One thing that has annoyed me with some personal implementation work is why does DAP use a cosmetically similar but not following spec version of JSONRPC? Why not just use JSONRPC especially considering LSP already does?
Because of organizational disorganization within the VS Code development teams. LSP and DAP are basically the VSCode APIs for implementing language support and debuggers but bolted onto an RPC layer without synchronization or consistency between the people/teams that develop them.
I would assume DAP predates (and possibly motivated) JSONRPC (edit: so it might have been working off of a draft spec). Hopefully someone knowledgeable can comment.
