[twill] Need help with a run_on_page_load function

[Matthew Wilson]

I really like the require extension, but when I looked inside, I didn't
see an obvious way to extend it to allow me to run any arbritary code at
every page load.  

So I wrote this run_on_page_load function:

    def run_on_page_load(funcname):
        "Run the function named funcname on every page load."

        try:
            f = globals()[funcname]
        except KeyError:
            parent_frame = inspect.currentframe(1)
            f = parent_frame.f_locals[funcname]

        # Now make a new function that discards the args passed in.
        def g(*args, **kwargs):
            return f()
        g.func_name = funcname

        # Add g to the post load hooks as long as it ain't already in there.
        b = get_browser()
        if not [x for x in b._post_load_hooks if x.func_name == funcname]:
            b._post_load_hooks.append(g)

Here's a simple demonstration:

    def show_if_500():
        "Dump out the HTML for the page if it returns a 500."

        b = get_browser()
        if b.get_code() == 500:
            show()
            raise TwillAssertionError("Page %s returned a 500 status!" 
                                      % b.get_url())

    # This will execute show_if_500 on every page.
    run_on_page_load(show_if_500.func_name)

I pass in the name name of the function rather than the function itself
because when I run the twill shell, any argument that I give my
run_on_page_load function are just passed in as strings:

    $ twill-sh

     -= Welcome to twill! =-

    current page:  *empty page* 
    >> extend_with tweed
    Imported extension module 'tweed'.
    (at /home/matt/svn-checkouts/tweed/tweed/__init__.pyc)

    Description:

    Some twill-related nonsense.

    current page:  *empty page* 
    >> run_on_page_load show_if_500
    current page:  *empty page* 

I don't know anything about how the parsing part of twill works.  Is
there a better way to implement run_on_page_load?


Matt

-- 
Programming, economics, gardening, life in Cleveland.
http://blog.tplus1.com