Provide simple access to descriptor declarations in C#

This is primarily for access to comments, which would be expected to be available in a protoc plugin.

The implementation has two fiddly aspects:

- We use a Lazy<T> to avoid building the map before cross-linking. An alternative would be to crosslink at the end of the constructor, and remove the calls to CrossLink elsewhere. This would be generally better IMO, but deviate from the Java code.
- The casts to IReadOnlyList<DescriptorBase> are unfortunate. They'll always work, because these lists are always ReadOnlyCollection<T> for a descriptor type... but we can't use IList<DescriptorBase> as that's not covariant, and it's annoyingly fiddly to change the field to be of type ReadOnlyCollection<T>.

1 files changed, 30 insertions, 0 deletions

diff --git a/csharp/protos/unittest_proto3.proto b/csharp/protos/unittest_proto3.proto
index ef4933a5..bf88f6bc 100644
--- a/csharp/protos/unittest_proto3.proto
+++ b/csharp/protos/unittest_proto3.proto
@@ -368,7 +368,9 @@ message FooResponse {}
 message FooClientMessage {}
 message FooServerMessage{}
 
+// This is a test service
 service TestService {
+  // This is a test method
   rpc Foo(FooRequest) returns (FooResponse);
   rpc Bar(BarRequest) returns (BarResponse);
 }
@@ -378,3 +380,31 @@ message BarRequest  {}
 message BarResponse {}
 
 message TestEmptyMessage {}
+
+// This is leading detached comment 1
+
+// This is leading detached comment 2
+
+// This is a leading comment
+message CommentMessage {
+  // Leading nested message comment
+  message NestedCommentMessage {
+    // Leading nested message field comment
+    string nested_text = 1;
+  }
+  
+  // Leading nested enum comment
+  enum NestedCommentEnum {
+    // Zero value comment
+    ZERO_VALUE = 0;
+  }
+  
+  // Leading field comment
+  string text = 1; // Trailing field comment
+}
+
+// Leading enum comment
+enum CommentEnum {
+  // Zero value comment
+  ZERO_VALUE = 0;
+}