We replace MANIFEST filtering in the modularized distributions by implementing a PEP 517/PEP 660 buildapi in sage_setup.

• PEP 660 build_editable via https://editables.readthedocs.io/en/latest/usage.html#mapping-individual-files-packages

• https://github.com/pypa/setuptools/blob/main/setuptools/command/editable_wheel.py

• https://www.python.org/dev/peps/pep-0660/ Editable installs for pyproject.toml based builds (wheel based)

• Clarification about how to implement namespace packages (as in PEP 420) via import hooks for PEP 660 use case python/cpython#92054 Clarification about how to implement namespace packages (as in PEP 420) via import hooks for PEP 660 use case

References (outdated):

• https://github.com/takluyver/flit/blob/master/flit_core/flit_core/buildapi.py
• https://flit.readthedocs.io/en/latest/pyproject_toml.html#
• Poetry issue #265 - Support for custom commands and functions - closed as wontfix
• https://pypi.org/project/enscons/ ?
• https://discuss.python.org/t/help-testing-pep-660-support-in-setuptools/16904
• Add packages flit and dependencies flit_core, pytoml #29846, sagelib: Declare build system dependencies using src/pyproject.toml #30581, Fix sagelib sdist (src/setup.py sdist) #21516

Component: build

Issue created by migration from https://trac.sagemath.org/ticket/29845