test: make Constants attribute docstring doctests actually run

Constants class attributes document their default with a bare string
literal after the assignment (e.g. patronymic_name_order = False /
"""..."""), Sphinx's attribute-docstring convention. That string is
never a real __doc__, so doctest.DocTestFinder (and pytest's
--doctest-modules) never discovers the .. doctest:: examples inside
it -- they can silently go stale, which already happened once for
middle_name_as_last.

Add tests/test_config_attribute_docstrings.py, which parses the
source with ast to recover those literals (the same info Sphinx's
static analysis reads) and runs any doctest examples through
doctest.DocTestParser/DocTestRunner, so pytest -q now exercises them.

Discovery also caught a second dormant docstring (empty_attribute_default)
with its own bugs: a missing space after >>> and an expectation of
literal None output where the REPL prints nothing for None.

Author: derek73

nameparser/config/__init__.py

@@ -323,9 +323,9 @@ class Constants:
         >>> from nameparser.config import CONSTANTS
         >>> CONSTANTS.empty_attribute_default = None
         >>> name = HumanName("John Doe")
-        >>> name.title
+        >>> print(name.title)
         None
-        >>>name.first
+        >>> name.first
         'John'
 
     """

tests/test_config_attribute_docstrings.py

@@ -0,0 +1,79 @@
+"""Exercise the doctest examples embedded in Constants attribute docstrings.
+
+nameparser.config.Constants documents several scalar attributes (e.g.
+patronymic_name_order, middle_name_as_last) with a bare string literal placed
+right after the class-attribute assignment -- Sphinx's "attribute docstring"
+convention, picked up by autodoc's source-level analysis for the built docs.
+
+That convention is invisible to Python at runtime: only module/class/function/
+method docstrings become a real __doc__, so a bare string following
+`attr = value` is evaluated and discarded. doctest.DocTestFinder walks __doc__
+attributes, so pytest's --doctest-modules (see pyproject.toml addopts) never
+finds the `.. doctest::` examples inside them -- they can go stale silently.
+
+This module parses the source with `ast` to recover those literals (the same
+information Sphinx's static analysis relies on) and runs any doctest examples
+found inside them explicitly, so a stale example fails the suite.
+"""
+import ast
+import doctest
+import io
+from pathlib import Path
+
+import pytest
+
+import nameparser.config as config_module
+from nameparser import HumanName
+from nameparser.config import CONSTANTS, Constants
+
+CONFIG_SOURCE_PATH = Path(config_module.__file__)
+
+
+def _constants_attribute_docstrings() -> dict[str, str]:
+    """Map attribute name -> bare-string-literal docstring, Constants class body only."""
+    tree = ast.parse(CONFIG_SOURCE_PATH.read_text(), filename=str(CONFIG_SOURCE_PATH))
+    (class_node,) = (
+        node for node in ast.walk(tree)
+        if isinstance(node, ast.ClassDef) and node.name == 'Constants'
+    )
+    docstrings = {}
+    body = class_node.body
+    for stmt, following in zip(body, body[1:]):
+        if not (isinstance(stmt, ast.Assign) and len(stmt.targets) == 1
+                and isinstance(stmt.targets[0], ast.Name)):
+            continue
+        if isinstance(following, ast.Expr) and isinstance(following.value, ast.Constant) \
+                and isinstance(following.value.value, str):
+            docstrings[stmt.targets[0].id] = following.value.value
+    return docstrings
+
+
+ATTRIBUTE_DOCSTRINGS = _constants_attribute_docstrings()
+
+DOCTEST_GLOBS = {'HumanName': HumanName, 'CONSTANTS': CONSTANTS, 'Constants': Constants}
+
+
+def _attrs_with_doctest_examples() -> list[str]:
+    parser = doctest.DocTestParser()
+    return sorted(
+        attr for attr, docstring in ATTRIBUTE_DOCSTRINGS.items()
+        if parser.get_examples(docstring)
+    )
+
+
+@pytest.mark.parametrize("attr", _attrs_with_doctest_examples())
+def test_constants_attribute_docstring_examples(attr: str) -> None:
+    docstring = ATTRIBUTE_DOCSTRINGS[attr]
+    test = doctest.DocTestParser().get_doctest(
+        docstring, DOCTEST_GLOBS, attr, str(CONFIG_SOURCE_PATH), 0,
+    )
+    output = io.StringIO()
+    failures, _ = doctest.DocTestRunner().run(test, out=output.write)
+    assert failures == 0, output.getvalue()
+
+
+def test_found_expected_attributes_with_doctest_examples() -> None:
+    """Guard the discovery mechanism itself: if this drops to zero, the AST
+    walk above stopped matching Constants's attribute-docstring pattern and
+    every parametrized case above is silently skipped rather than run."""
+    assert _attrs_with_doctest_examples()