block.body definitly exists unless it's a light client or using fast sync in storage chain mode

[liuchengxu]

From what I see, there are two cases that block.body can be omitted otherwise it should always exist:

• light client
  https://github.com/paritytech/substrate/blob/3f657a56b3c9bfe14613d213efc6570292ffaf86/client/network/src/protocol/sync.rs#L572

• fast sync in storage chain mode
  https://github.com/paritytech/substrate/blob/3f657a56b3c9bfe14613d213efc6570292ffaf86/client/network/src/protocol/sync.rs#L575

[nazar-pc]

Can we guarantee that it is impossible to run a light client node or use fast sync? Light client mode is not working/not available so that is fair I guess, but I'm not 100% sure what fast sync is.

Since we have customized struct for CLI arguments, maybe we should start stripping things down from it such that we don't allow configurations that are not working in the first place? There are quite a few arguments which are not applicable to Subspace in default flags.

[liuchengxu]

The main idea of fast sync can be visited at paritytech/substrate#8884. I don't think it works in our case.

maybe we should start stripping things down from it such that we don't allow configurations that are not working in the first place

Yes, definitely possible, but it also has to be a quite dirty trick. I used it to support the CLI config file by first filtering the raw CLI argument list and then feeding them into the internal CLI constructor in ChainX but really not a fan of it. Based on my experience, basically, no one will run into this trap as long as it's not the default behavior and you don't show the way to do it. So we could save some energy for now. Can be another PR if you'd like to prune the flags incompatible with subspace seriously.

[nazar-pc]

I used it to support the CLI config file by first filtering the raw CLI argument list and then feeding them into the internal CLI constructor in ChainX but really not a fan of it

I think there is a better way:

• https://github.com/paritytech/substrate/blob/master/client/cli/src/commands/mod.rs#L37-L44
• https://github.com/threefoldtech/tfchain/blob/development/substrate-node/node/src/cli.rs#L13-L41

We should be able to include some subcommands and skip others to get just the list we need.

[liuchengxu]

We should be able to include some subcommands and skip others to get just the list we need.

That works for the subcommands, but not for the inner params like NetworkParams in RunCmd, unless you reassemble or build a wrapper from the origin subcommand.

[nazar-pc]

We should still be able to copy-paste those structs, customize them and map to whatever Substrate expects before moving forward. We just need to make sure that someone who is typing subspace-node --help only gets useful and working options.

[liuchengxu]

Yeah, reassembling the subcommand can be less a dirty way.