ERC-20 Metadata Module

@perfect-abstractions/compose/token/ERC20/Metadata/ERC20MetadataMod.solCopy

Helper functions for writing token metadata and accessing metadata storage

Key Features

• setMetadata writes the name, symbol, and decimals in one call.
• No access control is performed. Use it from trusted initialization code only.
• Emits no event, so metadata changes leave no log for off-chain indexers.

Module Usage

Use helper functions from Compose using your own custom facets. See Facets & Modules for more information.

Storage​

State Variables​

ERC20MetadataStorage​

/** @custom:storage-location erc8042:erc20.metadata */
struct ERC20MetadataStorage {
  string name;
  string symbol;
  uint8 decimals;
}

Functions​

getStorage​

Returns a pointer to the ERC20MetadataStorage struct.

function getStorage() pure returns (ERC20MetadataStorage storage s);

Returns:

setMetadata​

Writes the token name, symbol, and decimals.

All three fields are overwritten on every call. There is no way to update one field and leave the others untouched, so pass the current values for the fields you are not changing, or write through getStorage instead.

There is no msg.sender or role check. Use only from trusted initialization code, or wrap it with your own checks in a facet.

function setMetadata(string memory _name, string memory _symbol, uint8 _decimals);

Parameters:

Best Practices​

• Call setMetadata once, from your diamond constructor or a one-time setup path, before anyone reads ERC20MetadataFacet.
• If you expose metadata updates as an external function, gate them. Anything that reaches this helper can rename the token.
• Settle on _decimals before launch. Changing it later reinterprets every balance already held, since balances are stored as raw integers.
• Keep the same STORAGE_POSITION and ERC20MetadataStorage layout as ERC20MetadataFacet. Do not introduce a second metadata slot.

Integration Notes​

Import the module under a namespace and call it from your diamond constructor:

import "src/token/ERC20/Metadata/ERC20MetadataMod.sol" as ERC20MetadataMod;

contract MyDiamond {
  constructor() {
      ERC20MetadataMod.setMetadata("My Token", "MTK", 18);
  }
}

ExampleDiamond wires the ERC-721 equivalent the same way, calling ERC721MetadataMod.setMetadata from its constructor.

ERC20MetadataStorage lives at keccak256("erc20.metadata"), which is a separate slot from the erc20 slot holding balances and allowances. Adding or removing metadata contracts never touches balances.

ERC20PermitFacet reads name from this same slot to build its EIP-712 domain. Changing the name after deployment invalidates permit signatures that have already been issued but not yet used.

Last updated:September 16, 2026

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