[Pas2js] Pas2JS: compiler extension to validate XML/XSLT files

[Ondrej Pokorny]

Hello!

A short background:

I've learned how to use Pas2JS to write web client applications. I 
developed for it a simple but very powerful method:
1.) The server sends JSON objects as responses.
2.) The client converts these JSON objects to XML and uses XSLT 
templates to generate XHTML for the browser.

XSLT is for Pas2JS project something like LFM for the LCL project (DFM 
for VCL). But even more powerful because all the captions, texts and 
values get automatically replaced with XSLT. That allows me to fill 
pages, forms and tables with data with just 2 calls simple calls 
(JSON2XML+XSLT).

I add these XSLT files directly into the LPI project and add them to 
resources with:
{$R *.xslt}
{$R uFormContainerActions.xslt}
etc.

Now I have a lot of XSLT files in the project that I edit within Lazarus 
itself and it works well! (I don't need any external editor.)

This brings me to my problem:

I want to validate these XSLT files on compile - I want to write an 
extension for it.

What I want: when the XSLT is not valid (unclosed tag, invalid 
character, ... whatsoever), the compilation should be aborted and 
Lazarus should jump to the error position in XSLT.

Where should I start? I see 2 possible routes:

1.) Pas2JS compiler extension: hook into handling {$R *.xslt} and abort 
compilation with an error in case of invalid xslt file.
2.) Lazarus extension: create a package that hooks into the Compile 
command and checks all XSLT/XML files in the project before the project 
is compiled with Pas2JS.

I would prefer (1) because it the XSLT don't have to be registered in 
the LPI project.

Is it possible to extend the Pas2JS compiler with a DLL that hooks into 
the  {$R} handler? Or if not, is it possible to create some system to 
write own Pas2JS compiler extensions? Or do you have any other 
recommendations how to solve this?

Thanks
Ondrej