m4 was nice in '85, but the syntax feels a bit dated. Since we use python for
meson, let's use a popular python templating engine to replace some m4 usage.
A little nicety is that typos are caught:
FAILED: sysusers.d/systemd-remote.conf
/usr/bin/meson --internal exe --capture sysusers.d/systemd-remote.conf -- /home/zbyszek/src/systemd/tools/meson-render-jinja2.py config.h ../sysusers.d/systemd-remote.conf.j2
Traceback (most recent call last):
File "/home/zbyszek/src/systemd/tools/meson-render-jinja2.py", line 28, in <module>
print(render(sys.argv[2], defines))
File "/home/zbyszek/src/systemd/tools/meson-render-jinja2.py", line 24, in render
return template.render(defines)
File "/usr/lib/python3.9/site-packages/jinja2/environment.py", line 1090, in render
self.environment.handle_exception()
File "/usr/lib/python3.9/site-packages/jinja2/environment.py", line 832, in handle_exception
reraise(*rewrite_traceback_stack(source=source))
File "/usr/lib/python3.9/site-packages/jinja2/_compat.py", line 28, in reraise
raise value.with_traceback(tb)
File "<template>", line 8, in top-level template code
jinja2.exceptions.UndefinedError: 'HAVE_MICROHTTP' is undefined
This checking mirrors what 349cc4a507 did for C defines.
