Add NU1703 warning for packages using deprecated MonoAndroid framework

src/NuGet.Core/NuGet.Commands/RestoreCommand/LockFileBuilder.cs

@@ -162,6 +162,8 @@ public LockFile CreateLockFile(LockFile previousLockFile,
                 .OrderBy(graph => graph.Framework.ToString(), StringComparer.Ordinal)
                 .ThenBy(graph => graph.RuntimeIdentifier, StringComparer.Ordinal))
             {
+                var librariesWithMonoAndroidWarnings = new HashSet<LibraryIdentity>();
+
                 var target = lockFile.Version >= LockFileFormat.AliasedVersion ?
                     new LockFileTarget
                     {
@@ -186,6 +188,8 @@ public LockFile CreateLockFile(LockFile previousLockFile,
                     && (target.TargetFramework is FallbackFramework
                         || target.TargetFramework is AssetTargetFallbackFramework);
 
+                bool checkMonoAndroidDeprecation = MonoAndroidDeprecation.ShouldCheck(project, targetGraph.Framework);
+
                 foreach (var graphItem in targetGraph.Flattened.OrderBy(x => x.Key))
                 {
                     var library = graphItem.Key;
@@ -226,7 +230,7 @@ public LockFile CreateLockFile(LockFile previousLockFile,
                         var package = packageInfo.Package;
                         var libraryDependency = tfi.Dependencies.FirstOrDefault(e => e.Name.Equals(library.Name, StringComparison.OrdinalIgnoreCase));
 
-                        (LockFileTargetLibrary targetLibrary, bool usedFallbackFramework) = LockFileUtils.CreateLockFileTargetLibrary(
+                        (LockFileTargetLibrary targetLibrary, bool usedFallbackFramework, NuGetFramework compileAssetFramework, NuGetFramework runtimeAssetFramework) = LockFileUtils.CreateLockFileTargetLibrary(
                             libraryDependency?.Aliases,
                             libraries[ValueTuple.Create(library.Name, library.Version)],
                             package,
@@ -280,6 +284,29 @@ public LockFile CreateLockFile(LockFile previousLockFile,
                                 librariesWithWarnings.Add(library);
                             }
                         }
+
+                        // Log NU1703 warning if the package uses the deprecated MonoAndroid framework
+                        if (checkMonoAndroidDeprecation
+                            && !librariesWithMonoAndroidWarnings.Contains(library)
+                            && (MonoAndroidDeprecation.IsMonoAndroidFramework(compileAssetFramework)
+                                || MonoAndroidDeprecation.IsMonoAndroidFramework(runtimeAssetFramework)))
+                        {
+                            var message = string.Format(CultureInfo.CurrentCulture,
+                                Strings.Warning_MonoAndroidFrameworkDeprecated,
+                                library.Name,
+                                library.Version);
+
+                            var logMessage = RestoreLogMessage.CreateWarning(
+                                NuGetLogCode.NU1703,
+                                message,
+                                library.Name,
+                                targetGraph.TargetGraphName);
+
+                            _logger.Log(logMessage);
+
+                            // only log the warning once per library
+                            librariesWithMonoAndroidWarnings.Add(library);
+                        }
                     }
                 }
 

src/NuGet.Core/NuGet.Commands/RestoreCommand/LockFileBuilderCache.cs

@@ -31,7 +31,7 @@ public class LockFileBuilderCache
         private readonly ConcurrentDictionary<CriteriaKey, List<(List<SelectionCriteria>, bool)>> _criteriaSets =
             new();
 
-        private readonly ConcurrentDictionary<(CriteriaKey, string path, string aliases, LibraryIncludeFlags, int dependencyCount), Lazy<(LockFileTargetLibrary, bool)>> _lockFileTargetLibraryCache =
+        private readonly ConcurrentDictionary<(CriteriaKey, string path, string aliases, LibraryIncludeFlags, int dependencyCount), Lazy<(LockFileTargetLibrary, bool, NuGetFramework, NuGetFramework)>> _lockFileTargetLibraryCache =
             new();
 
