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Incompatibilities
=================
.. _cmd: https://docs.python.org/3/library/cmd.html
``cmd2`` strives to be drop-in compatible with cmd_, however there are a few
things that are not.
Cmd.emptyline()
---------------
The `Cmd.emptyline()
<https://docs.python.org/3/library/cmd.html#cmd.Cmd.emptyline>`_ function is
called when an empty line is entered in response to the prompt. By default, in
cmd_ if this method is not overridden, it repeats and executes the last
nonempty command entered. However, no end user we have encountered views this
as expected or desirable default behavior. Thus, the default behavior in
``cmd2`` is to simply go to the next line and issue the prompt again. At this
time, ``cmd2`` completely ignores empty lines and the base class
cmd.emptyline() method never gets called and thus the emptyline() behavior
cannot be overridden.
Cmd.identchars
--------------
In cmd_, the `Cmd.identchars
<https://docs.python.org/3/library/cmd.html#cmd.Cmd.identchars>`_ attribute
contains the string of characters accepted for command names. Since version
0.9.0, ``cmd2`` has ignored ``identchars``. cmd_ uses those characters to split
the first "word" of the input, but the parsing logic in ``cmd2`` parses on
whitespace. This has the added benefit of full unicode support, unlike cmd_ or
versions of ``cmd2`` prior to 0.9.0.
Cmd.cmdqueue
------------
In cmd_, the `Cmd.cmdqueue
<https://docs.python.org/3/library/cmd.html#cmd.Cmd.cmdqueue>`_ attribute
contains A list of queued input lines. The cmdqueue list is checked in
``cmdloop()`` when new input is needed; if it is nonempty, its elements will be
processed in order, as if entered at the prompt.
Since version 0.9.13 ``cmd2`` has removed support for ``Cmd.cmdqueue``.
Reasoning about application behavior is much easier without this queue present.
If developers need this sort of thing, they can add it in their application.
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