[generator] Escape hyphens for callback names so they're valid C#.

src/Java.Interop.Tools.JavaCallableWrappers/Java.Interop.Tools.JavaCallableWrappers.csproj

@@ -36,6 +36,7 @@
   <ItemGroup>
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Java.Interop.Tools.JavaCallableWrappers\Crc64.cs" />
+    <Compile Include="Java.Interop.Tools.JavaCallableWrappers\IdentifierValidator.cs" />
     <Compile Include="Java.Interop.Tools.JavaCallableWrappers\JavaCallableWrapperGenerator.cs" />
     <Compile Include="Java.Interop.Tools.JavaCallableWrappers\JavaTypeScanner.cs" />
     <Compile Include="Java.Interop.Tools.JavaCallableWrappers\TypeNameMapGenerator.cs" />

src/Java.Interop.Tools.JavaCallableWrappers/Java.Interop.Tools.JavaCallableWrappers/IdentifierValidator.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+
+namespace Java.Interop.Tools.JavaCallableWrappers
+{
+	public static class IdentifierValidator
+	{
+		// https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/language-specification/lexical-structure#identifiers
+		private const string FormattingCharacter = @"\p{Cf}";
+		private const string ConnectingCharacter = @"\p{Pc}";
+		private const string DecimalDigitCharacter = @"\p{Nd}";
+		private const string CombiningCharacter = @"\p{Mn}\p{Mc}";
+		private const string LetterCharacter = @"\p{Lu}\p{Ll}\p{Lt}\p{Lm}\p{Lo}\p{Nl}";
+
+		private const string IdentifierPartCharacter = LetterCharacter +
+			DecimalDigitCharacter +
+			ConnectingCharacter +
+			CombiningCharacter +
+			FormattingCharacter;
+
+		private const string IdentifierStartCharacter = "(" + LetterCharacter + "_)";
+
+		private const string Identifier = IdentifierStartCharacter + "(" + IdentifierPartCharacter + ")";
+
+		// We use [^ ...] to detect any character that is NOT a match.
+		static Regex validIdentifier = new Regex ($"[^{Identifier}]", RegexOptions.Compiled);
+
+		public static string CreateValidIdentifier (string identifier, bool useEncodedReplacements = false)
+		{
+			if (string.IsNullOrWhiteSpace (identifier)) return string.Empty;
+
+			var normalizedIdentifier = identifier.Normalize ();
+
+			if (useEncodedReplacements)
+				return validIdentifier.Replace (normalizedIdentifier, new MatchEvaluator (EncodeReplacement));
+
+			return validIdentifier.Replace (normalizedIdentifier, "_");
+		}
+
+		// Makes uglier but unique identifiers by encoding each invalid character with its character value
+		static string EncodeReplacement (Match match) => $"_x{(ushort) match.Value [0]}_";
+	}
+}

src/Java.Interop.Tools.JavaCallableWrappers/Test/Java.Interop.Tools.JavaCallableWrappers-Tests.csproj

@@ -39,6 +39,7 @@
   <ItemGroup>
     <Compile Include="Java.Interop.Tools.JavaCallableWrappers\JavaCallableWrapperGeneratorTests.cs" />
     <Compile Include="Java.Interop.Tools.JavaCallableWrappers\Crc64Tests.cs" />
+    <Compile Include="Java.Interop.Tools.JavaCallableWrappers\IdentifierValidatorTests.cs" />
     <Compile Include="Java.Interop.Tools.JavaCallableWrappers\JavaNativeTypeManagerTests.cs" />
     <Compile Include="Java.Interop.Tools.JavaCallableWrappers\TypeNameMapGeneratorTests.cs" />
     <Compile Include="Java.Interop.Tools.JavaCallableWrappers\SupportDeclarations.cs" />

src/Java.Interop.Tools.JavaCallableWrappers/Test/Java.Interop.Tools.JavaCallableWrappers/IdentifierValidatorTests.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Java.Interop.Tools.JavaCallableWrappers;
+using Java.Interop.Tools.TypeNameMappings;
+using NUnit.Framework;
+
+namespace Java.Interop.Tools.JavaCallableWrappersTests
+{
+	[TestFixture]
+	public class IdentifierValidatorTests
+	{
+		[Test]
+		public void CreateValidIdentifier_Simple ()
+		{
+			Assert.AreEqual ("my_identifier_test", IdentifierValidator.CreateValidIdentifier ("my-identifier$test"));
+		}
+
+		[Test]
+		public void CreateValidIdentifier_Encoded ()
+		{
+			Assert.AreEqual ("my_x45_identifier_x36_test", IdentifierValidator.CreateValidIdentifier ("my-identifier$test", true));
+			Assert.AreEqual ("myidentifier_x55357__x56842_test", IdentifierValidator.CreateValidIdentifier ("myidentifier😊test", true));
+		}
+	}
+}

tools/generator/Java.Interop.Tools.Generator.ObjectModel/Method.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Linq;
+using Java.Interop.Tools.JavaCallableWrappers;
 using MonoDroid.Generation.Utilities;
 
 namespace MonoDroid.Generation
@@ -105,7 +106,7 @@ internal string CalculateEventName (Func<string, bool> checkNameDuplicate)
 
 		public string ConnectorName => $"Get{Name}{IDSignature}Handler";
 
-		public string EscapedCallbackName => $"cb_{JavaName}{IDSignature}";
+		public string EscapedCallbackName => IdentifierValidator.CreateValidIdentifier ($"cb_{JavaName}{IDSignature}", true);
 
 		public string EscapedIdName => "id_" + JavaName.Replace ("<", "_x60_").Replace (">", "_x62_") + IDSignature;
 

tools/generator/Tests/Unit-Tests/CodeGeneratorTests.cs

@@ -844,5 +844,23 @@ public void WritePropertyInvoker ()
 
 			Assert.AreEqual (GetExpected (nameof (WritePropertyInvoker)), writer.ToString ().NormalizeLineEndings ());
 		}
+
+		[Test]
+		public void WriteMethodWithInvalidJavaName ()
+		{
+			var @class = new TestClass ("java.lang.Object", "com.mypackage.foo");
+			var method = new TestMethod (@class, "has-hyp$hen");
+
+			method.Name = "nohyphen";
+
+			Assert.IsTrue (method.Validate (options, new GenericParameterDefinitionList (), new CodeGeneratorContext ()), "method.Validate failed!");
+			generator.WriteMethod (method, string.Empty, @class, true);
+
+			var result = writer.ToString ().NormalizeLineEndings ();
+
+			// Ensure we escape hyphens/dollar signs in callback names
+			Assert.False (result.Contains ("cb_has-hyp$hen"));
+			Assert.True (result.Contains ("cb_has_x45_hyp_x36_hen"));
+		}
 	}
 }