Make 1-1 relationship of witness and policy ID in TxMintValue instead of 1-*

[carbolymer]

Changelog

- description: |
    Make 1-1 relationship of witness and policy ID in TxMintValue instead of 1-*
    Remove exports: `parseValue`, `ParserValueRole`
    Add new type `PolicyAssets` representing minted assets within a single PolicyId
    Add `mkTxMintValue` helper function
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
   - breaking       # the API has changed in a breaking way
  # - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
   - refactoring    # QoL changes
  # - bugfix         # fixes a defect
  # - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
  # - documentation  # change in code docs, haddocks...

Context

Fixes:

• [FR] - TxMintValue shouldn't allow multiple script witnesses per PolicyId? #769

Previous related changes to TxMintValue:

• Refactor TxMintValue #663

Used in:

• Better representation of minting values in the code cardano-cli#1085

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff

[Jimbo4350]

One comment

[Jimbo4350]

Almost everywhere PolicyAssets is used in a Map i.e Map PolicyId PolicyAssets. Why not make this type:

newtype PolicyAssets = PolicyAssets (Map PolicyId (Map AssetName Quantity))?

And if we're doing that, we can just use the ledger type directly newtype MultiAsset = MultiAsset (Map PolicyID (Map AssetName Integer))

[carbolymer]

I agree. But the main purpose of this type is to use it in TxMintValue where we have one witness per policy ID. So we need some type aggregating assets and quantities. You can't do it in a nice way if you have a type Map PolicyId (Map AssetName Quantity) - you'd have to keep two maps (one with quantities and the otehr with witnesses) and make sure they're in sync... cumbersome and error prone.

[carbolymer]

An alternative would be to just use Map AssetName Quantity there, but it's annoying to handle: you'd need to write operations like merging or negating by hand. So this newtype provides MonoFunctor and Semigroup instances making those operations easier.