Changed request.xhr? to return boolean instead of 0 or nil

[miry]

Changed return values for request.xhr? to true or false instead of nil and 0.

[luke-gru]

not a bug, this PR has been made before (#5329) and has been rejected

[pixeltrix]

@miry we've been here before - I suggest that you read the discussion on 3756a3f for the back story.

[miry]

It is really confuse that a method with suffix ? does not return true or false. IMHO

Btw: https://github.com/rack/rack/blob/master/lib/rack/request.rb#L308

[pixeltrix]

@miry whether a predicate should return true or false was debated to death in #5329 and 3756a3f - going over it again serves no purpose.

[miry]

@pixeltrix What do you think to replace word in the comment from the true(or even all phrase) to something more close to solution?

http://apidock.com/rails/ActionDispatch/Request/xml_http_request%3F

[fxn]

That's how predicates are documented: "returns true if...", "says whether...". In the very exceptional cases when you really want to commit or refer to the true singleton, the documentation guidelines of Rails say you need to use fixed-width font. True and false in regular font are used all over the place.

[miry]

@fxn What were the conditions to use the Regexp?

If only for case issue, so to use downcase is faster.

https://gist.github.com/miry/5150174

[fxn]

The method checks for case-insensitive inclusion, not sure if that is needed though. I didn't write the original method and don't see any test checking inclusion.

Bear in mind that no matter how you rewrite it, the method does not document singletons. So even in the case of a refactor that returned singletons you still could not rely on them, the same way people cannot rely on nil/0 today.

[miry]

@fxn I don't care about return value now, just performance issue.