add support for PEP 621: we must not enrich static classifiers (pytho…

…n-poetry#708)

- if classifiers are declared in the [project] section they are static
- if classifiers are declared as dynamic in the [project] section, they can be declared in the [tool.poetry] section and enriched by license and requires-python information

src/poetry/core/factory.py

@@ -184,9 +184,10 @@ def _configure_package_metadata(
 
         package.requires_python = project.get("requires-python", "*")
         package.keywords = project.get("keywords") or tool_poetry.get("keywords", [])
-        package.classifiers = project.get("classifiers") or tool_poetry.get(
-            "classifiers", []
-        )
+        package.classifiers = (
+            static_classifiers := project.get("classifiers")
+        ) or tool_poetry.get("classifiers", [])
+        package.dynamic_classifiers = not static_classifiers
 
         if urls := project.get("urls"):
             package.homepage = urls.get("homepage") or urls.get("Homepage")

src/poetry/core/packages/project_package.py

@@ -45,6 +45,7 @@ def __init__(
         self.exclude: Sequence[Mapping[str, Any]] = []
         self.custom_urls: Mapping[str, str] = {}
         self._requires_python: str = "*"
+        self.dynamic_classifiers = True
 
         if self._python_versions == "*":
             self._python_constraint = parse_constraint("~2.7 || >=3.4")
@@ -111,6 +112,13 @@ def version(self) -> Version:
     def version(self, value: str | Version) -> None:
         self._set_version(value)
 
+    @property
+    def all_classifiers(self) -> list[str]:
+        if self.dynamic_classifiers:
+            return super().all_classifiers
+
+        return list(self.classifiers)
+
     @property
     def urls(self) -> dict[str, str]:
         urls = super().urls

tests/test_factory.py

@@ -279,19 +279,22 @@ def test_create_poetry(new_format: str) -> None:
         "Topic :: Software Development :: Libraries :: Python Modules",
     ]
 
-    assert package.all_classifiers == [
-        "License :: OSI Approved :: MIT License",
-        "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.6",
-        "Programming Language :: Python :: 3.7",
-        "Programming Language :: Python :: 3.8",
-        "Programming Language :: Python :: 3.9",
-        "Programming Language :: Python :: 3.10",
-        "Programming Language :: Python :: 3.11",
-        "Programming Language :: Python :: 3.12",
-        "Topic :: Software Development :: Build Tools",
-        "Topic :: Software Development :: Libraries :: Python Modules",
-    ]
+    if new_format:
+        assert package.all_classifiers == package.classifiers
+    else:
+        assert package.all_classifiers == [
+            "License :: OSI Approved :: MIT License",
+            "Programming Language :: Python :: 3",
+            "Programming Language :: Python :: 3.6",
+            "Programming Language :: Python :: 3.7",
+            "Programming Language :: Python :: 3.8",
+            "Programming Language :: Python :: 3.9",
+            "Programming Language :: Python :: 3.10",
+            "Programming Language :: Python :: 3.11",
+            "Programming Language :: Python :: 3.12",
+            "Topic :: Software Development :: Build Tools",
+            "Topic :: Software Development :: Libraries :: Python Modules",
+        ]
 
 
 def test_create_poetry_with_dependencies_with_subdirectory() -> None:
@@ -429,6 +432,63 @@ def test_create_poetry_python_version_not_compatible(tmp_path: Path) -> None:
     assert "not a subset" in str(e.value)
 
 
+@pytest.mark.parametrize(
+    ("content", "expected"),
+    [
+        (  # static
+            """\
+[project]
+name = "foo"
+version = "1"
+requires-python = "3.10"
+classifiers = ["License :: OSI Approved :: MIT License"]
+""",
+            ["License :: OSI Approved :: MIT License"],
+        ),
+        (  # dynamic
+            """\
+[project]
+name = "foo"
+version = "1"
+requires-python = "3.10"
+dynamic = [ "classifiers" ]
+
+[tool.poetry]
+classifiers = ["License :: OSI Approved :: MIT License"]
+""",
+            [
+                "License :: OSI Approved :: MIT License",
+                "Programming Language :: Python :: 3",
+                "Programming Language :: Python :: 3.10",
+            ],
+        ),
+        (  # legacy
+            """\
+[tool.poetry]
+name = "foo"
+version = "1"
+classifiers = ["License :: OSI Approved :: MIT License"]
+
+[tool.poetry.dependencies]
+python = "~3.10"
+""",
+            [
+                "License :: OSI Approved :: MIT License",
+                "Programming Language :: Python :: 3",
+                "Programming Language :: Python :: 3.10",
+            ],
+        ),
+    ],
+)
+def test_create_poetry_classifiers(
+    content: str, expected: list[str], tmp_path: Path
+) -> None:
+    (tmp_path / "pyproject.toml").write_text(content)
+    poetry = Factory().create_poetry(tmp_path)
+
+    assert poetry.package.all_classifiers == expected
+
+
 def test_validate() -> None:
     complete = fixtures_dir / "complete.toml"
     with complete.open("rb") as f: