0.0.28

.gitignore

@@ -12,3 +12,4 @@ build
 html
 .coverage
 CLAUDE.md
+AGENTS.md

printo/describe.py

@@ -1,3 +1,4 @@
+from keyword import iskeyword
 from typing import Any, Callable, Dict, Iterable, List, Optional, Tuple, Union
 
 from printo.reprs import superrepr
@@ -63,6 +64,16 @@ def describe_call(  # noqa: PLR0913
 ) -> str:
     from sigmatch import PossibleCallMatcher  # noqa: PLC0415
 
+    if not isinstance(class_name, str):
+        raise TypeError(f'class_name must be a string, got {type(class_name).__name__}.')
+
+    for part in class_name.split('.'):
+        identifier = part[1:-1] if part.startswith('<') and part.endswith('>') else part
+        if not identifier.isidentifier():
+            raise ValueError(f'class_name must be a valid Python identifier, a valid Python identifier wrapped in angle brackets, or a dot-separated series of those, got {class_name!r}.')
+        if iskeyword(identifier):
+            raise ValueError(f'class_name contains Python keyword {identifier!r}, which is not allowed: {class_name!r}.')
+
     PossibleCallMatcher('.').match(serializer, raise_exception=True)
 
     if item_limit is not None and item_limit < 0:

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = 'setuptools.build_meta'
 
 [project]
 name = 'printo'
-version = '0.0.27'
+version = '0.0.28'
 authors = [
   { name='Evgeniy Blinov', email='zheni-b@yandex.ru' },
 ]

tests/typing/test_describe_call.py

@@ -54,8 +54,9 @@ def test_describe_call_with_total_limit():
 
 @pytest.mark.mypy_testing
 def test_describe_call_invalid_class_name_type():
-    """mypy rejects int as class_name — expected str."""
-    describe_call(42, [], {})  # E: [arg-type]
+    """mypy and runtime validation both reject non-string class_name values."""
+    with pytest.raises(TypeError, match=match('class_name must be a string, got int.')):
+        describe_call(42, [], {})  # E: [arg-type]
 
 
 @pytest.mark.mypy_testing

tests/units/test_describe.py

@@ -1,6 +1,7 @@
 from typing import Any
 
 import pytest
+from full_match import match
 from sigmatch.errors import SignatureMismatchError
 
 from printo import describe_call, not_none
@@ -11,6 +12,87 @@ def test_empty_object():
     assert describe_call('ClassName', (), {}, serializer=lambda x: 'kek') == 'ClassName()'  # noqa: ARG005
 
 
+@pytest.mark.parametrize(
+    ('class_name', 'type_name'),
+    [
+        (42, 'int'),
+        (None, 'NoneType'),
+        (object(), 'object'),
+    ],
+)
+def test_class_name_must_be_string(class_name, type_name):
+    """Only strings can be used as the name in the described call."""
+    with pytest.raises(TypeError, match=match(f'class_name must be a string, got {type_name}.')):
+        describe_call(class_name, (), {})
+
+
+@pytest.mark.parametrize(
+    'class_name',
+    [
+        'ClassName',
+        '_private',
+        'package.module.ClassName',
+        '<locals>',
+        'function.<locals>.SomeClass',
+        'package.<private>.ClassName',
+    ],
+)
+def test_class_name_accepts_valid_identifiers_and_wrapped_identifiers(class_name):
+    """
+    Class names can be identifiers or <identifier> chunks.
+
+    Multiple valid chunks can be joined with dots.
+    """
+    assert describe_call(class_name, (), {}) == f'{class_name}()'
+
+
+@pytest.mark.parametrize(
+    'class_name',
+    [
+        '',
+        'not valid',
+        '123abc',
+        'a-b',
+        '<',
+        '>',
+        '<>',
+        '<123abc>',
+        '<not valid>',
+        '<a-b>',
+        '<locals',
+        'locals>',
+        '.',
+        '.ClassName',
+        'package.',
+        'package..ClassName',
+        'package.123Class',
+        'function.<>.Class',
+        'function.<not valid>.Class',
+    ],
+)
+def test_class_name_rejects_invalid_identifier_shapes(class_name):
+    """Malformed names are rejected before any repr string is produced."""
+    with pytest.raises(ValueError, match=match(f'class_name must be a valid Python identifier, a valid Python identifier wrapped in angle brackets, or a dot-separated series of those, got {class_name!r}.')):
+        describe_call(class_name, (), {})
+
+
+@pytest.mark.parametrize(
+    ('class_name', 'keyword'),
+    [
+        ('class', 'class'),
+        ('None', 'None'),
+        ('package.class', 'class'),
+        ('<class>', 'class'),
+        ('<None>', 'None'),
+        ('function.<class>.SomeClass', 'class'),
+    ],
+)
+def test_class_name_rejects_python_keywords(class_name, keyword):
+    """Python keywords are rejected even when their identifier shape is valid."""
+    with pytest.raises(ValueError, match=match(f'class_name contains Python keyword {keyword!r}, which is not allowed: {class_name!r}.')):
+        describe_call(class_name, (), {})
+
+
 @pytest.mark.parametrize(
     'args_converter',
     [