*EraBlockHeader typeclasses deprecating BHeaderView by aniketd · Pull Request #5560 · IntersectMBO/cardano-ledger

aniketd · 2026-02-04T15:37:30Z

Description

All QUESTIONs are addressed in code-review

Closes #5541

Checklist

teodanciu

Looks good to me, some questions and suggestions.

eras/shelley/impl/src/Cardano/Ledger/Shelley/Rules/Bbody.hs

eras/shelley/impl/testlib/Test/Cardano/Ledger/Shelley/ImpTest.hs

eras/shelley/impl/src/Cardano/Ledger/Shelley/BlockBody/Internal.hs

eras/alonzo/impl/CHANGELOG.md

teodanciu · 2026-02-18T17:13:37Z

eras/conway/impl/src/Cardano/Ledger/Conway/Rules/Bbody.hs


  initialRules = []
-  transitionRules = [conwayBbodyTransition @era >> alonzoBbodyTransition @era]
+  transitionRules = [alonzoBbodyTransition @era >> conwayBbodyTransition @era] -- QUESTION: would sorting this cause breakage?


How come you changed the order of these? I think it shouldn't matter, but is there a particular reason to do it?

I think it shouldn't matter

I think so too 👍

but is there a particular reason to do it?

Just intuitively, it reads more "appropriate" that checks and validations from earlier rules would be processed first, although the >> does not signify a value dependency, it does order the execution. But it could mean that predicate failures ordering is also changed.

It is not clear whether the potential change in predicate failure ordering will affect any downstream, such as the CLI. @neilmayhew do you have any idea about this?

eras/conway/impl/CHANGELOG.md

teodanciu · 2026-02-18T17:38:11Z

eras/dijkstra/impl/src/Cardano/Ledger/Dijkstra/Rules/Bbody.hs

+  TRC (BbodyEnv pp account, BbodyState ls b, DijkstraBbodySignal blk@Block {blockBody}) <-
+    judgmentContext
+
+  Shelley.validateBodySize @era


Same question about the ordering of these checks - any particularly reason you reversed them?

Same as for conway.

A block is made up of a header and a body. Ledger needs to process blocks but is nescient of the header type. One such header type is defined in the tpraos package and another is defined in consensus. Both these packages depend on core and the eras and so ledger cannot import from them. BHeaderView was an inferior[1] arrangement to convert a Block h era into a type with known fields. EraBlockHeader now defines a set of lenses for this, instead. Consensus[2] calls ledger's applyBlock and the BBODY rules, which need access to the values from the header, now with the help of lenses. So we wrap the unknown header type h in a GADT to pass to BBODY rules, called BbodySignal. For tests, we replace BHeaderView with TestBlockHeader and makeHeaderView with mkTestBlockHeaderNoNonce. Ref: #5541 [1]: #5467 (comment) [2]: https://github.com/IntersectMBO/ouroboros-consensus/blob/1940605fbbfb50032ab78e2268b85065c703cd2a/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Protocol/Praos.hs#L196-L202

Refactor shelley BBODY transition to export reusable validations to future eras and update the BBODY signal. Move isOverlaySlot calculation into incrBlocks.

Refactor alonzo BBODY transition to export reusable validations to future eras and update the BBODY signal.

Refactor conway BBODY transition to export reusable validations to future eras and update the BBODY signal.

Introduce DijkstraEraBlockHeader to have a lens to the previous nonce, and the DijkstraBbodySignal GADT to constrain the header existantially, same as for BbodySignal. Move PerasCert, PerasKey and validatePerasCert to dijkstra's BlockBody. Remove PrevEpochNonceNotPresent because the field is implicitly present in the signal to the BBODY rule now. Refactor the dijkstra BBODY rule to reuse validations from shelley, alonzo, conway, inlined, because the change in the type of Signal makes calling earlier BBODY transitions impossible.

aniketd · 2026-02-19T10:40:13Z

libs/cardano-protocol-tpraos/src/Cardano/Protocol/TPraos/BHeader.hs

+  blockHeaderIssuerL =
+    lens
+      (\(Block (BHeader bhb _) _) -> hashKey $ bheaderVk bhb)
+      (\(Block (BHeader bhb sig) body) _ -> Block (BHeader bhb sig) body) -- QUESTION: What does it mean to "unhash" and set this?


@teodanciu Any thoughts on this?

aniketd · 2026-02-19T10:40:20Z

libs/cardano-protocol-tpraos/src/Cardano/Protocol/TPraos/BHeader.hs

+  blockHeaderHSizeL =
+    lens
+      (\(Block bh _) -> originalBytesSize bh)
+      (\(Block bh body) _ -> Block bh body) -- QUESTION: What does it mean to do this here?


@teodanciu Any thoughts on this?

