Android: FileLogger.configure() hangs when SLF4J 2.x is on the classpath

[tian000]

Bug Description

FileLogger.configure() returns a promise that never resolves on Android when SLF4J 2.x ends up on the classpath (e.g. via a transitive dependency like Ktor 3.x). This causes any app that awaits the configure call to hang indefinitely at startup.

Root Cause

In FileLoggerModule.configureLogger(), line 83 casts the SLF4J logger factory to logback's LoggerContext:

LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();

logback-android:2.0.0 registers with SLF4J using the 1.x binding mechanism (org.slf4j.impl.StaticLoggerBinder). SLF4J 2.x ignores this mechanism — it uses a ServiceLoader-based provider system instead. When no provider is found, getILoggerFactory() returns NOPLoggerFactory, and the cast throws a ClassCastException.

The configure() method has no try/catch, so promise.resolve(null) never executes, leaving the JS promise permanently unresolved.

iOS is unaffected because it uses CocoaLumberjack, not SLF4J/Logback.

Reproduction

Any Android project using react-native-file-logger alongside a dependency that transitively pulls in org.slf4j:slf4j-api:2.x will hit this. Common culprits:

• io.ktor:ktor-client-*:3.x → slf4j-api:2.0.17
• io.mockk:mockk-jvm:1.13+ → slf4j-api:2.0.5

Gradle resolves to the highest version, so slf4j-api:1.7.33 (declared by this library) gets upgraded to 2.x.

Expected Behavior

configure() should resolve or reject the promise regardless of the SLF4J version on the classpath.

Suggested Fix

1. Replace the hard cast with a fallback that creates a standalone LoggerContext when getILoggerFactory() doesn't return one
2. Use the stored context consistently in renewAppender() and for the logger field used by write()
3. Wrap configure() in try/catch so the promise is always settled

I have a working patch and will open a PR shortly.

Environment

• react-native-file-logger: 0.7.2
• React Native: 0.79.x (New Architecture / TurboModules enabled)
• logback-android: 2.0.0
• SLF4J resolved version: 2.0.17 (from Ktor 3.3.1 transitive dep)