Writing a template which displays only relevant parents

[Yuya Nishihara]

On Sun, 7 Feb 2016 16:38:06 +0100, Dr Rainer Woitok wrote:
> On Friday, 2016-02-05 23:04:14 +0900, you wrote:
> >   {ifeq(count(revset('%d:%d', p1rev, rev)), 2, '*', '{p1rev}:{p1node|short}')}
> 
> Thanks for pointing this out.   I missed these  two examples in "hg help
> template".  Works like a charm now :-) at least result-wise.  But effic-
> iency-wise?  Consider what we are doing here:  we first compute a revset
> (which might be huge)  and then  we count its members  (which might take
> some time,  because the  revset might be huge)  just to  finally compare
> this count to 2.

revset computation can be lazy, but in this case, it will create a list of
all matches. It might be slow.

> What about a template specific function "py(expr)" which returns the re-
> sult of an arbitrary Python expression?

I generally don't like an idea that allows code injection. It isn't a template
library to be embedded in a web application.

FWIW, it will be easy to write an extension that adds a thin wrapper for
eval(expr).

> > ...
> > You can insert whitespaces in non-string part.
> > 
> >   x = blah blah{
> >       func(x,
> >       y)}
> 
> Did you test this with a real template?

It worked for me:

[ui]
logtemplate = rev: {
              rev
              } node: {short(
              node)}\n

>  I'm on Mercurial 3.7-rc+epsilon
> and I didn't get this to work.  What did work, however, was
> 
>    x = 'blah blah{
>        func(x,
>        y)}'
> 
> that is, to quote the whole template.  But since template syntax requir-
> es quoted strings embedded in quoted strings  embedded in quoted strings
> embedded ...  and so on,  and since  there are only  two types of string
> quotes, this now requires still more backslashes :-(

{"{"{rev}"}"} is fully valid since Mercurial 3.5. It's handled just like a
shell command expansion or string interpolation of Ruby. But if a string is
escaped, e.g. \"...\", it is pre-parsed as a string. This hack exists for
backward compatibility as there were two conflicting syntax rules before 3.5.

> > >    - Is there a way to "call" a user defined template from within anoth-
> > >      er user defined template?
> > > ...
> > 
> > Not yet, but I'm thinking of it.
> 
> Is there already some time-line or version-line for this new feature?

No. Please watch the issue if you're interested in.

https://bz.mercurial-scm.org/show_bug.cgi?id=4842