         /// <summary>
@@ -106,7 +106,7 @@ public ContentItemCollection GetContentItems(LockFileLibrary library, LocalPacka
         /// <summary>
         /// Try to get a LockFileTargetLibrary from the cache.
         /// </summary>
-        internal (LockFileTargetLibrary, bool) GetLockFileTargetLibrary(RestoreTargetGraph graph, NuGetFramework framework, LocalPackageInfo localPackageInfo, string aliases, LibraryIncludeFlags libraryIncludeFlags, List<LibraryDependency> dependencies, Func<(LockFileTargetLibrary, bool)> valueFactory)
+        internal (LockFileTargetLibrary, bool, NuGetFramework, NuGetFramework) GetLockFileTargetLibrary(RestoreTargetGraph graph, NuGetFramework framework, LocalPackageInfo localPackageInfo, string aliases, LibraryIncludeFlags libraryIncludeFlags, List<LibraryDependency> dependencies, Func<(LockFileTargetLibrary, bool, NuGetFramework, NuGetFramework)> valueFactory)
         {
             // Comparing RuntimeGraph for equality is very expensive,
             // so in case of a request where the RuntimeGraph is not empty we avoid using the cache.
@@ -117,7 +117,7 @@ public ContentItemCollection GetContentItems(LockFileLibrary library, LocalPacka
             var criteriaKey = new CriteriaKey(graph.TargetGraphName, framework);
             var packagePath = localPackageInfo.ExpandedPath;
             return _lockFileTargetLibraryCache.GetOrAdd((criteriaKey, packagePath, aliases, libraryIncludeFlags, dependencies.Count),
-                key => new Lazy<(LockFileTargetLibrary, bool)>(valueFactory)).Value;
+                key => new Lazy<(LockFileTargetLibrary, bool, NuGetFramework, NuGetFramework)>(valueFactory)).Value;
         }
 
         private class CriteriaKey : IEquatable<CriteriaKey>

src/NuGet.Core/NuGet.Commands/RestoreCommand/MonoAndroidDeprecation.cs

@@ -0,0 +1,58 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using NuGet.Frameworks;
+using NuGet.ProjectModel;
+
+namespace NuGet.Commands
+{
+    /// <summary>
+    /// Detects when a package uses the deprecated MonoAndroid framework instead of net6.0-android or later.
+    /// This warning is gated on .NET 11 SDK (SdkAnalysisLevel >= 11.0.100) and targeting net11.0-android or later.
+    /// </summary>
+    internal static class MonoAndroidDeprecation
+    {
+        /// <summary>
+        /// Determines whether the MonoAndroid deprecation check should be performed for the given project and target framework.
+        /// </summary>
+        /// <param name="project">The package spec containing restore metadata.</param>
+        /// <param name="framework">The target framework of the current graph.</param>
+        /// <returns>True if the deprecation check should be performed.</returns>
+        internal static bool ShouldCheck(PackageSpec project, NuGetFramework framework)
+        {
+            if (project.RestoreMetadata == null)
+            {
+                return false;
+            }
+
+            // Gate on SDK analysis level >= 11.0.100
+            if (!SdkAnalysisLevelMinimums.IsEnabled(
+                project.RestoreMetadata.SdkAnalysisLevel,
+                project.RestoreMetadata.UsingMicrosoftNETSdk,
+                SdkAnalysisLevelMinimums.V11_0_100))
+            {
+                return false;
+            }
+
+            // Only check for .NETCoreApp frameworks targeting android with version >= 11.0
+            return StringComparer.OrdinalIgnoreCase.Equals(framework.Framework, FrameworkConstants.FrameworkIdentifiers.NetCoreApp)
+                && framework.Version.Major >= 11
+                && framework.HasPlatform
+                && framework.Platform.Equals("android", StringComparison.OrdinalIgnoreCase);
+        }
+
+        /// <summary>
+        /// Checks whether the given framework is a MonoAndroid framework.
+        /// </summary>
+        /// <param name="framework">The framework to check, or null.</param>
+        /// <returns>True if the framework uses the MonoAndroid framework identifier.</returns>
+        internal static bool IsMonoAndroidFramework(NuGetFramework framework)
+        {
+            return framework != null
+                && StringComparer.OrdinalIgnoreCase.Equals(
+                    framework.Framework,
+                    FrameworkConstants.FrameworkIdentifiers.MonoAndroid);
+        }
+    }
+}

