[New] order: allow controlling intragroup spacing of type-only imports via newlines-between-types

[Xunnamius]

Depends on #3104

This PR implements in import/order: a new option analogous to newlines-between but specifically for controlling newlines between type-only imports.

A demo package containing this feature is temporarily available for easy testing:

npm install --save-dev eslint-plugin-import@npm:@-xun/eslint-plugin-import-experimental

Allow controlling intragroup spacing of type-only imports

This is implemented via newlines-between-types. The proposed documentation corresponding to this new feature can be previewed here.

Example

Given this code:

import type A from 'fs';
import type B from 'path';
import type C from '../foo.js';
import type D from './bar.js';
import type E from './';

import a from 'fs';
import b from 'path';

import c from '../foo.js';

import d from './bar.js';

import e from './';

And the following settings, the rule check will fail:

{
  "groups": ["type", "builtin", "parent", "sibling", "index"],
  "sortTypesAmongThemselves": true,
  "newlines-between": "always"
}

With --fix yielding:

import type A from 'fs';
import type B from 'path';

import type C from '../foo.js';

import type D from './bar.js';

import type E from './';

import a from 'fs';
import b from 'path';

import c from '../foo.js';

import d from './bar.js';

import e from './';

However, with the following settings, the rule check will succeed instead:

{
  "groups": ["type", "builtin", "parent", "sibling", "index"],
  "sortTypesAmongThemselves": true,
  "newlines-between": "always",
+ "newlines-between-types": "ignore"
}

sortTypesAmongThemselves allows sorting type-only and normal imports separately. By default, newlines-between will govern all newlines between import statements like normal.

I generally want my type-only imports to be sorted for ease of reference but never have newlines between them (save space) while I want my normal imports (which I tend to visually peruse more often) to be aesthetically pleasing, grouped, and sorted. newlines-between is too coarse-grained for this, so this PR introduces newlines-between-types, a setting identical to newlines-between except it only applies to type-only imports, and only when sortTypesAmongThemselves is enabled (i.e. it is backward-compatible).

When newlines-between and newlines-between-types conflict, newlines-between-types takes precedence for type-only imports. For normal imports, newlines-between-types is ignored entirely.

One issue that might warrant further discussion is which setting governs the newline separating type-only imports from normal imports. Right now, I have it so newlines-between-types controls this space, but perhaps it should be its own setting.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.12%. Comparing base (341178d) to head (d472b80).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3127      +/-   ##
==========================================
- Coverage   95.59%   92.12%   -3.47%     
==========================================
  Files          83       83              
  Lines        3629     3656      +27     
  Branches     1282     1304      +22     
==========================================
- Hits         3469     3368     -101     
- Misses        160      288     +128     

☔ View full report in Codecov by Sentry.
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[Xunnamius]

Like with the other PR, codecov is reporting patch coverage at 100% with no uncovered lines.

When I look at "indirect changes" I'm seeing the same src/rules/order.js file (among a bunch of seemingly unrelated files) but with uncovered lines that have nothing to do with the tests added by this PR. This PR also doesn't remove any tests, so I'm not quite sure what's going on there. Could be that some formerly-covered source was deleted. Everything else seems to have passed though :)

[ljharb]

should we use the schema to ensure that this option can't be set to true unless sortTypesGroup is also set to true?

[Xunnamius]

Sounds like a good idea to me. I was not aware that was a thing for eslint plugins :)

[ljharb]

it often requires a bit of gymnastics, but it's usually worth it for the DX.