teodanciu · 2026-02-19T14:05:34Z

libs/cardano-protocol-tpraos/src/Cardano/Protocol/TPraos/BHeader.hs

+instance Crypto c => EraBlockHeader (BHeader c) BabbageEra where
+  blockHeaderIssuerL =
+    lens
+      (\(Block (BHeader bhb _) _) -> hashKey $ bheaderVk bhb)
+      (\(Block (BHeader bhb sig) body) _ -> Block (BHeader bhb sig) body)
+  blockHeaderBSizeL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bsize bhb)
+      (\(Block (BHeader bhb sig) body) newSize -> Block (BHeader (bhb {bsize = newSize}) sig) body)
+  blockHeaderHSizeL =
+    lens
+      (\(Block bh _) -> originalBytesSize bh)
+      (\(Block bh body) _ -> Block bh body)
+  blockHeaderBHashL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bhash bhb)
+      (\(Block (BHeader bhb sig) body) newHash -> Block (BHeader (bhb {bhash = newHash}) sig) body)
+  blockHeaderSlotL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bheaderSlotNo bhb)
+      (\(Block (BHeader bhb sig) body) newSlot -> Block (BHeader (bhb {bheaderSlotNo = newSlot}) sig) body)
+  blockHeaderProtVerL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bprotver bhb)
+      (\(Block (BHeader bhb sig) body) protVer -> Block (BHeader (bhb {bprotver = protVer}) sig) body)
+
+instance Crypto c => EraBlockHeader (BHeader c) ConwayEra where
+  blockHeaderIssuerL =
+    lens
+      (\(Block (BHeader bhb _) _) -> hashKey $ bheaderVk bhb)
+      (\(Block (BHeader bhb sig) body) _ -> Block (BHeader bhb sig) body)
+  blockHeaderBSizeL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bsize bhb)
+      (\(Block (BHeader bhb sig) body) newSize -> Block (BHeader (bhb {bsize = newSize}) sig) body)
+  blockHeaderHSizeL =
+    lens
+      (\(Block bh _) -> originalBytesSize bh)
+      (\(Block bh body) _ -> Block bh body)
+  blockHeaderBHashL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bhash bhb)
+      (\(Block (BHeader bhb sig) body) newHash -> Block (BHeader (bhb {bhash = newHash}) sig) body)
+  blockHeaderSlotL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bheaderSlotNo bhb)
+      (\(Block (BHeader bhb sig) body) newSlot -> Block (BHeader (bhb {bheaderSlotNo = newSlot}) sig) body)
+  blockHeaderProtVerL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bprotver bhb)
+      (\(Block (BHeader bhb sig) body) protVer -> Block (BHeader (bhb {bprotver = protVer}) sig) body)
+
+instance Crypto c => EraBlockHeader (BHeader c) DijkstraEra where
+  blockHeaderIssuerL =
+    lens
+      (\(Block (BHeader bhb _) _) -> hashKey $ bheaderVk bhb)
+      (\(Block (BHeader bhb sig) body) _ -> Block (BHeader bhb sig) body)
+  blockHeaderBSizeL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bsize bhb)
+      (\(Block (BHeader bhb sig) body) newSize -> Block (BHeader (bhb {bsize = newSize}) sig) body)
+  blockHeaderHSizeL =
+    lens
+      (\(Block bh _) -> originalBytesSize bh)
+      (\(Block bh body) _ -> Block bh body)
+  blockHeaderBHashL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bhash bhb)
+      (\(Block (BHeader bhb sig) body) newHash -> Block (BHeader (bhb {bhash = newHash}) sig) body)
+  blockHeaderSlotL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bheaderSlotNo bhb)
+      (\(Block (BHeader bhb sig) body) newSlot -> Block (BHeader (bhb {bheaderSlotNo = newSlot}) sig) body)
+  blockHeaderProtVerL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bprotver bhb)
+      (\(Block (BHeader bhb sig) body) protVer -> Block (BHeader (bhb {bprotver = protVer}) sig) body)


Should these instances exist for for Babbage, Conway and Dijkstra? I would think not! Because BHeader is only used until Alonzo, no?

teodanciu · 2026-02-19T14:12:45Z

libs/cardano-protocol-tpraos/src/Cardano/Protocol/TPraos/BHeader.hs

+  blockHeaderProtVerL =
+    lens
+      (\(Block (BHeader bhb _) _) -> bprotver bhb)
+      (\(Block (BHeader bhb sig) body) protVer -> Block (BHeader (bhb {bprotver = protVer}) sig) body)


Actually I don't even know why these instances are necessary for each era?
Wouldn't this suffice?

instance (Era era, Crypto c) => EraBlockHeader (BHeader c) era where

aniketd force-pushed the aniketd/blockheader branch 2 times, most recently from 523aa23 to 6974084 Compare February 10, 2026 17:19

aniketd force-pushed the aniketd/blockheader branch 3 times, most recently from fcee41c to 3863781 Compare February 13, 2026 12:59

aniketd marked this pull request as ready for review February 13, 2026 13:01

aniketd requested a review from a team as a code owner February 13, 2026 13:01

aniketd requested review from Soupstraw, lehins and teodanciu February 13, 2026 13:01

aniketd force-pushed the aniketd/blockheader branch from 3863781 to ab6354e Compare February 17, 2026 13:21

teodanciu reviewed Feb 18, 2026

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aniketd added 7 commits February 19, 2026 13:53

Refactor ShelleyBBODY to use EraBlockHeader.

9460744

Refactor shelley BBODY transition to export reusable validations to future eras and update the BBODY signal. Move isOverlaySlot calculation into incrBlocks.

Refactor AlonzoBBODY to use EraBlockHeader.

5b493ec

Refactor alonzo BBODY transition to export reusable validations to future eras and update the BBODY signal.

Refactor ConwayBBODY to use EraBlockHeader.

db48be5

Refactor conway BBODY transition to export reusable validations to future eras and update the BBODY signal.

Instantiate EraBlockHeader for TPraos.BHeader

23cc203

EraBlockHeader: fix shelley-test and ledger-test

5b35f0a

aniketd force-pushed the aniketd/blockheader branch from ab6354e to 5b35f0a Compare February 19, 2026 08:24

aniketd commented Feb 19, 2026

View reviewed changes

aniketd requested review from Lucsanszky and neilmayhew February 19, 2026 10:49

teodanciu reviewed Feb 19, 2026

View reviewed changes

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aniketd commented Feb 4, 2026 •

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