Add striptags filter

[antogyn]

I migrated from swig to nunjucks and realized there was no striptags filter. There is already an opened issue : #359

One of the tests is very similar to this one (from jinja)

[carljm]

Looks like the build is failing. I'd be happy to merge this with a green build.

[antogyn]

The build is also failing on master (of this repo) with the same messages on my local machine with node 0.10 and 0.11. I don't think it comes from this PR

[antogyn]

There seems to be a problem with the last version of jshint. Using jshint 2.8.x fixes the problem on both versions. Should I make a second PR to fix this ?

[carljm]

Just pushed a fix to master to pin jshint to 2.8.x. Rebase on that and see if we get a green build.

[antogyn]

Done.

[ivan-kleshnin]

Not a very good implementation because it strips whitespace.
You often need to pipe striptags, nl2br, safe. For example when you're rendering email template from feedback form. You want to remove tags keeping original linebreaks.

{{ text | striptags | nl2br | safe }}

But nl2br is useless here because striptags just erases all whitespace.

.replace(/\s+/gi, ' ')

It would be better to squash every group of multiple spaces to single space and every group of multiple caret feeds to single one separately. Something like:

.replace(/ +/g, ' ').replace(/(\r\n?)+/g, '\n').replace(/\n+/g, '\n')

[carljm]

Can you file a pull request?

[ivan-kleshnin]

Yes, I'll give it a second look and make a PR.

[carljm]

Thank you!

[antogyn]

Keep in mind that what you propose is different from jinja's implementation and won't pass the same test jinja has.

[ivan-kleshnin]

Yes, I'll update tests accordingly.

[carljm]

Hmmm. Thanks for pointing that out, @antogyn. I think I prefer to maintain Jinja2 compatibility here by default, but I'm not opposed to adding this as an optional behavior controlled by a flag, e.g. preserve_whitespace=true (defaulting to false).

[ivan-kleshnin]

Yes, I was going to put it under non-default flag. Will try to send PR tomorrow.

[ivan-kleshnin]

Sorry for delay. A tons of work activity.
Recently sent this: #619
I named it preserve_linebreaks because it rather normalizes whitespace (and linebreaks...).