Switch to an async api

[SleepWalker]

refs #43

It was a mistake to say, that everything will fit in fixUrl :)

Nevertheless, I have finished with some draft implementation! And successfully tested it on my project. But there are, probably, quite a lot of changes...

I can reduce the amount of code, but I have some questions:

• according to the old logic valueCallback will return oldUrl in two cases: when the url should not be processed (isUrlShouldBeIgnored) and when UrlProcessor returned an empty url. Is the second case expected behavior or it is a bug? For now I've leaved this logic as it is and added warning for the case, when UrlProcessor returns bad value.
• For the flow with promises, I need to do two String.replace calls per url. I think, that this extra call is not expensive, but I can be wrong. So I've wrote separate code for sync and async replacements for now. If it is ok, I can wrap all UrlProcessor results in Promises and drop sync logic to reduce the amount of code.

And another one question: should I polyfill Promise for an old Node.js?

[niksy]

What is the status of this PR? Can we maybe help in getting this PR merged (e.g. testing various use cases)?

[SleepWalker]

@niksy I am using it for my projects and waiting for any feedback here.
@MoOx can you take a look?

[RReverser]

This is great. Is anyone still looking into this PR? Being able to handle asynchronous external deps would be very helpful.

[niksy]

@RReverser unfortunately no, and it's a real shame :( In the mean time, I've found that https://github.com/sebastian-software/postcss-smart-asset is fork of this module but has async support so you can try that. I've been using it myself and it works.

@sergcen any chance someone can look at this and help us get this merged? Async API would be really helpful.

[jonathantneal]

This branch is now out of sync with master to the point of conflicts. If there isn’t new activity soon, I would say this should unfortunately be closed.

[niksy]

It would be real shame if this is missed opportunity. I think postcss-url is one od the most used PostCSS plugins and having async API (by default, but that's another story) is must have today. Can we do something to merge this?

[MrMeison]

Don't panic, I repairing this PR :)

[SleepWalker]

@MrMeison There was no comment from maintainers for two years. There is no sense to write any code string, till we know, that this PR will be accepted.

[sergcen]

PR will be accepted after @MrMeison will fix conflicts

[MrMeison]

goto #134

[sergcen]

published 9.0.0 with beta dist-tag