[SDK] Add lex client seam and typed xrpc error matching (#11348)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/screens/Signup/state.ts

@@ -1,7 +1,6 @@
 import {createContext, useCallback, useContext} from 'react'
 import {LayoutAnimation} from 'react-native'
 import {type ComAtprotoServerDescribeServer} from '@atproto/api'
-import {XrpcResponseError} from '@atproto/lex'
 import {useLingui} from '@lingui/react/macro'
 import * as EmailValidator from 'email-validator'
 
@@ -9,9 +8,11 @@ import {DEFAULT_SERVICE} from '#/lib/constants'
 import {cleanError, isNetworkError} from '#/lib/strings/errors'
 import {createFullHandle} from '#/lib/strings/handles'
 import {getAge} from '#/lib/strings/time'
+import {matchXrpcError} from '#/lib/xrpc-error'
 import {useSessionApi} from '#/state/session'
 import {useOnboardingDispatch} from '#/state/shell'
 import {type AnalyticsContextType, useAnalytics} from '#/analytics'
+import {com} from '#/lexicons'
 
 export type ServiceDescription = ComAtprotoServerDescribeServer.OutputSchema
 
@@ -258,34 +259,13 @@ export const useSignupContext = () => useContext(SignupContext)
  * failure is unexpected and should be reported to Sentry.
  */
 function classifyExpectedSignupError(e: unknown): string | undefined {
-  /*
-   * TODO: `XrpcResponseError.error` is the open `LexErrorCode` union, so these
-   * codes are compared as plain strings and a typo silently never matches.
-   * Once the generated lexicons land, replace this (and every multi-code error
-   * site) with a shared helper that narrows against the method schema:
-   *
-   *   function matchXrpcError<M extends Procedure | Query>(
-   *     e: unknown,
-   *     method: Main<M>,
-   *   ): InferMethodError<M> | undefined
-   *
-   *   switch (matchXrpcError(e, com.atproto.server.createAccount)) {
-   *     case 'InvalidHandle': ...
-   *   }
-   *
-   * The return type is the method's declared-errors union, so a typo'd case is
-   * a compile error, and undeclared codes fall through to `undefined`. The
-   * helper should also match `e.method.nsid` so a declared code from a
-   * different call cannot match, mirroring the old per-method error classes.
-   */
-  if (e instanceof XrpcResponseError) {
-    switch (e.error) {
-      case 'InvalidHandle':
-      case 'HandleNotAvailable':
-      case 'InvalidPassword':
-      case 'UnsupportedDomain':
-        return e.error
-    }
+  const code = matchXrpcError(e, com.atproto.server.createAccount)
+  switch (code) {
+    case 'InvalidHandle':
+    case 'HandleNotAvailable':
+    case 'InvalidPassword':
+    case 'UnsupportedDomain':
+      return code
   }
   /* the server sends no typed error for this case */
   if (String(e).includes('Email already taken')) return 'EmailTaken'
@@ -376,7 +356,10 @@ export function useSubmitSignup() {
       } catch (err) {
         const e = err as Error
         let errMsg = e.toString()
-        if (e instanceof XrpcResponseError && e.error === 'InvalidInviteCode') {
+        if (
+          matchXrpcError(e, com.atproto.server.createAccount) ===
+          'InvalidInviteCode'
+        ) {
           dispatch({
             type: 'setError',
             value: l`Invite code not accepted. Check that you input it correctly and try again.`,