Apply null comparison pattern per copilot instructions

Use 'is null' and 'is not null' instead of '== null' and '!= null'

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: rmarinho

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

@@ -251,7 +251,7 @@ public async Task BootstrapAsync (string targetPath, IProgress<SdkBootstrapProgr
 				})
 				.FirstOrDefault ();
 
-			if (cmdlineTools == null || string.IsNullOrEmpty (cmdlineTools.DownloadUrl)) {
+			if (cmdlineTools is null || string.IsNullOrEmpty (cmdlineTools.DownloadUrl)) {
 				throw new InvalidOperationException ("Could not find command-line tools in the Android manifest feed.");
 			}
 
@@ -454,7 +454,7 @@ public async Task BootstrapAsync (string targetPath, IProgress<SdkBootstrapProgr
 		public async Task<(IReadOnlyList<SdkPackage> Installed, IReadOnlyList<SdkPackage> Available)> ListAsync (CancellationToken cancellationToken = default)
 		{
 			var sdkManagerPath = FindSdkManagerPath ();
-			if (sdkManagerPath == null)
+			if (sdkManagerPath is null)
 				throw new InvalidOperationException ("sdkmanager not found. Run BootstrapAsync first to install command-line tools.");
 
 			logger (TraceLevel.Info, "Running sdkmanager --list...");
@@ -476,11 +476,11 @@ public async Task BootstrapAsync (string targetPath, IProgress<SdkBootstrapProgr
 		/// <param name="cancellationToken">Cancellation token.</param>
 		public async Task InstallAsync (IEnumerable<string> packages, bool acceptLicenses = true, CancellationToken cancellationToken = default)
 		{
-			if (packages == null || !packages.Any ())
+			if (packages is null || !packages.Any ())
 				throw new ArgumentException ("At least one package must be specified.", nameof (packages));
 
 			var sdkManagerPath = FindSdkManagerPath ();
-			if (sdkManagerPath == null)
+			if (sdkManagerPath is null)
 				throw new InvalidOperationException ("sdkmanager not found. Run BootstrapAsync first.");
 
 			var packageList = string.Join (" ", packages.Select (p => $"\"{p}\""));
@@ -504,11 +504,11 @@ public async Task InstallAsync (IEnumerable<string> packages, bool acceptLicense
 		/// <param name="cancellationToken">Cancellation token.</param>
 		public async Task UninstallAsync (IEnumerable<string> packages, CancellationToken cancellationToken = default)
 		{
-			if (packages == null || !packages.Any ())
+			if (packages is null || !packages.Any ())
 				throw new ArgumentException ("At least one package must be specified.", nameof (packages));
 
 			var sdkManagerPath = FindSdkManagerPath ();
-			if (sdkManagerPath == null)
+			if (sdkManagerPath is null)
 				throw new InvalidOperationException ("sdkmanager not found. Run BootstrapAsync first.");
 
 			var packageList = string.Join (" ", packages.Select (p => $"\"{p}\""));
@@ -532,7 +532,7 @@ public async Task UninstallAsync (IEnumerable<string> packages, CancellationToke
 		public async Task UpdateAsync (CancellationToken cancellationToken = default)
 		{
 			var sdkManagerPath = FindSdkManagerPath ();
-			if (sdkManagerPath == null)
+			if (sdkManagerPath is null)
 				throw new InvalidOperationException ("sdkmanager not found. Run BootstrapAsync first.");
 
 			logger (TraceLevel.Info, "Updating all installed packages...");
@@ -554,7 +554,7 @@ public async Task UpdateAsync (CancellationToken cancellationToken = default)
 		public async Task AcceptLicensesAsync (CancellationToken cancellationToken = default)
 		{
 			var sdkManagerPath = FindSdkManagerPath ();
-			if (sdkManagerPath == null)
+			if (sdkManagerPath is null)
 				throw new InvalidOperationException ("sdkmanager not found. Run BootstrapAsync first.");
 
 			logger (TraceLevel.Info, "Accepting SDK licenses...");
@@ -574,7 +574,7 @@ public async Task AcceptLicensesAsync (CancellationToken cancellationToken = def
 		public async Task<IReadOnlyList<SdkLicense>> GetPendingLicensesAsync (CancellationToken cancellationToken = default)
 		{
 			var sdkManagerPath = FindSdkManagerPath ();
-			if (sdkManagerPath == null)
+			if (sdkManagerPath is null)
 				throw new InvalidOperationException ("sdkmanager not found. Run BootstrapAsync first.");
 
