How do include cython files in python meson-managed project?

Cython as a first class language is still in progress (I'm the author of that work), right now the right way is with a generator or custom target, then compile an extension module:

pyx_c = custom_target(
  'cython_file.c',
  output : 'cython_file.c',
  input : 'cython_file.pyx',
  command : [cython, '@INPUT@', '-o', '@OUTPUT@'],
)

import('python').find_installation().extension_module(
  'my_extension_module'
  pyx_c,
  install : true
)

Here's an example from the meson test suite, which is pretty close to my example above.

EDIT: cython as a first class language has landed. So if you can rely on Meson 0.59.0, you can just do:

import('python').find_installation().extension_module(
  'my_extension_module'
  'cython_file.pyx',
  install : true
)

The simplest way I found (completely code-side) was to add them like any other source file and when you need to import them in a python file

just add

from pyximport import install
install(language_level=3)

before importing.

Best way is @dcbaker's though. I wrote an example pygobject cython application to show that here.