src/NuGet.Core/NuGet.Commands/RestoreCommand/Utility/LockFileUtils.cs

@@ -34,7 +34,7 @@ public static LockFileTargetLibrary CreateLockFileTargetLibrary(
             RestoreTargetGraph targetGraph,
             LibraryIncludeFlags dependencyType)
         {
-            var (lockFileTargetLibrary, _) = CreateLockFileTargetLibrary(
+            var (lockFileTargetLibrary, _, _, _) = CreateLockFileTargetLibrary(
                 aliases: null,
                 library,
                 package,
@@ -57,8 +57,8 @@ public static LockFileTargetLibrary CreateLockFileTargetLibrary(
         /// <param name="targetFrameworkOverride">The original framework if the asset selection is happening for a fallback framework.</param>
         /// <param name="dependencies">The dependencies of this package.</param>
         /// <param name="cache">The lock file build cache.</param>
-        /// <returns>The LockFileTargetLibrary, and whether a fallback framework criteria was used to select it.</returns>
-        internal static (LockFileTargetLibrary, bool) CreateLockFileTargetLibrary(
+        /// <returns>The LockFileTargetLibrary, whether a fallback framework criteria was used to select it, the framework selected for compile assets, and the framework selected for runtime assets.</returns>
+        internal static (LockFileTargetLibrary, bool, NuGetFramework, NuGetFramework) CreateLockFileTargetLibrary(
                 string aliases,
                 LockFileLibrary library,
                 LocalPackageInfo package,
@@ -75,6 +75,8 @@ internal static (LockFileTargetLibrary, bool) CreateLockFileTargetLibrary(
                 () =>
                 {
                     LockFileTargetLibrary lockFileLib = null;
+                    NuGetFramework compileAssetFramework = null;
+                    NuGetFramework runtimeAssetFramework = null;
                     // This will throw an appropriate error if the nuspec is missing
                     var nuspec = package.Nuspec;
 
@@ -86,7 +88,7 @@ internal static (LockFileTargetLibrary, bool) CreateLockFileTargetLibrary(
 
                     for (var i = 0; i < orderedCriteriaSets.Count; i++)
                     {
-                        lockFileLib = CreateLockFileTargetLibrary(aliases, library, package, targetGraph.Conventions, dependencyType,
+                        (lockFileLib, compileAssetFramework, runtimeAssetFramework) = CreateLockFileTargetLibrary(aliases, library, package, targetGraph.Conventions, dependencyType,
                              framework, runtimeIdentifier, contentItems, nuspec, packageTypes, orderedCriteriaSets[i].orderedCriteria);
                         // Check if compatible assets were found.
                         // If no compatible assets were found and this is the last check
@@ -108,7 +110,7 @@ internal static (LockFileTargetLibrary, bool) CreateLockFileTargetLibrary(
 
                     lockFileLib.Freeze();
 
-                    return (lockFileLib, fallbackUsed);
+                    return (lockFileLib, fallbackUsed, compileAssetFramework, runtimeAssetFramework);
                 });
         }
 
