Only conditionally include <uses-sdk /> in the AndroidManifest.xml wh…

src/Xamarin.Android.Tools.AndroidSdk/AndroidAppManifest.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Linq;
 using System.Xml;
 using System.Collections.Generic;
@@ -45,7 +45,7 @@ public class AndroidAppManifest
 			if (manifest.Element ("uses-sdk") is XElement uses)
 				usesSdk = uses;
 			else
-				manifest.Add (usesSdk = new XElement ("uses-sdk"));
+				usesSdk = new XElement ("uses-sdk");
 		}
 
 		public static string CanonicalizePackageName (string packageNameOrAssemblyName)
@@ -71,7 +71,6 @@ public static AndroidAppManifest Create (string packageName, string appLabel, An
 			return new AndroidAppManifest (versions, XDocument.Parse (
 				@"<?xml version=""1.0"" encoding=""utf-8""?>
 <manifest xmlns:android=""http://schemas.android.com/apk/res/android"" android:versionCode=""1"" android:versionName=""1.0"">
-  <uses-sdk />
   <application android:label="""">
   </application>
 </manifest>")) {
@@ -102,6 +101,14 @@ public static AndroidAppManifest Load (XDocument doc, AndroidVersions versions)
 
 		public void Write (XmlWriter writer)
 		{
+			// Make sure that if the <uses-sdk /> XML element does not have any attributes (i.e. minSdkVersion
+			// and targetSdkVersion), do NOT write it into the output. This is to avoid issues like
+			// https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1874249/
+			if (usesSdk.HasAttributes && usesSdk.Parent == null)
+				manifest.Add (usesSdk);
+			else if (!usesSdk.HasAttributes && usesSdk.Parent != null)
+				usesSdk.Remove ();
+
 			doc.Save (writer);
 		}
 

tests/Xamarin.Android.Tools.AndroidSdk-Tests/AndroidAppManifestTests.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
@@ -172,5 +172,45 @@ public void CanGetAppTheme ()
 
 			Assert.AreEqual ("@android:style/Theme.Material.Light", manifest.ApplicationTheme);
 		}
+
+		[Test]
+		public void CanAddAndRemoveUsesSdk ()
+		{
+			XNamespace aNS  = "http://schemas.android.com/apk/res/android";
+			var versions    = new AndroidVersions (new AndroidVersion [0]);
+			var doc         = XDocument.Parse (@"
+				<manifest xmlns:android=""http://schemas.android.com/apk/res/android"" android:versionCode=""1"" android:versionName=""1.0"" package=""com.xamarin.Foo"">
+					<uses-sdk android:minSdkVersion=""8"" android:targetSdkVersion=""12"" />
+					<application android:label=""Foo"" android:icon=""@drawable/ic_icon"" android:theme=""@android:style/Theme.Material.Light"">
+					</application>
+				</manifest>");
+			var manifest    = AndroidAppManifest.Load (doc, versions);
+
+			manifest.MinSdkVersion = null;
+			manifest.TargetSdkVersion = null;
+
+			var sb = new StringBuilder ();
+			using (var writer = XmlWriter.Create (sb)) {
+				manifest.Write (writer);
+			}
+
+			var newDoc      = XDocument.Parse (sb.ToString ());
+			var usesSdk     = newDoc.Element ("manifest").Element ("uses-sdk");
+			Assert.IsNull (usesSdk, "uses-sdk should not exist");
+
+			manifest.MinSdkVersion = 8;
+			manifest.TargetSdkVersion = 12;
+
+			sb = new StringBuilder ();
+			using (var writer = XmlWriter.Create (sb)) {
+				manifest.Write (writer);
+			}
+
+			newDoc = XDocument.Parse (sb.ToString ());
+			usesSdk = newDoc.Element ("manifest").Element ("uses-sdk");
+			Assert.IsNotNull (usesSdk, "uses-sdk should exist");
+			Assert.AreEqual ("8", usesSdk.Attribute (aNS + "minSdkVersion").Value);
+			Assert.AreEqual ("12", usesSdk.Attribute (aNS + "targetSdkVersion").Value);
+		}
 	}
 }