[Xamarin.Android.Tools.AndroidSdk] Revert JDK validation

src/Xamarin.Android.Tools.AndroidSdk/Sdks/AndroidSdkUnix.cs

@@ -112,17 +112,6 @@ protected override string GetJavaSdkPath ()
 			return JdkInfo.GetKnownSystemJdkInfos (Logger).FirstOrDefault ()?.HomePath;
 		}
 
-		public override bool ValidateJavaSdkLocation (string loc)
-		{
-			var result = base.ValidateJavaSdkLocation (loc);
-
-			if (result) {
-				return File.Exists (Path.Combine (loc, "bin", "javac"));
-			}
-
-			return result;
-		}
-
 		protected override IEnumerable<string> GetAllAvailableAndroidNdks ()
 		{
 			var preferedNdkPath = PreferedAndroidNdkPath;

src/Xamarin.Android.Tools.AndroidSdk/Tests/AndroidSdkInfoTests.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.IO;
+using System.Text;
 
 using NUnit.Framework;
 
@@ -15,5 +17,142 @@ public void Constructor_NullLogger ()
 			Action<TraceLevel, string> logger = null;
 			Assert.Throws<ArgumentNullException> (() => new AndroidSdkInfo (logger));
 		}
+
+		[Test]
+		public void Constructor_Paths ()
+		{
+			var root    = Path.GetTempFileName ();
+			File.Delete (root);
+			Directory.CreateDirectory (root);
+
+			var sdk     = Path.Combine (root, "sdk");
+			var jdk     = Path.Combine (root, "jdk");
+
+			Directory.CreateDirectory (sdk);
+			Directory.CreateDirectory (jdk);
+
+			CreateFauxAndroidSdkDirectory (sdk, "26.0.0");
+			CreateFauxJavaSdkDirectory (jdk, "1.8.0", out var _, out var _);
+
+			var logs    = new StringWriter ();
+			Action<TraceLevel, string> logger = (level, message) => {
+				logs.WriteLine ($"[{level}] {message}");
+			};
+			var info    = new AndroidSdkInfo (logger, androidSdkPath: sdk, javaSdkPath: jdk, androidNdkPath: null);
+
+			Assert.AreEqual (sdk, info.AndroidSdkPath,  "AndroidSdkPath not preserved!");
+			Assert.AreEqual (jdk, info.JavaSdkPath,     "JavaSdkPath not preserved!");
+		}
+
+		static  bool    IsWindows   => OS.IsWindows;
+
+		static void CreateFauxAndroidSdkDirectory (string androidSdkDirectory, string buildToolsVersion, ApiInfo [] apiLevels = null)
+		{
+			var androidSdkToolsPath             = Path.Combine (androidSdkDirectory, "tools");
+			var androidSdkBinPath               = Path.Combine (androidSdkToolsPath, "bin");
+			var androidSdkPlatformToolsPath     = Path.Combine (androidSdkDirectory, "platform-tools");
+			var androidSdkPlatformsPath         = Path.Combine (androidSdkDirectory, "platforms");
+			var androidSdkBuildToolsPath        = Path.Combine (androidSdkDirectory, "build-tools", buildToolsVersion);
+
+			Directory.CreateDirectory (androidSdkDirectory);
+			Directory.CreateDirectory (androidSdkToolsPath);
+			Directory.CreateDirectory (androidSdkBinPath);
+			Directory.CreateDirectory (androidSdkPlatformToolsPath);
+			Directory.CreateDirectory (androidSdkPlatformsPath);
+			Directory.CreateDirectory (androidSdkBuildToolsPath);
+
+			File.WriteAllText (Path.Combine (androidSdkPlatformToolsPath,   IsWindows ? "adb.exe" : "adb"),             "");
+			File.WriteAllText (Path.Combine (androidSdkBuildToolsPath,      IsWindows ? "zipalign.exe" : "zipalign"),   "");
+			File.WriteAllText (Path.Combine (androidSdkBuildToolsPath,      IsWindows ? "aapt.exe" : "aapt"),           "");
