No digest item for a custom consensus engine

Hello! I work on a Substrate-based chain with a custom consensus engine and as suggested in https://github.com/paritytech/try-runtime-cli/blob/b45be7dfce89fd881be27171d3ea114ef19d832c/core/src/common/empty_block/inherents/providers.rs#L96-L98 reporting a case when SmartInherentProvider doesn't work for me.

Currently, providers.rs only accounts for BABE and AURA when constructing the digest for the empty block. In my case for QF Network's blockchain node QuantumFusion-network/qf-solochain we are developing a custom consensus engine called SPIN with its own engine ID SPIN_ENGINE_ID. Because of this there is no slot with the expected engine ID in the empty block and the slot number validation fails during try-runtime usage.

It is easy to add custom engine ID in a fork project like:

// core/src/common/empty_block/inherents/providers.rs#L128
let digest = vec![
    DigestItem::PreRuntime(
        BABE_ENGINE_ID,
        PreDigest::SecondaryPlain(SecondaryPlainPreDigest {
            slot,
            authority_index: 0,
        })
        .encode(),
    ),
    DigestItem::PreRuntime(AURA_ENGINE_ID, slot.encode()),
    DigestItem::PreRuntime(*b"spin", slot.encode()),
];

But perhaps there are some recommendations on how to properly support custom engine IDs in the digest? Thank you.

从 core/src/common/empty_block/inherents/providers.rs 开始，重点查看 SmartInherentProvider 以及 129-140 行附近的 digest 构造。检查 BABE 和 AURA 的处理方式以及所引用的验证路径；当建立并测试了一种受支持的方式，使自定义共识引擎 ID（例如 SPIN）能够提供预期的 digest 项时，即视为完成。