refactor(auth)!: Migrate to typescript

[MichaelVerdon]

Description

Related issues

Release Summary

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
  • Yes
• My change supports the following platforms;
  • Android
  • iOS
  • Other (macOS, web)
• My change includes tests;
  • e2e tests added or updated in packages/\*\*/e2e
  • jest tests added or updated in packages/\*\*/__tests__
• I have updated TypeScript types that are affected by my change.
• This is a breaking change;
  • Yes
  • No

Test Plan

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Project	Deployment	Actions	Updated (UTC)
react-native-firebase	Error		Mar 31, 2026 0:59am

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request undertakes a significant refactoring of the auth package, migrating its entire codebase to TypeScript. This transition enhances code quality, maintainability, and developer experience by introducing strong typing across the module's classes, methods, and internal structures. The changes also include updates to the modular API and minor adjustments to Firestore's query constraints to accommodate the new typing paradigm.

Highlights

• TypeScript Migration: The core auth package has been refactored and migrated to TypeScript, converting existing JavaScript files to .ts and adding comprehensive type definitions.
• File Renames and Additions: Several key files like ConfirmationResult, Settings, User, MultiFactorResolver, and getMultiFactorResolver have been renamed from .js to .ts and updated with type annotations. New TypeScript type definition files (types/auth.ts, types/internal.ts, types/namespaced.d.ts) and a new modular API implementation (modular.ts) were added.
• Modular API Refactoring: The modular API implementation has been refactored to align with TypeScript, including the removal of old JavaScript and declaration files for modular components.
• Firestore Query Enhancements: Minor updates were made to Firestore's modular query system, introducing a QueryConstraint interface and QueryConstraintBase class, and extending QueryConstraintType to support 'or' and 'and' composite filters.
• Build Configuration Updates: New tsconfig.json files were added for the auth package, and the root tsconfig.json was updated to correctly resolve TypeScript paths for @react-native-firebase/* packages.

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[gemini-code-assist]

Code Review

This pull request successfully migrates several core authentication files to TypeScript, significantly improving type safety and code clarity across the auth package. The changes involve adding explicit type annotations, refining interfaces, and updating the build configuration to support TypeScript compilation. The refactoring of Firestore query constraints also enhances type safety in that module.