What's `InherentDataProviders`? How can I use them?

Question

I've seen some code like this

move |_, ()| async move {
    let uncles =
        sp_authorship::InherentDataProvider::<<Block as BlockT>::Header>::check_inherents();
    let timestamp = sp_timestamp::InherentDataProvider::from_system_time();
    let slot =
        sp_consensus_babe::inherents::InherentDataProvider::from_timestamp_and_duration(
            *timestamp,
            slot_duration,
        );

    Ok((timestamp, slot, uncles))
},

But I don't know what it means. If I remove one of them, the node still can be compiled and running without any issue.

Or I should ask what is InherentData. What does it use for?

Answer 1

InherentDataProvider is a type that provides data to inherents.

Each inherent is added to a produced block. Each runtime decides on which inherents it wants to attach to its blocks. All data that is required for the runtime to create the inherents is stored in the InherentData. This InherentData is constructed by the node and given to the runtime.

• Source

As to the specific code that you are referencing, maybe these two PR's can help:

• https://github.com/paritytech/substrate/issues/8029
• https://github.com/paritytech/polkadot/pull/4973/files