Lexical Navigation

[Yannick Gingras]

Thank you for your response, Waqar!

You are right that "move to next matching indent" does almost
everything I need. The full lexical navigation would be cool to have,
but "matching indent" probably covers 70% of the actual use cases, at
least. I can't see however how to combine "matching indent" with a
selection like I can do with "matching bracket". The typical use case
here is that I would take a whole class or a whole function and move it
to a different file.

Is there a way to do selection with "matching indent"?

I will take a deeper look at the scripting API to see if I could do a
proof of concept for a more lexically aware navigation.

Thank you again for all the pointers.

On Fri, 2022-02-11 at 01:06 +0500, Waqar Ahmed wrote:
> Hi, 
> 
> I don't really do a lot of python so not sure if this will work for
> you, but there is a shortcut Ctrl+Alt+down/up which does some kind of
> scope jumping. Not sure how well it will work in a python file. For
> me, it allows me to jump to a function start / end quickly. 
> 
> But to really achieve what you want, I guess scripting is the only
> way forward at least for now. Our script api is kind of simple, and
> yeah there are no semantics available except for comment/string info.
> But it's still doable, if you want to try. 
> 
> Regarding LSP, it's a common misconception that the client has a lot
> semantic info available. It doesn't really, the server does and it's
> the server that really does all the work, the editor just does what
> the server says. I guess if we really try, we can accumulate some
> semantic info and then use that for other purposes but not sure if
> this will scale well or even if we want to do it. 
> 
> Lastly, it's unlikely that the external tools will allow moving
> cursor as the external tools are mostly meant for simple input ~
> process ~ output tasks. However,  allowing to execute a process via
> the scripting api is possible I think, but not implemented. 
> 
> All in all, I would suggest you to try the scripting api. Atm, all of
> Kate's indentation is implemented using the script api. 
> 
> 
> 
> On Mon, Feb 7, 2022, 11:29 AM Yannick Gingras <ygingras at ygingras.net>
> wrote:
> > In Lisp, Emacs offers a rather interesting code navigation. There
> > are
> > basically only 3 short-cuts that provide most of what anyone needs:
> > - go to outer scope;
> > - go to next item with same scope;
> > - go to previous item with same scope.
> > 
> > There might be go to inner scope, but after going outer scope, it's
> > typically just one key stroke away to go one scope down: right
> > arrow.
> > 
> > Take the following example (not any real Lisp dialect):
> > (def foo (a b c)
> >     (for (i x (enumerate (range b c))
> >         (ifeq (a x)
> >             (return i)))))
> > 
> > What the code does is not really important, but a Python version of
> > it
> > would look line this:
> > def foo(a, b, c):
> >     for i, x in enumerate(range(b, c)):
> >         if a == x:
> >             return i
> > 
> > Besides being a great example of how mind twisting Lisp can be, it
> > illustrate beautifully how one could take advantage of lexcical
> > navidation. Say I just finished typing the "enumerate" clause and I
> > want to add a default return if we don't find any `x` that is equal
> > to
> > `a`. I would go "outer scope" 3 times, "then next same scope" once.
> > It
> > would put me inside that big ugly series of closing parens:
> > ")))))",
> > right before the last one. I can then type Return and add my
> > default
> > return clause: (return nil). That's like "return None" in Python or
> > "return null" in great many language.
> > 
> > Kate already offers something really close to this, but not the
> > whole
> > solution. There is "go to matching bracket" and "previous and next
> > matching intent", which is just like go to next item with same
> > scope
> > in
> > Python. It's almost there! Wouldn't it be cool to be able to say:
> > "I'm
> > done with this for, I just want to add something right after it"?
> > To
> > do
> > that, one would need "go to outer scope", which neither exists for
> > brackets nor for indents, and a small variation to "move to to next
> > indent" that stops at the end of the current intent rather than
> > entering the next block and finding the first statement that has
> > the
> > same indent.
> > 
> > Of course, a general implementation that works for many languages
> > is
> > going to be a lot more complicated than the Lisp one, which has the
> > benefit of only having to match parentheses, but I feel like this
> > is
> > a
> > very natural way way to move around code that might justify the
> > implementation complexity.
> > 
> > I'm also not volunteering to implement this, at least not the whole
> > thing. I looked at the script API, and it would be doable there,
> > but
> > kind of hard because it's all character based and most of the
> > semantic
> > is not passed to the script. I think that the LSP Code Actions
> > protocol
> > would be the most logical way to do this since inside the LSP,
> > there
> > is
> > a lot of semantic info available. It looks pretty heavy, however,
> > so
> > I'm not sure this is where a proof of concept should go. The
> > external
> > tools plugin however supports everything that is needed. If I can
> > call
> > a Python script, I can easily get the semeantic info back (for
> > Python
> > code). I would just need a way to pass back to Kate where to move
> > the
> > cursor as a response.
> > 
> > Let me end with two unrealated questions:
> > - does that sound like a way to move around code that you would
> > like
> > to
> > use?
> > - is there any chance that the external tools plugin would allow me
> > to
> > move the cursor in a nearby future?
> > 
> > Sorry for the long message. I could not find a better way to
> > summerize
> > my thoughts.
> > 

-- 
Yannick Gingras
http://ygingras.net

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