Add fallback

Author: JamesNK

src/Grpc/JsonTranscoding/src/Microsoft.AspNetCore.Grpc.JsonTranscoding/GrpcJsonSettings.cs

@@ -50,10 +50,16 @@ public sealed class GrpcJsonSettings
     /// }
     /// </code>
     /// <para>
-    /// <c>STATUS</c> prefix is removed from enum values when <see cref="RemoveEnumPrefix"/> is set to <see langword="true"/>.
-    /// The enum values above will be read and written as <c>UNKNOWN</c> and <c>OK</c> instead of <c>STATUS_UNKNOWN</c>
-    /// and <c>STATUS_OK</c>.
+    /// When <see cref="RemoveEnumPrefix"/> is set to <see langword="true"/>:
     /// </para>
+    /// <list type="bullet">
+    /// <item>
+    /// <description>The <c>STATUS</c> prefix is removed from enum values. The enum values above will be read and written as <c>UNKNOWN</c> and <c>OK</c> instead of <c>STATUS_UNKNOWN</c> and <c>STATUS_OK</c>.</description>
+    /// </item>
+    /// <item>
+    /// <description>Original prefixed values are used as a fallback when reading JSON. For example, <c>STATUS_OK</c> and <c>OK</c> map to the <c>STATUS_OK</c> enum value.</description>
+    /// </item>
+    /// </list>
     /// <para>
     /// The Protobuf JSON specification requires enum values in JSON to match enum fields exactly.
     /// Enabling this option may reduce interoperability, as removing enum prefix might not be supported

src/Grpc/JsonTranscoding/src/Microsoft.AspNetCore.Grpc.JsonTranscoding/Internal/Json/EnumNameHelpers.cs

@@ -75,6 +75,10 @@ private static EnumMapping GetEnumMapping(string enumName, Type enumType)
 
         var writeMapping = nameMappings.ToDictionary(m => m.Value, m => m);
 
+        // Add original names as fallback when mapping enum values with removed prefixes.
+        // There are added to the dictionary first so they are overridden by the mappings with removed prefixes.
+        var removeEnumPrefixMapping = nameMappings.ToDictionary(m => m.OriginalName, m => m.OriginalName);
+
         // Protobuf codegen prevents collision of enum names when the prefix is removed.
         // For example, the following enum will fail to build because both fields would resolve to "OK":
         //
@@ -89,9 +93,10 @@ private static EnumMapping GetEnumMapping(string enumName, Type enumType)
         // (If you are using allow_alias, please assign the same number to each enum value name.)
         //
         // Just in case it does happen, map to the first value rather than error.
-        var removeEnumPrefixMapping = nameMappings
-            .GroupBy(m => m.RemoveEnumPrefixName)
-            .ToDictionary(g => g.Key, g => g.First().OriginalName, StringComparer.Ordinal);
+        foreach (var item in nameMappings.GroupBy(m => m.RemoveEnumPrefixName).Select(g => KeyValuePair.Create(g.Key, g.First().OriginalName)))
+        {
+            removeEnumPrefixMapping[item.Key] = item.Value;
+        }
 
         return new EnumMapping { WriteMapping = writeMapping, RemoveEnumPrefixMapping = removeEnumPrefixMapping };
     }

src/Grpc/JsonTranscoding/test/Microsoft.AspNetCore.Grpc.JsonTranscoding.Tests/ConverterTests/JsonConverterReadTests.cs

@@ -245,7 +245,9 @@ public void Enum_ReadString(string value, HelloRequest.Types.DataTypes.Types.Nes
 
     [Theory]
     [InlineData("UNSPECIFIED", PrefixEnumType.Types.PrefixEnum.Unspecified)]
+    [InlineData("PREFIX_ENUM_UNSPECIFIED", PrefixEnumType.Types.PrefixEnum.Unspecified)]
     [InlineData("FOO", PrefixEnumType.Types.PrefixEnum.Foo)]
+    [InlineData("PREFIX_ENUM_FOO", PrefixEnumType.Types.PrefixEnum.Foo)]
     [InlineData("BAR", PrefixEnumType.Types.PrefixEnum.Bar)]
     public void Enum_RemovePrefix_ReadString(string value, PrefixEnumType.Types.PrefixEnum expectedValue)
     {
@@ -258,6 +260,23 @@ public void Enum_RemovePrefix_ReadString(string value, PrefixEnumType.Types.Pref
         Assert.Equal(expectedValue, result.SingleEnum);
     }
 
+    [Theory]
+    [InlineData("UNSPECIFIED", CollisionPrefixEnumType.Types.CollisionPrefixEnum.Unspecified)]
+    [InlineData("COLLISION_PREFIX_ENUM_UNSPECIFIED", CollisionPrefixEnumType.Types.CollisionPrefixEnum.Unspecified)]
+    [InlineData("FOO", CollisionPrefixEnumType.Types.CollisionPrefixEnum.Foo)]
+    [InlineData("COLLISION_PREFIX_ENUM_FOO", CollisionPrefixEnumType.Types.CollisionPrefixEnum.CollisionPrefixEnumFoo)] // Match exact rather than fallback.
+    [InlineData("COLLISION_PREFIX_ENUM_COLLISION_PREFIX_ENUM_FOO", CollisionPrefixEnumType.Types.CollisionPrefixEnum.CollisionPrefixEnumFoo)]
+    public void Enum_RemovePrefix_Collision_ReadString(string value, CollisionPrefixEnumType.Types.CollisionPrefixEnum expectedValue)
+    {
+        var serviceDescriptorRegistry = new DescriptorRegistry();
+        serviceDescriptorRegistry.RegisterFileDescriptor(JsonTranscodingGreeter.Descriptor.File);
+
+        var json = @$"{{ ""singleEnum"": ""{value}"" }}";
+
+        var result = AssertReadJson<CollisionPrefixEnumType>(json, descriptorRegistry: serviceDescriptorRegistry, serializeOld: false, settings: new GrpcJsonSettings { RemoveEnumPrefix = true });
+        Assert.Equal(expectedValue, result.SingleEnum);
+    }
+
     [Fact]
     public void Enum_ReadString_NotAllowedValue()
     {

src/Grpc/JsonTranscoding/test/Microsoft.AspNetCore.Grpc.JsonTranscoding.Tests/Proto/transcoding.proto

@@ -246,3 +246,12 @@ message PrefixEnumType {
   }
   PrefixEnum single_enum = 1;
 }
+
+message CollisionPrefixEnumType {
+  enum CollisionPrefixEnum {
+    COLLISION_PREFIX_ENUM_UNSPECIFIED = 0;
+    COLLISION_PREFIX_ENUM_FOO = 1;
+    COLLISION_PREFIX_ENUM_COLLISION_PREFIX_ENUM_FOO = 2;
+  }
+  CollisionPrefixEnum single_enum = 1;
+}