The D1xx group of errors deals with missing docstring in public constructs: modules, classes, methods, etc. It is important to note how publicity is determined and what its effects are.
Publicity for all constructs is determined as follows: a construct is considered public if -
- Its immediate parent is public and
Its name does not start with a single or double underscore.
- Note, names that start and end with a double underscore are public (e.g.
__init__.py).
- Note, names that start and end with a double underscore are public (e.g.
A construct's immediate parent is the construct that contains it. For example, a method's parent is a class object. A class' parent is usually a module, but might also be a function, method, etc. A module can either have no parent, or it can have a parent that is a package.
In order for a construct to be considered public, its immediate parent must also be public. Since this definition is recursive, it means that all of its parents need to be public. The corollary is that if a construct is considered private, then all of its descendants are also considered private. For example, a class called _Foo is considered private. A method bar in _Foo is also considered private since its parent is a private class, even though its name does not begin with a single underscore.
Note, a construct's parent is recursively checked upward until we reach a directory in sys.path to avoid considering the complete filepath of a module. For example, consider the module /_foo/bar/baz.py. If PYTHONPATH is set to /, then baz.py is private. If PYTHONPATH is set to /_foo/, then baz.py is public.
Modules are parsed to look if __all__ is defined. If so, only those top level constructs are considered public. The parser looks for __all__ defined as a literal list or tuple. As the parser doesn't execute the module, any mutation of __all__ will not be considered.
The immediate effect of a construct being determined as private is that no D1xx errors will be reported for it (or its children, as the previous section explains). A private method, for instance, will not generate a D102 error, even if it has no docstring.
However, it is important to note that while docstring are optional for private construct, they are still required to adhere to your style guide. So if a private module _foo.py does not have a docstring, it will not generate a D100 error, but if it does have a docstring, that docstring might generate other errors.