From 85dce730b6d6b5cb6ef7219a471f750e1c672025 Mon Sep 17 00:00:00 2001
From: "DECIDEWARE\\mperdeck" <mperdeck@decideware.com>
Date: Thu, 27 Oct 2022 12:56:00 +1100
Subject: [PATCH] OData#277 change contract of IPropertyMapper.MapProperty, so
 it can now return null if the field should not be serialized at all (as in,
 ignored)

---
 .../Microsoft.AspNetCore.OData.xml                    |  5 ++++-
 .../Properties/SRResources.Designer.cs                |  2 +-
 .../Properties/SRResources.resx                       |  2 +-
 .../Query/Container/IPropertyMapper.cs                |  3 +++
 .../Query/Container/NamedPropertyOfT.cs               | 11 +++++++----
 .../Query/Wrapper/SelectExpandWrapper.cs              | 11 +++++++----
 6 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/Microsoft.AspNetCore.OData/Microsoft.AspNetCore.OData.xml b/src/Microsoft.AspNetCore.OData/Microsoft.AspNetCore.OData.xml
index 4d0e931a0..18808b539 100644
--- a/src/Microsoft.AspNetCore.OData/Microsoft.AspNetCore.OData.xml
+++ b/src/Microsoft.AspNetCore.OData/Microsoft.AspNetCore.OData.xml
@@ -6822,7 +6822,7 @@
         </member>
         <member name="P:Microsoft.AspNetCore.OData.SRResources.InvalidPropertyMapping">
             <summary>
-              Looks up a localized string similar to The key mapping for the property &apos;{0}&apos; can&apos;t be null or empty..
+              Looks up a localized string similar to The key mapping for the property &apos;{0}&apos; can&apos;t be empty..
             </summary>
         </member>
         <member name="P:Microsoft.AspNetCore.OData.SRResources.InvalidSegmentInSelectExpandPath">
@@ -7792,6 +7792,9 @@
             properties in the <see cref="T:Microsoft.OData.Edm.IEdmStructuredType"/> that will be used during the serialization of the $select
             and $expand projection by a given formatter. For example, to support custom serialization attributes of a
             particular formatter.
+            
+            It also allows you to ignore a field (ensure that the returned <see cref="T:System.Collections.Generic.IDictionary`2"/>
+            does not have a key for that field), by mapping the property name to null.
             </summary>
         </member>
         <member name="M:Microsoft.AspNetCore.OData.Query.Container.IPropertyMapper.MapProperty(System.String)">
diff --git a/src/Microsoft.AspNetCore.OData/Properties/SRResources.Designer.cs b/src/Microsoft.AspNetCore.OData/Properties/SRResources.Designer.cs
index 31011acb1..38e667b70 100644
--- a/src/Microsoft.AspNetCore.OData/Properties/SRResources.Designer.cs
+++ b/src/Microsoft.AspNetCore.OData/Properties/SRResources.Designer.cs
@@ -880,7 +880,7 @@ internal static string InvalidPropertyMapper {
         }
         
