How to flip arguments inside parens? (a, b) -> (b, a)

Transposing words, bound by default to `M-t`, should work here. Bring the point to the right of the comma and hit `M-t`.

In the same vein, if you have more complex arguments, for example wanting to swap the arguments to be interpolated in `(format tmpl (my-func arg) other-value)`, place point between `(my-func arg)` and `other-value` and type `C-M-t` (or `M-x transpose-sexps`).

Nope, that only works if the arguments are words. There is a `transpose-sexps` in `simple.el`, but that only works if the arguments are words or sexps. For complex function calls like this: someFunction(foo.bar(), baz, qux()) You'll need to use something better. There is a solution here that works most of the time: https://emacs.stackexchange.com/a/11067/654

>Nope, that only works if the arguments are words. Correct! That's why I chose to use the word "should" when I suggested it :) `M-t` almost always works in "transpose the args" scenarios for me.

`C-M-t` runs `transpose-sexps`, which *should* work for this — but your idea of an what an expression is may differ in non-Lisp languages or their modes.

> M-t almost always works in "transpose the args" scenarios for me. I feel like for most people `M-t` would almost always *fail*. If you had said `C-M-t` for `transpose-sexps` I might agree, but are your arguments really "almost always" only one word? It also doesn't work if an argument is a string. Just looking through a few files at work it's hard to find two single words next to each other. It's mostly non-single-word symbol names (camel/snake case), or one or more of the arguments has field/method access, like `foo(request.data, object.get_something())`. Using a `transpose-args` command also lets you not think about what type of thing the arguments are. You never have to think, "Would transpose-words work here? No, I need to use transpose-sexps. Actually wait that didn't work."

I've been using `c-transpose-args` from here, seems to work correctly for functions (but not for c++ templates, but maybe it's easy to fix): [https://github.com/elbeno/dotemacs/blob/master/.emacs.d/cpp-modes.el](https://github.com/elbeno/dotemacs/blob/master/.emacs.d/cpp-modes.el) (I think the original source is here: [https://emacs.stackexchange.com/a/47934](https://emacs.stackexchange.com/a/47934))

I wonder if there is a way to hook into LSP and get the expression from there instead of dealing with regex and trying to guess what’s happening

That's a good thought, that or maybe tree sitter. I don't know anything about the internals of each, but I'll check it out this week because I've always wanted a reliable version.

It seems there isn’t a generic way that always works M-t or C-M-t all fail in any slightly complex setting. The other custom functions rely on regex or custom rules instead of using LSP or tree sitter