[build] Make building documentation configurable

[Artturin]

Also pulled in https://git.alpinelinux.org/aports/tree/testing/ngs/busybox-compat.patch

[Artturin]

There seems to be a random segfault issue going on in the tests
https://github.com/ngs-lang/ngs/actions/runs/9910596236/job/27381341997?pr=672#step:4:270 (darwin)
Previous CI run https://github.com/ngs-lang/ngs/actions/runs/9910403102/job/27380707730?pr=672 (arch)
I got it once locally(NixOS) but after rebuilding it worked.

[ilyash-b]

• See inline comment
• I'm thinking of 3 modes switch: build, don't build, build if pandoc is available (default). What do you think?

[ilyash-b]

More appropriate would be BUILD_MAN I think.

[Artturin]

* I'm thinking of 3 modes switch: build, don't build, build if `pandoc` is available (default). What do you think?

Build if available is not easy to do in cmake.

find_program(PANDOC pandoc)

Outside if (BUILD_MAN)

Stops the build with CMake Error at CMakeLists.txt:134 (message): Could not find pandoc if pandoc isn't found

In meson it would be as simple.

pandoc = find_program('pandoc', required : get_option('man'))
if pandoc.found()
   ...
endif

And having the man option as auto

[ilyash-b]

* I'm thinking of 3 modes switch: build, don't build, build if `pandoc` is available (default). What do you think?

Build if available is not easy to do in cmake.

find_program(PANDOC pandoc)

Outside if (BUILD_MAN)

This part I did not understand.

Stops the build with CMake Error at CMakeLists.txt:134 (message): Could not find pandoc if pandoc isn't found

Docs:

If the program is found the result is stored in the variable and the search will not be repeated unless the variable is cleared. If nothing is found, the result will be <VAR>-NOTFOUND.

Added find_program(PANDOC pandoc) in the middle of the file. No error. Please elaborate.

Edit: added find_program(PANDOC pandoc-not-found), not the above

[Artturin]

* I'm thinking of 3 modes switch: build, don't build, build if `pandoc` is available (default). What do you think?

Build if available is not easy to do in cmake.

find_program(PANDOC pandoc)

Outside if (BUILD_MAN)

This part I did not understand.

Stops the build with CMake Error at CMakeLists.txt:134 (message): Could not find pandoc if pandoc isn't found

Docs:

If the program is found the result is stored in the variable and the search will not be repeated unless the variable is cleared. If nothing is found, the result will be -NOTFOUND.

Added find_program(PANDOC pandoc) in the middle of the file. No error. Please elaborate.

Edit: added find_program(PANDOC pandoc-not-found), not the above

My bad, I forgot to remove the

if(NOT PANDOC)
	  message(FATAL_ERROR "Could not find pandoc")
endif()

The error message had the line of the error message in it put I overlooked it

PR Ready

[ilyash-b]

I'm thinking of 3 modes switch: build, don't build, build if pandoc is available (default).

I'm still for this design unless convinced otherwise. It should be possible to have control as follows (not solvable with single boolean flag):

• "I need the man pages to be built". Fails if there is no pandoc
• "I don't need the man pages to be built". Skips completely. Doesn't even check for pandoc presence.
• "I don't mind. Build the man pages if possible". If pandoc is not available, gives a message and moves on, doesn't fail. Builds the man pages if pandoc is there. This should be the default.

[Artturin]

I'm thinking of 3 modes switch: build, don't build, build if pandoc is available (default).

I'm still for this design unless convinced otherwise. It should be possible to have control as follows (not solvable with single boolean flag):

* "I need the man pages to be built". Fails if there is no `pandoc`

* "I don't need the man pages to be built". Skips completely. Doesn't even check for `pandoc` presence.

* "I don't mind. Build the man pages if possible". If `pandoc` is not available, gives a message and moves on, doesn't fail. Builds the man pages if `pandoc` is there. This should be the default.

Found the way to do it in https://cmake.org/pipermail/cmake/2016-October/064342.html

[ilyash-b]

Thanks!

[Artturin]

🚀

@jirutka The changes in your patch are now merged (in this PR and a few others) https://git.alpinelinux.org/aports/tree/testing/ngs/cmakelists.patch