fix(utils): make hasErrorCode safe for nullish catch bindings

src/utils/utils.ts

@@ -9,7 +9,19 @@ interface ErrorWithCode extends Error {
   code: string
 }
 
+/**
+ * Narrow an `unknown` catch binding to an error carrying a `code`.
+ *
+ * `null` and `undefined` are legal `unknown` values — `throw null` and
+ * `Promise.reject()` with no reason both produce one — so they have to be ruled
+ * out before the property is read. Reading `.code` off a nullish value throws
+ * `TypeError: Cannot read properties of null`, which is the opposite of what a
+ * guard is for: the caller loses the error it was about to inspect or rethrow
+ * and gets one that says nothing about what actually failed.
+ */
 export const hasErrorCode = (error: unknown): error is ErrorWithCode => {
-  const untypedError = error as Partial<ErrorWithCode>
-  return !!untypedError.code
+  if (error === null || error === undefined) {
+    return false
+  }
+  return !!(error as Partial<ErrorWithCode>).code
 }

test/sdk/misc.spec.ts

@@ -6,6 +6,7 @@ import {
 } from "../../src/constants"
 import {
   decodeTokenIds,
+  hasErrorCode,
   remapSharedStorefrontAddress,
 } from "../../src/utils/utils"
 import { BAYC_CONTRACT_ADDRESS } from "../utils/constants"
@@ -172,4 +173,21 @@ describe("SDK: misc", () => {
       ])
     })
   })
+
+  describe("hasErrorCode", () => {
+    it("should return true for an error carrying a code", () => {
+      expect(hasErrorCode({ code: "CALL_EXCEPTION" })).toBe(true)
+      expect(hasErrorCode(new Error("boom"))).toBe(false)
+    })
+
+    it("should return false for nullish input instead of throwing", () => {
+      // `null` and `undefined` are legal `unknown` values and both reach a
+      // `catch` binding (`throw null`, `Promise.reject()`). The guard read
+      // `.code` straight off the argument, so it threw a TypeError and hid the
+      // error its caller was about to rethrow.
+      expect(() => hasErrorCode(null)).not.toThrow()
+      expect(hasErrorCode(null)).toBe(false)
+      expect(hasErrorCode(undefined)).toBe(false)
+    })
+  })
 })