Implement RStudio Connection Contract

[krlmlr]

Link: https://rstudio.github.io/rstudio-extensions/connections-contract.html

Should be possible by changing the implementation of the generic to

setGeneric("dbConnect",
  def = function(drv, ...) {
    con <- standardGeneric("dbConnect")
    register_con_with_rstudio(con)
    con
  },
  valueClass = "DBIConnection"
)

instead of the current implementation:

setGeneric("dbConnect",
  def = function(drv, ...) standardGeneric("dbConnect"),
  valueClass = "DBIConnection"
)

Similar for dbDisconnect(). I'm not sure about the connectionUpdated() entry point, because DBI currently doesn't provide notification.

Implementation sketch by @edgararuiz: https://gist.github.com/edgararuiz/0533b3daf70a41b70acd75c1e6a2b7a3.

Happy to review a PR. CC @nwstephens @jimhester.

[krlmlr]

This might need to wait until we have fleshed out r-dbi/DBI#24 in DBI.

[edgararuiz-zz]

A function that wraps connectionUpdated() can be added to DBI operations that make changes to the DB, such as dbWriteTable() and dbRemoveTable().

[nwstephens]

@krlmlr Just checking in on this issue. We consistently find ourselves wanting to demo RSQLite connections with Shiny apps. It would be great to have the connections contract working for Shiny developers who want to use database backends.

[krlmlr]

@jimhester: Do you have time to look into this?

[krlmlr]

Just agreed with @edgararuiz that he would take a look.

• Implement a function dbiRegisterCallbacks() and dbiUnregisterCallbacks()
  • dbiRegisterCallbacks <- function(name, ..., connect, disconnect, write_table, remove_table, clear_result)
  • dbiUnregisterCallbacks <- function(name)
• Add calls to the callbacks in the relevant generic

[znmeb]

Is this still blocked? I have a use case for it.

[krlmlr]

The yet-to-be-implemented conmgr will handle all new connections. In DBI, we'll call methods in conmgr if this package is installed. Clients will be able to register their own callbacks there.

[dpprdan]

@krlmlr I see that conmgr has been archived. Are there any new plans w.r.t. RStudion Connection Contracts in DBI?

Probably https://github.com/rstudio/connections

[krlmlr]

The connections package seems to wrap "DBIConnection" objects to achieve the desired result. I suspect we can simplify life for that package by providing callbacks.

[krlmlr]

https://github.com/rstudio/connections looks like the way to go. Perhaps we can provide connection events as part of a rewrite. Closing for now, bookmarking this issue.

[edgararuiz]

Right, connections is an external package the wraps DBI so it can open, update and close the Connections pane. The idea would be integrate the routines from connections into DBI. connections has a dependency on rscontract (https://github.com/rstudio/rscontract). The rscontract package is an interface tool that makes it easier to create and customize the Contract. I can see that eventually, DBI would have that same dependency.