Re-enable managing imports by rustfmt

[cyplo]

As we're using VSCode mainly now - it's hard for me to rely on 'organize imports' from CLion to keep the imports clean thus making rustfmt responsible for that.

[cyplo]

needs https://github.com/balena-io-modules/balena-temen/pull/48

[zrzka]

@cyplo I'd like to have this one closed without merging and changing rustfmt behavior. Reasons:

• IDE agnostic, I basically don't care what editor do you / I / others use and we shouldn't switch the way how the code is formatted
• semantics optimisation of imports (like CLion does) is nice and we agreed on it
• we should do it manually if rustfmt / VSCode can't do it, it's not that hard nor time consuming
  • we can also send PR to rustfmt
  • we can also send PR to VSCode plugin
• rustfmt breaks use statements comments (not always) and it's a mess

In other words, this order still stands:

• std
• extern crates
• crate
• super
• self

Example before:

use std::collections::HashMap;
use rand::{self, RngCore};
use serde_json::Value;
use uuid::Uuid;
use super::Result;
use crate::context::Context;
use crate::error::Result;
use self::uuidv4 as uu;

Example after:

use std::collections::HashMap;

use rand::{self, RngCore};
use serde_json::Value;
use uuid::Uuid;

use crate::context::Context;
use crate::error::Result;

use super::Result;

use self::uuidv4 as uu;

[zrzka]

Not mentioning, that sometimes, this rule can be skipped and import can be organised by a "function" / ... like:

// JSON related crates
...

// YAML related crates
...

[cyplo]

Alrighty, probably worth taking a look into making rustfmt smarter as you said then - I wrote this down in the list of things to do later :)

[zrzka]

@cyplo what happens when you split import to groups manually (empty lines between groups) and then run rustfmt? Does rustfmt keep groups and reorders items in each group individually?

[zrzka]

Maybe this is a way, like semi automate it. Groups manually, but keep them sorted.

[cyplo]

will take a look based on this code in this PR, with default rustfmt settings and let you know

[cyplo]

It seems that I can introduce arbitrary groups by putting in new lines between them. Then within the group rustfmt keeps the group sorted. But it does not reshuffle/resort between the groups themselves nor it does not seem to change the order of the groups introduced by me. All of this is with the default settings - tested on the branch for this PR.

Would that work @zrzka ? Or do you see a place where this would break or want to experiment with it yourself ?

[zrzka]

@cyplo then I think you can reopen it ... I'd like to stick with ...

* std
* extern crates
* crate
* super
* self

... order. And if rustfmt doesn't regroup them, I'm ok with rustfmt touching / ordering them.

Also it's not a hard rule, it's about readability only, so, if there will be a mistake, we can always PR it.

[cyplo]

Will play with how CLion and rustfmt interact and if they don't fight I will reopen this one and ping you :)