[BUG] - Cardano.API.Block.getBlockHeader Not Implemented for Alonzo Era

[bwbush]

External

Area
Other Cardano Node API for Alzono Ledger

Summary
Cardano.API.Block.getBlock is not implemented for the Alonzo era: see https://github.com/input-output-hk/cardano-node/blob/4c59442958072657812c6c0bb8e0b4ab85ce1ba2/cardano-api/src/Cardano/Api/Block.hs#L252.

Steps to reproduce
Pattern match against Cardano.Api.Block and access the BlockHeader there.

getBlockHeader: Alonzo era not implemented yet                                                                                                                                                          
CallStack (from HasCallStack):                                                                                                                                                                                  
 error, called at src/Cardano/Api/Block.hs:252:28 in cardano-api-1.29.0-7V17SdPKJdQHtDCNFR9H0F:Cardano.Api.Block                                                                                               

Expected behavior
Pattern matching on Cardano.API.Block or calling Cardano.API.Block.getBlockHeader should work for Alonzo as it does for other eras.

System info (please complete the following information):

• OS Name: NixOS
• OS Version: 20.03.3328.6d1a044fc9f
• Node version 1.29.0 - linux-x86_64 - ghc-8.10 git rev 4c59442

Additional context
Is there a workaround for this? I've been using this function to find the slot number of the current block (not the tip) when running a chain sync client: I need that in order to monitor rollbacks and revise the cached history of the parts of the ledger relevant to my application.

[bwbush]

I just verified that running scan-blocks of cardano-node/cardano-client-demo/ on testnet (not the hardcoded mainnet) fails with this same error, just after block 2877000 when it reaches Alonzo:

scan-blocks: getBlockHeader: Alonzo era not implemented yet
CallStack (from HasCallStack):
  error, called at src/Cardano/Api/Block.hs:252:28 in cardano-api-1.29.0-inplace:Cardano.Api.Block