docs: rewrote instructions on how to author a rule

[elijah-potter]

In #478, it became clear that a lot of information was missing from the instructions for contributing a new rule to Harper.

This PR is a complete rewrite of that documentation.

@hippietrail, does this make more sense?

[hippietrail]

Might I suggest something like this:

You need to add it in two places. First add a "module declaration":

mod an_a;
mod avoid_curses;
mod boring_words;
// [svp! df:+]mod my_rule;

Then a little further down add a "public use declaration":

pub use an_a::AnA;
pub use avoid_curses::AvoidCurses;
pub use boring_words::BoringWords;
// [svp! df:+]pub use my_rule::MyRule;

[elijah-potter]

I feel that the single code block with both edits is simpler. The correct placement of the lines will be handled by rustfmt before we merge the PR.

[hippietrail]

In #478, it became clear that a lot of information was missing from the instructions for contributing a new rule to Harper.

This PR is a complete rewrite of that documentation.

@hippietrail, does this make more sense?

Yes it's better and better. I made one suggestion. I also think it would be more helpful for non-rust-coders to include an example where I think it's now just unimplemented().

But also my attempt at a new rule still doesn't work now that I've set up just and using just lint instead of cargo run. It builds and runs and checks the file but only finds the old lints.

[elijah-potter]

But also my attempt at a new still doesn't work now that I've set up just and using just lint instead of cargo run. It builds and runs and checks the file but only finds the old lints.

That's odd. Would you mind opening a draft PR so I can get a look at what's going on?

[hippietrail]

But also my attempt at a new still doesn't work now that I've set up just and using just lint instead of cargo run. It builds and runs and checks the file but only finds the old lints.

That's odd. Would you mind opening a draft PR so I can get a look at what's going on?

Gave it a shot: #494 By the way I don't think the new docs mentioned changing package.json but I changed it anyway.