Support for IProgress<T> allows a JSON-RPC server to report progress to the client periodically so that the client can start processing those
results without having to wait for all results to be retrieved before responding.
With this support client can now include an object that implements IProgress<T> on the invocation parameters. The Report method on that
instance should have the processing that the client will do with the results reported by the server.
Since IProgress<T> is not directly serializable to JSON, a JSON token that tracks that IProgress<T> instance will be written in its place
in the outgoing message.
The request sent to the server will look like this:
{
"jsonrpc": "2.0",
"id": 153,
"method": "someMethodName",
"params": {
"units": 5,
"progress": "some-JSON-token"
}
}The progress argument may have any name or position. Its value will be determined by the IJsonRpcMessageFormatter and may be any valid JSON token.
A value of null is specially recognized as an indication that the client does not want progress updates from the server.
Reports from the server will come in the form of special notifications to the $/progress method, which will include the token that replaced the object
implementing IProgress<T> and the values to report. Whenever the client receives this kind of notification, it will invoke the IProgress<T> instance
associated with the original request the client placed.
This reporting will continue until the client receives the actual JSON-RPC response message for the request.
Any $/progress notifications from the server with the matching JSON progress token will be discarded after that point.
When the method called on the server takes an IProgress<T> parameter, the JSON token that supplies the argument for that parameter will be considered
the progress token used to send progress via $/progress back to the client. The server method will be invoked with an instance of IProgress<T>
which may be used as normal until the server method completes, after which the IProgress<T> becomes inert.
This new IProgress<T> instance will send a special kind of notification ($/progress) whenever results are reported on the server method, using
the token given by the client and the reported values as parameters.
The progress notification will look like this:
{
"jsonrpc": "2.0",
"method": "$/progress",
"params": {
"token": "some-JSON-token",
"value": { "some": "status-token" }
}
}