1.7.0-Beta

Core API significant improvements

• New Channel implementation with significant performance improvements across the API (#3621).
• New select operator implementation: faster, more lightweight, and more robust (#3020).
• Mutex and Semaphore now share the same underlying data structure (#3020).
• Dispatchers.IO is added to K/N (#3205)
  • newFixedThreadPool and Dispatchers.Default implementations on K/N were wholly rewritten to support graceful growth under load (#3595).
• kotlinx-coroutines-test rework:
  • Add the timeout parameter to runTest for the whole-test timeout, 10 seconds by default (#3270). This replaces the configuration of quiescence timeouts, which is now deprecated (#3603).
  • The withTimeout exception messages indicate if the timeout used the virtual time (#3588).
  • TestCoroutineScheduler, runTest, and TestScope API are promoted to stable (#3622).
  • runTest now also fails if there were uncaught exceptions in coroutines not inherited from the test coroutine (#1205).

Breaking changes

• Old K/N memory model is no longer supported (#3375).
• New generic upper bounds were added to reactive integration API where the language since 1.8.0 dictates (#3393).
• kotlinx-coroutines-core and kotlinx-coroutines-jdk8 artifacts were merged into a single artifact (#3268).
• Artificial stackframes in stacktrace recovery no longer contain the \b symbol and are now navigable in IDE and supplied with proper documentation (#2291).
• CoroutineContext.isActive returns true for contexts without any job in them (#3300).

Bug fixes and improvements

• Kotlin version is updated to 1.8.10.
• JPMS is supported (#2237). Thanks @lion7!
• BroadcastChannel and all the corresponding API are deprecated (#2680).
• Added all supported K/N targets (#3601, #812, #855).
• K/N Dispatchers.Default is backed by the number of threads equal to the number of available cores (#3366).
• Fixed an issue where some coroutines' internal exceptions were not properly serializable (#3328).
• Introduced Job.parent API (#3201).
• Fixed a bug when TestScheduler leaked cancelled jobs (#3398).
• TestScope.timeSource now provides comparable time marks (#3617). Thanks @hfhbd!
• Fixed an issue when cancelled withTimeout handles were preserved in JS runtime (#3440).
• Ensure awaitFrame only awaits a single frame when used from the main looper (#3432). Thanks @pablobaxter!
• Obsolete Class-Path attribute was removed from kotlinx-coroutines-debug.jar manifest (#3361).
• Fixed a bug when updateThreadContext operated on the parent context (#3411).
• Added new Flow.filterIsInstance extension (#3240).
• Dispatchers.Default thread name prefixes are now configurable with system property (#3231).
• Added Flow.timeout operator as @FlowPreview (#2624). Thanks @pablobaxter!
• Improved the performance of the future builder in case of exceptions (#3475). Thanks @He-Pin!
• Mono.awaitSingleOrNull now waits for the onComplete signal (#3487).
• Channel.isClosedForSend and Channel.isClosedForReceive are promoted from experimental to delicate (#3448).
• Fixed a data race in native EventLoop (#3547).
• Dispatchers.IO.limitedParallelism(valueLargerThanIOSize) no longer creates an additional wrapper (#3442). Thanks @dovchinnikov!
• Various @FlowPreview and @ExperimentalCoroutinesApi are promoted to experimental and stable respectively (#3542, #3097, #3548).
• Performance improvements in Dispatchers.Default and Dispatchers.IO (#3416, #3418).
• Fixed a bug when internal suspendCancellableCoroutineReusable might have hanged (#3613).
• Introduced internal API to process events in the current system dispatcher (#3439).
• Global CoroutineExceptionHandler is no longer invoked in case of unprocessed future failure (#3452).
• Performance improvements and reduced thread-local pressure for the withContext operator (#3592).
• Improved performance of DebugProbes (#3527).
• Fixed a bug when the coroutine debugger might have detected the state of a coroutine incorrectly (#3193).
• Various documentation improvements and fixes.

