Change WireTask inputs to a serializable type

[stephanenicolas]

Solves issue #1515.

[stephanenicolas]

This is the main change: WireInput cannot be serialized during instant execution (a.k.a config caching) because it has a configuration which is not serializable.
The workaround is to use the Locations data class which seem to be handled well by Gradle. I could test and this seem to work well.
https://issuetracker.google.com/issues/153711618

[stephanenicolas]

This means the toLocations method is now called during configuration. Before, it was run during an afterEvaluate block which is pretty much the same. There might be a better way to organize things so that the dependency resolution would be performed at execution time, as it should but I don't know the plugin enough to refactor it this way.

[eskatos]

You could try make WireTask.sourceInput a ListProperty<Location> and wire a Provider<Location> to it here. Maybe changing WireInput.toLocation() to directly return the provider. This would defer dependency resolution to the task execution on a vintage build, and to the task graph calculation on a configuration-cache enabled build.

[stephanenicolas]

I agree that it would be better, and I thought about using properties but all fields indeed should use lazy properties when it applies and it does for most of them.
That would be a nice refresh for the wire plugin. Can it be done in a different PR though @eskatos ? My goal is not really to modernize the plugin but to have instant execution working.

[oldergod]

I think we don't wanna make toLocations on configuration. I wonder if we could just pass a list of string, then within the Plugin, do something like File(string).toLocation

[swankjesse]

This makes our cache key a function of our configurations’ dependencies. If these configurations dependencies change, will our cache be invalidated? If so this is good!

Alternately – can we change our cache key to be the configuration object or the dependencies object? This needs to be recomputed when that changes.

[stephanenicolas]

@swankjesse @eskatos , I adopted the solution of @eskatos after talking with Rodrigo from Gradle. I didn't know that providers are evaluated after the configuration of the task, when configurations are resolved and the tasks are serialized.

So,in this case, @oldergod , we don't resolve configurations (via the call to toLocations()) during configuration, but right after. When the task is serialized, that's where gradle wants to resolve configuration and we use this information in the plugin exactly at this moment to provide the locations.

@swankjesse I am also wondering if we shouldn't change the @Internal annotation for @Input, and maybe apply some kind of normalizer to help the up-to-date check / caching.

[stephanenicolas]

I could test and make sure it works:

• gradle nightly 6.6-20200603220033+0000
• AGP 4.1.0-alpha09
• KGP 1.3.72
• plus this PR for 3.3.0-SNAPSHOT

And everything works perfectly :D

[oldergod]

Looks good to me. @jrodbx could you give a look?

[jrodbx]

LGTM

[oldergod]

Thank you Stéphane