Diamond Inspect Facet

It lets you inspect the diamond’s routing table and retrieve the registered facet list.

Key Features

• Query which facet a function selector is routed to.
• Enumerate registered facets (and their exported selectors).
• Read the diamond’s composition from shared diamond storage (DIAMOND_STORAGE_POSITION).

Storage

State Variables

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

Diamond Storage

Definition

/** storage-location: erc8042:erc8153.diamond */
struct DiamondStorage {
  mapping(bytes4 functionSelector => FacetNode) facetNodes;
  FacetList facetList;
}

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

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

---

Facet

Used as a return type for the facets function.

Definition

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

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

---

facetFunctionSelectors

Gets the function selectors exported by the given facet and returns them as bytes4[].

If the diamond is not currently routing the facet for the facet’s first exported selector, this function returns an empty array. If _facet does not implement exportSelectors() with the expected packing, the call will revert.

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

Parameters:

Property	Type	Description
_facet	address	Facet contract address. Must implement exportSelectors() (packed bytes4 selectors).

Returns:

Property	Type	Description
facetSelectors	bytes4[]	Unpacked selectors returned by facet.exportSelectors(), or an empty array if the facet is not registered.

---

facetAddresses

Gets the facet addresses used by the diamond. If facetList.facetCount is 0, this returns an empty array.

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

Returns:

Property	Type	Description
allFacets	address[]	Facet addresses in the diamond's internal traversal order.

---

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.

Selector Packing Notes (exportSelectors())

exportSelectors() returns a packed bytes blob where each bytes4 selector is encoded into 4 consecutive bytes (a bytes.concat(sel1, sel2, ...) style packing).

DiamondInspectFacet follows that convention:

• facetFunctionSelectors(facet) calls facet.exportSelectors() and unpacks the packed bytes into a bytes4[].
• facets() does the same for every facet discovered in the diamond.

Best Practices

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

Security Considerations

Most functions are view/pure and do not mutate state.

However, facetFunctionSelectors() and facets() perform external calls to IFacet(facet).exportSelectors(). If the provided address is not a valid IFacet implementation (or if exportSelectors() reverts / returns unexpected data), these calls can revert.

From on-chain code, avoid passing untrusted facet addresses.

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Last updated:March 13, 2026