[Zope] default dtml attrs, exception handling

Tue, 23 Feb 1999 14:31:04 -0800

> Quinn Dunkan wrote:
> 
> > Is there a way to specify default dtml tag arguments?  I have a bit of dtml
> > that renders a database entry.  Currently I fill null values from python, b
> ut
> > I'd like to be able to specify them from dtml.  Unfortunately that seems to
> > mean putting a null= tag on every single #var, and changing them all when I
> > change one.  Is there a way you could put something like:
> > 
> > <!--#defaults -->
> >     <!--#var null="(not given)" -->
> > <!--#/defaults -->
> > 
> > at the top of your document to accomplish that?  Or is there some other way
> > I'm missing?
> 
> There are a couple ways. If you are using DTML from Python, you can
> specify a defaults in the DocumentTemplate constructor as keyword
> arguments.
> 
> t=DocumentTemplate.HTML("""<!--#var foo-->""",foo="bar")
> 
> I believe that this is in the DTML User's Guide. If it isn't, it should
> be.
> 
> Using the Zope framework, probably the easiest thing to do is to set
> default values as properties on Folders or Documents.

Oops, either my question wasn't clear, or I'm not understanding your answer.
I do know about setting #var tags via keyword arguments, that's the Main DTML
Thing.  What I meant was default tag _attributes_.  So where I currently would
have to type:

<!--#var entry1 null="(not given)" -->
<!--#var entry2 null="(not given)" -->
<!--#var entry3 null="(dead parrot)" -->
...

I could type:
<!--#defaults -->
    <!--#var null="(not given)" -->
<!--#/defaults -->

<!--#var entry1  -->
<!--#var entry2  -->
<!--#var entry3 null="(dead parrot)" -->
...

And have it come out the same.
Actually, current null behaviour is hard for
me to use, since the %s format will print anything successfully, and most of
my entries are strings (I don't suppose there's a version of %s which doesn't
automatically try to str() or repr() its argument?).  Unless there is a
workaround, it seems it would be usefull to have a none= attribute so that:

<!--#var entry none="(not given)" -->

is shorthand for:

<!--#if "entry is None" -->
    <!--#var entry -->
<!--#/if -->

At least for me, this would be a more intuitive tag than null.  I'll take a
look at Zope Hacks to see if it includes adding tag attributes...

> > A suggestion for exception handling:
> > Currently, it appears that exceptions are caught and handled by a Response
> > object.  It has hard-coded responses to exceptions, but you can make your o
> wn
> > error pages by making your own exception with a __str__ method that returns
> > text that contains "<html>".  As far as I can tell, though, there is no way
>  to
> > replace the generic exception handler (so that if os.stat throws os.error (
> or
> > OSError, they changed it in 1.5.2b1 (stop it, guys!)) you get something of
> > your choosing rather than "Sorry, an error occurred."  Also, there is no wa
> y
> > to decide per-exception how to handle tracebacks.  Even if you just want to
> > raise a "invalid search string" FormError exception, you still spew a
> > meaningless traceback at the user.  It can be hidden if you unset Z_DEBUG_M
> ODE
> > or __bobo_hide_tracebacks__ = 1, but then what if you want "real" errors to
> > spew a traceback?
> > 
> > Currently, I do stuff like:
> > 
> > error_doc = HTMLFile('error.dtml')
> > 
> > class BoboError(Exception):
> >     title = "Generic Error"
> >     def __init__(self, msg):
> >         self.msg = msg
> >     def __str__(self):
> >         return error_doc(self)
> > 
> > and then subclass BoboError.  Unfortunately, I can't figure out how to hide
> > tracebacks...
> > 

Another thing for which there isn't much documentation in Trinkets or
Technical Intro is authentication (Bobo-style).  Sticking a

__allow_groups__ = {
    'group' : {'user' : 'password' },
}
__roles__ = ['group']

in the module top level and doing the usual RewriteRule apache chicanery seems
to work.  However, what I can't find is some way to specify the 'permission
denied' page.  Once again, "You are not authorized..." seems to be hard-coded
in ZPublisher.  Is there any way to customize this per-object?

No one has written in support or contradiction of these ideas, so I don't know
if I'm just missing the Right Way to do these things, or everyone is just
busy.  Should I submit them to the Collector?  Would patches be accepted?  I
hesitate to go and hack DC's code when I'm not fully Zenful, but then I'd like
to put some code where my mouth is, and these things would be useful to me
too.  And then, I'm using ZP/ZT without the Zope Framework, which perhaps
brings up different issues than a "pure Zope" site.

> > I also have two questions re dtml: From my reading of
> > DT_String.FileMixin.read_raw, the source file is reread every time the dtml
>  is
> > cook()ed, which is only the first time it is __called__.  There is some
> > mucking around with a __changed__ method, which I assume is an unimplemente
> d
> > attempt to not reread the file if its mtime is the same as before.
> 
> __changed__ is part of the BoboPOS persistence machinery.
> 
> >  Is
> > __changed__ supposed to del self.cooked?  What's going on here?
> > Rereading dtmls is desirable so I don't have to restart pcgis just because 
> the
> > dtml changed...
> 
> I'm not up on the latest details, but Jim tells me that if
> ZOPE_DEBUG_MODE is set, then Documents should re-read their source
> files... But I don't think this answers your question.

Hmm, not in my version (1.9.0):

% grep ZOPE_DEBUG_MODE ~zope/lib/python/DocumentTemplate/*.py
1%

I assume it's in 1.10.  But why not have DTs reload all the time, if their
mtimes have changed?  The only overhead I can see would be one extra stat()
syscall per request, which is not so bad.  Actually, there's a good reason to
not have them reload: you can edit a bunch of dtmls restart the script to have
them all update at once.  So maybe a flag to File/HTMLFile?  Or a
__dtml_reload__ setting?  Once again, should I submit these things to
Collector?  Should I submit some sort of patch?

> > The second question:
> > I've seen references to the ability to create your own dtml tags, but no
> > mention in the DTML docs on how to do that.  Is this possible?
> 
> Yes, but its not currently documented. Andrew K. made a stab at
> documentation on his starship Zope Hacks page.
> 
> > If so, where
> > can I read about it?  I'd actually like to create my own html tags, so I
> > can use DT as a generic html/whatever generator, at least until I can do
> > it in XML.  Does this seem reasonable?
> 
> Yes, DTML can generate any kind of text you want. In fact, there is no
> need to hack DTML to allow you to do this.

Oops... I was referring to DTML's _input_ text.  I know I can generate
anything with  or %(.*?). tags, but I was wondering about whole
new html tags.  So I could say:

<film>
    <title> Planet of the Evil Monster Marsh Mutant </title>
    <synopsis> The evil monster marsh mutant kills everyone. </synopsis>
</film>

Like I can say:

\film{Planet of the Evil Monster Marsh Mutant}{
    The evil monster marsh mutant kills everyone.
}

in LaTeX.  I know some people have done work with plugging python's xml
parsers into zope, maybe I'll take a look at that.  Thanks for the pointer to
Zope Hacks, though.

DateTime + Y2K:

DateTime chokes on dates with a year < 32.  Python's decision here is:
00-68 = 2000-2068, 68-99 = 1968-1999, which is the posix recommendation.  But
in any case, perhaps it could raise an AmbiguousYear exception or something,
or allow the user to configure where the "split" occures.  Ideally we just
require four-digit years, of course, but sometimes we're parsing files whose
format we have no control over :)

this is long enough, I'll save the rest for later :)

thanks!