Flowtype comments markers

[qzb]

Flowtype supports annotating code with comments (only block comments /* ... */). It uses three different markers ( :, ::, flow-include), none of them is currently recognized by standard. Flowtype ignores whitespaces before markers, so standard doesn't brake anything, but placing spaces before these markers is inconsistent - they are not required before other markers like * and !. My proposition is to add : and :: to list of markers for block comments. I'm not sure if flow-include should be also added, it is just an alias for ::, and markers like this looks kind of strange without whitespace:

/*flow-include declare type foo = number */    // looks strange, currently disallowed
/* flow-include declare type foo = number */   // looks ok

On other hand space before : marker could actually improve readability:

function foo (arg /* : number */) {}   // with whitespace - currently valid
function foo (arg /*: number */) {}    // without whitespace - currently invalid

[josephfrazier]

I just ran up against this, but didn't know that Flowtype ignores whitespace before markers. Thanks for pointing out how to work around it!

It looks like gajus/eslint-plugin-flowtype#87 might be the place to add support for the syntax without whitespace.

[feross]

I think it's probably fine to add an exception for : and ::. The point of this rule is generally to avoid writing comments like //this is a comment.

Can you provide a link to the Flow documentation where this comment marker is discussed?

[cesarandreu]

Comment Syntax section in the docs points to the following blog post.

[feross]

This will be part of standard v9. Since it's relaxing a rule, there is no impact on the ecosystem. Except of course, now you can use Flow Comments!

🎉