BLD: migrate to the mesonpy build backend

.gitattributes

@@ -0,0 +1,6 @@
+# exclude files that shouldn't be included in source distributions
+.* export-ignore
+tests/pytest_mpl_baseline/** export-ignore
+_typos.toml export-ignore
+uv.lock export-ignore
+src/gpgi/_lib.py export-ignore

.github/workflows/cd.yml

@@ -5,8 +5,7 @@ on:
   pull_request:
     paths:
     - pyproject.toml
-    - setup.py
-    - MANIFEST.in
+    - meson.*
     - .github/workflows/cd.yml
   workflow_dispatch:
 
@@ -46,7 +45,9 @@ jobs:
       uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - uses: astral-sh/setup-uv@4db96194c378173c656ce18a155ffc14a9fc4355 # v5.2.2
     - name: Build sdist
-      run: uv build --sdist
+      run: |
+        uv sync --only-dev
+        uv build --sdist
     - name: Upload sdist
       uses: actions/upload-artifact@65c4c4a1ddee5b72f698fdd19549f0f0fb45cf08 # v4.6.0
       with:

.github/workflows/ci.yml

@@ -24,7 +24,6 @@ jobs:
     - uses: astral-sh/setup-uv@4db96194c378173c656ce18a155ffc14a9fc4355 # v5.2.2
     - name: Check build
       run: |
-        uvx check-manifest
         uv sync --only-dev
         uv build
 
@@ -61,12 +60,14 @@ jobs:
       with:
         python-version: ${{ matrix.python-version }}
 
-    # TODO: add --no-editable
-    - run: |
-        uv sync --only-dev
-        uv sync --group covcheck
-      env:
-        GPGI_PY_LIB: ${{ matrix.marker == 'PY_LIB' }}
+    - run: uv sync --group covcheck --no-install-project
+    - if: ${{ matrix.marker != 'PY_LIB' }}
+      # using editable mode for simplicity regarding coverage analysis
+      run: uv pip install --editable . --no-deps
+    - if: ${{ matrix.marker == 'PY_LIB' }}
+      # disabling caching here to avoid shadowing the pure Python module
+      # with a remnant .so from a previous run
+      run: uv pip install --editable . --no-deps -Csetup-args='-Dpylib=true' --no-cache
     - name: Test
       run: uv run --no-sync coverage run --parallel-mode -m pytest --color=yes
 
@@ -253,6 +254,10 @@ jobs:
         echo "PYTHON_GIL=0" >> $GITHUB_ENV
         echo
     - name: Build
+      # ninja is a system level requirement to meson-python
+      # it is automatically obtained from PyPI if lacking at the system level
+      # when building a package in isolation, which is why it's not listed
+      # under our build-system requirements.
       run: |
         uv venv
         uv lock --upgrade --prerelease=allow --no-build

