IronRuby, Silverlight and executing code dynamically in the browser

I’m toying around with the idea of a simple in-browser “coding
environment”
for IronRuby, think JSFiddle but for DLR languages. I’m fairly new to
IronRuby, but have lots of Silverlight experience. I have gotten the
basics
up and running, but have ran into a couple issues.

My initial idea was to use the virtual file system the IronPython
Silverlight Host creates when it downloads files included using
tags. However, turns out this virtual file system is read-only, so I
cannot
write new Ruby files after the application is loaded.

My second idea was to simply use the DynamicEngine and simply execute
the
code. The code I’ve written looks something like this:

        def run_tests
            code = window.eval("codeEditor.getCode()").to_s
            test = window.eval("testEditor.getCode()").to_s

            puts code

            begin
                dyneng = DynamicEngine.new
                engine = dyneng.runtime.get_engine("ruby")
                scope = dyneng.create_scope

                errorFormatter = ErrorFormatter::Sink.new

                resultCode =

engine.create_script_source_from_string(code).compile(errorFormatter).execute(scope)
resultTest =
engine.create_script_source_from_string(test).compile(errorFormatter).execute(scope)

                puts resultCode
                puts resultTest
            rescue => ex
                puts ex.to_s
            end
        end

It basically gets two pieces of Ruby code, then creates a new engine,
creates script source, compiles it, and then executes it. If I do this
with
valid Ruby code everything works as expected. However, if I try to
execute
invalid code I was expecting my error handler to execute. But this does
not
happen. All I get is an error in the FireBug console saying:

“Error calling method on NPObject!”

So does anyone have suggestions on how to handle errors when executing
the
code dynamically in the browser. Secondly, does anyone have suggestions
for
alternative approaches to implementing this - i.e. make the virtual file
system writable (write to isolated storage perhaps?).

Best regards,
Jonas Follesø

Hey Jonas, nice running into here (love your blog)!

You could try writing your own virtual filesystem. Check out my blog
for
some inspiration:
http://charlesstrahan.com/blog/2010/05/05/enumerating-resources-in-silverlight/

I’m currently working on just that. My current project (porting RPG
Maker
XP to Silverlight - already finished the desktop port) requires such
functionality for enumerating file system entries (think Dir.glob), and
saving game state to “disk”. I’m trying to tease out my VFS into
something
extensible; you can find my code here:
http://github.com/cstrahan/silverlightvfs

There’s not much there, but perhaps the PathUtil could be handy:
http://github.com/cstrahan/silverlightvfs/blob/master/src/SilverlightVFS/PathUtil.cs

The more I work on abstracting out the core of the VFS, the more I feel
like
it’s hard to make a “one-fits-all” sort of solution; the use cases can
vary
a lot. I almost think it would be better to publish some guidance and a
reference implementation, rather than try to create some architecture
that
is either too abstract or, conversely, not extensible enough to be
useful…

Let me know where you go with your project - it sounds cool.

Cheers,
-Charles

Hi Charles,

And thanks for the comment about my blog - really appreciate it!

I had a look at your blog post for a custom virtual file system - and I
do
think that is the best long-term approach. This would enable a nice “in
browser” coding experience where you can add files, reference other
files
etc. all client side running in the browser.

If you look at the code in the
http://github.com/ironruby/ironruby/blob/master/Hosts/Silverlight/Microsoft.Scripting.Silverlight/BrowserVirtualFilesystem.csfile,
there is a class called IsolatedStorageVirtualFilesystem that extends
the BrowserVirtualFileSystem. The class overrides the GetFileInternal
method, throwing an not implemented exception, and have a TODO comment.
So I
guess this would be a good starting point.

Alternatively you could extend the HttpVirtualFilesystem, which is the
file
system used by the standard Browser PAL. The HttpVirtualFileSystem will
use
the XapVirtualFileSystem to check if a file exists in the XAP, if not it
will try to download it. My suggestion would be to add an extra check -
if
it doesn’t exist on the server, then check Isolated Storage.

You would probably also have to extend BrowserScriptHost class and
BrowserPAL, which currently expose the BrowserVirtualFileSystem, and
instead
use the IsolatedStorageVirtualFileSystem, as well as changing the
OpenInputFileStream method, which throws an exception if any other file
mode
than Open or Read is passed in. This is the exception that bites you if
you
dry to use Ruby file APIs to write a file in a standard DLR app today.

It would be nice if someone who worked on the Silverlight hosting
environment for IronRuby could chip in with suggestions on how to best
implement write support in the virtual file system. I would be more than
happy trying to implement this and submit a patch.

As for your blog post on enumerating resources that looks handy - as
file
enumeration is also something that would be useful (when the app loads
it
would be nice to check which files have been stored in isolated storage,
and
that way enabling devs to save their work in isolated storage between
sessions).

I had a look at your SilverlightVFS code - but I guess the thing I don’t
quite get is the proper way to “blog” a new file system into the
Silverlight
PAL.

  • Jonas

On Fri, Jul 23, 2010 at 12:16 AM, Charles S. <

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