1.6.4

• Added TestScope.backgroundScope for launching coroutines that perform work in the background and need to be cancelled at the end of the test (#3287).
• Fixed the POM of kotlinx-coroutines-debug having an incorrect reference to kotlinx-coroutines-bom, which cause the builds of Maven projects using the debug module to break (#3334).
• Fixed the Publisher.await functions in kotlinx-coroutines-reactive not ensuring that the Subscriber methods are invoked serially (#3360). Thank you, @EgorKulbachka!
• Fixed a memory leak in withTimeout on K/N with the new memory model (#3351).
• Added the guarantee that all Throwable implementations in the core library are serializable (#3328).
• Moved the documentation to https://kotlinlang.org/api/kotlinx.coroutines/ (#3342).
• Various documentation improvements.

1.6.3

• Updated atomicfu version to 0.17.3 (#3321), fixing the projects using this library with JS IR failing to build (#3305).

1.6.2

• Fixed a bug with ThreadLocalElement not being correctly updated when the most outer suspend function was called directly without kotlinx.coroutines (#2930).
• Fixed multiple data races: one that might have been affecting runBlocking event loop, and a benign data race in Mutex (#3250, #3251).
• Obsolete TestCoroutineContext is removed, which fixes the kotlinx-coroutines-test JPMS package being split between kotlinx-coroutines-core and kotlinx-coroutines-test (#3218).
• Updated the ProGuard rules to further shrink the size of the resulting DEX file with coroutines (#3111, #3263). Thanks, @agrieve!
• Atomicfu is updated to 0.17.2, which includes a more efficient and robust JS IR transformer (#3255).
• Kotlin is updated to 1.6.21, Gradle version is updated to 7.4.2 (#3281). Thanks, @wojtek-kalicinski!
• Various documentation improvements.

1.6.1

• Rollback of time-related functions dispatching on Dispatchers.Main.
  This behavior was introduced in 1.6.0 and then found inconvenient and erroneous (#3106, #3113).
• Reworked the newly-introduced CopyableThreadContextElement to solve issues uncovered after the initial release (#3227).
• Fixed a bug with ThreadLocalElement not being properly updated in racy scenarios (#2930).
• Reverted eager loading of default CoroutineExceptionHandler that triggered ANR on some devices (#3180).
• New API to convert a CoroutineDispatcher to a Rx scheduler (#968, #548). Thanks @recheej!
• Fixed a memory leak with the very last element emitted from flow builder being retained in memory (#3197).
• Fixed a bug with limitedParallelism on K/N with new memory model throwing ClassCastException (#3223).
• CoroutineContext is added to the exception printed to the default CoroutineExceptionHandler to improve debuggability (#3153).
• Static memory consumption of Dispatchers.Default was significantly reduced (#3137).
• Updated slf4j version in kotlinx-coroutines-slf4j from 1.7.25 to 1.7.32.

1.6.0

Note that this is a full changelog relative to the 1.5.2 version. Changelog relative to 1.6.0-RC3 can be found at the end.

kotlinx-coroutines-test rework

• kotlinx-coroutines-test became a multiplatform library usable from K/JVM, K/JS, and K/N.
• Its API was completely reworked to address long-standing issues with consistency, structured concurrency and correctness (#1203, #1609, #2379, #1749, #1204, #1390, #1222, #1395, #1881, #1910, #1772, #1626, #1742, #2082, #2102, #2405, #2462
  ).
• The old API is deprecated for removal, but the new API is based on the similar concepts (README), and the migration path is designed to be graceful: migration guide.

Dispatchers

• Introduced CoroutineDispatcher.limitedParallelism that allows obtaining a view of the original dispatcher with limited parallelism (#2919).
• Dispatchers.IO.limitedParallelism usages ignore the bound on the parallelism level of Dispatchers.IO itself to avoid starvation (#2943).
• Introduced new Dispatchers.shutdown method for containerized environments (#2558).
• newSingleThreadContext and newFixedThreadPoolContext are promoted to delicate API (#2919).

Breaking changes

• When racing with cancellation, the future builder no longer reports unhandled exceptions into the global CoroutineExceptionHandler. Thanks @vadimsemenov! (#2774, #2791).
• Mutex.onLock is deprecated for removal (#2794).
• Dispatchers.Main is now used as the default source of time for delay and withTimeout when present (#2972).
  • To opt-out from this behaviour, kotlinx.coroutines.main.delay system property can be set to false.
• Java target of coroutines build is now 8 instead of 6 (#1589).
• Source-breaking change: extension collect no longer resolves when used with a non-in-place argument of a functional type. This is a candidate for a fix, uncovered after 1.6.0, see #3107 for the additional details.

