Replace settings.json with x.py setup note

[clubby789]

rust-lang/rust#107757 moves the recommended settings.json setup into x.py setup, so update the dev guide accordingly.

cc @jyn514

[jyn514]

This looks great, thanks! I would like to wait until the rust-lang/rust PR merges before merging this but otherwise LGTM :)

[RalfJung]

I think this is unfortunate; having the file content available on a website made it much easier to update the file when changes are required (which happens fairly regularly, 1-2 times a year): when things behave strangely, I would just go to https://rustc-dev-guide.rust-lang.org/building/suggested.html#configuring-rust-analyzer-for-rustc and see what is different from my config.

Doing ./x.py setup instead doesn't work, it asks me a question instead of just printing the desired vscode settings:

Welcome to the Rust project! What do you want to do with x.py?
a) library: Contribute to the standard library
b) compiler: Contribute to the compiler itself
c) codegen: Contribute to the compiler, and also modify LLVM or codegen
d) tools: Contribute to tools which depend on the compiler, but do not modify it directly (e.g. rustdoc, clippy, miri)
e) user: Install Rust from source
Please choose one (a/b/c/d/e): 

The correct answer for me is "a, b, c, d". 😂 Also my config.toml already works for all of these cases, I don't want it to be changed please. (Nor do I have any idea what the various answers would do -- so there's a perceived risk that just picking something breaks stuff for me. Giving me a choice without telling me about its consequences does not feel great.)

How can I get the recommended vscode settings without having the tool change my config.toml?

[jyn514]

@RalfJung you can run cp src/etc/vscode_settings.json .VSCode/settings.json. I'm happy to make a note of that in the docs, are you interested in making a PR with that change? ;)

Separately, setup is doing enough things now that I think allowing things like setup hook and setup vscode makes sense so you don't have to go through the whole flow.

[RalfJung]

you can run cp src/etc/vscode_settings.json .VSCode/settings.json

No that won't work, my settings.json contains a bunch of custom stuff as well.

Maybe the wiki page could just link to https://github.com/rust-lang/rust/blob/master/src/etc/vscode_settings.json ?

[jyn514]

Maybe the wiki page could just link to https://github.com/rust-lang/rust/blob/master/src/etc/vscode_settings.json ?

👍 seems good - we do that already for the nvim paragraph but it's not rendered so it's not obvious.