99.9999%* of apps don't need anything nearly as 'fancy' as this, if resolving breadth-first is critical they can just make multiple calls (which can have very little overhead depending on how you do it). * I made it up - and by extension, the status quo is 'correct'.
Multiple calls?! That sounds like n*n+1. Gross :P
I think the issue with the example json is that it's sent in OOP+ORM style (ie nested objects), whereas you could just send it as rows of objects, something like this;
{
header: "Welcome to my blog",
post_content: "This is my article",
post_comments: [21,29,88], # the numbers are the comment ID's
footer: "Hope you like it",
comments: {21: "first", 29: "second", 88: "third" }
}
syntax = "proto3";
service DirectiveAffectsService {
rpc Get(GetPageWithPostParams) returns (PageWithPost);
}
message GetPageWithPostParams {
string post_id = 1;
}
message PageWithPost {
string page_header = 1;
string page_footer = 2;
string post_content = 3;
repeated string post_comments = 4;
repeated CommentInPost comments_for_post = 5;
}
message CommentInPost {
string comment_id = 1;
string comment_text = 2;
}