$(AndroidUseAapt2) runs ConvertResourcesCases a lot

[jonathanpeppers]

Steps to Reproduce

1. Enable $(AndroidUseAapt2) in a Xamarin.Forms project
2. You will see ConvertResourcesCases run ~9 times

See #2348, where I saw this firsthand. I think if we fixed this, $(AndroidUseAapt2) could possibly be enabled by default?

Expected Behavior

With $(AndroidUseAapt2), ConvertResourcesCases should take approximately the same amount of time as a build without $(AndroidUseAapt2).

Actual Behavior

$(AndroidUseAapt2) runs ConvertResourcesCases a bit too much.

Version Information

Reports of this in the 15.9 preview, and I have reproduced on master.

Log File

ConvertResourcesCases3.zip

[dellis1972]

When Aapt2 is enabled we have to generate a flata archive for each library resource (i.e everything in the lp directory. As part of that process we are calling ConvertResourcesCases to ensure that the library resources are fixed up BEFORE we put them in the flata. This happens on the very first build of the app, and unless a Clean is called will be a one off. aapt2 will then use those flata files in the link process later in the build.

Now we could make use of the new logic to Skip ConvertResourcesCases for those known libraries which we know do not need processing so help speed things up.

[jonathanpeppers]

What I'm seeing from these logs, if I just pick one of the files ConvertResourcesCases is processing, this log shows up 9 times during the initial build:

  Processing: C:\Users\myuser\Desktop\Git\xamarin-android\tests\Xamarin.Forms-Performance-Integration\Droid\obj\Debug\90\lp\22\jl\res\values\values.xml   10/30/2018 4:28:18 PM > 1/1/0001 12:00:00 AM

So it would be ok for ConvertResourcesCases to run 9 times, if it wasn't running on the same files. But looking at ConvertResourcesCases, it seems like it's meant to run on all of them in one shot...

I'm wondering if ConvertResourcesCases could be moved to a new target and use DependsOnTargets? Then it could probably be setup to run once during the build? I will test and see if this breaks anything.

[dellis1972]

Ah right, yes. That is probably it. Aapt2 will need to run for each lp but the conversion should only run either across the whole lot or only for the res dir for that lp.