Fix delayed middleware loading issue

[Cartmanishere]

Hi,

This is an attempt to fix issue around delayed middleware loading.
The relevant discussion is present at #533

Instead of adding the handler delay to the delayed-handlers atom in the macro, this takes care of adding
it in the atom through a function.

Fixes:
#447
#533
#657

[Cartmanishere]

Test for this are failing. The failures seem related to cljs and are not caused by the changes in this PR.

[bbatsov]

Did you manage to confirm that the suggested fix solves the race conditions? //cc @vspinu

Also - this needs a changelog entry.

Test for this are failing. The failures seem related to cljs and are not caused by the changes in this PR.

Yeah, there's a ticket for this #678 but I haven't been able to find time to investigate things further.

[Cartmanishere]

This is not a race condition per se. The problem is that we are relying on compile time side effects to be present at runtime. This works in normal scenario but breaks when the middlewares are compiled from within an application.

So to fix this, instead of relying on compile time side effects, we handle it at runtime. This fixes the issue. #447 has a reproducible example against which you can check. I have verified the same.

[bbatsov]

Got it. Thanks for tackling this! 🙇‍♂️ I'll cut a new release right away, as that is an important fix.

[timvisher]

This is seriously exciting. 😂