[rr-]

An item with no description now has None as its description in every style, never "". Before, an item with nothing after its colon got an empty string, while one with no colon at all got None. Users had to check for both.

Before:

>>> parse("Short.\n\n:param x:").params[0].description
''

After:

>>> parse("Short.\n\n:param x:").params[0].description is None
True

DocstringMeta and its subclasses store an empty description as None, so the parsers and items that users build give the same answer. Compose now writes each item so that it reads back with None:

• A typed item with no description goes out as its type field alone, as a None one already did.
• An untyped item, or one whose field carries its own type such as ReST :param int x:, keeps that field.
• An Epydoc return with no type keeps its @return: field.
• A Google raises type goes out alone unless it ends in a space. The colon after it keeps that space.

This is a breaking change: code that compares descriptions to "" has to compare to None now.

Parity against main: 3085 of 29157 docstrings differ (43 case, 40 stdlib, 3002 generated). Nearly all of them are parse output going from '' to None. The compose diffs are the field choices listed above. The round-trip invariant passes with no new exclusions.

Bench against main: 1.01x at most.