Diamond Inspect Facet

Inspect diamond facets and selectors

Key Features

• Provides functions for querying facet addresses by selector.
• Enables retrieval of all registered facet addresses and their selectors.
• Includes exportSelectors for mechanism discovery.
• Operates on shared diamond storage via DIAMOND_STORAGE_POSITION.

Overview

This facet provides essential introspection capabilities for diamonds. It exposes functions to query facet addresses, their associated function selectors, and a comprehensive list of all registered facets. Developers integrate this facet to understand the diamond's internal structure and composition programmatically.

Storage

FacetNode

Definition

struct FacetNode {
  address facet;
  bytes4 prevFacetNodeId;
  bytes4 nextFacetNodeId;
}

---

FacetList

Definition

struct FacetList {
  bytes4 headFacetNodeId;
  bytes4 tailFacetNodeId;
  uint32 facetCount;
  uint32 selectorCount;
}

---

DiamondStorage

Definition

struct DiamondStorage {
  mapping(bytes4 functionSelector => FacetNode) facetNodes;
  FacetList facetList;
}

---

Facet

Definition

struct Facet {
  address facet;
  bytes4[] functionSelectors;
}

State Variables

Property	Type	Description
DIAMOND_STORAGE_POSITION	bytes32	Diamond storage slot position for this module (Value: keccak256("erc8153.diamond"))

Functions

facetAddress

Gets the facet address that handles the given selector. If facet is not found return address(0).

function facetAddress(bytes4 _functionSelector) external view returns (address facet);

Parameters:

Property	Type	Description
_functionSelector	bytes4	The function selector.

Returns:

Property	Type	Description
facet	address	The facet address.

---

facetFunctionSelectors

Gets the function selectors that are handled by the given facet. If facet is not found return empty array.

function facetFunctionSelectors(address _facet) external view returns (bytes4[] memory facetSelectors);

Parameters:

Property	Type	Description
_facet	address	The facet address.

Returns:

Property	Type	Description
facetSelectors	bytes4[]	The function selectors.

---

facetAddresses

Gets the facet addresses used by the diamond. If no facets are registered return empty array.

function facetAddresses() external view returns (address[] memory allFacets);

Returns:

Property	Type	Description
allFacets	address[]	The facet addresses.

---

facets

Returns the facet address and function selectors of all facets in the diamond.

function facets() external view returns (Facet[] memory facetsAndSelectors);

Returns:

Property	Type	Description
facetsAndSelectors	Facet[]	An array of Facet structs containing each facet address and its function selectors.

---

exportSelectors

Exports the function selectors of the DiamondInspectFacet This function is use as a selector discovery mechanism for diamonds

function exportSelectors() external pure returns (bytes memory);

Returns:

Property	Type	Description
-	bytes	selectors The exported function selectors of the DiamondInspectFacet

Best Practices

Best Practice

• Integrate this facet to enable external inspection of diamond facet mappings.
• Use facetAddress to determine which facet handles a specific function selector.
• Utilize facets and facetFunctionSelectors for comprehensive diamond structure analysis.

Security Considerations

Security

All functions in this facet are view or pure, posing no direct reentrancy or state-changing risks. Input validation for facetAddress and facetFunctionSelectors is handled by the diamond proxy's dispatch mechanism. Follow standard Solidity security practices.

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Last updated:March 13, 2026