Expose whether a channel is closing in `ChannelDetails`

[valentinewallace]

Currently, there's no definitive way to know that a channel has closed via ChannelDetails. !is_channel_ready && confirmations >= confirmations_required gets you close, but it's still possible that you've just been disconnected to the counterparty since before the channel's confirmation.

We might want to switch from is_channel_ready to an enum with the channel's current status. Or maybe we could add some kind of list_closed_channels util.

[TheBlueMatt]

Trivial and user-requested so tagging 116.

[henghonglee]

@valentinewallace I'd like to work on this.

Some observations (CMIIW)
1/ is_channel_ready flags (as well as ChannelDetail) are generated only when we want to list_xxx_channels
there is some use in router.rs for channel details to represent routehops but seems from ChannelDetail
documentation that isn't the real intention of the type
2/ ChannelDetail's are a read/write-able persistable thing (not yet sure why since it's generated on-demand).
this might need changes if we switch from is_channel_ready to an enum
3/ Most of the real underly details are dependent on the "true" state in channel.rs using
the ChannelDetails::from_channel fn.

Have a couple of questions.
What is the definition of closed channel right now? and from what I'm reading in the codebase it seems like
self.channel_state == ChannelState::ShutdownComplete as u32 ?
can we base the new enum value off that?

[wpaulino]

1/ is_channel_ready flags (as well as ChannelDetail) are generated only when we want to list_xxx_channels
there is some use in router.rs for channel details to represent routehops but seems from ChannelDetail
documentation that isn't the real intention of the type

Yeah the type is public so you're free to use it as you like, the docs there are more about conveying when a channel will be in such a state.

ChannelDetail's are a read/write-able persistable thing (not yet sure why since it's generated on-demand).
this might need changes if we switch from is_channel_ready to an enum

See the rationale here: #1294. I don't think switching is_channel_ready to an enum applies here, as the docs state, it's just meant to track whether we completed the funding process of the channel. This can be true, and usually will be, for closed channels.

What is the definition of closed channel right now? and from what I'm reading in the codebase it seems like
self.channel_state == ChannelState::ShutdownComplete as u32 ?

This only applies to channels closed cooperatively that have not had their closing transaction confirmed yet. As soon as a closing transaction confirms (regardless of it being cooperative or not), we delete the channel state in ChannelManager.

[henghonglee]

@valentinewallace @wpaulino sorry for the delay, spent some time tracing the code to understand more about channel closures and how they get propagated through the system

currenlty added the shutting down flag as a new field. do let me know if thats not the right direction.