Extension needs to listen to LS telemetry

[MikhailArkhipov]

It appears that all the LSP message telemetry/event does is to fire event back on the extension which then should be submitting telemetry to the VS Code API.

[jakebailey]

FWIW it'd be good to know if there's some specific schema that this event needs to be providing to mesh with the telemetry that the extension is already sending. The LSP spec defines the telemetry event to just include an arbitrary object, so if there's a specific format needed in practice that'd be great to know.

[MikhailArkhipov]

@jakebailey - AFAIK it is

        /**
         * Sends a telemetry event
         * @param {string} eventName The event name
         * @param {object} properties An associative array of strings
         * @param {object} measures An associative array of numbers
         */
        // tslint:disable-next-line:member-access
        public sendTelemetryEvent(eventName: string, properties?: {
            [key: string]: string;
        }, measures?: {
            [key: string]: number;
            // tslint:disable-next-line:no-empty
        }): void;

Event name will be 'Microsoft Python Language Server'. Data then can be either string or dictionary.

[jakebailey]

The event name might need to be more specific. Take the bit that actually starts the language server:

https://github.com/Microsoft/vscode-python/blob/a14db37b4375cbbd109cb40b8e0c91652cfbf8f9/src/client/activation/languageServer/languageServer.ts#L164-L173

and the constants:

https://github.com/Microsoft/vscode-python/blob/a14db37b4375cbbd109cb40b8e0c91652cfbf8f9/src/client/telemetry/constants.ts#L35-L41

But we can definitely upgrade from object to something like this (not final):

[Serializable]
public struct TelemetryEvent {
	public string eventName;
	public Dictionary<string, string> properties;
	public Dictionary<string, int> measures; // TS "number" is more than just int, though.
}