I guess they're not the same in the sense that they're officially
supported. This was kind of the whole point of my question, which is,
to what point are these things supposed to be the way you do things?
Like I said, they can be problematic. For example, take the seemingly
innocent (add-hook 'before-save-hook 'delete-trailing-whitespace),
which is the universally recommended way make emacs to clear
whitespace on save. As far as I can tell, with this active, it is
impossible to save without clearing whitespace, unless you clear the
hook. With the global-set-key solution, I can easily save without
clearing by doing M-x save-buffer.
I don't know about "universally recommended"; as you point out, this really isn't a nice solution, at a minimum you should wrap `delete-trailing-white-space' in a function you can configure to be on/off on a per-file basis through a variable.
It's the easy solution. And people like easy.
It's necessary for you to differenciate between recommended practices and "practices I saw from a snippet posted to emacswiki". `add-hook' solutions are hacks. The end-user should not have to call add-hook. Package maintainers should define minor-modes that manage hooks for the end-user, or use the customize facilities to do something even smarter. I'm sure there is a "delete trailing white space" minor-mode out there somewhere.
Hooks are fine if all they do is enable some mode, because I can
easily turn that off if I don't want it. But other than that, you run
into the above issue. Or maybe there's an easy way to bypass hooks
that I just don't know about.
There's other potential problems that are shared by hooks and monkey
patching, like expected invariants that are no longer met. I suppose
the very existence of hooks means that there really can be no expected
invariants about anything. But to me, this is impossible (you have to
expect that what you use will work, or else you can't really say
anything about your program).
Defadvice are hacks. You (as the end-user) should not have to use it.
However, where would we be without it?
How would you change a certain aspect of a package you use daily? You'd redefine the relevant function. Now, clearly defadvice provides a structure that is superior to plain function redefinition.
The manual is clear on this. Defadvice is a last resort solution, not a line of first defense.
And by the way, I wasn't just referring to defadvice for monkey
patching. That actually seems like a better way to do it, because at
least it warns you. I was also talking about how in emacs lisp,
pretty much everything is a global variable,
so you can often "fix" something by just changing some internal variable to do what you want
(usually with knowledge of how it is used internally).
You (as the end-user) should not have to do this. If you had to set a "magic" internal variable to get what you want, then that's a bug in the package. The variables meant to be customized by the end-user are clearly marked and documented through the customize facility.
Aaron Meurer