xunit/xunit#3244: xUnit2017 analyzer's code fixer generate incompatible code

Author: bradwilson

src/xunit.analyzers.fixes/X2000/AssertCollectionContainsShouldNotUseBoolCheckFixer.cs

@@ -5,6 +5,7 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CodeActions;
 using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Editing;
 using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
@@ -63,11 +64,18 @@ static async Task<Document> UseContainsCheck(
 				if (invocationExpressionSyntax.Expression is MemberAccessExpressionSyntax anyMethodInvocation)
 				{
 					var anyTarget = anyMethodInvocation.Expression;
+					var isTrailingNull =
+						invocationExpressionSyntax.ArgumentList.Arguments.Count == 2
+						&& invocationExpressionSyntax.ArgumentList.Arguments[1].Expression.Kind() == SyntaxKind.NullLiteralExpression;
+					var existingArguments =
+						isTrailingNull
+							? SeparatedList([invocationExpressionSyntax.ArgumentList.Arguments[0]])
+							: invocationExpressionSyntax.ArgumentList.Arguments;
 
 					editor.ReplaceNode(
 						invocation,
 						invocation
-							.WithArgumentList(ArgumentList(SeparatedList(invocationExpressionSyntax.ArgumentList.Arguments.Insert(1, Argument(anyTarget)))))
+							.WithArgumentList(ArgumentList(SeparatedList(existingArguments.Insert(1, Argument(anyTarget)))))
 							.WithExpression(memberAccess.WithName(IdentifierName(replacement)))
 					);
 				}

src/xunit.analyzers.tests/Fixes/X2000/AssertCollectionContainsShouldNotUseBoolCheckFixerTests.cs

@@ -27,12 +27,18 @@ public void TestMethod() {{
 	[InlineData(
 		/* lang=c#-test */ @"[|Assert.True(items.Contains(""b"", StringComparer.Ordinal))|]",
 		/* lang=c#-test */ @"Assert.Contains(""b"", items, StringComparer.Ordinal)")]
+	[InlineData(
+		/* lang=c#-test */ @"[|Assert.True(items.Contains(""b"", null))|]",
+		/* lang=c#-test */ @"Assert.Contains(""b"", items)")]
 	[InlineData(
 		/* lang=c#-test */ @"[|Assert.False(items.Contains(""b""))|]",
 		/* lang=c#-test */ @"Assert.DoesNotContain(""b"", items)")]
 	[InlineData(
 		/* lang=c#-test */ @"[|Assert.False(items.Contains(""b"", StringComparer.Ordinal))|]",
 		/* lang=c#-test */ @"Assert.DoesNotContain(""b"", items, StringComparer.Ordinal)")]
+	[InlineData(
+		/* lang=c#-test */ @"[|Assert.False(items.Contains(""b"", null))|]",
+		/* lang=c#-test */ @"Assert.DoesNotContain(""b"", items)")]
 	public async Task ReplacesBooleanAssert(
 		string beforeAssert,
 		string afterAssert)