Re: nested @ignore does not work

[Gavin Smith]

On Wed, Dec 28, 2022 at 03:16:16PM +0100, Patrice Dumas wrote:
> On Tue, Dec 27, 2022 at 12:56:50PM +0100, Patrice Dumas wrote:
> > On Sat, Dec 03, 2022 at 01:41:44AM +0000, Gavin Smith wrote:
> > > Not a big deal but I noticed that nested @ignore does not work with
> > > texi2any, although it does work with texinfo.tex.  For example:
> > 
> > Indeed, @ignore are implemented like @verbatim.  However, @macro which
> > is in the same block commands category can nest.
> > 
> > > I don't have a strong preference as to whether nested @ignore should
> > > work or not but it should be consistent between the two processors.
> > > I think we should take whichever is the easiest to implement.
> > 
> > I'll change texi2any.
> 
> I have done it, but I am not so happy with the result.  Indeed, nested
> @ignore now appears in the tree, but the tree is quite complicated for a
> case of an ignored block.  Maybe it would be better not to have an
> explicit element in the tree, but keep count of the opened @ignore
> blocks.

That sounds right.

> It is also not clear to me whether this is right to have nesting by type
> of block command.  I am not sure that Texinfo TeX does it like that too.
> Indeed, @if* nest together, @ignore nest with @ignore and @r?macro nest
> together.  My guess is that in Texinfo TeX all should nest together.

Each type of ignored block (e.g. @ignore, @ifhtml) can nest through the
\doignore macro in texinfo.tex, but only with other blocks of the same
type.  So when ignoring @ignore, @ignore nested in @ignore is taken
account of; likewise with ignoring @ifhtml.  If an @ifset or @ifclear
conditional fails, the ignoring keeps track of nested @ifset, respectively
@ifclear, blocks.

There is no explicit handling of handling other commands other than
the one currently being ignored.  I don't see that this is a problem.


> Maybe we should take one step back and think on what nesting we would
> want?
> 
> For example, if we want to have @ignore nesting to be able to ignore a
> long slice of code, it will fail if there is in it
> 
> @macro a
> @end ignore
> @end macro

If this is inside an @ignore block in texinfo.tex, I expect the
"@end ignore" line will terminate an @ignore block.  There is no
handling of other block commands (like @macro in this case).

Such a macro appears to be useless, as it cannot be expanded to terminate
an @ignore block.  If this macro @a{} is used following an @ignore line,
it will be skipped over when looking for the @end ignore line.

See also (texinfo)Conditional Nesting in the manual.


> @ifset notset
> @end ignore
> @end ifset


I can't see how this is a useful use case.  If someone has a pair

    @ifset notset
    @ignore
    @end ifset
    
    ...
    
    @ifset notset
    @end ignore
    @end ifset

then this may actualy work with the @ignore matching the @end ignore, but
the following should be used instead:

   @ifclear notset

   ...

   @end ifclear