@@ -165,7 +167,7 @@ private static void ApplyAliases(string aliases, LockFileItem item)
         /// <summary>
         /// Populate assets for a <see cref="LockFileLibrary"/>.
         /// </summary>
-        internal static LockFileTargetLibrary CreateLockFileTargetLibrary(
+        internal static (LockFileTargetLibrary lockFileLib, NuGetFramework compileAssetFramework, NuGetFramework runtimeAssetFramework) CreateLockFileTargetLibrary(
             string aliases,
             LockFileLibrary library,
             LocalPackageInfo package,
@@ -198,13 +200,16 @@ internal static LockFileTargetLibrary CreateLockFileTargetLibrary(
                 orderedCriteria,
                 contentItems,
                 applyAliases,
+                out NuGetFramework compileFramework,
                 managedCodeConventions.Patterns.CompileRefAssemblies,
                 managedCodeConventions.Patterns.CompileLibAssemblies);
 
             // Runtime
             lockFileLib.RuntimeAssemblies = GetLockFileItems(
                 orderedCriteria,
                 contentItems,
+                additionalAction: null,
+                out NuGetFramework runtimeFramework,
                 managedCodeConventions.Patterns.RuntimeAssemblies);
 
             // Embed
@@ -242,7 +247,7 @@ internal static LockFileTargetLibrary CreateLockFileTargetLibrary(
             // Apply filters from the <references> node in the nuspec
             ApplyReferenceFilter(lockFileLib, framework, nuspec);
 
-            return lockFileLib;
+            return (lockFileLib, compileFramework, runtimeFramework);
         }
 
         private static void AddMSBuildAssets(
@@ -659,15 +664,17 @@ private static List<LockFileItem> ConvertToProjectPaths(
         }
 
         /// <summary>
-        /// Create lock file items for the best matching group.
+        /// Create lock file items for the best matching group, and optionally output the selected framework.
         /// </summary>
         /// <remarks>Enumerate this once after calling.</remarks>
         private static IList<LockFileItem> GetLockFileItems(
             List<SelectionCriteria> criteria,
             ContentItemCollection items,
             Action<LockFileItem> additionalAction,
+            out NuGetFramework selectedFramework,
             params PatternSet[] patterns)
         {
+            selectedFramework = null;
             List<LockFileItem> result = null;
             // Loop through each criteria taking the first one that matches one or more items.
             foreach (var managedCriteria in criteria)
@@ -678,6 +685,12 @@ private static IList<LockFileItem> GetLockFileItems(
 
                 if (group != null)
                 {
+                    if (group.Properties.TryGetValue(
+                        ManagedCodeConventions.PropertyNames.TargetFrameworkMoniker, out object tfmObj))
+                    {
+                        selectedFramework = tfmObj as NuGetFramework;
+                    }
+
                     result = new(group.Items.Count);
                     foreach (var item in group.Items.NoAllocEnumerate())
                     {
@@ -711,7 +724,7 @@ private static IList<LockFileItem> GetLockFileItems(
             ContentItemCollection items,
             params PatternSet[] patterns)
         {
-            return GetLockFileItems(criteria, items, additionalAction: null, patterns);
+            return GetLockFileItems(criteria, items, additionalAction: null, out _, patterns);
         }
 
         /// <summary>

src/NuGet.Core/NuGet.Commands/Strings.resx

@@ -167,6 +167,11 @@
   <data name="Log_ImportsFallbackWarning" xml:space="preserve">
     <value>Package '{0}' was restored using '{1}' instead of the project target framework '{2}'. This package may not be fully compatible with your project.</value>
   </data>
+  <data name="Warning_MonoAndroidFrameworkDeprecated" xml:space="preserve">
+    <value>Package '{0}' {1} uses the deprecated MonoAndroid framework instead of 'net6.0-android' or later. Consider upgrading to a newer version of this package or contacting the package author.</value>
+    <comment>{0} - package id
+{1} - package version</comment>
+  </data>
   <data name="Log_CycleDetected" xml:space="preserve">
     <value>Cycle detected.</value>
   </data>

