vue/padding-line-between-tags with new 'consistent' option

[mesqueeb]

What rule do you want to change?
vue/padding-line-between-tags
https://eslint.vuejs.org/rules/padding-line-between-tags.html#vue-padding-line-between-tags

Does this change cause the rule to produce more or fewer warnings?
depends on the config

How will the change be implemented? (New option, new default behavior, etc.)?
new option "blankLine": "consistent"

I don't want blank lines in between all siblings or after specific tags.

What I would love:

• no blank lines between siblings: GOOD
• blank lines between siblings: also GOOD
• under the same parent blank lines between some siblings, but not others: BAD

Inconsistent spacing between same parent siblings is really inconsistent and drives me crazy. However, I do not want to force or disallow blank lines, I feel it's often a case-by-case choice depending how cluttered a parent with siblings looks.

My rule wish is:

{
  "vue/padding-line-between-tags": ["error", [
    { "blankLine": "consistent", "prev": "*", "next": "*" }
  ]]
}

Please provide some example code that this change will affect:

GOOD

<template>
  <header>
    <div></div>
    <div></div>
    <div></div>
  </header>

  <div></div>
  
  <div />
  
  <footer></footer>
</template>

GOOD

<template>
  <header>
    <div></div>

    <div></div>
    
    <div></div>
  </header>
  <div></div>
  <div />
  <footer></footer>
</template>

BAD

<template>
  <header>
    <div></div>

    <div></div>
    <div></div>
  </header>
  <div></div>

  <div />
  <footer></footer>
</template>

[FloEdelmann]

CC @dev1437 and @amiranagram, follow-up to #1832 and #1966.

[dev1437]

#1982 @FloEdelmann, but we will definitely need more edge cases defined and tests for them. If @mesqueeb wants to try the current behaviour and see if there are any issues, that would be great.

[mesqueeb]

@dev1437 sure! And thanks so much for this implementation!

I think it's easiest for me to test it if you could release it to npm once. @FloEdelmann are you comfortable releasing it to npm once?

I can open new issues for any lint bugs for this rule i come across in the future.

[FloEdelmann]

@mesqueeb We can't just merge and release a non-tested feature. If you can't test it in a repo, maybe you can have a look at test cases in the PR #1982 and see if you disagree with the behavior there, or suggest new test cases that are likely to fail.

[mesqueeb]

@FloEdelmann i'd love to run it on my codebase once. From there if I find failures, I'll add those as test cases.

I'll try to set up a fork and let you know how it goes. : )

[ota-meshi]

I think we need to look more into how the new option work.
#1982 (comment)

[ota-meshi]

I think that it is better to regard one element as one group and check whether it is consistent in the group. However, the definition of groups is currently inflexible, so it might be a good idea to change the prev and next options to allow CSS selectors.

[ota-meshi]

I reconsidered that it might be better to check between elements where the matched blankLine returns consistent, instead of groups.

[dev1437]

I've updated this, so now it should only consider blocks that have consistent rule and are siblings