Auto indent on insert_at_line_start

[CptPotato]

First attempt at #4859. This makes I and A automatically indent, but only if the line is empty. Otherwise it behaves exactly as before. I thought about also handling indentation when the line only contains white space, but I left this out for now. Either way, this is a breaking change.

I roughly followed the implementation of open_above/open_below. Though, I'm not sure if the implementation is very good, all the text editing functions in the code base are new to me.

Here's the result of insert_at_line_start / I with this change (the only difference is on the empty line):

before	master	this PR

I tried to handle all edge cases (i.e. cursor is at document start/end, multiple selections) and so far it seems to work. I also plan to make insert_at_line_end behave similarly.

Edit: insert_at_line_end now works the same.

closes #4859

[pascalkuthe]

I haven't looked too closely at the implementation yet but this does seem very useful to me and like a better default too. Thanks for working on this!

That being said we might want to keep the old behaviour as a seperate command so people that don't like this change can rebind.

[pascalkuthe]

The idea is good I think, the implementation can be simplified (and is not quite correct, see review comments)

[CptPotato]

Thanks for the detailed review and pointers @pascalkuthe. I expected that I was doing a lot of these things sub-optimally. I'll try to address these issues soon.

[pascalkuthe]

Two minor nits otherwise the implementation now LGTM.

[CptPotato]

I made the last suggested changes, thanks again.

I also created a second commit that adds the same behavior to insert_at_line_end by moving the indent code to a separate function.

[CptPotato]

Should I look into creating a test for the new behavior?

[pascalkuthe]

Should I look into creating a test for the new behavior?

I believe there is currently no tests for the existing behaviour so I wouldn't consider it a blocking issue but more tests are always good so if you want to add them go ahead

[CptPotato]

I added a test and found one remaining issue (which I fixed).

The test is a little ugly but it's the best I could do 👀
It checks both insert_at_line_start/end on all lines with this snippet:

fn foo() {
    if let Some(_) = None {

    }
 
}

fn bar() {

}

(there's one line with existing whitespace)

Is this okay or should I change the test?

[CptPotato]

Looks like some recent changes are causing conflicts.

Let me know when somebody wants to review this and I'll resolve them.

[pascalkuthe]

I have been testing this for a bit and did a pretty thorough review a while ago. Once the bugfix release (23.3.1) is done we can resolve the conflicts here (should be pretty easy) I think we can land this

[CptPotato]

Sorry for the long delay. I rebased onto latest master, should be good to go now.

[the-mikedavis]

I have a small style nit but otherwise I think this looks great (especially the integration tests!)

[pascalkuthe]

thanks for working on this! This is a great QOL improvement