From 3ca801076a1e3fbe3b8922b2429524df20def6a4 Mon Sep 17 00:00:00 2001
From: Eilon Lipton <Eilon@users.noreply.github.com>
Date: Tue, 12 Mar 2024 15:17:24 -0700
Subject: [PATCH] Fix passing null/undefined params to method invoke (#54)

Fixes #48
---
 HybridWebView/HybridWebView.cs                     |  2 +-
 HybridWebView/KnownStaticFiles/HybridWebView.js    |  5 ++++-
 MauiCSharpInteropWebView/MainPage.xaml.cs          | 12 +++++++++++-
 .../Resources/Raw/hybrid_root/methodinvoke.html    | 14 +++++++++++---
 4 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/HybridWebView/HybridWebView.cs b/HybridWebView/HybridWebView.cs
index 5f7d001..8e1d565 100644
--- a/HybridWebView/HybridWebView.cs
+++ b/HybridWebView/HybridWebView.cs
@@ -220,7 +220,7 @@ public virtual async Task OnProxyRequestMessage(HybridWebViewProxyEventArgs args
 
             var paramObjectValues =
                 invokeData.ParamValues?
-                    .Zip(invokeMethod.GetParameters(), (s, p) => JsonSerializer.Deserialize(s, p.ParameterType))
+                    .Zip(invokeMethod.GetParameters(), (s, p) => s == null ? null : JsonSerializer.Deserialize(s, p.ParameterType))
                     .ToArray();
 
             return invokeMethod.Invoke(JSInvokeTarget, paramObjectValues);
diff --git a/HybridWebView/KnownStaticFiles/HybridWebView.js b/HybridWebView/KnownStaticFiles/HybridWebView.js
index 54e4bfc..806dce0 100644
--- a/HybridWebView/KnownStaticFiles/HybridWebView.js
+++ b/HybridWebView/KnownStaticFiles/HybridWebView.js
@@ -20,7 +20,10 @@ window.HybridWebView = {
                 paramValues = [paramValues];
             }
             for (var i = 0; i < paramValues.length; i++) {
-                paramValues[i] = JSON.stringify(paramValues[i]);
+                // Let 'null' and 'undefined' be passed as-is, but stringify all other values
+                if (paramValues[i] != null) {
+                    paramValues[i] = JSON.stringify(paramValues[i]);
+                }
             }
         }
 
diff --git a/MauiCSharpInteropWebView/MainPage.xaml.cs b/MauiCSharpInteropWebView/MainPage.xaml.cs
index 719e434..9a528dd 100644
--- a/MauiCSharpInteropWebView/MainPage.xaml.cs
+++ b/MauiCSharpInteropWebView/MainPage.xaml.cs
@@ -175,7 +175,7 @@ private void WriteToLog(string message)
 
     private sealed class MyJSInvokeTarget
     {
-        private MainPage _mainPage;
+        private readonly MainPage _mainPage;
 
         public MyJSInvokeTarget(MainPage mainPage)
         {
@@ -187,6 +187,16 @@ public void CallMeFromScript(string message, int value)
             _mainPage.WriteToLog($"I'm a .NET method called from JavaScript with message='{message}' and value={value}");
         }
 
+        public void CallEmptyParams(string thisIsNull, int thisIsUndefined)
+        {
+            _mainPage.WriteToLog($"I'm a .NET method called from JavaScript with null='{thisIsNull}' and undefined={thisIsUndefined}");
+        }
+
+        public void CallNoParams()
+        {
+            _mainPage.WriteToLog($"I'm a .NET method called from JavaScript with no params");
+        }
+
         /// <summary>
         /// An example of a round trip method that takes an input multiple parameters and returns a simple value type (string).
         /// </summary>
diff --git a/MauiCSharpInteropWebView/Resources/Raw/hybrid_root/methodinvoke.html b/MauiCSharpInteropWebView/Resources/Raw/hybrid_root/methodinvoke.html
index daf249d..8c66779 100644
--- a/MauiCSharpInteropWebView/Resources/Raw/hybrid_root/methodinvoke.html
+++ b/MauiCSharpInteropWebView/Resources/Raw/hybrid_root/methodinvoke.html
@@ -11,15 +11,21 @@
             return sum;
         }
 
-        /* Async invoke examples */
-
-
         function CallDotNetMethod() {
             Log('Calling a method in .NET with some parameters');
 
             HybridWebView.SendInvokeMessageToDotNet("CallMeFromScript", ["msg from js", 987]);
         }
 
+        function CallEmptyParams() {
+            HybridWebView.SendInvokeMessageToDotNet("CallEmptyParams", [null, undefined]);
+        }
+
+        function CallNoParams() {
+            HybridWebView.SendInvokeMessageToDotNet("CallNoParams");
+        }
+
+        /* Async invoke examples */
         async function invokeRoundTripDotNetMethod() {
             var r = await HybridWebView.SendInvokeMessageToDotNetAsync('RoundTripCallFromScript', ["param1", 123]);
             Log(r);
@@ -64,6 +70,8 @@ <h1>HybridWebView demo: Method invoke</h1>
             <b>Sync invoke - Call .NET, no response</b>
             <br />
             <button type="button" onclick="CallDotNetMethod()">Call .NET method with some parameters</button>
+            <button type="button" onclick="CallEmptyParams()">Call .NET method with null/undefined parameters</button>
+            <button type="button" onclick="CallNoParams()">Call .NET method with no parameters</button>
         </p>
 
         <p>