fmt: group and order imports

[Gladear]

Imports should be grouped by "type" (vlib, .vmodules, program modules) and ordered alphabetically, so they are easier to find in a big list of imports.

e.g.

import os
import time

import gg // once it is moved to an external module
import ui

import internal.mod1
import internet.mod2

[atakanyenel]

I could tackle this with:

// vlib/v/fmt/fmt.v
pub fn (mut f Fmt) imports(imports []ast.Import) {
    if f.did_imports || imports.len == 0 {
        return
    }
    mut sorted_imports:=imports.clone()
    sorted_imports.sort(a.mod<b.mod) // new lines
    f.did_imports = true
    mut import_formatted := false // also used this instead of an integer
    mut already_imported := map[string]bool{}

    for imp in sorted_imports {
...

This currently only works for sorting. One catch is that, this breaks

• v -progress test-cleancode
• v -progress test-fmt

HEAVILY. So to introduce this to the codebase, there will be a large scale change in everyones forks.

[JalonSolov]

As V is still in Alpha status, large scale changes should be expected from time to time.

[atakanyenel]

The one concern I have is speed regression of fmt. clone and sort are expensive operations. Nevertheless, once imports are sorted in the first run, next runs can do a is_sorted operation(which is linear) and get rid of both clone and sort all together.

---

For grouping, the type of the import should come from ast, which currently doesn't have that kind of info in pub struct Import.

[JalonSolov]

"Make it work first, then optimize."

And you should never optimize without benchmarking, profiling, and considering use-cases. For example, there's really no need to even try to optimize some things because they are executed so seldom that it simply isn't worth the optimization effort.

[serkonda7]

I think grouling is avlot more important than the alphabetical order, therefore I'm against an incomplete implementation.