Add deprecation messages for `namespace_packages`.

The docs in
https://setuptools.pypa.io/en/latest/userguide/package_discovery.html
and
https://packaging.python.org/en/latest/guides/packaging-namespace-packages/
suggest that this field is deprecated.

2 files changed, 23 insertions, 3 deletions

diff --git a/setuptools/tests/config/test_apply_pyprojecttoml.py b/setuptools/tests/config/test_apply_pyprojecttoml.py
index 4f541697..ca6082e3 100644
--- a/setuptools/tests/config/test_apply_pyprojecttoml.py
+++ b/setuptools/tests/config/test_apply_pyprojecttoml.py
@@ -6,6 +6,7 @@ To run these tests offline, please have a look on ``./downloads/preload.py``
 import io
 import re
 import tarfile
+from inspect import cleandoc
 from pathlib import Path
 from unittest.mock import Mock
 from zipfile import ZipFile
@@ -14,6 +15,7 @@ import pytest
 from ini2toml.api import Translator
 
 import setuptools  # noqa ensure monkey patch to metadata
+from setuptools._deprecation_warning import SetuptoolsDeprecationWarning
 from setuptools.dist import Distribution
 from setuptools.config import setupcfg, pyprojecttoml
 from setuptools.config import expand
@@ -211,6 +213,21 @@ def test_license_and_license_files(tmp_path):
     assert dist.metadata.license == "LicenseRef-Proprietary\n"
 
 
+class TestDeprecatedFields:
+    def test_namespace_packages(self, tmp_path):
+        pyproject = tmp_path / "pyproject.toml"
+        config = """
+        [project]
+        name = "myproj"
+        version = "42"
+        [tool.setuptools]
+        namespace-packages = ["myproj.pkg"]
+        """
+        pyproject.write_text(cleandoc(config), encoding="utf-8")
+        with pytest.warns(SetuptoolsDeprecationWarning, match="namespace_packages"):
+            pyprojecttoml.apply_configuration(makedist(tmp_path), pyproject)
+
+
 class TestPresetField:
     def pyproject(self, tmp_path, dynamic, extra_content=""):
         content = f"[project]\nname = 'proj'\ndynamic = {dynamic!r}\n"
diff --git a/setuptools/tests/config/test_setupcfg.py b/setuptools/tests/config/test_setupcfg.py
index 1f35f836..904b1ef8 100644
--- a/setuptools/tests/config/test_setupcfg.py
+++ b/setuptools/tests/config/test_setupcfg.py
@@ -7,6 +7,7 @@ from unittest.mock import Mock, patch
 import pytest
 
 from distutils.errors import DistutilsOptionError, DistutilsFileError
+from setuptools._deprecation_warning import SetuptoolsDeprecationWarning
 from setuptools.dist import Distribution, _Distribution
 from setuptools.config.setupcfg import ConfigHandler, read_configuration
 from ..textwrap import DALS
@@ -409,7 +410,7 @@ class TestMetadata:
             'requires = some, requirement\n',
         )
 
-        with pytest.deprecated_call():
+        with pytest.warns(SetuptoolsDeprecationWarning, match="requires"):
             with get_dist(tmpdir) as dist:
                 metadata = dist.metadata
 
@@ -518,7 +519,8 @@ class TestOptions:
             'python_requires = >=1.0, !=2.8\n'
             'py_modules = module1, module2\n',
         )
-        with get_dist(tmpdir) as dist:
+        deprec = pytest.warns(SetuptoolsDeprecationWarning, match="namespace_packages")
+        with deprec, get_dist(tmpdir) as dist:
             assert dist.zip_safe
             assert dist.include_package_data
             assert dist.package_dir == {'': 'src', 'b': 'c'}
@@ -572,7 +574,8 @@ class TestOptions:
             '  http://some.com/here/1\n'
             '  http://some.com/there/2\n',
         )
-        with get_dist(tmpdir) as dist:
+        deprec = pytest.warns(SetuptoolsDeprecationWarning, match="namespace_packages")
+        with deprec, get_dist(tmpdir) as dist:
             assert dist.package_dir == {'': 'src', 'b': 'c'}
             assert dist.packages == ['pack_a', 'pack_b.subpack']
             assert dist.namespace_packages == ['pack1', 'pack2']