Migrate from setuptools to meson-python build backend

.github/workflows/main.yml

@@ -118,7 +118,7 @@ jobs:
         needs: [dist]
 
 env:
-    # Ubuntu packages to install so that the project's "setup.py sdist" can succeed
+    # Ubuntu packages to install so that building the sdist can succeed
     DIST_PREREQ: libpari-dev pari-doc libbz2-dev bzip2
     # Name of this project in the Sage distribution
     SPKG:        cypari

README.rst

@@ -42,14 +42,10 @@ From source with pip
 
 Requirements:
 
-- PARI/GP >= 2.9.4 (header files and library); see
+  PARI/GP >= 2.9.4 (header files and library); see
   https://doc.sagemath.org/html/en/reference/spkg/pari#spkg-pari
   for availability in distributions (GNU/Linux, conda-forge, Homebrew, FreeBSD),
   or install from source.
-- Python >= 3.9
-- pip
-- `cysignals <https://pypi.python.org/pypi/cysignals/>`_ >= 1.11.3
-- Cython >= 3.0
 
 Install cypari2 via the Python Package Index (PyPI) via
 
@@ -139,10 +135,22 @@ same computations be done via
 The complete documentation of cypari2 is available at http://cypari2.readthedocs.io and
 the PARI/GP documentation at http://pari.math.u-bordeaux.fr/doc.html
 
-Contributing
-------------
+Contributing & Development
+--------------------------
 
 CyPari 2 is maintained by the SageMath community.
 
 Open issues or submit pull requests at https://github.com/sagemath/cypari2
 and join https://groups.google.com/group/sage-devel to discuss.
+
+To get started with development, you can set up an environment using Conda 
+as follows:
+
+::
+    $ conda create -n cypari2-dev python cython pari=*=*_pthread ninja meson-python cysignals c-compiler
+    $ conda activate cypari2-dev
+
+Afterwards, you can build and install the package in editable mode: 
+
+::
+    $ pip install -e . --no-build-isolation

cypari2/gen.pyx

@@ -1789,9 +1789,9 @@ cdef class Gen(Gen_base):
         while sp[0] == c'0':
             sp = sp + 1
         sp -= 1
-        sp[0] = 'x'
+        sp[0] = c'x'
         sp -= 1
-        sp[0] = '0'
+        sp[0] = c'0'
         if signe(x) < 0:
             sp -= 1
             sp[0] = c'-'

cypari2/meson.build

@@ -0,0 +1,44 @@
+py.install_sources(
+  '__init__.py',
+  'closure.pxd',
+  'convert.pxd',
+  'gen.pxd',
+  'handle_error.pxd',
+  'pari_instance.pxd',
+  'paridecl.pxd',
+  'paripriv.pxd',
+  'pycore_long.pxd',
+  'stack.pxd',
+  'string_utils.pxd',
+  'types.pxd',
+  'cypari.h',
+  'pycore_long.h',
+  'auto_paridecl.pxd',
+  'auto_gen.pxi',
+  'auto_instance.pxi',
+  subdir: 'cypari2'
+)
+
+
+extension_data = {
+  'closure': files('closure.pyx'),
+  'stack': files('stack.pyx'),
+  'custom_block': files('custom_block.pyx'),
+  'convert': files('convert.pyx'),
+  'string_utils': files('string_utils.pyx'),
+  'handle_error': files('handle_error.pyx'),
+  'gen': files('gen.pyx'),
+  'pari_instance': files('pari_instance.pyx')
+}
+
+foreach name, pyx : extension_data
+  py.extension_module(
+    name,
+    sources: pyx,
+    subdir: 'cypari2',
+    install: true,
+    #include_directories: [inc_dirs, 'cypari2'],
+    dependencies: [cysignals, pari],
+  )
+endforeach
+

meson.build

@@ -0,0 +1,53 @@
+project('cypari2', 
+  ['c', 'cython'],
+  version: files('VERSION'),
+  license: 'GPL v3',
+  default_options: ['c_std=c17', 'cpp_std=c++17', 'python.install_env=auto'],
+  meson_version: '>=1.2',
+)
+
+# Python module
+# https://mesonbuild.com/Python-module.html
+py = import('python').find_installation(pure: false)
+
+# Compilers
+cc = meson.get_compiler('c')
+cython = meson.get_compiler('cython')
+# Workaround as described in https://cython.readthedocs.io/en/latest/src/userguide/special_methods.html#arithmetic-methods
+add_project_arguments('-X c_api_binop_methods=True', language: 'cython')
+
+# Dependencies  
+inc_cysignals = run_command(
+  py,
+  [
+    '-c',
+    '''
+from os.path import relpath
+import cysignals
+path = cysignals.__file__.replace('__init__.py', '')
+try:
+  print(relpath(path))
+except Exception:
+  print(path)
+    '''.strip(),
+  ],
+  check: true,
+).stdout().strip()
+cysignals = declare_dependency(include_directories: inc_cysignals)
+# Cannot be found via pkg-config
+pari = cc.find_library('pari', required: true)
+
+# Run code generation step
+code_gen_result = run_command(
+  py.full_path(), '-c',
+  '''
+import sys
+sys.path.insert(0, ".")
+from autogen import rebuild
+rebuild(force=True)
+print("Code generation successful")
+  ''',
+  check: true
+)
+
+subdir('cypari2')

pyproject.toml

@@ -1,36 +1,22 @@
 [build-system]
-requires = [
-    "setuptools",
-    "Cython>=3.0",
-    "cysignals>=1.11.3",
-]
-# We need access to the autogen package at build time.
-# Hence we declare a custom build backend.
-build-backend = "_custom_build_meta"  # just re-exports setuptools.build_meta definitions
-backend-path = ["."]
+requires = ["meson-python>=0.15.0", "cython>=3.0", "cysignals>=1.11.3"]
+build-backend = "mesonpy"
 
 [project]
 name = "cypari2"
 description = "A Python interface to the number theory library PARI/GP"
 authors = [
-    {name = "Luca De Feo, Vincent Delecroix, Jeroen Demeyer, Vincent Klein"},
+    { name = "Luca De Feo, Vincent Delecroix, Jeroen Demeyer, Vincent Klein" },
 ]
 maintainers = [
-    {name = "SageMath developers", email = "[email protected]"},
-]
-dependencies = [
-    "cysignals>=1.11.3",
+    { name = "SageMath developers", email = "[email protected]" },
 ]
+dependencies = ["cysignals>=1.11.3"]
 requires-python = ">=3.9"
 readme = "README.rst"
-license = {text = "GNU General Public License, version 2 or later"}
+license = { text = "GNU General Public License, version 2 or later" }
 keywords = ["PARI/GP number theory"]
-dynamic = [
-    "version",
-]
+dynamic = ["version"]
 
 [project.urls]
 Homepage = "https://github.com/sagemath/cypari2"
-
-[tool.setuptools.dynamic]
-version = {file = "VERSION"}