Move compression code from BuildApk to utility class (#9383)

Context: #9382

To further simplify `BuildApk`, move assembly compression code
to a separate utility class.  This also lets us compress assemblies
from tasks other than `BuildApk`.

Author: grendello

src/Xamarin.Android.Build.Tasks/Tasks/BuildApk.cs

@@ -515,49 +515,7 @@ string CompressAssembly (ITaskItem assembly)
 					return assembly.ItemSpec;
 				}
 
-				if (bool.TryParse (assembly.GetMetadata ("AndroidSkipCompression"), out bool value) && value) {
-					Log.LogDebugMessage ($"Skipping compression of {assembly.ItemSpec} due to 'AndroidSkipCompression' == 'true' ");
-					return assembly.ItemSpec;
-				}
-
-				string key = CompressedAssemblyInfo.GetDictionaryKey (assembly);
-				AndroidTargetArch arch = MonoAndroidHelper.GetTargetArch (assembly);
-				if (!compressedAssembliesInfo.TryGetValue (arch, out Dictionary<string, CompressedAssemblyInfo> assembliesInfo)) {
-					throw new InvalidOperationException ($"Internal error: compression assembly info for architecture {arch} not available");
-				}
-
-				if (!assembliesInfo.TryGetValue (key, out CompressedAssemblyInfo info) || info == null) {
-					Log.LogDebugMessage ($"Assembly missing from {nameof (CompressedAssemblyInfo)}: {key}");
-					return assembly.ItemSpec;
-				}
-
-				EnsureCompressedAssemblyData (assembly.ItemSpec, info.DescriptorIndex);
-				string assemblyOutputDir;
-				string subDirectory = assembly.GetMetadata ("DestinationSubDirectory");
-				string abi = MonoAndroidHelper.GetAssemblyAbi (assembly);
-				if (!String.IsNullOrEmpty (subDirectory)) {
-					assemblyOutputDir = Path.Combine (compressedOutputDir, abi, subDirectory);
-				} else {
-					assemblyOutputDir = Path.Combine (compressedOutputDir, abi);
-				}
-				AssemblyCompression.CompressionResult result = AssemblyCompression.Compress (compressedAssembly, assemblyOutputDir);
-				if (result != AssemblyCompression.CompressionResult.Success) {
-					switch (result) {
-						case AssemblyCompression.CompressionResult.EncodingFailed:
-							Log.LogMessage ($"Failed to compress {assembly.ItemSpec}");
-							break;
-
-						case AssemblyCompression.CompressionResult.InputTooBig:
-							Log.LogMessage ($"Input assembly {assembly.ItemSpec} exceeds maximum input size");
-							break;
-
-						default:
-							Log.LogMessage ($"Unknown error compressing {assembly.ItemSpec}");
-							break;
-					}
-					return assembly.ItemSpec;
-				}
-				return compressedAssembly.DestinationPath;
+				return AssemblyCompression.Compress (Log, assembly, compressedAssembliesInfo, compressedOutputDir);
 			}
 		}
 

src/Xamarin.Android.Build.Tasks/Utilities/AssemblyCompression.cs

@@ -1,8 +1,14 @@
 using System;
+using System.Collections.Generic;
 using System.Buffers;
 using System.IO;
 
 using K4os.Compression.LZ4;
+using Microsoft.Android.Build.Tasks;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+using Xamarin.Android.Tasks;
+using Xamarin.Android.Tools;
 
 namespace Xamarin.Android.Tasks
 {
@@ -49,7 +55,7 @@ public void SetData (string sourcePath, uint descriptorIndex)
 
 		static readonly ArrayPool<byte> bytePool = ArrayPool<byte>.Shared;
 
-		public static CompressionResult Compress (AssemblyData data, string outputDirectory)
+		static CompressionResult Compress (AssemblyData data, string outputDirectory)
 		{
 			if (data == null)
 				throw new ArgumentNullException (nameof (data));
@@ -104,5 +110,57 @@ public static CompressionResult Compress (AssemblyData data, string outputDirect
 
 			return CompressionResult.Success;
 		}
+
+		public static string Compress (
+			TaskLoggingHelper log,
+			ITaskItem assembly,
+			IDictionary<AndroidTargetArch, Dictionary<string, CompressedAssemblyInfo>> compressedAssembliesInfo,
+			string compressedOutputDir)
+		{
+			if (bool.TryParse (assembly.GetMetadata ("AndroidSkipCompression"), out bool value) && value) {
+				log.LogDebugMessage ($"Skipping compression of {assembly.ItemSpec} due to 'AndroidSkipCompression' == 'true' ");
+				return assembly.ItemSpec;
+			}
+
+			string key = CompressedAssemblyInfo.GetDictionaryKey (assembly);
+			AndroidTargetArch arch = MonoAndroidHelper.GetTargetArch (assembly);
+			if (!compressedAssembliesInfo.TryGetValue (arch, out Dictionary<string, CompressedAssemblyInfo> assembliesInfo)) {
+				throw new InvalidOperationException ($"Internal error: compression assembly info for architecture {arch} not available");
+			}
+
+			if (!assembliesInfo.TryGetValue (key, out CompressedAssemblyInfo info) || info == null) {
+				log.LogDebugMessage ($"Assembly missing from {nameof (CompressedAssemblyInfo)}: {key}");
+				return assembly.ItemSpec;
+			}
+
+			AssemblyData compressedAssembly = new AssemblyData (assembly.ItemSpec, info.DescriptorIndex);
+			string assemblyOutputDir;
+			string subDirectory = assembly.GetMetadata ("DestinationSubDirectory");
+			string abi = MonoAndroidHelper.GetAssemblyAbi (assembly);
+			if (!String.IsNullOrEmpty (subDirectory) && !(subDirectory.EndsWith ($"{abi}/", StringComparison.Ordinal) || subDirectory.EndsWith ($"{abi}\\", StringComparison.Ordinal))) {
+				assemblyOutputDir = Path.Combine (compressedOutputDir, abi, subDirectory);
+			} else {
+				assemblyOutputDir = Path.Combine (compressedOutputDir, abi);
+			}
+
+			CompressionResult result = AssemblyCompression.Compress (compressedAssembly, assemblyOutputDir);
+			if (result != CompressionResult.Success) {
+				switch (result) {
+					case AssemblyCompression.CompressionResult.EncodingFailed:
+						log.LogMessage ($"Failed to compress {assembly.ItemSpec}");
+						break;
+
+					case AssemblyCompression.CompressionResult.InputTooBig:
+						log.LogMessage ($"Input assembly {assembly.ItemSpec} exceeds maximum input size");
+						break;
+
+					default:
+						log.LogMessage ($"Unknown error compressing {assembly.ItemSpec}");
+						break;
+				}
+				return assembly.ItemSpec;
+			}
+			return compressedAssembly.DestinationPath;
+		}
 	}
 }