meson.build

@@ -0,0 +1,77 @@
+project('gpgi', 'c', 'cython', meson_version: '>=1.5.0')
+
+# detect missing dependencies early
+py = import('python').find_installation(pure: false)
+cy = meson.get_compiler('cython')
+cython = find_program(cy.cmd_array()[0])
+
+numpy_compile_flags = [
+  # keep in sync with pyproject.toml
+  '-DNPY_TARGET_VERSION=NPY_1_25_API_VERSION',
+  '-DNPY_NO_DEPRECATED_API=NPY_1_25_API_VERSION',
+]
+
+# copied from PyWavelets
+# https://github.com/PyWavelets/pywt/blob/becef5486174c77727ea2a60e6392744b2cc1d4a/pywt/_extensions/meson.build#L13
+# When building against numpy 1.x is dropped, this can be simplified: the else branch
+# becomes unreachable, so `required: false` can be omitted.
+
+_numpy_dep = dependency('numpy', required: false)
+if _numpy_dep.found()
+  np_dep = declare_dependency(dependencies: _numpy_dep, compile_args: numpy_compile_flags)
+else
+  # For cross-compilation it is often not possible to run the Python interpreter
+  # in order to retrieve numpy's include directory. It can be specified in the
+  # cross file instead:
+  #   [properties]
+  #   numpy-include-dir = /abspath/to/host-pythons/site-packages/numpy/core/include
+  #
+  # This uses the path as is, and avoids running the interpreter.
+  incdir_numpy = meson.get_external_property('numpy-include-dir', 'not-given')
+  if incdir_numpy == 'not-given'
+    incdir_numpy = run_command(py,
+      [
+        '-c',
+        '''import os
+import numpy as np
+try:
+  incdir = os.path.relpath(np.get_include())
+except Exception:
+  incdir = np.get_include()
+print(incdir)
+    '''
+      ],
+      check: true
+    ).stdout().strip()
+  endif
+  inc_np = include_directories(incdir_numpy)
+  np_dep = declare_dependency(include_directories: inc_np, compile_args: numpy_compile_flags)
+endif
+
+if get_option('pylib')
+  py.install_sources('src/gpgi/_lib.py', subdir: 'gpgi')
+else
+  py.extension_module(
+      '_lib',
+      'src/gpgi/_lib.pyx',
+      subdir: 'gpgi',
+      install: true,
+      dependencies : [np_dep],
+      c_args: numpy_compile_flags,
+  )
+endif
+
+# meson doesn't have an equivalent to setuptools.packages.find
+# at the time of writing, so, listing every module explicitly here
+py.install_sources(
+    'src/gpgi/__init__.py',
+    'src/gpgi/_boundaries.py',
+    'src/gpgi/_data_types.py',
+    'src/gpgi/_lib.pyi',
+    'src/gpgi/_load.py',
+    'src/gpgi/_spatial_data.py',
+    'src/gpgi/_typing.py',
+    'src/gpgi/py.typed',
+    'src/gpgi/typing.py',
+    subdir: 'gpgi'
+)

meson.options

@@ -0,0 +1,6 @@
+option(
+    'pylib',
+    type : 'boolean',
+    value : false,
+    description : 'build as a pure Python library',
+)

pyproject.toml

@@ -1,11 +1,11 @@
 [build-system]
 # keep in sync with dependency-groups
 requires = [
-    "setuptools>=61.2",
+    "meson-python>=0.17.1",
     "Cython>=3.0",
     "numpy>=1.25.0",
 ]
-build-backend = "setuptools.build_meta"
+build-backend = "mesonpy"
 
 [project]
 name = "gpgi"
@@ -22,8 +22,8 @@ classifiers = [
 ]
 requires-python = ">=3.11"
 dependencies = [
-    # keep in sync with NPY_TARGET_VERSION (setup.py)
     # keep in sync with build-time requirements (dev group)
+    # keep in sync with NPY_TARGET_VERSION (meson.build)
     "numpy>=1.25, <3",
 ]
 
@@ -67,25 +67,21 @@ typecheck = [
 # This could be simplified/reunifed depending on what happens on the following
 # upstream issue
 # https://github.com/astral-sh/uv/issues/7052
+#
+# ninja is a system level requirement to meson-python
+# it is automatically obtained from PyPI if lacking at the system level
+# when building a package in isolation, which is why it's not listed
+# under build-system requires.
 dev = [
-    "setuptools>=61.2",
+    "meson-python>=0.17.1",
+    "ninja>=1.11.1.3",
     "Cython>=3.0.12",
     "numpy>=1.25.0, <3", # keep in sync with runtime requirement
 ]
 
 [tool.uv]
 no-build-isolation-package = ["gpgi"]
 
-[tool.setuptools]
-license-files = [
-    "LICENSE",
-]
-include-package-data = false
-
-[tool.setuptools.packages.find]
-where = ["src"]
-namespaces = false
-
 [tool.coverage.run]
 source = [
     "src/gpgi",
@@ -138,7 +134,6 @@ convention = "numpy"
 
 [tool.ruff.lint.per-file-ignores]
 "tests/**" = ["D"]
-"setup.py" = ["D"]
 "_backports.py" = ["D"]
 
 [tool.mypy]