Improve decodeMessage: safer error handling and modern ethers imports

packages/utils/src/decode-message.ts

@@ -1,6 +1,4 @@
-import type { BigNumberish } from "ethers"
-import { decodeBytes32String } from "ethers/abi"
-import { toBeHex } from "ethers/utils"
+import { BigNumberish, decodeBytes32String, toBeHex } from "ethers"
 
 /**
  * Typically used for decoding on-chain Semaphore messages.
@@ -9,9 +7,20 @@ import { toBeHex } from "ethers/utils"
  * This function help devs converting bigint messages to text again.
  * If the original message was not text the output of this
  * function won't probably be human-readable text.
+ *
+ * Note: If the input is not a valid bytes32 string, the function will return null instead of throwing.
+ * This makes the function safer to use with untrusted or dynamic input.
+ *
  * @param message The Semaphore message as a bigint.
- * @returns The Semaphore message as a text.
+ * @returns The Semaphore message as a text, or null if decoding fails.
  */
 export default function decodeMessage(message: BigNumberish) {
-    return decodeBytes32String(toBeHex(message, 32))
+    try {
+        // Attempt to decode the message as a bytes32 string.
+        // If the input is not valid, return null instead of throwing an error.
+        return decodeBytes32String(toBeHex(message, 32))
+    } catch {
+        // Decoding failed (invalid input or not a valid bytes32 string)
+        return null
+    }
 }