Emit Event on Shared Signer Configuration

This PR adds an event that is emitted on shared signer configuration.
Note that the event is emitted in the context of the configured Safe
account. In order to prevent event `topic0` collisions, we chose an
explicitely verbose name.

modules/passkey/contracts/4337/SafeWebAuthnSharedSigner.sol

@@ -32,11 +32,6 @@ contract SafeWebAuthnSharedSigner is SignatureValidator {
      */
     uint256 private constant _SIGNER_MAPPING_SLOT = 0x2e0aed53485dc2290ceb5ce14725558ad3e3a09d38c69042410ad15c2b4ea4e8;
 
-    /**
-     * @notice An error indicating a `CALL` to a function that should only be `DELEGATECALL`-ed.
-     */
-    error NotDelegateCalled();
-
     /**
      * @notice Address of the shared signer contract itself.
      * @dev This is used for determining whether or not the contract is being `DELEGATECALL`-ed when
@@ -49,6 +44,23 @@ contract SafeWebAuthnSharedSigner is SignatureValidator {
      */
     uint256 public immutable SIGNER_SLOT;
 
+    /**
+     * @notice Emitted when the shared signer is configured for an account.
+     * @dev Note that the configured account is not included in the event data. Since configuration
+     * is done as a `DELEGATECALL`, the contract emitting the event is the configured account. This
+     * is also why the event name is prefixed with `SafeWebAuthnSharedSigner`, in order to avoid
+     * event `topic0` collisions with other contracts (seeing as "configured" is a common term).
+     * @param x The x-coordinate of the public key.
+     * @param y The y-coordinate of the public key.
+     * @param verifiers The P-256 verifiers to use.
+     */
+    event SafeWebAuthnSharedSignerConfigured(uint256 x, uint256 y, P256.Verifiers verifiers);
+
+    /**
+     * @notice An error indicating a `CALL` to a function that should only be `DELEGATECALL`-ed.
+     */
+    error NotDelegateCalled();
+
     /**
      * @notice Create a new shared WebAuthn signer instance.
      */
@@ -133,6 +145,8 @@ contract SafeWebAuthnSharedSigner is SignatureValidator {
         signerStorage.x = signer.x;
         signerStorage.y = signer.y;
         signerStorage.verifiers = signer.verifiers;
+
+        emit SafeWebAuthnSharedSignerConfigured(signer.x, signer.y, signer.verifiers);
     }
 
     /**

modules/passkey/test/4337/SafeWebAuthnSharedSigner.spec.ts

@@ -170,6 +170,32 @@ describe('SafeWebAuthnSharedSigner', () => {
       expect(await ethers.provider.getStorage(account, BigInt(signerSlot) + 2n)).to.equal(config.verifiers)
     })
 
+    it('Should emit an event', async () => {
+      const { safeSingleton, proxyFactory, sharedSigner, mockVerifier } = await setupTests()
+
+      const config = {
+        x: ethers.id('publicKey.x'),
+        y: ethers.id('publicKey.y'),
+        verifiers: ethers.toBeHex(await mockVerifier.getAddress(), 32),
+      }
+
+      const initializer = safeSingleton.interface.encodeFunctionData('setup', [
+        [sharedSigner.target],
+        1,
+        sharedSigner.target,
+        sharedSigner.interface.encodeFunctionData('configure', [config]),
+        ethers.ZeroAddress,
+        ethers.ZeroAddress,
+        0,
+        ethers.ZeroAddress,
+      ])
+
+      const account = await proxyFactory.createProxyWithNonce.staticCall(safeSingleton, initializer, 0)
+      await expect(proxyFactory.createProxyWithNonce(safeSingleton, initializer, 0))
+        .to.emit(sharedSigner.attach(account), 'SafeWebAuthnSharedSignerConfigured')
+        .withArgs(config.x, config.y, config.verifiers)
+    })
+
     it('Should revert if not DELEGATECALL-ed', async () => {
       const { sharedSigner } = await setupTests()