Rule Proposal: lines-around-directive

[mysticatea]

From requirePaddingNewLinesAfterUseStrict and disallowPaddingNewLinesAfterUseStrict.

This rule will require/disallow blank lines before/after a chunk of directive prologues.

{
    "lines-around-directive": ["error", "always" or "never"],
    // or
    "lines-around-directive": ["error", {
        "after": "always" or "never",
        "before": "always" or "never"
    }]
}

Valid:

/*eslint lines-around-directive: ["error", "always"]*/

// header comment?

"use strict";

foo();

function foo() {
    "use strict";  // ignore at the head of block. this is warned by padded-blocks.
    "use asm";     // ignore between directives.

    foo();
}

/*eslint lines-around-directive: ["error", "never"]*/

// header comment?
"use strict";
foo();

function foo() {

    "use strict";  // ignore at the head of block. this is warned by padded-blocks.
    "use asm";     // ignore between directives.
    foo();
}

Invalid:

/*eslint lines-around-directive: ["error", "always"]*/

// header comment?
"use strict";
foo();

function foo() {
    "use strict";
    foo();
}

/*eslint lines-around-directive: ["error", "never"]*/

// header comment?

"use strict";

foo();

function foo() {
    "use strict";

    foo();
}

[mysticatea]

Can we check lines between Shebang and directive prologues?

[ilyavolodin]

@mysticatea We should be able to, since shebang is commented out before parsing, we just have to check comment value.

[nzakas]

Do we need to check padding before? That would almost always be covered by padded-blocks, wouldn't it?

[mysticatea]

I had imaged the previous padding for shebang and header comment.

#!/usr/bin/env node

"use strict"

/**
 * header comment
 */

"use strict"

[nzakas]

I see. So then this rule's before would not apply in blocks?

[mysticatea]

/*eslint lines-around-directives*/

function a() {
    "use strict";
}

function a() {

    "use strict";
}

function a() {
    /*
     * comment
     */

    "use strict";
}

[mysticatea]

Sorry, I clicked a wrong button...

I'm thinking before would apply if there is a comment at the top of blocks.

[nzakas]

Doesn't padded-blocks already cover that case, too?

[mysticatea]

padded-blocks checks lines before the top comment in the block.

function foo() {
    <!-- by padded-blocks -->
    /*COMMENT*/
    <!-- by lines-around-directives -->
    "use strict";
    <!-- by lines-around-directives -->
    doSomething()
    <!-- by padded-blocks -->
}

[nzakas]

Ah, I see. Got it.

👍

[kaicataldo]

Anything else left to discuss here? I'm happy to champion this one. I'm looking for a JSCS compat issue to work on this weekend and this seems like a good one :)

@eslint/eslint-team thoughts?

[platinumazure]

👍 from me.

[alberto]

👍

[mikesherov]

👍