Implement withLatestFrom for multiple flows (3-10 flows) with optimized Array-based implementation

[Copilot]

This PR extends the withLatestFrom operator to support combining multiple flows (3-10 flows), addressing the issue request for "withLatestFrom for many flows".

Changes Made

Core Implementation

• Added 8 new overloads of withLatestFrom in src/commonMain/kotlin/com/hoc081098/flowext/withLatestFrom.kt supporting 3-10 flows
• Refactored implementation to eliminate code duplication by introducing a new public Array-based function that all overloads use internally
• Includes both transform function variants and a convenience overload returning Triple<A, B, C> for 3 flows
• Proper resource management with coroutineScope and job cancellation

Array-Based Core Function

• New public function withLatestFrom(others: Array<out Flow<*>>, transform: suspend (A, Array<Any?>) -> R) that serves as the foundation for all multi-flow overloads
• Uses Array<AtomicRef<Any?>> for efficient thread-safe latest value storage
• Eliminates code duplication while maintaining the same API and performance characteristics
• Code reduction: 48% smaller implementation (736 → 382 lines)

API Examples

// 3 flows with Triple return
val result = sourceFlow
  .withLatestFrom(flow2, flow3)
  .collect { (a, b, c) -> println("$a, $b, $c") }

// 4 flows with custom transform
val result = sourceFlow
  .withLatestFrom(flow2, flow3, flow4) { a, b, c, d -> 
    "$a-$b-$c-$d" 
  }

// Up to 10 flows supported
val result = sourceFlow
  .withLatestFrom(f2, f3, f4, f5, f6, f7, f8, f9, f10) { a, b, c, d, e, f, g, h, i, j ->
    // Transform logic here
  }

// Direct Array-based usage (public API)
val result = sourceFlow
  .withLatestFrom(arrayOf(flow2, flow3, flow4)) { value, others ->
    // Custom transformation with others[0], others[1], others[2]
  }

Test Coverage

• Added comprehensive tests in src/commonTest/kotlin/com/hoc081098/flowext/WithLatestFromTest.kt
• Tests cover basic functionality, timing semantics, error handling, cancellation, and null values
• All 259 tests pass, ensuring no regressions

Implementation Details

• Uses the same INTERNAL_NULL_VALUE pattern for null handling as existing code
• Follows the exact same concurrency model with launch(start = CoroutineStart.UNDISPATCHED)
• Consistent with the library's patterns established in combine.kt
• Proper cleanup of atomic references in finally blocks
• Maintainable design: All typed overloads delegate to the Array-based function, making future changes easier

The implementation maintains the core semantics of withLatestFrom: the source flow drives emissions, and only emits when all other flows have emitted at least once, using the latest values from each flow.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>withLatestFrom for many flows</issue_title> <issue_description></issue_description>

<agent_instructions>unit tests, docs, and readme.md</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes hoc081098/FlowExt#184

---

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[hoc081098]

@copilot I see the code pattern is duplicate? Could you introduce a new function that accepts a Array or List of Flows, then 3-10 flows overloads use this function. The new function should be public.

[Copilot]

@copilot I see the code pattern is duplicate? Could you introduce a new function that accepts a Array or List of Flows, then 3-10 flows overloads use this function. The new function should be public.

I've refactored the code to eliminate duplication as requested. Created a new public function that accepts Array<out Flow<*>> and updated all 3-10 flow overloads to use it. This reduced the file from 736 to 382 lines (48% reduction) while maintaining the same API and passing all 259 tests. The changes are in commit b468010.

[!WARNING]

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• dl.google.com
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED --add-opens=java.xml/javax.xml.namespace=ALL-UNNAMED -XX:+UseParallelGC -Xmx4g -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp /home/REDACTED/.gradle/wrapper/dists/gradle-9.0.0-bin/d6wjpkvcgsg3oed0qlfss3wgl/gradle-9.0.0/lib/gradle-daemon-main-9.0.0.jar -javaagent:/home/REDACTED/.gradle/wrapper/dists/gradle-9.0.0-bin/d6wjpkvcgsg3oed0qlfss3wgl/gradle-9.0.0/lib/agents/gradle-instrumentation-agent-9.0.0.jar org.gradle.launcher.daemon.bootstrap.GradleDaemon 9.0.0 (dns block)

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