[TrimmableTypeMap] Improve array handling

src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/Model/TypeMapAssemblyData.cs

@@ -40,6 +40,12 @@ sealed class TypeMapAssemblyData
 	/// </summary>
 	public List<AliasHolderData> AliasHolders { get; } = new ();
 
+	/// <summary>
+	/// Maximum array rank for which the generator emits per-rank <c>__ArrayMapRank{N}</c>
+	/// sentinel TypeDefs and <c>TypeMap</c> entries. 0 disables.
+	/// </summary>
+	public int MaxArrayRank { get; set; }
+
 	/// <summary>
 	/// Assembly names that need [IgnoresAccessChecksTo] for cross-assembly n_* calls.
 	/// </summary>
@@ -77,6 +83,12 @@ sealed record TypeMapAttributeData
 	/// True for 2-arg unconditional entries (ACW types, essential runtime types).
 	/// </summary>
 	public bool IsUnconditional => TargetTypeReference == null;
+
+	/// <summary>
+	/// 1-based array rank when this entry should use a <c>__ArrayMapRank{value}</c>
+	/// sentinel as its <c>TGroup</c> instead of the default model anchor.
+	/// </summary>
+	public int? AnchorRank { get; init; }
 }
 
 /// <summary>

src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/ModelBuilder.cs

@@ -40,21 +40,28 @@ static class ModelBuilder
 	/// <param name="peers">Scanned Java peer types (typically from a single input assembly).</param>
 	/// <param name="outputPath">Output .dll path — used to derive assembly/module names if not specified.</param>
 	/// <param name="assemblyName">Explicit assembly name. If null, derived from <paramref name="outputPath"/>.</param>
-	public static TypeMapAssemblyData Build (IReadOnlyList<JavaPeerInfo> peers, string outputPath, string? assemblyName = null)
+	/// <param name="maxArrayRank">
+	/// Emit per-rank array <c>TypeMap</c> entries + <c>__ArrayMapRank{N}</c> sentinels
+	/// for ranks 1..<paramref name="maxArrayRank"/>. 0 disables array entry emission.
+	/// </param>
+	public static TypeMapAssemblyData Build (IReadOnlyList<JavaPeerInfo> peers, string outputPath, string? assemblyName = null, int maxArrayRank = 0)
 	{
 		if (peers is null) {
 			throw new ArgumentNullException (nameof (peers));
 		}
 		if (outputPath is null) {
 			throw new ArgumentNullException (nameof (outputPath));
 		}
+		if (maxArrayRank < 0) {
+			throw new ArgumentOutOfRangeException (nameof (maxArrayRank), maxArrayRank, "Must be >= 0.");
+		}
 
 		assemblyName ??= Path.GetFileNameWithoutExtension (outputPath);
-		string moduleName = Path.GetFileName (outputPath);
 
 		var model = new TypeMapAssemblyData {
 			AssemblyName = assemblyName,
-			ModuleName = moduleName,
+			ModuleName = Path.GetFileName (outputPath),
+			MaxArrayRank = maxArrayRank,
 		};
 
 		// Invoker types are NOT emitted as separate proxies or TypeMap entries —
@@ -89,6 +96,10 @@ public static TypeMapAssemblyData Build (IReadOnlyList<JavaPeerInfo> peers, stri
 			}
 
 			EmitPeers (model, jniName, peersForName, assemblyName, usedProxyNames);
+
+			if (maxArrayRank > 0) {
+				EmitArrayEntries (model, jniName, peersForName, maxArrayRank);
+			}
 		}
 
 		// Compute IgnoresAccessChecksTo from cross-assembly references
@@ -392,4 +403,54 @@ static TypeMapAttributeData BuildEntry (JavaPeerInfo peer, JavaPeerProxyData? pr
 
 	static string AssemblyQualify (string typeName, string assemblyName)
 		=> $"{typeName}, {assemblyName}";
+
+	/// <summary>
+	/// Emits per-rank <c>[L&lt;jni&gt;;</c>-shaped TypeMap entries for one peer, anchored to
+	/// the per-assembly <c>__ArrayMapRank{N}</c> sentinels. Skips open generics, primitive
+	/// JNI keyword keys (handled by the legacy primitive-array path), and alias groups.
+	/// </summary>
+	static void EmitArrayEntries (TypeMapAssemblyData model, string jniName, List<JavaPeerInfo> peersForName, int maxArrayRank)
+	{
+		if (jniName.Length == 1 && IsJniPrimitiveKeyword (jniName [0])) {
+			return;
+		}
+		if (peersForName.Count != 1) {
+			return;
+		}
+
+		var peer = peersForName [0];
+		if (peer.IsGenericDefinition) {
+			return;
+		}
+
+		for (int rank = 1; rank <= maxArrayRank; rank++) {
+			string arrayTypeRef = AssemblyQualify (peer.ManagedTypeName + Brackets (rank), peer.AssemblyName);
+			model.Entries.Add (new TypeMapAttributeData {
+				JniName = jniName,
+				ProxyTypeReference = arrayTypeRef,
+				TargetTypeReference = arrayTypeRef,
+				AnchorRank = rank,
+			});
+		}
+	}
+
+	static string Brackets (int rank) => rank switch {
+		1 => "[]",
+		2 => "[][]",
+		3 => "[][][]",
+		_ => BuildBrackets (rank),
+	};
+
+	static string BuildBrackets (int rank)
+	{
+		var sb = new StringBuilder (rank * 2);
+		for (int i = 0; i < rank; i++) {
+			sb.Append ("[]");
+		}
+		return sb.ToString ();
+	}
+
+	static bool IsJniPrimitiveKeyword (char c)
+		=> c == 'Z' || c == 'B' || c == 'C' || c == 'S' || c == 'I'
+			|| c == 'J' || c == 'F' || c == 'D' || c == 'V';
 }