Creates a standard method supportsFeature(bytes4) in the same spirit as supportsInterface(bytes4) to publish and detect what features a smart contract implements that lack a derivable ERC-165 interface.
Ethereum Name Service (ENS) has maintained backwards compatibility with contracts created in 2016 through extensive use of ERC-165. Unfortunately, not all contract capabilities can be expressed through an unique interface.
Features allow expression of contract capabilities that preserve existing interfaces. This proposal standardizes the concept of features and standardizes the identification (naming) of features.
Defining a new standard avoids unnecessary pollution of the ERC-165 selector namespace with synthetic interfaces representing features.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 and RFC 8174.
For this standard, a feature is any property of a contract that cannot be expressed via ERC-165.
A feature name SHOULD be a reverse domain name that uniquely defines its implication, eg. eth.ens.resolver.extended.multicall is the multicall feature for an extended ENS resolver contract.
A feature identifier is defined as the first four-bytes of the keccak256-hash of its name, eg. bytes4(keccak256("eth.ens.resolver.extended.multicall")) = 0x96b62db8.
A contract that is compliant with this specification SHALL implement the following interface:
The ERC-165 interface identifier for this interface is 0x582de3e7.
supportsFeature(featureId) to determine if it implements the desired feature.Note: a contract that implements features MAY implement no features.
Since feature names cannot be derived from a contract interface, they are derived from a reverse domain name to reduce collisions and permit a human-readable representention that briefly describes its implication.
Callers unaware of features or any specific feature experience no change in behavior.
ENS already implements this ERC.
As with ERC-165, declaring support for a feature does not guarantee that the contract implements it.
Copyright and related rights waived via CC0.