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Add AsyncStream support for Firebase Auth #15362

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@peterfriese peterfriese commented Sep 28, 2025 •
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To better align the Firebase Auth SDK with modern Swift concurrency, this PR introduces AsyncStream-based APIs for observing authentication state and ID token changes.

Key Features & Benefits

  • Modern Concurrency: New authStateChanges and idTokenChanges properties on Auth return an AsyncStream<User?>, allowing developers to use for await loops to monitor authentication events, which is more idiomatic in modern Swift.
  • Improved Ergonomics: These new APIs provide a more intuitive and readable alternative to the traditional closure-based listeners (addStateDidChangeListener and addIDTokenDidChangeListener).
  • Resource Safety: The streams are designed to be safely cancelled, preventing potential resource leaks. This is validated by comprehensive unit tests.

Implementation Details

  • The new async properties are housed in a new FirebaseAuth/Sources/Auth+Async.swift file.
  • Unit tests have been added in FirebaseAuth/Tests/Unit/AuthAsyncTests.swift to cover sign-in, sign-out, token refresh, and stream cancellation scenarios.
  • The FirebaseAuth/CHANGELOG.md has been updated to reflect these new features.
  • The new APIs are documented with clear usage examples, following Apple's documentation best practices.

Example Usage

Monitoring Authentication State

func monitorAuthState() async {
  for await user in Auth.auth().authStateChanges {
    if let user = user {
      print("User signed in: \(user.uid)")
      // Update UI or perform actions for a signed-in user.
    } else {
      print("User signed out.")
      // Update UI or perform actions for a signed-out state.
    }
  }
}

Monitoring ID Token Changes

func monitorIDTokenState() async {
  for await user in Auth.auth().idTokenChanges {
    if let user = user {
      print("ID token changed for user: \(user.uid)")
      // The user's ID token has been refreshed.
      // You can get the new token by calling user.getIDToken()
      do {
        let token = try await user.getIDToken()
        print("New ID token: \(token)")
        // Send the new token to your backend server, etc.
      } catch {
        print("Error getting ID token: \(error)")
      }
    }
  }
}

@peterfriese
Add authStateChanges async stream to Auth
1b0c295 
This commit introduces an `AsyncStream`-based API for observing authentication state changes, aligning the Firebase Auth SDK with modern Swift concurrency patterns.

The new `authStateChanges` computed property on `Auth` returns an `AsyncStream<User?>` that emits the current user whenever the authentication state changes. This provides a more ergonomic alternative to the traditional closure-based `addStateDidChangeListener`.

Key changes include:
- The implementation of `authStateChanges` in a new `Auth+Async.swift` file.
-  Comprehensive unit tests in `AuthAsyncTests.swift` covering the stream's behavior for sign-in, sign-out, and cancellation scenarios to prevent resource leaks.
- An entry in the `FirebaseAuth/CHANGELOG.md` for the new feature.
- Detailed API documentation for `authStateChanges`, including a clear usage example, following Apple's documentation best practices.
@peterfriese peterfriese self-assigned this Sep 28, 2025
@peterfriese peterfriese linked an issue Sep 28, 2025 that may be closed by this pull request
Implement AsyncStream support for Firebase Auth #15361
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paulb777
paulb777 reviewed Sep 30, 2025
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@peterfriese
Add idTokenChanges async stream to Auth
69d2f30 
This commit introduces an `AsyncStream`-based API for observing ID token changes, aligning the Firebase Auth SDK with modern Swift concurrency patterns.

The new `idTokenChanges` computed property on `Auth` returns an `AsyncStream<User?>` that emits the current user whenever the ID token changes. This provides a more ergonomic alternative to the traditional closure-based `addIDTokenDidChangeListener`.

Key changes include:
- The implementation of `idTokenChanges` in `Auth+Async.swift`.
- Comprehensive unit tests in `IdTokenChangesAsyncTests.swift` covering the stream's behavior.
- Renamed `AuthAsyncTests.swift` to `AuthStateChangesAsyncTests.swift` to better reflect its content.
@peterfriese
Remove explicit return statements
f8f9386
@peterfriese
Update changelog
ac13e18
@peterfriese peterfriese marked this pull request as ready for review September 30, 2025 09:06
@ncooke3
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ncooke3 commented Oct 2, 2025

/gemini review

gemini-code-assist[bot]
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Code Review

This pull request introduces AsyncStream-based APIs for observing authentication state and ID token changes, which is a great step towards modernizing the Firebase Auth SDK for Swift concurrency. The implementation is clean, well-documented, and includes a good set of unit tests.

My review includes a few suggestions to enhance the new APIs and tests:

  • Broadening the API availability to support older OS versions where Swift concurrency is available.
  • Improving the robustness of the unit tests by replacing Task.sleep with expectations.
  • Refactoring duplicated setup code in the tests to improve maintainability.

ncooke3
ncooke3 reviewed Oct 2, 2025
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Implement AsyncStream support for Firebase Auth
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