Add function for reading and caching PEP 518 spec

colcon_core/python_project/spec.py

@@ -0,0 +1,49 @@
+# Copyright 2022 Open Source Robotics Foundation, Inc.
+# Licensed under the Apache License, Version 2.0
+
+try:
+ # Python 3.11+
+ from tomllib import load as toml_load
+except ImportError:
+ from tomli import load as toml_load
+
+
+SPEC_NAME = 'pyproject.toml'
+
+_DEFAULT_BUILD_SYSTEM = {
+ 'build-backend': 'setuptools.build_meta:__legacy__',
+ 'requires': ['setuptools >= 40.8.0', 'wheel'],
+}
+
+
+def load_spec(project_path):
+ """
+ Load build system specifications for a Python project.
+
+ :param project_path: Path to the root directory of the project
+ """
+ spec_file = project_path / SPEC_NAME
+ try:
+ with spec_file.open('rb') as f:
+ spec = toml_load(f)
+ except FileNotFoundError:
+ spec = {}
+
+ spec.setdefault('build-system', _DEFAULT_BUILD_SYSTEM)
+
+ return spec
+
+
+def load_and_cache_spec(desc):
+ """
+ Get the cached spec for a package descriptor.
+
+ If the spec has not been loaded yet, load and cache it.
+
+ :param desc: The package descriptor
+ """
+ spec = desc.metadata.get('python_project_spec')
+ if spec is None:
+ spec = load_spec(desc.path)
+ desc.metadata['python_project_spec'] = spec
+ return spec

debian/patches/setup.cfg.patch

@@ -19,5 +19,5 @@ Author: Dirk Thomas <web@dirk-thomas.net>
 + # pytest-repeat
 + # pytest-rerunfailures
  setuptools>=30.3.0
+ tomli>=1.0.0; python_version < "3.11"
  packages = find:
- zip_safe = false

setup.cfg

@@ -39,6 +39,7 @@ install_requires =
  pytest-repeat
  pytest-rerunfailures
  setuptools>=30.3.0
+ tomli>=1.0.0; python_version < "3.11"
 packages = find:
 zip_safe = false
 

stdeb.cfg

@@ -1,6 +1,6 @@
 [colcon-core]
 No-Python2:
-Depends3: python3-distlib, python3-empy (<4), python3-packaging, python3-pytest, python3-setuptools, python3 (>= 3.8) | python3-importlib-metadata
+Depends3: python3-distlib, python3-empy (<4), python3-packaging, python3-pytest, python3-setuptools, python3 (>= 3.8) | python3-importlib-metadata, python3 (>= 3.11) | python3-tomli (>= 1)
 Recommends3: python3-pytest-cov
 Suggests3: python3-pytest-repeat, python3-pytest-rerunfailures
 Replaces3: colcon

test/spell_check.words

@@ -4,6 +4,7 @@ apache
 argparse
 asyncio
 autouse
+backend
 backported
 basepath
 bazqux
@@ -85,6 +86,7 @@ prepending
 proactor
 purelib
 pydocstyle
+pyproject
 pytest
 pytests
 pythondontwritebytecode
@@ -136,6 +138,9 @@ testsuite
 thomas
 tmpdir
 todo
+toml
+tomli
+tomllib
 traceback
 tryfirst
 tuples

test/test_pyproject_spec.py

@@ -0,0 +1,53 @@
+# Copyright 2024 Open Source Robotics Foundation, Inc.
+# Licensed under the Apache License, Version 2.0
+
+from colcon_core.package_descriptor import PackageDescriptor
+from colcon_core.python_project.spec import load_and_cache_spec
+
+
+def test_pyproject_missing(tmp_path):
+ desc = PackageDescriptor(tmp_path)
+
+ spec = load_and_cache_spec(desc)
+ assert spec.get('build-system') == {
+ 'build-backend': 'setuptools.build_meta:__legacy__',
+ 'requires': ['setuptools >= 40.8.0', 'wheel'],
+ }
+
+
+def test_pyproject_empty(tmp_path):
+ desc = PackageDescriptor(tmp_path)
+
+ (tmp_path / 'pyproject.toml').write_text('')
+
+ spec = load_and_cache_spec(desc)
+ assert spec.get('build-system') == {
+ 'build-backend': 'setuptools.build_meta:__legacy__',
+ 'requires': ['setuptools >= 40.8.0', 'wheel'],
+ }
+
+
+def test_specified(tmp_path):
+ desc = PackageDescriptor(tmp_path)
+
+ (tmp_path / 'pyproject.toml').write_text('\n'.join((
+ '[build-system]',
+ 'build-backend = "my_build_backend.meta"',
+ 'requires = ["my-build-backend"]',
+ )))
+
+ spec = load_and_cache_spec(desc)
+ assert spec.get('build-system') == {
+ 'build-backend': 'my_build_backend.meta',
+ 'requires': ['my-build-backend'],
+ }
+
+ # truncate the pyproject.toml and call again
+ # this verifies that the spec is cached
+ (tmp_path / 'pyproject.toml').write_text('')
+
+ spec = load_and_cache_spec(desc)
+ assert spec.get('build-system') == {
+ 'build-backend': 'my_build_backend.meta',
+ 'requires': ['my-build-backend'],
+ }