Preventing newlines in :preserve'd text from being escaped

[Twisol]

Hello,

So far I really love Haml, but I have an issue with it where it comes
to preformatted text.I have a fairly large amount of preformatted text
(generated on the fly by a Rails helper) that I'm trying to include
into my page. Using the :preserve filter, it /looks/ fine, but in the
source it's all on one line, word-wrapped to about thirty, and
completely indecipherable.

I discussed this briefly with Nex3 on IRC, but he had to run. While
writing this message, though, I did have an idea: would it be possible
to add another tag prefix, using either a _ (underscore) or a |
(pipe), to tell Haml that the tag's indentation (or at least its
content) should be reset? Nex3 had mentioned that Haml couldn't
determine when it was safe to perserve the literal newlines because it
automatically indents text, but if you used | to reset indentation, it
seems like it would be safer for Haml to do. If that was possible, I
think "%pre|<" would work perfectly for my purposes.

Otherwise, some advice would be very much appreciated! Thanks in
advance,
~Jonathan Castello

[Nathan Weizenbaum]

First of all, filters like :preserve aren't meant for handling dynamically-generated text; they're meant for handling literal, in-template text with maybe some dynamic stuff sprinkled in. If you're dynamically generating text, it's better to use the #preserve helper (or ~, which is a shortcut for same).

As for the source code aesthetics, as I mentioned on IRC, there's really no good way to tell when it's possible to not use newline entities. Declaring it in the template won't work, because it's *not* safe in that template - the template still needs to be included in the layout, which will re-indent it and cause the whitespace to go wrong. The only potential solution is to have some way of declaring "this template is never going to be included in another template", something that might be added in the future.

[Chris Eppstein]

Can't haml have some concept of a pre-formatted bit that gets set and then is sticky for the rest of the handling of that template? If the bit is set, haml layouts wouldn't re-indent those strings. This decision could be made dynamically and helpers could be made to help manage the formatting bit.

chris

(Implementation suggestion: haml can return an extended string object for tracking the state of preformatting)

[Nathan Weizenbaum]

Potentially, yes, but that would dramatically increase the cost of string concatenation, which is something we desperately want to avoid, since string concatenation happens a lot during the rendering of a Haml template.

[Twisol]

I've converted the offending preformatted partials back to ERb, since
this seems like a good place for it. Now my only issue is the
indentation, because the layout file is still Haml. If the | mark I
suggested was added, to reset indentation, it would make it easier to
include ERb partials like this, and my problem would be duly solved.

[Nathan Weizenbaum]

Converting the partials to ERB isn't going to help, since (as you noted) the issue comes from the Haml layout re-indenting the code. I don't see how a syntactic marker could help this, unless you want the entire partial to be un-indented. A better solution would be to make an unpreserve helper that you wrap your partial calls in in the layout that converts newline entities into actual newlines.

[Twisol]

That's exactly what I'd like to do: make the entire partial
unindented. I envision a | mark resetting the indentation level for
the tag it's used on; if there are nested tags, they would still be
indented, but relative to the reset level. When used with my ERb
partials, I'm basically saying that I'm taking indentation into my own
hands, which is precisely what I require for my preformatted text.

I'll look into writing an unpreserve helper, but I still like the
(perceived) elegance of my | suggestion. Thanks for your time.

[Twisol]

After attempting to write an 'unpreserve' helper (which merely gsub's
HTML-entity newlines into literal newlines), I'm still suffering the
exact same indentation issues. It seems like, currently, there's just
no way to stop indentation -and- preserve literal newlines. :perserve
does the former, and ~ the latter, but I can't for the life of me
produce both effects.

[Nathan Weizenbaum]

I guess you'd need unpreserve along with some way of not indenting the partial. Or you could simply run #unpreserve on the finished template once it's rendered. In any case, I don't want to add new syntax to Haml for what amounts to a relatively minor, purely aesthetic issue.

[Twisol]

Pardon my naiveté, but could you give me an example of how to go about
doing that? I've tried using my homemade unpreserve helper at many
points along the chain of partials, with no real success.

[Nathan Weizenbaum]

You'll need to get access to the final template text and unpreserve that. That'll take some monkeypatching of Rails to get right.