Honor JSON annotations when using `capnp convert`.

c++/src/capnp/compiler/capnp-test.sh

@@ -38,6 +38,7 @@ else
 fi
 
 SCHEMA=`dirname "$0"`/../test.capnp
+JSON_SCHEMA=`dirname "$0"`/../compat/json-test.capnp
 TESTDATA=`dirname "$0"`/../testdata
 
 SUFFIX=${TESTDATA#*/src/}
@@ -74,6 +75,9 @@ $CAPNP convert binary:json --short $SCHEMA TestAllTypes < $TESTDATA/binary | cmp
 $CAPNP convert json:binary $SCHEMA TestAllTypes < $TESTDATA/pretty.json | cmp $TESTDATA/binary - || fail json to binary
 $CAPNP convert json:binary $SCHEMA TestAllTypes < $TESTDATA/short.json | cmp $TESTDATA/binary - || fail short json to binary
 
+$CAPNP convert json:binary $JSON_SCHEMA TestJsonAnnotations < $TESTDATA/annotated.json | cmp $TESTDATA/annotated-json.binary || fail annotated json to binary
+$CAPNP convert binary:json $JSON_SCHEMA TestJsonAnnotations < $TESTDATA/annotated-json.binary | cmp $TESTDATA/annotated.json || fail annotated json to binary
+
 # ========================================================================================
 # DEPRECATED encode/decode
 

c++/src/capnp/compiler/capnp.c++

@@ -714,6 +714,13 @@ public:
         return kj::str("unknown format: ", to);
       }
 
+      if (convertFrom == Format::JSON || convertTo == Format::JSON) {
+        // We need annotations to process JSON.
+        // TODO(someday): Find a way that we can process annotations from json.capnp without
+        //   requiring other annotation-only imports like c++.capnp
+        annotationFlag = Compiler::COMPILE_ANNOTATIONS;
+      }
+
       return true;
     } else {
       return "invalid conversion, format is: <from>:<to>";
@@ -1038,6 +1045,7 @@ private:
         MallocMessageBuilder message;
         JsonCodec codec;
         codec.setPrettyPrint(pretty);
+        codec.handleByAnnotation(rootType);
         auto root = message.initRoot<DynamicStruct>(rootType);
         codec.decode(text, root);
         return writeConversion(root.asReader(), output);
@@ -1096,6 +1104,7 @@ private:
       case Format::JSON: {
         JsonCodec codec;
         codec.setPrettyPrint(pretty);
+        codec.handleByAnnotation(rootType);
         auto text = codec.encode(reader.as<DynamicStruct>(rootType));
         output.write({text.asBytes(), kj::StringPtr("\n").asBytes()});
         return;

c++/src/capnp/testdata/annotated.json

+{ "names-can_contain!anything Really": "foo",
+  "flatFoo": 123,
+  "flatBar": "abc",
+  "renamed-flatBaz": {"hello": true},
+  "flatQux": "cba",
+  "pfx.foo": "this is a long string in order to force multi-line pretty printing",
+  "pfx.renamed-bar": 321,
+  "pfx.baz": {"hello": true},
+  "pfx.xfp.qux": "fed",
+  "union-type": "renamed-bar",
+  "barMember": 789,
+  "multiMember": "ghi",
+  "dependency": {"renamed-foo": "corge"},
+  "simpleGroup": {"renamed-grault": "garply"},
+  "enums": ["qux", "renamed-bar", "foo", "renamed-baz"],
+  "innerJson": [123, "hello", {"object": true}] }