[Java.Interop.Tools.JavaCallableWrappers] NRT Support (#1012)

Context: 3226a4b
Context: 7068f4b
Enable [C# 8 Nullable Reference Types][0] for
`Java.Interop.Tools.JavaCallableWrappers.dll`.
[0]: https://docs.microsoft.com/en-us/dotnet/csharp/nullable-references

Author: jonpryor

src/Java.Interop.NamingCustomAttributes/Android.Runtime/RegisterAttribute.cs

@@ -1,3 +1,5 @@
+#nullable enable
+
 usingSystem;
 
 usingMono.Cecil;
@@ -10,9 +12,9 @@ namespace Android.Runtime {
 #endif // !JCW_ONLY_TYPE_NAMES
 sealedclassRegisterAttribute:Attribute,Java.Interop.IJniNameProviderAttribute{
 
-stringconnector;
+string?connector;
 stringname;
-stringsignature;
+string?signature;
 
 publicRegisterAttribute(stringname)
 {
@@ -26,22 +28,22 @@ public RegisterAttribute (string name, string signature, string connector)
 this.signature=signature;
 }
 #if HAVE_CECIL
-publicRegisterAttribute(stringname,CustomAttributeoriginAttribute)
+publicRegisterAttribute(stringname,CustomAttribute?originAttribute)
 :this(name)
 {
 OriginAttribute=originAttribute;
 }
 
-publicRegisterAttribute(stringname,stringsignature,stringconnector,CustomAttributeoriginAttribute)
+publicRegisterAttribute(stringname,stringsignature,stringconnector,CustomAttribute?originAttribute)
 :this(name,signature,connector)
 {
 OriginAttribute=originAttribute;
 }
 
-publicCustomAttributeOriginAttribute{get;}
+publicCustomAttribute?OriginAttribute{get;}
 #endif // HAVE_CECIL
 
-publicstringConnector{
+publicstring?Connector{
 get{returnconnector;}
 set{connector=value;}
 }
@@ -51,7 +53,7 @@ public string Name {
 set{name=value;}
 }
 
-publicstringSignature{
+publicstring?Signature{
 get{returnsignature;}
 set{signature=value;}
 }

src/Java.Interop.NamingCustomAttributes/Java.Interop/ExportAttribute.cs

@@ -1,3 +1,5 @@
+#nullable enable
+
 usingSystem;
 
 namespaceJava.Interop{
@@ -15,15 +17,15 @@ public ExportAttribute ()
 {
 }
 
-publicExportAttribute(stringname)
+publicExportAttribute(string?name)
 {
 Name=name;
 }
 
-publicstringName{get;privateset;}
-publicstringSuperArgumentsString{get;set;}
-publicType[]Throws{get;set;}
-internalstring[]ThrownNames{get;set;}// msbuild internal use
+publicstring?Name{get;privateset;}
+publicstring?SuperArgumentsString{get;set;}
+publicType[]?Throws{get;set;}
+internalstring[]?ThrownNames{get;set;}// msbuild internal use
 }
 }
 

src/Java.Interop.Tools.Diagnostics/Java.Interop.Tools.Diagnostics/Diagnostic.cs

@@ -148,7 +148,7 @@ namespace Java.Interop.Tools.Diagnostics {
 //
 
 publicstaticclassDiagnostic{
-publicstaticvoidError(intcode,SequencePointlocation,stringmessage,paramsobject[]args)
+publicstaticvoidError(intcode,SequencePoint?location,stringmessage,paramsobject[]args)
 {
 thrownewXamarinAndroidException(code,message,args){
 Location=location,

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

@@ -4,6 +4,7 @@
  <TargetFramework>netstandard2.0</TargetFramework>
  <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
  <LangVersion>8.0</LangVersion>
+ <Nullable>enable</Nullable>
  <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
  <SignAssembly>true</SignAssembly>
  <AssemblyOriginatorKeyFile>..\..\product.snk</AssemblyOriginatorKeyFile>

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

@@ -31,9 +31,9 @@ public static class IdentifierValidator
 // We use [^ ...] to detect any character that is NOT a match.
 staticRegexvalidIdentifier=newRegex($"[^{Identifier}]",RegexOptions.Compiled);
 
-publicstaticstringCreateValidIdentifier(stringidentifier,booluseEncodedReplacements=false)
+publicstaticstringCreateValidIdentifier(string?identifier,booluseEncodedReplacements=false)
 {
-if(string.IsNullOrWhiteSpace(identifier))returnstring.Empty;
+if(identifier==null||string.IsNullOrWhiteSpace(identifier))returnstring.Empty;
 
 varnormalizedIdentifier=identifier.Normalize();