Fix ethers v5 and v6 handling (#198)

Close #187

packages/siwe/lib/client.ts

@@ -4,11 +4,9 @@ import {
   ParsedMessage,
   parseIntegerNumber,
 } from '@spruceid/siwe-parser';
-// @ts-expect-error -- ethers v6 compatibility hack
-import { providers } from 'ethers';
 import * as uri from 'valid-url';
 
-import { getAddress, verifyMessage } from './ethersCompat';
+import { getAddress, Provider, verifyMessage } from './ethersCompat';
 import {
   SiweError,
   SiweErrorType,
@@ -194,7 +192,7 @@ export class SiweMessage {
    * @param signature Signature to match the address in the message.
    * @param provider Ethers provider to be used for EIP-1271 validation
    */
-  async validate(signature: string, provider?: providers.Provider) {
+  async validate(signature: string, provider?: Provider) {
     console.warn(
       'validate() has been deprecated, please update your code to use verify(). validate() may be removed in future versions.'
     );

packages/siwe/lib/ethersCompat.ts

@@ -1,10 +1,4 @@
-import {
-  // @ts-expect-error -- ethers v6 compatibility hack
-  utils,
-  verifyMessage as ethersVerifyMessage,
-  hashMessage as ethersHashMessage,
-  getAddress as ethersGetAddress,
-} from 'ethers';
+import { ethers } from 'ethers';
 
 type Ethers6BigNumberish = string | number | bigint;
 
@@ -34,16 +28,35 @@ type Ethers6SignatureLike =
     yParityAndS?: string;
   };
 
-export const verifyMessage =
-  utils?.verifyMessage ??
-  (ethersVerifyMessage as (
+let ethersVerifyMessage = null;
+let ethersHashMessage = null;
+let ethersGetAddress = null;
+
+try {
+  // @ts-expect-error -- v6 compatibility hack
+  ethersVerifyMessage = ethers.utils.verifyMessage;
+  // @ts-expect-error -- v6 compatibility hack
+  ethersHashMessage = ethers.utils.hashMessage;
+  // @ts-expect-error -- v6 compatibility hack
+  ethersGetAddress = ethers.utils.getAddress;
+} catch {
+  ethersVerifyMessage = ethers.verifyMessage as (
     message: Uint8Array | string,
     sig: Ethers6SignatureLike
-  ) => string);
+  ) => string;
+
+  ethersHashMessage = ethers.hashMessage as (
+    message: Uint8Array | string
+  ) => string;
+
+  ethersGetAddress = ethers.getAddress as (address: string) => string;
+}
 
-export const hashMessage =
-  utils?.hashMessage ??
-  (ethersHashMessage as (message: Uint8Array | string) => string);
+// @ts-expect-error -- v6 compatibility hack
+type ProviderV5 = ethers.providers.Provider
+type ProviderV6 = ethers.Provider
 
-export const getAddress =
-  utils?.getAddress ?? (ethersGetAddress as (address: string) => string);
+export type Provider = ProviderV6 extends undefined ? ProviderV5 : ProviderV6
+export const verifyMessage = ethersVerifyMessage;
+export const hashMessage = ethersHashMessage;
+export const getAddress = ethersGetAddress;