Issue 104700: Clarify error message for collection property with no getter

- Added verification to distinguish between different error types.
- Renamed existing test to more accurately reflect that it tests required properties without a setter.
- Added a new test to ensure that a collection property without a getter throws an InvalidOperationException.

Author: julien98Qc

src/libraries/System.Text.Json/src/Resources/Strings.resx

@@ -758,4 +758,7 @@
   <data name="JsonSchemaExporter_DepthTooLarge" xml:space="preserve">
     <value>The depth of the generated JSON schema exceeds the JsonSerializerOptions.MaxDepth setting.</value>
   </data>
+  <data name="JsonPropertyRequiredAndCollectionPropertyMissingGetter" xml:space="preserve">
+    <value>JsonPropertyInfo '{0}' defined in type '{1}' is marked required but is a collection property and does not specify a getter.</value>
+  </data>
 </root>

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonPropertyInfo.cs

@@ -448,19 +448,7 @@ internal void Configure()
 
             if (IsRequired)
             {
-                if (!CanDeserialize &&
-                    !(AssociatedParameter?.IsRequiredParameter is true &&
-                      Options.RespectRequiredConstructorParameters))
-                {
-                    ThrowHelper.ThrowInvalidOperationException_JsonPropertyRequiredAndNotDeserializable(this);
-                }
-
-                if (IsExtensionData)
-                {
-                    ThrowHelper.ThrowInvalidOperationException_JsonPropertyRequiredAndExtensionData(this);
-                }
-
-                Debug.Assert(!IgnoreNullTokensOnRead);
+                EnsureRequiredPropertyIsDeserializable();
             }
 
             IsConfigured = true;
@@ -472,6 +460,31 @@ internal void Configure()
         [RequiresDynamicCode(JsonSerializer.SerializationRequiresDynamicCodeMessage)]
         internal abstract void DetermineReflectionPropertyAccessors(MemberInfo memberInfo, bool useNonPublicAccessors);
 
+        private void EnsureRequiredPropertyIsDeserializable()
+        {
+            if (!CanDeserialize)
+            {
+                bool isCollectionProperty = (EffectiveConverter.ConverterStrategy & (ConverterStrategy.Enumerable | ConverterStrategy.Dictionary)) != 0;
+                bool isRequiredParameterRespected = AssociatedParameter?.IsRequiredParameter is true && Options.RespectRequiredConstructorParameters;
+
+                if (isCollectionProperty)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_JsonPropertyRequiredAndCollectionPropertyMissingGetter(this);
+                }
+                else if (!isRequiredParameterRespected)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_JsonPropertyRequiredAndNotDeserializable(this);
+                }
+            }
+
+            if (IsExtensionData)
+            {
+                ThrowHelper.ThrowInvalidOperationException_JsonPropertyRequiredAndExtensionData(this);
+            }
+
+            Debug.Assert(!IgnoreNullTokensOnRead);
+        }
+
         private void CacheNameAsUtf8BytesAndEscapedNameSection()
         {
             Debug.Assert(Name != null);

src/libraries/System.Text.Json/src/System/Text/Json/ThrowHelper.Serialization.cs

@@ -275,6 +275,12 @@ public static void ThrowInvalidOperationException_SerializerPropertyNameNull(Jso
             throw new InvalidOperationException(SR.Format(SR.SerializerPropertyNameNull, jsonPropertyInfo.DeclaringType, jsonPropertyInfo.MemberName));
         }
 
+        [DoesNotReturn]
+        public static void ThrowInvalidOperationException_JsonPropertyRequiredAndCollectionPropertyMissingGetter(JsonPropertyInfo jsonPropertyInfo)
+        {
+            throw new InvalidOperationException(SR.Format(SR.JsonPropertyRequiredAndCollectionPropertyMissingGetter, jsonPropertyInfo.Name, jsonPropertyInfo.DeclaringType));
+        }
+
         [DoesNotReturn]
         public static void ThrowInvalidOperationException_JsonPropertyRequiredAndNotDeserializable(JsonPropertyInfo jsonPropertyInfo)
         {

src/libraries/System.Text.Json/tests/Common/RequiredKeywordTests.cs

@@ -564,7 +564,7 @@ public async Task ChangingPropertiesWithRequiredKeywordToNotBeRequiredAllowsDese
         }
 
         [Fact]
-        public async Task RequiredNonDeserializablePropertyThrows()
+        public async Task RequiredPropertyWithoutSetterThrows()
         {
             JsonSerializerOptions options = Serializer.GetDefaultOptionsWithMetadataModifier(static ti =>
             {
@@ -610,6 +610,23 @@ public class ClassWithRequiredExtensionDataProperty
             public required Dictionary<string, JsonElement>? TestExtensionData { get; set; }
         }
 
+        [Fact]
+        public async Task RequiredCollectionPropertyWithoutGetterThrows()
+        {
+            string json = """{"Foo":"foo","Bar":"bar"}""";
+            InvalidOperationException exception = await Assert.ThrowsAsync<InvalidOperationException>(
+                async () => await Serializer.DeserializeWrapper<ClassWithRequiredCollectionPropertyWithoutGetter>(json));
+            Assert.Contains(nameof(ClassWithRequiredCollectionPropertyWithoutGetter.TestCollectionPropertyWithoutGetter), exception.Message);
+        }
+
+        public class ClassWithRequiredCollectionPropertyWithoutGetter
+        {
+            public required Dictionary<string, JsonElement>? TestCollectionPropertyWithoutGetter
+            {
+                set => TestCollectionPropertyWithoutGetter = value;
+            }
+        }
+
         [Fact]
         public async Task RequiredKeywordAndJsonRequiredCustomAttributeWorkCorrectlyTogether()
         {