+			File.WriteAllText (Path.Combine (androidSdkToolsPath,           IsWindows ? "lint.bat" : "lint"),           "");
+
+			List<ApiInfo> defaults = new List<ApiInfo> ();
+			for (int i = 10; i < 26; i++) {
+				defaults.Add (new ApiInfo () {
+					Id = i.ToString (),
+				});
+			}
+			foreach (var level in ((IEnumerable<ApiInfo>) apiLevels) ?? defaults) {
+				var dir = Path.Combine (androidSdkPlatformsPath, $"android-{level.Id}");
+				Directory.CreateDirectory(dir);
+				File.WriteAllText (Path.Combine (dir, "android.jar"), "");
+			}
+		}
+
+		struct ApiInfo {
+			public  string      Id;
+		}
+
+		protected string CreateFauxJavaSdkDirectory (string javaPath, string javaVersion, out string javaExe, out string javacExe)
+		{
+			javaExe             = IsWindows ? "Java.cmd" : "java.bash";
+			javacExe            = IsWindows ? "Javac.cmd" : "javac.bash";
+			var jarSigner       = IsWindows ? "jarsigner.exe" : "jarsigner";
+			var javaBinPath     = Path.Combine (javaPath, "bin");
+
+			Directory.CreateDirectory (javaBinPath);
+
+			CreateFauxJavaExe (Path.Combine (javaBinPath, javaExe), javaVersion);
+			CreateFauxJavacExe (Path.Combine (javaBinPath, javacExe), javaVersion);
+
+			File.WriteAllText (Path.Combine (javaBinPath, jarSigner), "");
+			return javaPath;
+		}
+
+		void CreateFauxJavaExe (string javaExeFullPath, string version)
+		{
+			var sb  = new StringBuilder ();
+			if (IsWindows) {
+				sb.AppendLine ("@echo off");
+				sb.AppendLine ($"echo java version \"{version}\"");
+				sb.AppendLine ($"echo Java(TM) SE Runtime Environment (build {version}-b13)");
+				sb.AppendLine ($"echo Java HotSpot(TM) 64-Bit Server VM (build 25.101-b13, mixed mode)");
+			} else {
+				sb.AppendLine ("#!/bin/bash");
+				sb.AppendLine ($"echo \"java version \\\"{version}\\\"\"");
+				sb.AppendLine ($"echo \"Java(TM) SE Runtime Environment (build {version}-b13)\"");
+				sb.AppendLine ($"echo \"Java HotSpot(TM) 64-Bit Server VM (build 25.101-b13, mixed mode)\"");
+			}
+			File.WriteAllText (javaExeFullPath, sb.ToString ());
+			if (!IsWindows) {
+				Exec ("chmod", $"u+x \"{javaExeFullPath}\"");
+			}
+		}
+
+		void CreateFauxJavacExe (string javacExeFullPath, string version)
+		{
+			var sb  = new StringBuilder ();
+			if (IsWindows) {
+				sb.AppendLine ("@echo off");
+				sb.AppendLine ($"echo javac {version}");
+			} else {
+				sb.AppendLine ("#!/bin/bash");
+				sb.AppendLine ($"echo \"javac {version}\"");
+			}
+			File.WriteAllText (javacExeFullPath, sb.ToString ());
+			if (!IsWindows) {
+				Exec ("chmod", $"u+x \"{javacExeFullPath}\"");
+			}
+		}
+
+		protected void Exec (string exe, string args)
+		{
+			var psi     = new ProcessStartInfo {
+				FileName                = exe,
+				Arguments               = args,
+				UseShellExecute         = false,
+				RedirectStandardInput   = false,
+				RedirectStandardOutput  = false,
+				RedirectStandardError   = false,
+				CreateNoWindow          = true,
+				WindowStyle             = ProcessWindowStyle.Hidden,
+
+			};
+			var proc    = Process.Start (psi);
+			if (!proc.WaitForExit ((int) TimeSpan.FromSeconds(30).TotalMilliseconds)) {
+				proc.Kill ();
+				proc.WaitForExit ();
+			}
+		}
 	}
 }