src/NuGet.Core/NuGet.Commands/Utility/SdkAnalysisLevelMinimums.cs

@@ -37,6 +37,7 @@ internal static class SdkAnalysisLevelMinimums
         /// <summary>
         /// Minimum SDK Analysis Level required for:
         /// <list type="bullet">
+        /// <item>warning when packages use the deprecated MonoAndroid framework</item>
         /// <item>error when TargetFramework alias contains non-ASCII characters</item>
         /// </list>
         /// </summary>

src/NuGet.Core/NuGet.Commands/xlf/Strings.cs.xlf

@@ -1496,6 +1496,12 @@ NuGet vyžaduje zdroje HTTPS. Další informace najdete na https://aka.ms/nuget-
         <target state="translated">{0} neposkytuje inkluzivní dolní mez pro závislost {1}. Místo toho bylo přeloženo: {2}.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Warning_MonoAndroidFrameworkDeprecated">
+        <source>Package '{0}' {1} uses the deprecated MonoAndroid framework instead of 'net6.0-android' or later. Consider upgrading to a newer version of this package or contacting the package author.</source>
+        <target state="new">Package '{0}' {1} uses the deprecated MonoAndroid framework instead of 'net6.0-android' or later. Consider upgrading to a newer version of this package or contacting the package author.</target>
+        <note>{0} - package id
+{1} - package version</note>
+      </trans-unit>
       <trans-unit id="Warning_PackageWithKnownVulnerability">
         <source>Package '{0}' {1} has a known {2} severity vulnerability, {3}</source>
         <target state="translated">Balíček „{0}“ {1} má známé {2} ohrožení zabezpečení závažnosti, {3}</target>

src/NuGet.Core/NuGet.Commands/xlf/Strings.de.xlf

@@ -1496,6 +1496,12 @@ NuGet erfordert HTTPS-Quellen. Weitere Informationen finden Sie unter https://ak
         <target state="translated">{0} stellt keine inklusive untere Grenze für Abhängigkeiten {1} bereit. {2} wurde stattdessen aufgelöst.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Warning_MonoAndroidFrameworkDeprecated">
+        <source>Package '{0}' {1} uses the deprecated MonoAndroid framework instead of 'net6.0-android' or later. Consider upgrading to a newer version of this package or contacting the package author.</source>
+        <target state="new">Package '{0}' {1} uses the deprecated MonoAndroid framework instead of 'net6.0-android' or later. Consider upgrading to a newer version of this package or contacting the package author.</target>
+        <note>{0} - package id
+{1} - package version</note>
+      </trans-unit>
       <trans-unit id="Warning_PackageWithKnownVulnerability">
         <source>Package '{0}' {1} has a known {2} severity vulnerability, {3}</source>
         <target state="translated">Das Paket "{0}" {1} weist eine bekannte {2} Schweregrad-Sicherheitsanfälligkeit auf, {3}.</target>

src/NuGet.Core/NuGet.Commands/xlf/Strings.es.xlf

@@ -1496,6 +1496,12 @@ NuGet requiere orígenes HTTPS. Consulte https://aka.ms/nuget-https-everywhere p
         <target state="translated">{0} no proporciona un límite inferior inclusivo para la dependencia {1}. {2} se resolvió en su lugar.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Warning_MonoAndroidFrameworkDeprecated">
+        <source>Package '{0}' {1} uses the deprecated MonoAndroid framework instead of 'net6.0-android' or later. Consider upgrading to a newer version of this package or contacting the package author.</source>
+        <target state="new">Package '{0}' {1} uses the deprecated MonoAndroid framework instead of 'net6.0-android' or later. Consider upgrading to a newer version of this package or contacting the package author.</target>
+        <note>{0} - package id
+{1} - package version</note>
+      </trans-unit>
       <trans-unit id="Warning_PackageWithKnownVulnerability">
         <source>Package '{0}' {1} has a known {2} severity vulnerability, {3}</source>
         <target state="translated">El paquete "{0}" {1} tiene una vulnerabilidad de gravedad {2} conocida, {3}</target>