Refactor: Put json.capnp into its own namespace.

This avoids the need for a weird struct-as-namespace pattern inside json.capnp.

c++/src/capnp/compat/json-test.capnp

@@ -21,8 +21,7 @@
 
 @0xc9d405cf4333e4c9;
 
-using Json = import "json.capnp".JsonAnnotations;
-using JsonValue = import "json.capnp".JsonValue;
+using Json = import "json.capnp";
 
 $import "/capnp/c++.capnp".namespace("capnp");
 

c++/src/capnp/compat/json.c++

@@ -951,7 +951,7 @@ public:
           case JSON_FLATTEN_ANNOTATION_ID:
             KJ_REQUIRE(type.isStruct(), "only struct types can be flattened", fieldName, typeName);
             flattened = true;
-            info.prefix = anno.getValue().getStruct().getAs<JsonFlattenFlags>().getPrefix();
+            info.prefix = anno.getValue().getStruct().getAs<json::FlattenOptions>().getPrefix();
             break;
           case JSON_DISCRIMINATOR_ANNOTATION_ID:
             KJ_REQUIRE(fieldProto.isGroup(), "only unions can have discriminator");

c++/src/capnp/compat/json.capnp

@@ -21,15 +21,15 @@
 
 @0x8ef99297a43a5e34;
 
-$import "/capnp/c++.capnp".namespace("capnp");
+$import "/capnp/c++.capnp".namespace("capnp::json");
 
-struct JsonValue {
+struct Value {
   union {
     null @0 :Void;
     boolean @1 :Bool;
     number @2 :Float64;
     string @3 :Text;
-    array @4 :List(JsonValue);
+    array @4 :List(Value);
     object @5 :List(Field);
     # Standard JSON values.
 
@@ -48,45 +48,44 @@ struct JsonValue {
 
   struct Field {
     name @0 :Text;
-    value @1 :JsonValue;
+    value @1 :Value;
   }
 
   struct Call {
     function @0 :Text;
-    params @1 :List(JsonValue);
+    params @1 :List(Value);
   }
 }
 
-struct JsonFlattenFlags {
-  prefix @0 :Text = "";
-  # Optional: Adds the given prefix to flattened field names.
-}
-
-struct JsonAnnotations {
-  # These are wrapped in this struct for namespacing purposes. Typical usage:
-  #
-  #     using Json = import "/capnp/compat/json.capnp".JsonAnnotations;
-  #
-  # And then later on:
-  #
-  #     myField @0 :Text $Json.name("my_field");
+# ========================================================================================
+# Annotations to control parsing. Typical usage:
+#
+#     using Json = import "/capnp/compat/json.capnp";
+#
+# And then later on:
+#
+#     myField @0 :Text $Json.name("my_field");
 
-  annotation name @0xfa5b1fd61c2e7c3d (field, enumerant, method, group, union): Text;
-  # Define an alternative name to use when encoding the given item in JSON. This can be used, for
-  # example, to use snake_case names where needed, even though Cap'n Proto uses strictly camelCase.
-  #
-  # (However, because JSON is derived from JavaScript, you *should* use camelCase names when
-  # defining JSON-based APIs. But, when supporting a pre-existing API you may not have a choice.)
+annotation name @0xfa5b1fd61c2e7c3d (field, enumerant, method, group, union): Text;
+# Define an alternative name to use when encoding the given item in JSON. This can be used, for
+# example, to use snake_case names where needed, even though Cap'n Proto uses strictly camelCase.
+#
+# (However, because JSON is derived from JavaScript, you *should* use camelCase names when
+# defining JSON-based APIs. But, when supporting a pre-existing API you may not have a choice.)
 
-  annotation flatten @0x82d3e852af0336bf (field, group, union): JsonFlattenFlags;
-  # Specifies that an aggregate field should be flattened into its parent.
-  #
-  # In order to flatten a member of a union, the union (or, for an anonymous union, the parent
-  # struct type) must have the $jsonDiscribinator annotation.
+annotation flatten @0x82d3e852af0336bf (field, group, union): FlattenOptions;
+# Specifies that an aggregate field should be flattened into its parent.
+#
+# In order to flatten a member of a union, the union (or, for an anonymous union, the parent
+# struct type) must have the $jsonDiscribinator annotation.
 
-  annotation discriminator @0xcfa794e8d19a0162 (struct, union): Text;
-  # Specifies that a union's variant will be decided not by which fields are present, but instead
-  # by a special discriminator field with the given name. The value of the discriminator field is
-  # a string naming which variant is active. This allows the members of the union to have the
-  # $jsonFlatten annotation.
+struct FlattenOptions {
+  prefix @0 :Text = "";
+  # Optional: Adds the given prefix to flattened field names.
 }
+
+annotation discriminator @0xcfa794e8d19a0162 (struct, union): Text;
+# Specifies that a union's variant will be decided not by which fields are present, but instead
+# by a special discriminator field with the given name. The value of the discriminator field is
+# a string naming which variant is active. This allows the members of the union to have the
+# $jsonFlatten annotation.

c++/src/capnp/compat/json.h

@@ -27,6 +27,11 @@
 
 namespace capnp {
 
+typedef json::Value JsonValue;
+// For backwards-compatibility.
+//
+// TODO(cleanup): Consider replacing all uses of JsonValue with json::Value?
+
 class JsonCodec {
   // Flexible class for encoding Cap'n Proto types as JSON, and decoding JSON back to Cap'n Proto.
   //