fix number of positional arguments in deprecation warning messages

- ignore `cls` and `self`
- use 'arg' for `supported_number=1`
- follow-up f4f2daa, 99b4e62
- see also #215

graphviz/_tools.py

@@ -106,13 +106,16 @@ def promote_pathlike_directory(directory: typing.Union[os.PathLike, str, None],
 
 def deprecate_positional_args(*,
                               supported_number: int,
+                              ignore_argnames: typing.Sequence[str] = ('cls', 'self'),
                               category: typing.Type[Warning] = PendingDeprecationWarning,
                               stacklevel: int = 1):
     """Mark supported_number of positional arguments as the maximum.
 
     Args:
         supported_number: Number of positional arguments
             for which no warning is raised.
+        ignore_argnames: Name(s) of arguments to ignore
+            ('cls' and 'self' by default).
         category: Type of Warning to raise
             or None to return a nulldecorator
             returning the undecorated function.
@@ -143,7 +146,8 @@ def nulldecorator(func):
     def decorator(func):
         signature = inspect.signature(func)
         argnames = [name for name, param in signature.parameters.items()
-                    if param.kind == inspect.Parameter.POSITIONAL_OR_KEYWORD]
+                    if param.kind == inspect.Parameter.POSITIONAL_OR_KEYWORD
+                    and name not in ignore_argnames]
         log.debug('deprecate positional args: %s.%s(%r)',
                   func.__module__, func.__qualname__,
                   argnames[supported_number:])
@@ -162,7 +166,8 @@ def wrapper(*args, **kwargs):
                 wanted = ', '.join(f'{name}={value!r}'
                                    for name, value in deprecated.items())
                 warnings.warn(f'The signature of {func.__name__} will be reduced'
-                              f' to {supported_number} positional args'
+                              f' to {supported_number} positional arg'
+                              f"{'s' if supported_number > 1 else ''}"
                               f' {list(supported)}: pass {wanted}'
                               ' as keyword arg(s)',
                               stacklevel=stacklevel,

graphviz/saving.py

@@ -50,7 +50,7 @@ def filepath(self) -> str:
         """The target path for saving the DOT source file."""
         return os.path.join(self.directory, self.filename)
 
-    @_tools.deprecate_positional_args(supported_number=2)
+    @_tools.deprecate_positional_args(supported_number=1)
     def save(self, filename: typing.Union[os.PathLike, str, None] = None,
              directory: typing.Union[os.PathLike, str, None] = None, *,
              skip_existing: typing.Optional[bool] = False) -> str:

graphviz/sources.py

@@ -39,7 +39,7 @@ class Source(rendering.Render, saving.Save,
     """
 
     @classmethod
-    @_tools.deprecate_positional_args(supported_number=2)
+    @_tools.deprecate_positional_args(supported_number=1)
     def from_file(cls, filename: typing.Union[os.PathLike, str],
                   directory: typing.Union[os.PathLike, str, None] = None,
                   format: typing.Optional[str] = None,
@@ -73,7 +73,7 @@ def from_file(cls, filename: typing.Union[os.PathLike, str],
                    renderer=renderer, formatter=formatter,
                    loaded_from_path=filepath)
 
-    @_tools.deprecate_positional_args(supported_number=2)
+    @_tools.deprecate_positional_args(supported_number=1)
     def __init__(self, source: str,
                  filename: typing.Union[os.PathLike, str, None] = None,
                  directory: typing.Union[os.PathLike, str, None] = None,
@@ -122,7 +122,7 @@ def source(self) -> str:
             source += '\n'
         return source
 
-    @_tools.deprecate_positional_args(supported_number=2)
+    @_tools.deprecate_positional_args(supported_number=1)
     def save(self, filename: typing.Union[os.PathLike, str, None] = None,
              directory: typing.Union[os.PathLike, str, None] = None, *,
              skip_existing: typing.Optional[bool] = None) -> str:

tests/backend/test_piping.py

@@ -75,7 +75,7 @@ def test_pipe_pipe_invalid_data_mocked(mocker, sentinel, mock_run, quiet):
          reason='https://gitlab.com/graphviz/graphviz/-/issues/1269'))])
 def test_pipe(capsys, engine, format_, renderer, formatter, pattern,
               data=b'graph { spam }'):
-    with pytest.deprecated_call():
+    with pytest.deprecated_call(match=r'3 positional args'):
         out = graphviz.pipe(engine, format_, data,
                             renderer, formatter).decode('ascii')
 

tests/backend/test_rendering.py

@@ -60,7 +60,7 @@ def test_render(capsys, tmp_path, engine, format_, renderer, formatter,
     assert lpath.write_bytes(data) == len(data) == lpath.stat().st_size
     rendered = lpath.with_suffix(f'{lpath.suffix}.{expected_suffix}')
 
-    with pytest.deprecated_call():
+    with pytest.deprecated_call(match=r'3 positional args'):
         result = graphviz.render(engine, format_, str(lpath),
                                  renderer, formatter)
 

tests/test_all_classes.py

@@ -210,7 +210,7 @@ def test_save_mocked(mocker, dot, filename='nonfilename', directory='nondirector
     mock_makedirs = mocker.patch('os.makedirs', autospec=True)
     mock_open = mocker.patch('builtins.open', mocker.mock_open())
 
-    with pytest.deprecated_call():
+    with pytest.deprecated_call(match=r'1 positional arg\b'):
         assert dot.save(filename, directory) == dot.filepath
 
     assert dot.filename == filename

tests/test_sources.py

@@ -42,22 +42,23 @@ def test_filepath(platform, source):
 
 
 def test_from_file(tmp_path, filename='hello.gv', directory='source_hello',
-                   data='digraph { hello -> world }', encoding='utf-8'):
+                   data='digraph { hello -> world }', encoding='utf-8',
+                   deprecation_match=r'1 positional arg\b'):
     lpath = tmp_path / directory
     lpath.mkdir()
     (lpath / filename).write_text(data, encoding=encoding)
 
-    with pytest.deprecated_call():
+    with pytest.deprecated_call(match=deprecation_match):
         source = graphviz.Source.from_file(filename, str(lpath))
     assert source.encoding == 'utf-8'
 
-    with pytest.deprecated_call():
+    with pytest.deprecated_call(match=deprecation_match):
         source = graphviz.Source.from_file(filename, str(lpath), encoding=None)
     assert source.encoding == locale.getpreferredencoding()
 
     renderer = 'xdot'
     formatter = 'core'
-    with pytest.deprecated_call():
+    with pytest.deprecated_call(match=deprecation_match):
         source = graphviz.Source.from_file(filename, str(lpath),
                                            encoding=encoding,
                                            renderer=renderer,