Finalize sorting of class bodies

Before sorting topologically, ssort currently pre-sorts class members in the following order:

• Docstring.
• Special attributes (__slots__ and __doc__).
• Regular class attributes.
• Lifecycle d’under methods (e.g. __init__ or __del__) in fixed order.
• Regular methods in original order.
• All other d’under methods, in fixed order.

I think this is basically sensible but, unlike topological sorting of top-level statements, there is no strong argument for it to be this way.

I’d like to invite comments or opinions on how this order could be improved before the 1.0 release.

[drcongo]

I quite like @AnonymouX47’s order, it’s not dissimilar to ours and makes sense to my brain, but yeah, it’s likely to be a very personal preference for most users.

[AnonymouX47]

The fact is… no matter how much deliberation happens, the group order chosen will be opinionated in one way or the other.

So, I propose that a reasonable default order be chosen but beyond that, a user should be able to customize the grouping and group ordering as desired and even (maybe later) be able to include user-defined groups and change the group a statement belongs to.

---

So, ssort can define a default set of groups and a default group ordering for top-level statements and class members separately.

For the custom group ordering, there could be:

• a CLI option or config option for a global setting
• a particularly-styled comment at the top of a module (after imports) for module-specific setting
• a particularly-styled comment at the top of a class (after the docstring) for class-specific setting

For the addition of custom groups and to change the group a statement belongs:

• a particularly-styled comment on the same line as a statement (or its header, for definitions) or just immediately above the statement.

A statement can belong to only one group.

---

The particularly-styled comment can be of the form:

# ssort: <group1>, <group2>, <group3>

for custom group ordering

and

# ssort: <group>

for custom grouping. If <group> isn’t among the default, then it’s added to the set of groups for that module or class.