Address review findings: fix tests, deduplicate JNI parsing

- Fix UCO attribute test to verify actual UnmanagedCallersOnlyAttribute
  type name instead of just Assert.NotEmpty(attrs)
- Replace non-asserting NegativeEdgeCase Theory with three Facts that
  each assert a specific expected behavior
- Remove duplicate SkipSingleType method; ParseParameterTypeStrings
  now reuses ParseSingleType to advance the index

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

Author: simonrozsival

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

@@ -41,7 +41,7 @@ public static List<string> ParseParameterTypeStrings (string jniSignature)
 		int i = 1; // skip opening '('
 		while (i < jniSignature.Length && jniSignature [i] != ')') {
 			int start = i;
-			SkipSingleType (jniSignature, ref i);
+			ParseSingleType (jniSignature, ref i);
 			result.Add (jniSignature.Substring (start, i - start));
 		}
 		return result;
@@ -85,25 +85,6 @@ static JniParamKind ParseSingleType (string sig, ref int i)
 		}
 	}
 
-	static void SkipSingleType (string sig, ref int i)
-	{
-		switch (sig [i]) {
-		case 'V': case 'Z': case 'B': case 'C': case 'S':
-		case 'I': case 'J': case 'F': case 'D':
-			i++;
-			break;
-		case 'L':
-			i = sig.IndexOf (';', i) + 1;
-			break;
-		case '[':
-			i++;
-			SkipSingleType (sig, ref i);
-			break;
-		default:
-			throw new ArgumentException ($"Unknown JNI type character '{sig [i]}' in '{sig}' at index {i}");
-		}
-	}
-
 	/// <summary>Encodes the CLR type for a JNI parameter kind into a signature type encoder.</summary>
 	public static void EncodeClrType (SignatureTypeEncoder encoder, JniParamKind kind)
 	{

tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Generator/TypeMapAssemblyGeneratorTests.cs

@@ -170,10 +170,16 @@ public void Generate_AcwProxy_HasUnmanagedCallersOnlyAttribute ()
 .Select (h => reader.GetMethodDefinition (h))
 .First (m => reader.GetString (m.Name).Contains ("_uco_"));
 
-var attrs = ucoMethod.GetCustomAttributes ()
+var attrNames = ucoMethod.GetCustomAttributes ()
 .Select (h => reader.GetCustomAttribute (h))
+.Select (a => {
+var ctorHandle = (MemberReferenceHandle) a.Constructor;
+var ctor = reader.GetMemberReference (ctorHandle);
+var typeRef = reader.GetTypeReference ((TypeReferenceHandle) ctor.Parent);
+return $"{reader.GetString (typeRef.Namespace)}.{reader.GetString (typeRef.Name)}";
+})
 .ToList ();
-Assert.NotEmpty (attrs);
+Assert.Contains ("System.Runtime.InteropServices.UnmanagedCallersOnlyAttribute", attrNames);
 }
 }
 
@@ -321,17 +327,22 @@ public void ParseReturnType_MapsToCorrectKind (string signature, JniParamKind ex
 public class NegativeEdgeCase
 {
 
-[Theory]
-[InlineData ("")]
-[InlineData ("not-a-sig")]
-[InlineData ("(")]
-public void ParseParameterTypes_InvalidSignature_ThrowsOrReturnsEmpty (string signature)
+[Fact]
+public void ParseParameterTypes_EmptyString_ReturnsEmptyList ()
 {
-try {
-var result = JniSignatureHelper.ParseParameterTypes (signature);
-Assert.NotNull (result);
-} catch (Exception ex) when (ex is ArgumentException || ex is IndexOutOfRangeException || ex is FormatException) {
+Assert.Empty (JniSignatureHelper.ParseParameterTypes (""));
 }
+
+[Fact]
+public void ParseParameterTypes_InvalidSignature_Throws ()
+{
+Assert.ThrowsAny<ArgumentException> (() => JniSignatureHelper.ParseParameterTypes ("not-a-sig"));
+}
+
+[Fact]
+public void ParseParameterTypes_UnterminatedSignature_ReturnsEmptyList ()
+{
+Assert.Empty (JniSignatureHelper.ParseParameterTypes ("("));
 }
 
 }