misc syntactic & type-checking clean-up

src/libs/crypto/passkeyHelpers.ts

@@ -55,8 +55,8 @@ export function isoUint8ArrayConcat(arrays: Uint8Array[]): Uint8Array {
 }
 
 // from https://github.com/MasterKale/SimpleWebAuthn/blob/master/packages/server/src/helpers/iso/isoCrypto/getWebCrypto.ts
-let webCrypto: unknown = undefined;
-export function getWebCrypto() {
+let webCrypto: { subtle: SubtleCrypto } | undefined = undefined;
+export function getWebCrypto(): Promise<{ subtle: SubtleCrypto }> {
   /**
    * Hello there! If you came here wondering why this method is asynchronous when use of
    * `globalThis.crypto` is not, it's to minimize a bunch of refactor related to making this
@@ -67,22 +67,25 @@ export function getWebCrypto() {
    * TODO: If it's after February 2025 when you read this then consider whether it still makes sense
    * to keep this method asynchronous.
    */
-  const toResolve = new Promise((resolve, reject) => {
-    if (webCrypto) {
-      return resolve(webCrypto);
-    }
-    /**
-     * Naively attempt to access Crypto as a global object, which popular ESM-centric run-times
-     * support (and Node v20+)
-     */
-    const _globalThisCrypto = _getWebCryptoInternals.stubThisGlobalThisCrypto();
-    if (_globalThisCrypto) {
-      webCrypto = _globalThisCrypto;
-      return resolve(webCrypto);
-    }
-    // We tried to access it both in Node and globally, so bail out
-    return reject(new MissingWebCrypto());
-  });
+  const toResolve: Promise<{ subtle: SubtleCrypto }> = new Promise(
+    (resolve, reject) => {
+      if (webCrypto) {
+        return resolve(webCrypto);
+      }
+      /**
+       * Naively attempt to access Crypto as a global object, which popular ESM-centric run-times
+       * support (and Node v20+)
+       */
+      const _globalThisCrypto =
+        _getWebCryptoInternals.stubThisGlobalThisCrypto();
+      if (_globalThisCrypto) {
+        webCrypto = _globalThisCrypto;
+        return resolve(webCrypto);
+      }
+      // We tried to access it both in Node and globally, so bail out
+      return reject(new MissingWebCrypto());
+    },
+  );
   return toResolve;
 }
 export class MissingWebCrypto extends Error {
@@ -96,7 +99,7 @@ export class MissingWebCrypto extends Error {
 export const _getWebCryptoInternals = {
   stubThisGlobalThisCrypto: () => globalThis.crypto,
   // Make it possible to reset the `webCrypto` at the top of the file
-  setCachedCrypto: (newCrypto: unknown) => {
+  setCachedCrypto: (newCrypto: { subtle: SubtleCrypto }) => {
     webCrypto = newCrypto;
   },
-};
+};