Re: Introspecting yas tab binding

[Psionic K <psionik@positron.solutions>]

> What is "Yas minor mode"?  I don't see it in Emacs 29 or in Emacs 30.

I will ignore what appears to me to be some kind of sarcastic
perversion of reality attempting to imply "go away, this is not
Emacs", which it most surely is not, and rephrase the question to
focus on Emacs specific elements.

I have identified a command by viewing lossage called
`mysterious-command`.  It is called in some situations when I press
TAB, but not always.

`where-is' reports that `mysterious-command' is not bound on any key.
Lossage reports:

 <tab>          ;; mysterious-command

I have found `mysterious-command' in a keymap menu item, and the key
definition matches the command I observe, but I cannot get debug to
trigger when using `debug-on-entry' on the function assigned as the
`:filter' in that menu item, so I'm unsure if the menu item is related
at all.

I can get a debugger for `mysterious-command' itself, which displays a
stack beginning with `command-execute', called only with
`mysterious-command'.   I need to discover how `mysterious-command' is
arrived at to work backwards toward the mechanism used to make it only
receive the TAB key in certain situations.

Evaluating (key-binding (kbd "TAB")) shows that the binding is
situational, returning different commands depending on the location of
the point, but still not how.   After following the code into
`lookup_key_1', I am expecting attaching a debugger will reveal that
the external state, the keymap with the menu item, is changed between
calls, but again not where this behavior originates.

What Emacs facilities might uncover the states and execution flow
responsible for this situational behavior for the TAB key sequence?
How can I identify or rule out the menu item's responsibility?