Support a datasource which may be a map

[csmarchbanks]

In recent versions of Grafana the datasource can be either a string or a
map with entries for type and uid. Support both of these cases by using
an interface which will allow backwards compatiblity.

Alternatively, I could change Datasource to a more concrete type that
can marshal/unmarshal from a string or map, but that would break anyone
just setting it to a string right now. Let me know what you think!

See grafana/grafana#33817 for more context on the
change in Grafana.

[GiedriusS]

I am kind of hesitant to open the floodgates for more interface{}. Go with generics is just around the corner and with generics, we should be able to gently solve this problem by using union constraints (https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md#union-constraint-element), right?

[csmarchbanks]

I am OK with that, I can keep my branch open so that users who need this before generics are available/have not upgraded yet. I guess it really depends on how fast you want to move this library to generics.

[colega]

Oh, I haven't seen this PR. I submitted a different one without generics but also without interface{}: #201

[telmich]

Hey everyone! I was wondering whether this might be merged soon? This might solve mpostument/grafana-sync#43 which is blocking some parts for us.

[rdesgroppes]

Pretty please...

[safaci2000]

@GiedriusS I gave the generics bit a go, but there's a few issues unless someone has some insight I think you may be limited to using interface or the Reference type that @colega introduced.

Here's my attempt at using it.

https://go.dev/play/p/Ogk59A6RHbC

The main issue I see is that you would have to know ahead of time what the data type is in order to serialize the code.

You'd likely have to create a

t := Board[map[string]string]{}
json.Unarmshall(json, t)

It fails to address the core of the issue which is we don't know if it'll be a map or a string. If anyone has any suggestion on how to use generics AND allow for nondeterministic behavior or the response i'm happy to try to add this in.

[thre3eye]

Just a heads-up that we're all still waiting :)

As far as I can tell the instructions on the main site won't work until a fix is pushed out https://grafana.com/docs/grafana-cloud/metrics-control-usage/control-prometheus-metrics-usage/usage-analysis-cortextool/

Thanks

[GiedriusS]

I'll take a look soon, a bit on vacation ATM.

[safaci2000]

Any updates on this change?

[safaci2000]

@GiedriusS any thoughts on this PR or alternate approaches you'd prefer?

[GiedriusS]

Let's merge this as is and wait for proper sum type support in Go ;(