 			logger (TraceLevel.Verbose, "Checking for pending licenses...");
@@ -632,11 +632,11 @@ public async Task<IReadOnlyList<SdkLicense>> GetPendingLicensesAsync (Cancellati
 		/// <param name="cancellationToken">Cancellation token.</param>
 		public async Task AcceptLicensesAsync (IEnumerable<string> licenseIds, CancellationToken cancellationToken = default)
 		{
-			if (licenseIds == null || !licenseIds.Any ())
+			if (licenseIds is null || !licenseIds.Any ())
 				return;
 
 			var sdkManagerPath = FindSdkManagerPath ();
-			if (sdkManagerPath == null)
+			if (sdkManagerPath is null)
 				throw new InvalidOperationException ("sdkmanager not found. Run BootstrapAsync first.");
 
 			// Accept licenses by writing the hash to the licenses directory
@@ -676,7 +676,7 @@ internal static IReadOnlyList<SdkLicense> ParseLicenseOutput (string output)
 				// License header: "License android-sdk-license:"
 				if (line.StartsWith ("License ", StringComparison.OrdinalIgnoreCase) && line.TrimEnd ().EndsWith (":")) {
 					// Save previous license if any
-					if (currentLicenseId != null && currentLicenseText.Length > 0) {
+					if (currentLicenseId is not null && currentLicenseText.Length > 0) {
 						licenses.Add (new SdkLicense {
 							Id = currentLicenseId,
 							Text = currentLicenseText.ToString ().Trim ()
@@ -692,7 +692,7 @@ internal static IReadOnlyList<SdkLicense> ParseLicenseOutput (string output)
 
 				// End of license text when we see the accept prompt
 				if (line.Contains ("Accept?") || line.Contains ("(y/N)")) {
-					if (currentLicenseId != null && currentLicenseText.Length > 0) {
+					if (currentLicenseId is not null && currentLicenseText.Length > 0) {
 						licenses.Add (new SdkLicense {
 							Id = currentLicenseId,
 							Text = currentLicenseText.ToString ().Trim ()
@@ -705,7 +705,7 @@ internal static IReadOnlyList<SdkLicense> ParseLicenseOutput (string output)
 				}
 
 				// Accumulate license text
-				if (inLicenseText && currentLicenseId != null) {
+				if (inLicenseText && currentLicenseId is not null) {
 					// Skip separator lines
 					if (!line.TrimStart ().StartsWith ("-------", StringComparison.Ordinal)) {
 						currentLicenseText.AppendLine (line);
@@ -714,7 +714,7 @@ internal static IReadOnlyList<SdkLicense> ParseLicenseOutput (string output)
 			}
 
 			// Add last license if not yet added
-			if (currentLicenseId != null && currentLicenseText.Length > 0) {
+			if (currentLicenseId is not null && currentLicenseText.Length > 0) {
 				licenses.Add (new SdkLicense {
 					Id = currentLicenseId,
 					Text = currentLicenseText.ToString ().Trim ()
@@ -776,7 +776,7 @@ internal static (IReadOnlyList<SdkPackage> Installed, IReadOnlyList<SdkPackage>
 					continue;
 				}
 
-				if (currentSection == null || string.IsNullOrWhiteSpace (trimmed))
+				if (currentSection is null || string.IsNullOrWhiteSpace (trimmed))
 					continue;
 
 				// Skip header and separator lines
@@ -900,7 +900,7 @@ async Task DownloadFileAsync (string url, string destinationPath, long expectedS
 					await fileStream.WriteAsync (buffer, 0, bytesRead, cancellationToken).ConfigureAwait (false);
 					totalRead += bytesRead;
 
-					if (totalSize > 0 && progress != null) {
+					if (totalSize > 0 && progress is not null) {
 						var percent = (int) ((totalRead * 100) / totalSize);
 						progress.Report (new SdkBootstrapProgress {
 							Phase = SdkBootstrapPhase.Downloading,
@@ -957,7 +957,7 @@ static void SetExecutablePermissions (string directory, Action<TraceLevel, strin
 							};
 							var process = Process.Start (psi);
 							process?.WaitForExit ();
-							if (process == null || process.ExitCode != 0) {
+							if (process is null || process.ExitCode != 0) {
 								throw new InvalidOperationException ($"chmod failed for '{file}' with exit code {process?.ExitCode ?? -1}");
 							}
 						}