Prototype 'meta' column alternative to message table

[jamesaoverton]

All the VALVE implementations so far output to a message table, which identifies the table/row/column then specifies the message information. This is a flexible approach, but this requires the original table to have a primary key or row ID, and it can be difficult/annoying/expensive to combine the value and message when trying to render a table of highlighted cells.

I'd like to try another approach that keeps the message data in the table. Given a column such as 'weight' with datatype INT, we will have a second column 'weight_meta' with type TEXT. The 'weight_meta' column will store JSON that includes the message (when appropriate). For the first version, I would be happy with this:

weight	weight_meta
100	NULL
NULL	{"value":"99g","message":"Must be an integer"}

Eventually I would like to support multiple messages with more information, something like this:

{
  "value": "99g",
  "messages": [{
      "rule": "datatype:integer",
      "level": "error",
      "message": "Must be a positive integer"
  }]
}

What should the SQL for an in() condition look like for this approach?