Background

ink! v6 supports both the native ink! and Solidity ABI specifications.
Currently, ink! contracts can specify the target ABI using the abi config argument of the contract attribute macro (i.e. #[ink::contract(abi = "..")]).

Motivation

However, this means the specified ABI is only accessible to the contract attribute proc-macro during codegen.
This is problematic because the specified ABI is also relevant to other ink! entities (e.g. trait definitions, events and - in the future - errors) that can be defined either outside of contract module, or in separate standalone crates.

Design

• Introduce a Cargo.toml section [package.metadata.ink-lang] with a field abi and possible values "ink", "sol" and "all" e.g.

  [package]
  name = "flipper"
  # ... more stuff
    
  [package.metadata.ink-lang]
  abi = "sol"

  NOTE: Cargo will warn about "unused" keys by default except for keys in "package.metadata" (see details)

• Introduce a rustc cfg setting/flag ink_abi with possible values "ink", "sol" and "all" which is used to propagate the package.metadata.ink-lang.abi value defined in Cargo.toml as described above into the build environment

• Update cargo-contract to:

  • Read the value of the package.metadata.ink-lang.abi field from Cargo.toml (if present)
  • Validate the specified value and issue warnings/errors as appropriate
  • Set the ink_abi cfg flag as appropriate (e.g. --cfg 'ink_abi="sol"')
  • Update the cargo contract new subcommand to support ABI specification via a CLI arg (i.e. cargo contract new --abi <ink|sol|all>)
  • Add cargo contract test subcommand for propagating the ABI specified in Cargo.toml into the build environment for tests

• Update proc-macros for ink! entities to support the new cfg option (e.g. #[cfg(ink_abi = "sol")] - see also) to generate ABI specific code

Implementation

• cargo-contract
  • Support setting ABI in Cargo.toml and propagate ABI into build environment via cfg flag cargo-contract#2033
  • Add cargo contract test subcommand cargo-contract#2034
• ink
  • Support ABI cfg flag in codegen #2501

Docs

• ABI docs ink-docs#411
• Replace uses of cargo test with cargo contract test in ink! v6 docs ink-docs#410