around was for each developer to modify their own
copy of the shell sample to add argument parsing.

That didn't sound right to me. If it's a standard expected feature of JavaScript
shells, there ought to be standard support for it in v8.

While researching how to implement this feature I discovered that it was already
mostly implemented. The V8::SetFlagsFromCommandLine function already recognized
the "--" flag and saved away the arguments. All that was missing was a public
way of retrieving the saved arguments, and some utility code to convert them to
a JavaScript array and install them as a global variable.

I found some code that implemented this in the d8 shell. So I took the liberty
of extracting that code and making it a public API, which is now called from
both the shell sample and the d8 shell.

[Søren Thygesen Gjesse, 2009-05-04 07:12:51]

The sample shell in the V8 repository is supposed to be just a sample, and
therefore has just the most basic features to illustrate various V8 constructs.

For more advanced shell features the developer shell D8 is supposed to be used,
and is the place for the whatever features are required for an advanced V8 based
JavaScript  shell.

From you comments it looks as if you have already used D8, if there are some
shortcommings in D8 we would rather see these fixed in D8.