`http2.connect` callback not called if `createConnection` returns a socket that's already connected

[pietermees]

• Version: v9.10.1
• Platform: all
• Subsystem: http2

http2.connect accepts a callback that is invoked when the Http2Session is in a connected state by adding the callback as a listener to the Http2Session connect event here:

node/lib/internal/http2/core.js

Line 2700 in e37effe

session.once('connect', listener);

However, when one provides the createConnection option and the provided function returns a Socket that is already connected to a remote host, the Http2Session constructor will synchronously raise the connect event, causing the http2.connect listener to not be fired:

node/lib/internal/http2/core.js

Line 909 in e37effe

if (socket.connecting) {

The following two changes could resolve the issue:

1. Expose an Http2Session#connecting property, just like Socket#connecting so the connection state of the Http2Session can be inspected after the constructor has returned
2. Modify http2.connect to check session.connecting to choose between invoking listener immediately or adding it as a listener to the session's connect event.

[pietermees]

Actually, it seems like there is already a connecting property on Http2Session, it's just not documented:

node/lib/internal/http2/core.js

Line 961 in e37effe

get connecting() {

[apapirovski]

Fixed by #19842