         /// <summary>
-        ///   Looks up a localized string similar to The key mapping for the property &apos;{0}&apos; can&apos;t be null or empty..
+        ///   Looks up a localized string similar to The key mapping for the property &apos;{0}&apos; can&apos;t be empty..
         /// </summary>
         internal static string InvalidPropertyMapping {
             get {
diff --git a/src/Microsoft.AspNetCore.OData/Properties/SRResources.resx b/src/Microsoft.AspNetCore.OData/Properties/SRResources.resx
index e43617960..91a0110b8 100644
--- a/src/Microsoft.AspNetCore.OData/Properties/SRResources.resx
+++ b/src/Microsoft.AspNetCore.OData/Properties/SRResources.resx
@@ -496,7 +496,7 @@
     <value>A binary operator with incompatible types was detected. Found operand types '{0}' and '{1}' for operator kind '{2}'.</value>
   </data>
   <data name="InvalidPropertyMapping" xml:space="preserve">
-    <value>The key mapping for the property '{0}' can't be null or empty.</value>
+    <value>The key mapping for the property '{0}' can't be empty.</value>
   </data>
   <data name="ODataFunctionNotSupported" xml:space="preserve">
     <value>Unknown function '{0}'.</value>
diff --git a/src/Microsoft.AspNetCore.OData/Query/Container/IPropertyMapper.cs b/src/Microsoft.AspNetCore.OData/Query/Container/IPropertyMapper.cs
index 2f349f28d..2ad722ac7 100644
--- a/src/Microsoft.AspNetCore.OData/Query/Container/IPropertyMapper.cs
+++ b/src/Microsoft.AspNetCore.OData/Query/Container/IPropertyMapper.cs
@@ -23,6 +23,9 @@ namespace Microsoft.AspNetCore.OData.Query.Container
     /// properties in the <see cref="IEdmStructuredType"/> that will be used during the serialization of the $select
     /// and $expand projection by a given formatter. For example, to support custom serialization attributes of a
     /// particular formatter.
+    /// 
+    /// It also allows you to ignore a field (ensure that the returned <see cref="IDictionary{TKey,TValue}"/>
+    /// does not have a key for that field), by mapping the property name to null.
     /// </summary>
     public interface IPropertyMapper
     {
diff --git a/src/Microsoft.AspNetCore.OData/Query/Container/NamedPropertyOfT.cs b/src/Microsoft.AspNetCore.OData/Query/Container/NamedPropertyOfT.cs
index 1fc96e4f0..a8de825cd 100644
--- a/src/Microsoft.AspNetCore.OData/Query/Container/NamedPropertyOfT.cs
+++ b/src/Microsoft.AspNetCore.OData/Query/Container/NamedPropertyOfT.cs
@@ -27,12 +27,15 @@ public override void ToDictionaryCore(Dictionary<string, object> dictionary, IPr
             if (Name != null && (includeAutoSelected || !AutoSelected))
             {
                 string mappedName = propertyMapper.MapProperty(Name);
-                if (String.IsNullOrEmpty(mappedName))
+                if (mappedName != null)
                 {
-                    throw Error.InvalidOperation(SRResources.InvalidPropertyMapping, Name);
-                }
+                    if (String.IsNullOrEmpty(mappedName))
+                    {
+                        throw Error.InvalidOperation(SRResources.InvalidPropertyMapping, Name);
+                    }
 
-                dictionary.Add(mappedName, GetValue());
+                    dictionary.Add(mappedName, GetValue());
+                }
             }
         }
 
diff --git a/src/Microsoft.AspNetCore.OData/Query/Wrapper/SelectExpandWrapper.cs b/src/Microsoft.AspNetCore.OData/Query/Wrapper/SelectExpandWrapper.cs
index d74171d1a..194155a62 100644
--- a/src/Microsoft.AspNetCore.OData/Query/Wrapper/SelectExpandWrapper.cs
+++ b/src/Microsoft.AspNetCore.OData/Query/Wrapper/SelectExpandWrapper.cs
@@ -144,12 +144,15 @@ public IDictionary<string, object> ToDictionary(Func<IEdmModel, IEdmStructuredTy
                     if (TryGetPropertyValue(property.Name, out propertyValue))
                     {
                         string mappingName = mapper.MapProperty(property.Name);
-                        if (String.IsNullOrWhiteSpace(mappingName))
+                        if (mappingName != null)
                         {
-                            throw Error.InvalidOperation(SRResources.InvalidPropertyMapping, property.Name);
-                        }
+                            if (String.IsNullOrWhiteSpace(mappingName))
+                            {
+                                throw Error.InvalidOperation(SRResources.InvalidPropertyMapping, property.Name);
+                            }
 
-                        dictionary[mappingName] = propertyValue;
+                            dictionary[mappingName] = propertyValue;
+                        }
                     }
                 }
             }