Support custom options in C#

This consists of:
- Changing the codegen for the fixed set of options protos, to parse unknown fields instead of skipping them
- Add a new CustomOptions type in the C# support library
- Expose CustomOptions properties from the immutable proto wrappers in the support library

Only single-value options are currently supported, and fetching options values requires getting the type right
and knowing the field number. Both of these can be addressed at a later time.

Fixes #2143, at least as a first pass.

1 files changed, 24 insertions, 8 deletions

diff --git a/csharp/src/Google.Protobuf/Reflection/Descriptor.cs b/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
index d743e516..ceab9b06 100644
--- a/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
+++ b/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
@@ -2779,6 +2779,8 @@ namespace Google.Protobuf.Reflection {
       get { return Descriptor; }
     }
 
+    internal CustomOptions CustomOptions{ get; private set; } = CustomOptions.Empty;
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public FileOptions() {
       OnConstruction();
@@ -3299,7 +3301,7 @@ namespace Google.Protobuf.Reflection {
       while ((tag = input.ReadTag()) != 0) {
         switch(tag) {
           default:
-            input.SkipLastField();
+            CustomOptions = CustomOptions.ReadOrSkipUnknownField(input);
             break;
           case 10: {
             JavaPackage = input.ReadString();
@@ -3411,6 +3413,8 @@ namespace Google.Protobuf.Reflection {
       get { return Descriptor; }
     }
 
+    internal CustomOptions CustomOptions{ get; private set; } = CustomOptions.Empty;
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public MessageOptions() {
       OnConstruction();
@@ -3646,7 +3650,7 @@ namespace Google.Protobuf.Reflection {
       while ((tag = input.ReadTag()) != 0) {
         switch(tag) {
           default:
-            input.SkipLastField();
+            CustomOptions = CustomOptions.ReadOrSkipUnknownField(input);
             break;
           case 8: {
             MessageSetWireFormat = input.ReadBool();
@@ -3689,6 +3693,8 @@ namespace Google.Protobuf.Reflection {
       get { return Descriptor; }
     }
 
+    internal CustomOptions CustomOptions{ get; private set; } = CustomOptions.Empty;
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public FieldOptions() {
       OnConstruction();
@@ -3980,7 +3986,7 @@ namespace Google.Protobuf.Reflection {
       while ((tag = input.ReadTag()) != 0) {
         switch(tag) {
           default:
-            input.SkipLastField();
+            CustomOptions = CustomOptions.ReadOrSkipUnknownField(input);
             break;
           case 8: {
             ctype_ = (global::Google.Protobuf.Reflection.FieldOptions.Types.CType) input.ReadEnum();
@@ -4062,6 +4068,8 @@ namespace Google.Protobuf.Reflection {
       get { return Descriptor; }
     }
 
+    internal CustomOptions CustomOptions{ get; private set; } = CustomOptions.Empty;
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public OneofOptions() {
       OnConstruction();
@@ -4147,7 +4155,7 @@ namespace Google.Protobuf.Reflection {
       while ((tag = input.ReadTag()) != 0) {
         switch(tag) {
           default:
-            input.SkipLastField();
+            CustomOptions = CustomOptions.ReadOrSkipUnknownField(input);
             break;
           case 7994: {
             uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
@@ -4174,6 +4182,8 @@ namespace Google.Protobuf.Reflection {
       get { return Descriptor; }
     }
 
+    internal CustomOptions CustomOptions{ get; private set; } = CustomOptions.Empty;
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public EnumOptions() {
       OnConstruction();
@@ -4317,7 +4327,7 @@ namespace Google.Protobuf.Reflection {
       while ((tag = input.ReadTag()) != 0) {
         switch(tag) {
           default:
-            input.SkipLastField();
+            CustomOptions = CustomOptions.ReadOrSkipUnknownField(input);
             break;
           case 16: {
             AllowAlias = input.ReadBool();
@@ -4352,6 +4362,8 @@ namespace Google.Protobuf.Reflection {
       get { return Descriptor; }
     }
 
+    internal CustomOptions CustomOptions{ get; private set; } = CustomOptions.Empty;
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public EnumValueOptions() {
       OnConstruction();
@@ -4467,7 +4479,7 @@ namespace Google.Protobuf.Reflection {
       while ((tag = input.ReadTag()) != 0) {
         switch(tag) {
           default:
-            input.SkipLastField();
+            CustomOptions = CustomOptions.ReadOrSkipUnknownField(input);
             break;
           case 8: {
             Deprecated = input.ReadBool();
@@ -4498,6 +4510,8 @@ namespace Google.Protobuf.Reflection {
       get { return Descriptor; }
     }
 
+    internal CustomOptions CustomOptions{ get; private set; } = CustomOptions.Empty;
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public ServiceOptions() {
       OnConstruction();
@@ -4613,7 +4627,7 @@ namespace Google.Protobuf.Reflection {
       while ((tag = input.ReadTag()) != 0) {
         switch(tag) {
           default:
-            input.SkipLastField();
+            CustomOptions = CustomOptions.ReadOrSkipUnknownField(input);
             break;
           case 264: {
             Deprecated = input.ReadBool();
@@ -4644,6 +4658,8 @@ namespace Google.Protobuf.Reflection {
       get { return Descriptor; }
     }
 
+    internal CustomOptions CustomOptions{ get; private set; } = CustomOptions.Empty;
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public MethodOptions() {
       OnConstruction();
@@ -4783,7 +4799,7 @@ namespace Google.Protobuf.Reflection {
       while ((tag = input.ReadTag()) != 0) {
         switch(tag) {
           default:
-            input.SkipLastField();
+            CustomOptions = CustomOptions.ReadOrSkipUnknownField(input);
             break;
           case 264: {
             Deprecated = input.ReadBool();