Template processor forces a newline at the end of the output

[Eleanor Berger]

The template processor inserts a newline \n character at the end of the output even if it's not there. In some cases, it is important that no such new line appears, but this result is currently impossible to achieve.

http://mail.zope.org/pipermail/zpt/2004-July/005386.html

[Matthew Paul Thomas (mpt)]

For example, in mpt/launchpad/2008-05-translation, see <http://translations.launchpad.dev/evolution/trunk/+pots/evolution-2.2/es/+translate>. There should be only a 1px white line between the segments, not the current space caused by a line break.

[Steve Alexander (stevea)]

The fix in Zope is needed in lib/zope/tal/talinterpreter.py, in __call__. These lines should be removed:

if self.col > 0:
    self._stream_write("\n")
    self.col = 0

The full discussion in the mailing list spans two months.

  http://mail.zope.org/pipermail/zpt/2004-June/005372.html
  http://mail.zope.org/pipermail/zpt/2004-June/005373.html
  http://mail.zope.org/pipermail/zpt/2004-July/005386.html

The code in question hasn't been touched in many months.

  http://svn.zope.org/zope.tal/trunk/src/zope/tal/talinterpreter.py?rev=75193&view=markup

[Fred Drake (fdrake)]

The catch, of course, is that we can't know if there's anyone that
relies on it for other reasons. I'd be happy to rip it out otherwise.

Removing that code causes many tests to break, and all the breakage
appears incidental rather than fundamental.

Would people be happy with the current behavior as a default, and a
way to set an attribute of the TALInterpreter instance to use the
cleaner behavior? An attribute on the page template object could then
be used to record the application's requirements.

[Steve Alexander (stevea)]

Fred, I don't think we need to tread so carefully. If we change this behaviour in a major release, and document the change in the release notes, I think that's enough. It's far easier to insert a newline into templates manually than to remove one that the libraries brokenly stick in.

Zope already suffers too much from excessive complexity to support backwards compatibility that almost no one uses.

This change is in line with the published TAL spec. I think the current behaviour is counter-intuitive and arguably taking a great liberty with the TAL spec, in introducing extra characters.

I very much support updating the tests to not have extra new-lines and updating the code, and documenting the change in the change notes, and releasing this.

[Christian Reis (kiko)]

Fred, c'mon, if not just for Launchpad, let's do it for the kittens. <wink>

[Fred Drake (fdrake)]

Fixed in subversion revision 87220.

Tested with Python 2.4.4, 2.5.2.

Released in zope.tal 3.5.0 (http://pypi.python.org/pypi/zope.tal/3.5.0/).