[ci] Add DevDiv required Roslyn analyzers, fix errors (#704)

As part of building secure software, Microsoft DevDiv has a set of
[Roslyn anaylzers][0] dealing with security that should be run on every
managed assembly.

Adds these analyzers and fix any errors they introduce.


~~ Running Analyzers ~~

In order to run the Roslyn analyzers, the NuGet package
[`Microsoft.CodeAnalysis.FxCopAnalyzers`][1] must be added to each
project.  Rather than do this manually now, and for each new project
in the future, we instead add this to the `Directory.Build.props` file,
which automatically adds it to all projects.

By default, adding the NuGet package runs all included analyzers at
each analyzer's default severity level.  At this time, we are only
concerned with the prescribed security set, so we use
`.editorconfig` to set those analyzers as `error`, and all other
analyzers as `none`.

Projects that wish to opt out of running the analyzers can set 
`<DisableRoslynAnalyzers>True</DisableRoslynAnalyzers>`.

~~ Fixing Errors ~~

The only errors surfaced by these analyzers is
[CA3075: Insecure DTD Processing][2].  These were fixed by using
`new XmlReaderSettings { XmlResolver = null }`, which will not attempt
to resolve and download any DTD files.


~~ Move `NullableAttributes.cs` ~~

`NullableAttributes.cs` is moved to the `src\utils` directory.  

This file was added to `Java.Interop.Tools.JavaCallableWrappers.csproj`
via `..\Java.Interop\`.  However, because the file resided in the
directory containing the strict `.editorconfig` for `Java.Interop.dll`,
it was applying those `.editorconfig` rules to
`Java.Interop.Tools.JavaCallableWrappers.dll`.


Moving it to a neutral directory fixed this.

~~ Other Notes ~~

Updating the `Java.Interop.dll` to the latest analyzer NuGet version
triggered some errors we had handled for that specific assembly, which
likely did not exist in the old analyzers and thus were not being
surfaced as errors.  They do not appear to be rules that we are
actually concerned with, so they were disabled:

  * CA1021 - Don't use out parameters
  * CA1045 - Don't use reference parameters
  * CA1822 - Mark methods static if they don't reference instance members
  * CA1002 - Don't expose generic Lists

[0]: https://github.com/dotnet/roslyn-analyzers
[1]: https://www.nuget.org/packages/Microsoft.CodeAnalysis.FxCopAnalyzers/
[2]: https://docs.microsoft.com/en-us/visualstudio/code-quality/ca3075?view=vs-2019

Directory.Build.props

@@ -68,4 +68,13 @@
     <_RunJNIEnvGen Condition=" '$(JIBuildingForNetCoreApp)' == 'True' ">dotnet "$(_JNIEnvGenPath)"</_RunJNIEnvGen>
     <_RunJNIEnvGen Condition=" '$(JIBuildingForNetCoreApp)' != 'True' ">$(Runtime) "$(_JNIEnvGenPath)"</_RunJNIEnvGen>
   </PropertyGroup>
+
+  <!-- Add Roslyn analyzers NuGet to all projects -->
+  <ItemGroup Condition=" '$(DisableRoslynAnalyzers)' != 'True' ">
+    <PackageReference Include="Microsoft.CodeAnalysis.FxCopAnalyzers" Version="3.3.0">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
 </Project>

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

@@ -25,7 +25,7 @@
     <Compile Include="..\Java.Interop.Tools.TypeNameMappings\Java.Interop.Tools.TypeNameMappings\JavaNativeTypeManager.cs">
       <Link>JavaNativeTypeManager.cs</Link>
     </Compile>
-    <Compile Include="..\Java.Interop\NullableAttributes.cs">
+    <Compile Include="..\utils\NullableAttributes.cs">
       <Link>NullableAttributes.cs</Link>
     </Compile>
   </ItemGroup>

