pyproject: upgrade to modern setuptools

It turns out `--global-option` still works, even though it is deprecated.
So let's adopt modern setuptools, reintroduce use of `--global-option`,
and update licensing metadata to new conventions.

Author: indygreg

.github/workflows/external-zstd.yml

@@ -28,10 +28,8 @@ jobs:
           persist-credentials: false
 
       - name: Build
-        env:
-          PIP_CONSTRAINT: 'ci/constraints.txt'
         run: |
-          python -m pip install --config-settings=--build-option=--system-zstd .
+          python -m pip install --config-settings=--global-option=--system-zstd .
 
   macOS:
     runs-on: 'macos-13'
@@ -57,7 +55,5 @@ jobs:
           persist-credentials: false
 
       - name: Build
-        env:
-          PIP_CONSTRAINT: 'ci/constraints.txt'
         run: |
-          python -m pip install --config-settings=--build-option=--system-zstd .
+          python -m pip install --config-settings=--global-option=--system-zstd .

.github/workflows/pypy.yml

@@ -46,7 +46,7 @@ jobs:
 
       - name: Build
         run: |
-          python -m pip -v wheel --constraint ci/constraints.txt -w wheelhouse .
+          python -m pip -v wheel -w wheelhouse .
 
   test:
     strategy:

.github/workflows/sphinx.yml

@@ -16,11 +16,9 @@ jobs:
         with:
           version: "0.8.11"
       - name: Run Sphinx
-        env:
-          PIP_CONSTRAINT: 'ci/constraints.txt'
         run: |
           uv venv --python 3.13 venv
           source venv/bin/activate
           uv pip install -r ci/requirements.docs.txt
-          uv pip install --config-settings=--build-option=--no-c-backend .
+          uv pip install --config-settings=--global-option=--no-c-backend .
           make -C docs html

.github/workflows/test.yml

@@ -113,4 +113,4 @@ jobs:
         run: |
           # We need --reinstall to get uv to pick up the config settings change.
           # Unsure if this is a bug.
-          uv -v run --locked --config-settings-package 'zstandard:--build-option=--rust-backend' --reinstall pytest --numprocesses=auto --hypothesis-profile=${HYPOTHESIS_PROFILE} -v
+          uv -v run --locked --config-settings-package 'zstandard:--global-option=--rust-backend' --reinstall pytest --numprocesses=auto --hypothesis-profile=${HYPOTHESIS_PROFILE} -v

.readthedocs.yaml

@@ -9,8 +9,8 @@ build:
   jobs:
     create_environment:
       - python3 -m venv venv
-      - venv/bin/python3 -m pip install -c ci/constraints.txt -r ci/requirements.docs.txt
-      - venv/bin/python3 -m pip install --config-settings=--build-option=--no-c-backend .
+      - venv/bin/python3 -m pip install -r ci/requirements.docs.txt
+      - venv/bin/python3 -m pip install --config-settings=--global-option=--no-c-backend .
     build:
       htmlzip:
         - make -C docs html SPHINXBUILD=$(pwd)/venv/bin/sphinx-build BUILDDIR=$READTHEDOCS_OUTPUT

ci/constraints.txt

@@ -50,12 +50,7 @@ Legacy Format Support
 To enable legacy zstd format support which is needed to handle files compressed
 with zstd < 1.0 you need to provide an installation option::
 
-   $ pip install zstandard --install-option="--legacy"
-
-and since pip 7.0 it is possible to have the following line in your
-requirements.txt::
-
-   zstandard --install-option="--legacy"
+   $ pip install zstandard --config-settings='--global-option=--legacy'
 
 All Install Arguments
 =====================
@@ -86,11 +81,14 @@ All Install Arguments
 ``--rust-backend``
    Compile the Rust backend (not yet feature complete).
 
-If you invoke ``setup.py``, simply pass the aforementioned arguments. e.g.
-``python3.9 setup.py --no-cffi-backend``. If using ``pip``, use the
-``--install-option`` argument. e.g.
-``python3.9 -m pip install zstandard --install-option --warning-as-errors``.
-Or in a pip requirements file: ``zstandard --install-option="--rust-backend"``.
+Packaging tools newer than ~2023 likely require using a PEP 517
+build backend instead of invoking ``setup.py`` directly. In order to send
+custom arguments to our ``setup.py``, you need to use ``--config-settings``.
+e.g. ``python3 -m pip install zstandard --config-settings='--global-option=--no-cffi-backend'``.
+
+Older packaging tools allowed you to use e.g.
+``python3 -m pip install zstandard --install-option --no-cffi-backend`` or
+just ``python3 setup.py --no-cffi-backend`` directly.
 
 In addition, the following environment variables are recognized:
 

docs/installing.rst

@@ -27,6 +27,14 @@ Version History
   wheels. (Enabling this test coverage did not uncover any failures.)
 * The ``pyproject.toml`` build backend has been switched from
   ``setuptools.build_meta:__legacy__`` to ``setuptools.build_meta``.
+* The setuptools build dependency has been upgraded from <69.0.0 to >=77.0.0.
+  Modern versions of setuptools broke
+  ``--config-settings=--build-option=...`` as part of implementing PEP 660.
+  A workaround is to use `--config-settings=--global-option=...`` instead.
+  `--global-option`` apparently is deprecated and the setuptools folks have yet
+  to figure out how to thread config settings into ``setup.py`` invocations.
+  (`--build-option`` is sent to the ``build_wheel`` command but not the
+  ``build_editable`` command.)
 
 0.24.0 (released 2025-08-17)
 ============================

docs/news.rst

@@ -6,12 +6,11 @@ readme = { file = "README.rst", content-type = "text/x-rst" }
 authors = [
     { name = "Gregory Szorc", email = "[email protected]" },
 ]
-license = { text = "BSD" }
+license = "BSD-3-Clause"
 requires-python = ">=3.9"
 classifiers = [
     "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: BSD License",
     "Programming Language :: C",
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
@@ -36,7 +35,7 @@ Documentation = "https://python-zstandard.readthedocs.io/en/latest/"
 requires = [
     "cffi>=1.17.0 ; platform_python_implementation != 'PyPy'",
     "packaging",
-    "setuptools",
+    "setuptools>=77.0.0",
 ]
 build-backend = "setuptools.build_meta"
 
@@ -82,19 +81,3 @@ test-command = [
     "set PYTHON_ZSTANDARD_IMPORT_POLICY=cffi",
     "pytest -v --numprocesses=auto",
 ]
-
-# This is needed to suppress generation of license-file, which isn't
-# compatible with metadata version 2.1, which our pinned setuptools
-# version currently uses.
-# TODO delete this after we adopt modern setuptools.
-[tool.setuptools]
-license-files = []
-
-[tool.uv]
-build-constraint-dependencies = [
-    # 69.0.0 breaks handling of --config-settings=--build-option, which our CI
-    # relies on. So constrained to an older version until we figure out a
-    # workaround. See comment at
-    # https://github.com/pypa/pip/issues/11859#issuecomment-2132287974.
-    "setuptools<69.0.0",
-]