feat: add hint for new noarch: python syntax

conda_smithy/lint_recipe.py

@@ -26,6 +26,7 @@
 from conda_smithy.linter import conda_recipe_v1_linter
 from conda_smithy.linter.hints import (
     hint_check_spdx,
+    hint_noarch_python_use_python_min,
     hint_pip_no_build_backend,
     hint_pip_usage,
     hint_shellcheck_usage,
@@ -469,6 +470,20 @@ def run_conda_forge_specific(
         meta, "outputs", lints, recipe_version=recipe_version
     )
 
+    build_section = get_section(meta, "build", lints, recipe_version)
+    noarch_value = build_section.get("noarch")
+
+    if recipe_version == 1:
+        test_section = get_section(meta, "tests", lints, recipe_version)
+        test_reqs = []
+        for test_element in test_section:
+            test_reqs += (test_element.get("requirements") or {}).get(
+                "run"
+            ) or []
+    else:
+        test_section = get_section(meta, "test", lints, recipe_version)
+        test_reqs = test_section.get("requires") or []
+
     # Fetch list of recipe maintainers
     maintainers = extra_section.get("recipe-maintainers", [])
 
@@ -580,6 +595,16 @@ def run_conda_forge_specific(
                 "The ``conda-forge.yml`` file is not allowed to have duplicate keys."
             )
 
+    # 10: check for proper noarch python syntax
+    hint_noarch_python_use_python_min(
+        requirements_section.get("host") or [],
+        requirements_section.get("run") or [],
+        test_reqs,
+        outputs_section,
+        noarch_value,
+        hints,
+    )
+
 
 def _format_validation_msg(error: jsonschema.ValidationError):
     """Use the data on the validation error to generate improved reporting.

conda_smithy/linter/hints.py

@@ -232,3 +232,29 @@ def hint_pip_no_build_backend(host_or_build_section, package_name, hints):
                 "If your recipe has built with only `pip` in the `host` section in the past, you likely should "
                 "add `setuptools` to the `host` section of your recipe."
             )
+
+
+def hint_noarch_python_use_python_min(
+    host_reqs, run_reqs, test_reqs, outputs_section, noarch_value, hints
+):
+    if noarch_value == "python" and not outputs_section:
+        for section_name, syntax, reqs in [
+            ("host", "python {{ python_min }}.*", host_reqs),
+            ("run", "python >={{ python_min }}", run_reqs),
+            ("test.requires", "python ={{ python_min }}", test_reqs),
+        ]:
+            for req in reqs:
+                if (
+                    req.strip().split()[0] == "python"
+                    and req != "python"
+                    and syntax in req
+                ):
+                    break
+            else:
+                hints.append(
+                    f"noarch: python recipes should almost always follow the syntax in "
+                    f"[CFEP-25](https://conda-forge.org/docs/maintainer/knowledge_base/#noarch-python). "
+                    f"For the `{section_name}` section of the recipe, you should almost always use `{syntax}` "
+                    f"for the `python` entry. You may need to override the `python_min` variable if the package "
+                    f"requires a newer Python version than the currently supported minimum version on `conda-forge`."
+                )

news/2115-noarch-python-hints.rst

@@ -0,0 +1,23 @@
+**Added:**
+
+* Added hints for new ``noarch: python`` syntax for CFEP-25. (#2115)
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

tests/test_lint_recipe.py

@@ -3002,5 +3002,193 @@ def test_hint_pip_no_build_backend(
     ), lints
 
 
+@pytest.mark.parametrize(
+    "meta_str,expected_hints",
+    [
+        (
+            textwrap.dedent(
+                """
+                package:
+                  name: python
+
+                requirements:
+                  run:
+                    - python
+                """
+            ),
+            [],
+        ),
+        (
+            textwrap.dedent(
+                """
+                package:
+                  name: python
+
+                build:
+                  noarch: python
+
+                requirements:
+                  run:
+                    - python
+                """
+            ),
+            [
+                "python {{ python_min }}.*",
+                "python >={{ python_min }}",
+                "python ={{ python_min }}",
+            ],
+        ),
+        (
+            textwrap.dedent(
+                """
+                package:
+                  name: python
+
+                build:
+                  noarch: python
+
+                requirements:
+                  host:
+                    - python
+                """
+            ),
+            [
+                "python {{ python_min }}.*",
+                "python >={{ python_min }}",
+                "python ={{ python_min }}",
+            ],
+        ),
+        (
+            textwrap.dedent(
+                """
+                package:
+                  name: python
+
+                build:
+                  noarch: python
+
+                test:
+                  requires:
+                    - python
+                """
+            ),
+            [
+                "python {{ python_min }}.*",
+                "python >={{ python_min }}",
+                "python ={{ python_min }}",
+            ],
+        ),
+        (
+            textwrap.dedent(
+                """
+                package:
+                  name: python
+
+                build:
+                  noarch: python
+
+                requirements:
+                  run:
+                    - python >={{ python_min }}
+                """
+            ),
+            [
+                "python {{ python_min }}.*",
+                "python ={{ python_min }}",
+            ],
+        ),
+        (
+            textwrap.dedent(
+                """
+                package:
+                  name: python
+
+                build:
+                  noarch: python
+
+                requirements:
+                  host:
+                    - python {{ python_min }}.*
+                  run:
+                    - python >={{ python_min }}
+                """
+            ),
+            [
+                "python ={{ python_min }}",
+            ],
+        ),
+        (
+            textwrap.dedent(
+                """
+                package:
+                  name: python
+
+                build:
+                  noarch: python
+
+                requirements:
+                  host:
+                    - python {{ python_min }}.*
+                  run:
+                    - python >={{ python_min }}
+
+                test:
+                  requires:
+                    - python ={{ python_min }}
+                """
+            ),
+            [],
+        ),
+        (
+            textwrap.dedent(
+                """
+                package:
+                  name: python
+
+                build:
+                  noarch: python
+
+                requirements:
+                  host:
+                    - python {{ python_min }}.*
+                  run:
+                    - python
+
+                test:
+                  requires:
+                    - python ={{ python_min }}
+                """
+            ),
+            ["python >={{ python_min }}"],
+        ),
+    ],
+)
+def test_hint_noarch_python_use_python_min(
+    meta_str,
+    expected_hints,
+):
+    meta = get_yaml().load(meta_str)
+    lints = []
+    hints = []
+    linter.run_conda_forge_specific(
+        meta,
+        None,
+        lints,
+        hints,
+        recipe_version=0,
+    )
+
+    # make sure we have the expected hints
+    if expected_hints:
+        for expected_hint in expected_hints:
+            assert any(expected_hint in hint for hint in hints), hints
+    else:
+        assert all(
+            "noarch: python recipes should almost always follow the syntax in"
+            not in hint
+            for hint in hints
+        )
+
+
 if __name__ == "__main__":
     unittest.main()