src/Java.Interop/.editorconfig

@@ -18,15 +18,12 @@ dotnet_diagnostic.CA2213.severity = error
 dotnet_diagnostic.CA2242.severity = error
 dotnet_diagnostic.CA2000.severity = error
 dotnet_diagnostic.CA2220.severity = error
-dotnet_diagnostic.CA1822.severity = error
 dotnet_diagnostic.CA2241.severity = error
 dotnet_diagnostic.CA1012.severity = error
 dotnet_diagnostic.CA1019.severity = error
 dotnet_diagnostic.CA1040.severity = error
 dotnet_diagnostic.CA1023.severity = error
 dotnet_diagnostic.CA1044.severity = error
-dotnet_diagnostic.CA1021.severity = error
-dotnet_diagnostic.CA1045.severity = error
 dotnet_diagnostic.CA1020.severity = error
 dotnet_diagnostic.CA1051.severity = error
 dotnet_diagnostic.CA1034.severity = error
@@ -67,7 +64,6 @@ dotnet_diagnostic.CA1027.severity = error
 dotnet_diagnostic.CA1005.severity = error
 dotnet_diagnostic.CA1004.severity = error
 dotnet_diagnostic.CA1000.severity = error
-dotnet_diagnostic.CA1002.severity = error
 dotnet_diagnostic.CA1006.severity = error
 dotnet_diagnostic.CA1010.severity = error
 dotnet_diagnostic.CA1007.severity = error

src/Java.Interop/Java.Interop.csproj

@@ -19,7 +19,7 @@
     <DefineConstants>DEBUG;$(DefineConstants)</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
-    <Compile Condition=" '$(TargetFramework)' != 'netstandard2.0' " Remove="NullableAttributes.cs" />
+    <Compile Condition=" '$(TargetFramework)' == 'netstandard2.0' " Include="..\utils\NullableAttributes.cs" />
     <Compile Remove="Java.Interop\JniLocationException.cs" />
   </ItemGroup>
   <PropertyGroup>
@@ -49,10 +49,6 @@
     <None Include="Documentation\Java.Interop\IJavaPeerable.xml" />
     <None Include="Documentation\Java.Interop\JniManagedPeerStates.xml" />
     <None Include="Documentation\Java.Interop\JniEnvironment.References.xml" />
-    <PackageReference Include="Microsoft.CodeAnalysis.FxCopAnalyzers" Version="2.9.7">
-      <PrivateAssets>all</PrivateAssets>
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-    </PackageReference>
     <ProjectReference Include="..\..\build-tools\jnienv-gen\jnienv-gen.csproj"
         ReferenceOutputAssembly="false"
     />

tests/Xamarin.Android.Tools.ApiXmlAdjuster-Tests/JavaApiTestHelper.cs

@@ -20,7 +20,7 @@ public class JavaApiTestHelper
 		public static JavaApi GetLoadedApi ()
 		{
 			var api = new JavaApi ();
-			using (var xr = XmlReader.Create (ApiPath))
+			using (var xr = XmlReader.Create (ApiPath, new XmlReaderSettings { XmlResolver = null }))
 				api.Load (xr, false);
 			return api;
 		}

tools/generator/ApiVersionsProvider.cs

@@ -9,7 +9,7 @@ public class ApiVersionsProvider
 	{
 		public void Parse (string apiVersionsFilePath)
 		{
-			using (var reader = XmlReader.Create (apiVersionsFilePath))
+			using (var reader = XmlReader.Create (apiVersionsFilePath, new XmlReaderSettings { XmlResolver = null }))
 				Parse (reader);
 		}
 

tools/generator/CodeGenerator.cs

@@ -85,7 +85,7 @@ static void Run (CodeGeneratorOptions options, DirectoryAssemblyResolver resolve
 			string apiXmlFile = filename;
 			string apiSourceAttr = null;
 
-			using (var xr = XmlReader.Create (filename)) {
+			using (var xr = XmlReader.Create (filename, new XmlReaderSettings { XmlResolver = null })) {
 				xr.MoveToContent ();
 				apiSourceAttr = xr.GetAttribute ("api-source");
 			}