The meson build switched to generating the file grammars and using meson
to build the manpages/ARM. This is because meson doesn't work well when
writing files outside the build directory.
However, this has been suboptimal when someone only wants to build the
documentation (like RTD). Sphinx can now be used outside meson like it
was with autoconf.
Grammars are now updated by the developer with CI checking if one is
needed or not, like clang-format.
Meson is a modern build system that has seen a rise in adoption and some
version of it is available in almost every platform supported.
Compared to automake, meson has the following advantages:
* Meson provides a significant boost to the build and configuration time
by better exploiting parallelism.
* Meson is subjectively considered to be better in readability.
These merits alone justify experimenting with meson as a way of
improving development time and ergonomics. However, there are some
compromises to ensure the transition goes relatively smooth:
* The system tests currently rely on various files within the source
directory. Changing this requirement is a non-trivial task that can't
be currently justified. Currently the last compiled build directory
writes into the source tree which is in turn used by pytest.
* The minimum version supported has been fixed at 0.61. Increasing this
value will require choosing a baseline of distributions that can
package with meson. On the contrary, there will likely be an attempt
to decrease this value to ensure almost universal support for building
BIND 9 with meson.
It turns out the tree of dictionaries is not the best structure to
represent our grammar, unfortunatelly. The problem is that "zone" has
several context-dependent variants which change meaning of "zone" based
on inner field "type".
Redesigning the whole structure does not seem to be worth, so I settled
on this terrible hack.
