[cmd/flag]: validation is skipping empty flag value

[Bidon15]

Celestia Node version

v0.12.1

OS

linux

Install tools

No response

Others

No response

Steps to reproduce it

celestia light start --p2p.network= --node.store=/home/celestia/.celestia-light-mocha-4 --core.ip=full.consensus.mocha-4.celestia-mocha.com --gateway --da.grpc.namespace=000008e5f679bf7116cb --da.grpc.listen=0.0.0.0:26650

Expected result

start fails with error that p2p.network is failed due to empty value provided

Actual result

celestia mainnet is started

Relevant log output

No response

Notes

No response

[Wondertan]

start --p2p.network= --node.

The empty network is actually provided. Doesn't look like a problem.

[Bidon15]

this is a UX problem that when a user is providing emptiness, node needs to reject such behaviours and ask for a specific value instead of accepting emptiness.

Emptiness is fine when there is no flag at all.

The current bug displays a UX problem when a user expects the light node to join mocha testnet, but ended up in celestia mainnet

[Wondertan]

On the first read, I misunderstood the issue due to reading the following as Actual Result, rather than Expected, and I thought you wanted to make it work with empty string.

start fails with error that p2p.network is failed due to empty value provided

In fact that's the opposite so the issue makes sense

[sontrinh16]

hmmm i believe because of this line. We can return an error here instead if we want to reject it

[00x-dx]

I have pushed a fix at #3004. Ideally a shorthand network notation is good to have.