`shortcuts` should not be a publicly accessible attribute

[kotfu]

We have some inconsistencies in our api and our documentation. In 0.9.12 we added shortcuts as an optional argument to __init__(), and changed the initialization code associated with these shortcuts. This created the following issues:

• the changelog said nothing about disabling the .shortcuts attribute. Prior to 0.9.12 you could modify that attribute to change the shortcuts. After 0.9.12, the only way to change the shortcuts is to pass them to __init__()
• What's the point of the shortcuts attribute on a cmd object if the caller has to pass it in, and it's read only? When cmd2 code needs it, can get it from the statement_parser, and code that instantiates cmd2.Cmd() or a subclass thereof already know it because they passed it in.
• the docstring for the init method says you should pass shortcuts as a dictionary, and then the initialization code processes those and stores a tuple in the shortcuts attribute (which has a property to access it). It seems inconsistent to pass a dictionary and access a tuple.
• The DEFAULT_SHORTCUTS variable should really be in constants.py, not cmd2.py

[tleonhardt]

Well shoot, I did a much better job discussing these changes in the PR #648 than I did in the changelog!

One decision that was made was to intentionally make shortcuts, multiline commands, and terminators immutable where they get passed in to init() at startup, then get passed the StatementParser and within that they get converted to an immutable tuple.

The point was to break out certain things that maybe should be constant over time for a given application and not be user-modifiable during runtime and enforce their immutability. In particular we wanted to remove the requirement that certain things needed to get set prior to calling super.init().

The concept behind passing a dictionary was to make it easy for devs to progressively build up shortcuts in a mutable type if they so chose before instantiating a cmd2.Cmd instance. But maybe your right and it is unnecessarily confusing.

Completely agree that the default shortcuts should be in constants.py.

I’m open to whatever changes you think make the most sense to help achieve a more consistent API.

[kotfu]

I agree with the philosophy of making certain attributes immutable, including shortcuts. I've put my broad thoughts for a more consistent API into a note on #677 (consider minimizing the public API)

[tleonhardt]

This can and should be addressed as part of #677