[Xamarin.Android.Build.Tasks] cache aapt2 version in AppDomain (#2975)

jonathanpeppers · jonpryor · commit 9bfd568096e5 · 2019-04-12T15:16:42.000-04:00
If you have `$(AndroidUseAapt2)` set to `True` (which is the default on master as of 1624c3f), the `<ResolveAndroidTooling/>` tooling task seems to take longer: aapt2: 83 ms ResolveAndroidTooling 2 calls aapt: 4 ms ResolveAndroidTooling 2 calls I figured out this was due to how we shell out to `aapt2 version` to check the version of `aapt2`. We should use `IBuildEngine4.RegisterTaskObject()` and cache the result of this call! * I used a key that contains the path to `aapt2`, so if that someone changes the path to `aapt2` used, it should obtain the `aapt2` version again. * I don't think we actually need to invalidate the cached value on anything else because we are shipping `aapt2` now (4ccbeb7). But what if there is a Xamarin.Android update? If you install a new `.vsix`, Visual Studio on Windows requires that you restart the IDE. If you install a `.pkg` on macOS, you need to restart the IDE *anyway*, because it keeps all system MSBuild `.targets` files in memory... Weird things will happen if you install a Xamarin.Android `.pkg` on macOS and don't restart Visual Studio for Mac. After this change, when the `aapt2 version` call is cached: 2 ms ResolveAndroidTooling 2 calls This was the "Hello World" sample project in this repo.
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/ResolveAndroidTooling.cs b/src/Xamarin.Android.Build.Tasks/Tasks/ResolveAndroidTooling.cs
@@ -235,6 +235,16 @@ bool GetAapt2Version ()
 		{
 			var sb = new StringBuilder ();
 			var aapt2Tool = Path.Combine (Aapt2ToolPath, Aapt2);
+
+			// Try to use a cached value for Aapt2Version
+			var key = ($"{nameof (ResolveAndroidTooling)}.{nameof (Aapt2Version)}", aapt2Tool);
+			var cached = BuildEngine4.GetRegisteredTaskObject (key, RegisteredTaskObjectLifetime.AppDomain) as string;
+			if (!string.IsNullOrEmpty (cached)) {
+				Log.LogDebugMessage ($"Using cached value for {nameof (Aapt2Version)}: {cached}");
+				Aapt2Version = cached;
+				return true;
+			}
+
 			try {
 				MonoAndroidHelper.RunProcess (aapt2Tool, "version", (s, e) => {
 					if (!string.IsNullOrEmpty (e.Data))
@@ -253,6 +263,7 @@ bool GetAapt2Version ()
 			Log.LogDebugMessage ($"`{aapt2Tool} version` returned: ```{versionInfo}```");
 			if (versionNumberMatch.Success && Version.TryParse (versionNumberMatch.Groups ["version"]?.Value.Replace (":", "."), out Version versionNumber)) {
 				Aapt2Version = versionNumber.ToString ();
+				BuildEngine4.RegisterTaskObject (key, Aapt2Version, RegisteredTaskObjectLifetime.AppDomain, allowEarlyCollection: false);
 				return true;
 			}
 			return false;
