feat: join lines joins two ifs into else if

[matklad]

bors r+
🤖

[bors]

Build succeeded:

• Rust (macos-latest)
• Rust (ubuntu-latest)
• Rust (windows-latest)
• TypeScript (ubuntu-latest)
• TypeScript (windows-latest)

[jhpratt]

Is there any other place joining lines has behavior other than just joining the lines? This seems quite counterintuitive to me.

[flodiebold]

It already removes braces and commas. If you just want to join lines, you can use the editor's built-in functionality; the whole point of this function is to be smarter. And there's really no good reason to join } and if { into } if {, unless you want } else if {. I think there are probably a lot of other similar opportunities to DWIM.

[jhpratt]

That's just syntactic, not semantic, setting aside macros for obvious reasons. Imo "no other reason you'd do that" is quite dangerous when I join lines. Personally, I overrode the editor's built-in join lines to be r-a because I expect it to be a drop-in replacement.

[flodiebold]

Undo is just a keypress away. Still, I don't see any situation where you'd join these lines without intending this change. But I'm sure @matklad would be open to making this configurable ;)

[jhpratt]

It's more the unexpectedness factor for me. I don't think that "join lines" should do anything but save for some syntactic cleanup. I have no issue waiting for a response, though 🙂

[matklad]

Yeah, adding a config flag should be fine. I guess, I probably should heed my own advice and proactively add flags for other bits of functionality here :)

Couple of more things to do:

• document special cases that join lines has
• consider renaming it to just "join"?

[rogerdahl]

At first glance, this looks like an automated refactoring which shouldn't change semantics, but if the two predicates are not mutually exclusive, or if there are side effects, it will. So it seems like it could be a footgun for the unwary... Is there a way to tell if something is an automated refactoring or a code editing shortcut?

[matklad]

@rogerdahl explicitly invoked actions are "do what I mean" rather than "do not change semantics". If the user invokes join lines (which is an explicit shortcut) between two ifs, that's a signal for the IDE that they want to join the two lines.

[matklad]

Note that this behavior is now configurable: https://github.com/rust-analyzer/rust-analyzer/pull/9503/files#diff-00784dde03b1be151004f435a4ca74754cb674a9e789840e12760d8f3ac1728fR727

[jhpratt]

Thank you!