meson: Make tests and examples optional

[ryonakano]

This allows building apps a little faster for developers who just want to include live-chart as a submodule of their app.

[eli-schwartz]

I would suggest instead marking the testsuite-only program with build_by_default: false.

[ryonakano]

@eli-schwartz Could you tell me how to make the test optional using build_by_default: false? This branch now always compiles the test:

user@elementary-8:~/work/live-chart$ meson setup builddir --prefix=/usr
The Meson build system
Version: 1.3.2
Source dir: /home/user/work/live-chart
Build dir: /home/user/work/live-chart/builddir
Build type: native build
Project name: live-chart
Project version: 1.10.0
C compiler for the host machine: cc (gcc 13.3.0 "cc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0")
C linker for the host machine: cc ld.bfd 2.42
Vala compiler for the host machine: valac (valac 0.56.17)
Host machine cpu family: x86_64
Host machine cpu: x86_64
Library m found: YES
Found pkg-config: YES (/usr/bin/pkg-config) 1.8.1
Run-time dependency gtk4 found: YES 4.14.2
Run-time dependency gee-0.8 found: YES 0.20.6
Build targets in project: 12

live-chart 1.10.0

  User defined options
    prefix: /usr

Found ninja-1.11.1 at /usr/bin/ninja
user@elementary-8:~/work/live-chart$ meson compile -C builddir/
INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /usr/bin/ninja -C /home/user/work/live-chart/builddir
ninja: Entering directory `/home/user/work/live-chart/builddir'
[118/118] Linking target tests/livechart-test
user@elementary-8:~/work/live-chart$ ls -la builddir/tests               
total 600
drwxrwxr-x 3 user user   4096  1月 22 12:22 .
drwxrwxr-x 9 user user   4096  1月 22 12:22 ..
-rwxrwxr-x 1 user user 599848  1月 22 12:22 livechart-test
drwxrwxr-x 3 user user   4096  1月 22 12:22 livechart-test.p
user@elementary-8:~/work/live-chart$ 

[eli-schwartz]

Ah sorry I should probably clarify this is based on https://mesonbuild.com/Release-notes-for-1-7-0.html#test-targets-no-longer-built-by-default

It is technically semantically correct for build_by_default to behave the way I suggested (and is implemented in the release notes), but meson has been buggy for a while and built them anyway. I recently got around to fixing that, and the current release candidate for meson 1.7.0rc2 will avoid compiling the test.

I am not sure it makes sense to introduce a new option that, effectively, only matters for people using something other than the latest version of meson (which will be the case within a week or two once the final release is out) and additionally is only a speed improvement. Better to be forward-looking here.

[ryonakano]

Ah, is it only meson >= 1.7.0rc2 that making tests optional using build_by_default: false works as expected, right? I think we should prefer the previous way (providing a new option) than this way then at least for now, because live-chart is a library, not an app, so we shouldn't force people who want use it to use really newer versions of dependencies and compilers.

[lcallarec]

LGTM

@ryonakano : there is still an open conversation. Tell me if I can merge your PR.