Fix handling of parameters with default null

AutomaticInterface/AutomaticInterface/Builder.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text.RegularExpressions;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
@@ -9,6 +10,9 @@ namespace AutomaticInterface;
 
 public static class Builder
 {
+    private static Regex ParamWithDefaultValueRegex { get; } =
+    new(pattern: @"^(?<type>\S+)(?<rest>\s+\S+\s+=.+)$", options: RegexOptions.Compiled);
+
     private static string InheritDoc(ISymbol source) =>
         $"/// <inheritdoc cref=\"{source.ToDisplayString().Replace('<', '{').Replace('>', '}')}\" />"; // we use inherit doc because that should be able to fetch documentation from base classes.
 
@@ -155,7 +159,19 @@ private static void AddMethod(InterfaceBuilder codeGenerator, IMethodSymbol meth
 
         var paramResult = new HashSet<string>();
         method
-            .Parameters.Select(x => x.ToDisplayString(FullyQualifiedDisplayFormat))
+            .Parameters.Select(x =>
+            {
+                var dispString = x.ToDisplayString(FullyQualifiedDisplayFormat);
+                if (x.HasExplicitDefaultValue && x.ExplicitDefaultValue is null && x.NullableAnnotation != NullableAnnotation.Annotated)
+                {
+                    var match = ParamWithDefaultValueRegex.Match(dispString);
+                    if (match.Success)
+                    {
+                        dispString = $"{match.Groups["type"].Value}?{match.Groups["rest"].Value}";
+                    }
+                }
+                return dispString;
+            })
             .ToList()
             .ForEach(x => paramResult.Add(x));
 
@@ -193,7 +209,7 @@ private static void ActivateNullableIfNeeded(
         IMethodSymbol method
     )
     {
-        var hasNullableParameter = method.Parameters.Any(x => IsNullable(x.Type));
+        var hasNullableParameter = method.Parameters.Any(x => IsNullable(x.Type) || (x.HasExplicitDefaultValue && x.ExplicitDefaultValue is null));
 
         var hasNullableReturn = IsNullable(method.ReturnType);
 

AutomaticInterface/Tests/Methods/Methods.BooleanWithNonNull.verified.txt

@@ -16,7 +16,7 @@ namespace AutomaticInterfaceExample
     public partial interface IDemoClass
     {
         /// <inheritdoc cref="AutomaticInterfaceExample.DemoClass.GetFinalDocumentsByIDFails(string, string, bool, bool?, System.Threading.CancellationToken)" />
-        global::System.Threading.Tasks.Task<global::System.IO.Stream?> GetFinalDocumentsByIDFails(string agreementID, string docType, bool amt = false, bool? attachSupportingDocuments = true, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken));
+        global::System.Threading.Tasks.Task<global::System.IO.Stream?> GetFinalDocumentsByIDFails(string agreementID, string docType, bool amt = false, bool? attachSupportingDocuments = true, global::System.Threading.CancellationToken? cancellationToken = default(global::System.Threading.CancellationToken));
 
     }
 }

AutomaticInterface/Tests/Methods/Methods.WorksWithOptionalNullParameters.verified.txt

@@ -6,13 +6,15 @@
 // </auto-generated>
 //--------------------------------------------------------------------------------------------------
 
+#nullable enable
 namespace AutomaticInterfaceExample
 {
     [global::System.CodeDom.Compiler.GeneratedCode("AutomaticInterface", "")]
     public partial interface IDemoClass
     {
         /// <inheritdoc cref="AutomaticInterfaceExample.DemoClass.TryStartTransaction(string)" />
-        bool TryStartTransaction(string data = null);
+        bool TryStartTransaction(string? data = null);
 
     }
 }
+#nullable restore

AutomaticInterface/Tests/Misc/Misc.CustomNameSpace.verified.txt

@@ -16,7 +16,7 @@ namespace CustomNameSpace
     public partial interface IDemoClass
     {
         /// <inheritdoc cref="AutomaticInterfaceExample.DemoClass.GetFinalDocumentsByIDFails(string, string, bool, bool?, System.Threading.CancellationToken)" />
-        global::System.Threading.Tasks.Task<global::System.IO.Stream?> GetFinalDocumentsByIDFails(string agreementID, string docType, bool amt = false, bool? attachSupportingDocuments = true, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken));
+        global::System.Threading.Tasks.Task<global::System.IO.Stream?> GetFinalDocumentsByIDFails(string agreementID, string docType, bool amt = false, bool? attachSupportingDocuments = true, global::System.Threading.CancellationToken? cancellationToken = default(global::System.Threading.CancellationToken));
 
     }
 }

AutomaticInterface/Tests/Misc/Misc.WorksWithOptionalStructParameters.verified.txt

@@ -6,13 +6,15 @@
 // </auto-generated>
 //--------------------------------------------------------------------------------------------------
 
+#nullable enable
 namespace AutomaticInterfaceExample
 {
     [global::System.CodeDom.Compiler.GeneratedCode("AutomaticInterface", "")]
     public partial interface IDemoClass
     {
         /// <inheritdoc cref="AutomaticInterfaceExample.DemoClass.TryStartTransaction(AutomaticInterfaceExample.MyStruct)" />
-        bool TryStartTransaction(global::AutomaticInterfaceExample.MyStruct data = default(global::AutomaticInterfaceExample.MyStruct));
+        bool TryStartTransaction(global::AutomaticInterfaceExample.MyStruct? data = default(global::AutomaticInterfaceExample.MyStruct));
 
     }
 }
+#nullable restore