fix: add has trap to lazy auth proxy so auth routes resolve handler (#139)

* fix: add has trap to lazy auth proxy so auth routes resolve handler

The lazy `auth` Proxy only trapped `get`, leaving `has` to forward to its
empty target. better-auth's `toNextJsHandler` checks `"handler" in auth`
per request; that returned false, so it fell through to calling
`auth(request)`, which isn't callable. Result: every /api/auth/* POST threw
"TypeError: ... is not a function" in production (e.g. sign-in/social).

Add a `has` trap forwarding to the real instance. Stays build-time safe: the
check only runs inside toNextJsHandler's per-request closure, never at module
load, so env-validation decoupling is preserved.

* fix: type lazy proxy get-traps to satisfy no-unsafe lint

The get-traps assigned `Reflect.get(...)`'s `any` return, tripping
@typescript-eslint/no-unsafe-{assignment,return,call,member-access} (12
errors, pre-existing red on main since the proxies landed). Annotate the
forwarded value as `unknown` and cast on the function branch so binding is
type-checked. Runtime behavior is unchanged.

Author: ephraimduncan

packages/auth/index.ts

@@ -78,8 +78,13 @@ const getAuth = () => {
 export const auth = new Proxy({} as Auth, {
   get(_target, property) {
     const authClient = getAuth();
-    const value = Reflect.get(authClient, property);
-    return typeof value === 'function' ? value.bind(authClient) : value;
+    const value: unknown = Reflect.get(authClient, property);
+    return typeof value === 'function'
+      ? (value as (...args: unknown[]) => unknown).bind(authClient)
+      : value;
+  },
+  has(_target, property) {
+    return Reflect.has(getAuth(), property);
   },
 });
 

packages/db/index.ts

@@ -30,8 +30,10 @@ const getQueryClient = () => {
 export const queryClient = new Proxy({} as Client, {
   get(_target, property) {
     const client = getQueryClient();
-    const value = Reflect.get(client, property);
-    return typeof value === 'function' ? value.bind(client) : value;
+    const value: unknown = Reflect.get(client, property);
+    return typeof value === 'function'
+      ? (value as (...args: unknown[]) => unknown).bind(client)
+      : value;
   },
   set(_target, property, value) {
     return Reflect.set(getQueryClient(), property, value);
@@ -55,8 +57,10 @@ const getDb = () => {
 export const db = new Proxy({} as Database, {
   get(_target, property) {
     const database = getDb();
-    const value = Reflect.get(database, property);
-    return typeof value === 'function' ? value.bind(database) : value;
+    const value: unknown = Reflect.get(database, property);
+    return typeof value === 'function'
+      ? (value as (...args: unknown[]) => unknown).bind(database)
+      : value;
   },
   set(_target, property, value) {
     return Reflect.set(getDb(), property, value);