Context

Currently, there are two asset types: Numeric and Store. Because they are quite different entities, it is proposed to separate them. See #4087 for details.

• Fixes [suggestion] Eliminate AssetType inconsistencies #4087
• Closes feat!: separate fungible and non-fungible assets #5097
• Data integrity in World #4672 (comment)

Solution

This PR removes Store asset type and instead introduces new Nft entity. Nft is similar to AssetDefinition (from implementation point of view), see #4672 (comment) for types visualization.

Naming:

• NFT (added):
  • nft$domain
• Numeric assets (no change):
  • asset#domain#account@domain or asset##account@domain

ISI changes:

• Before:
  • Both numeric and store assets:
    • Register<Asset> / Unregister<Asset>
  • Only for numeric assets:
    • Mint<Numeric, Asset> / Burn<Numeric, Asset>
    • Transfer<Asset, Numeric, Account>
  • Only for store assets:
    • Transfer<Asset, Metadata, Account>
      • Transfer asset from one account to another
      • Very strange instruction, first of all Metadata argument is ignored. Also looks like we have bug in implementation, and asset is not moved, but copied
    • SetKeyValue<Asset>
      • Creates asset implicitly if it is not registered
    • RemoveKeyValue<ASset>
• After:
  • Numeric assets or just assets:
    • No register/unregister instructions. Use Mint<Numeric, Asset> instead of register, and Burn<Numeric, Asset> to zero value instead of unregister.
    • Mint<Numeric, Asset> / Burn<Numeric, Asset>
    • Transfer<Asset, Numeric, Account>
  • Nft:
    • Register<Nft> / Unregister<Nft>
    • Transfer<Account, NftId, Account>
      • Transfer NFT to another account
    • SetKeyValue<Nft>
      • Error if NFT is not registered
    • RemoveKeyValue<Nft>

Queries changes:

• Added query FindNfts

Permission changes:

• Removed permissions:
  • CanRegisterAsset / CanUnregisterAsset
  • CanModifyAssetMetadata
• Added permissions:
  • CanRegisterNft / CanUnregisterNft
  • CanTransferNft
  • CanModifyNftMetadata

Migration Guide

If you use only numeric assets, and don't use store assets:

• Removed Register<Asset> / Unregister<Asset> ISI for numeric assets.
  • Use Mint<Numeric, Asset> instead of Register<Asset>
  • Use Burn<Numeric, Asset> to zero value instead of Unregister<Asset>
• Asset changes: value field was inlined (previously had type AssetValue, now has type Numeric)
• AssetDefinition changes: type_: AssetType field was replaced with spec: NumericSpec field
• genesis.json: it is needed to change from

"Register": {
  "AssetDefinition": {
    "type": "Numeric",
    ...

to

"Register": {
  "AssetDefinition": {
    "spec": {
      "scale": null
    },
    ...

(if you had "type": "Numeric(N)", replace with "scale": N)

If you use store assets:

• Removed AssetDefinition::store, AssetType::Store, AssetValue::Store. Use Nft instead
• Detailed description of changes is in the Solution section

Review notes

Files with important changes:

• crates/iroha_data_model/src/nft.rs - New structs Nft and NftId
• crates/iroha_data_model/src/asset.rs - Changes to Asset and AssetDefinition
• crates/iroha_core/src/smartcontracts/isi/nft.rs - ISI and Queries implementation for NFT
• crates/iroha_executor/src/default/mod.rs - default executor visit_* methods for NFT
• crates/iroha_cli/src/main.rs - CLI changes

Todo:

• Fix python tests (e.g. test_register_asset_definitions.py)

Checklist

• I've read CONTRIBUTING.md.
• (optional) I've written unit tests for the code changes.
• All review comments have been resolved.
• All CI checks pass.