Bug fixes and improvements

• Kotlin is updated to 1.6.0.
• Kotlin/Native new memory model is now supported in regular builds of coroutines conditionally depending on whether kotlin.native.binary.memoryModel is enabled (#2914).
• Introduced CopyableThreadContextElement for mutable context elements shared among multiple coroutines. Thanks @yorickhenning! (#2893).
• transformWhile, awaitClose, ProducerScope, merge, runningFold, runingReduce, and scan are promoted to stable API (#2971).
• SharedFlow.subscriptionCount no longer conflates incoming updates and gives all subscribers a chance to observe a short-lived subscription (#2488, #2863, #2871).
• Flow exception transparency mechanism is improved to be more exception-friendly (#3017, #2860).
• Cancellation from flat* operators that leverage multiple coroutines is no longer propagated upstream (#2964).
• SharedFlow.collect now returns Nothing (#2789, #2502).
• DisposableHandle is now fun interface, and corresponding inline extension is removed (#2790).
• FlowCollector is now fun interface, and corresponding inline extension is removed (#3047).
• Deprecation level of all previously deprecated signatures is raised (#3024).
• The version file is shipped with each JAR as a resource (#2941).
• Unhandled exceptions on K/N are passed to the standard library function processUnhandledException (#2981).
• A direct executor is used for Task callbacks in kotlinx-coroutines-play-services (#2990).
• Metadata of coroutines artifacts leverages Gradle platform to have all versions of dependencies aligned (#2865).
• Default CoroutineExceptionHandler is loaded eagerly and does not invoke ServiceLoader on its exception-handling path (#2552).
• Fixed the R8 rules for ServiceLoader optimization (#2880).
• Fixed BlockHound integration false-positives (#2894, #2866, #2937).
• Fixed the exception handler being invoked several times on Android, thanks to @1zaman (#3056).
• SendChannel.trySendBlocking is now available on Kotlin/Native (#3064).
• The exception recovery mechanism now uses ClassValue when available (#2997).
• JNA is updated to 5.9.0 to support Apple M1 (#3001).
• Obsolete method on internal Delay interface is deprecated (#2979).
• Support of deprecated CommonPool is removed.
• @ExperimentalTime is no longer needed for methods that use Duration (#3041).
• JDK 1.6 is no longer required for building the project (#3043).
• New version of Dokka is used, fixing the memory leak when building the coroutines and providing brand new reference visuals (https://kotlin.github.io/kotlinx.coroutines/) (#3051, #3054).

1.6.0-RC3

• Fixed the error in 1.6.0-RC2 because of which Flow.collect couldn't be called due to the @InternalCoroutinesApi annotation (#3082)
• Fixed some R8 warnings introduced in 1.6.0-RC (#3090)
• TestCoroutineScheduler now provides a TimeSource with its virtual time via the timeSource property. Thanks @hfhbd! (#3087)

1.6.0-RC2

• @ExperimentalTime is no longer needed for methods that use Duration (#3041).
• FlowCollector is now fun interface, and corresponding inline extension is removed (#3047).
• Fixed the exception handler being invoked several times on Android, thanks to @1zaman (#3056).
• The deprecated TestCoroutineScope is no longer sealed, to simplify migration from it (#3072).
• runTest gives more informative errors when it times out waiting for external completion (#3071).
• SendChannel.trySendBlocking is now available on Kotlin/Native (#3064).
• Fixed the bug due to which Dispatchers.Main was not used for delay and withTimeout (#3046).
• JDK 1.6 is no longer required for building the project (#3043).
• New version of Dokka is used, fixing the memory leak when building the coroutines and providing brand new reference visuals (https://kotlin.github.io/kotlinx.coroutines/) (#3051, #3054).

1.6.0-RC

kotlinx-coroutines-test rework

• kotlinx-coroutines-test became a multiplatform library usable from K/JVM, K/JS, and K/N.
• Its API was completely reworked to address long-standing issues with consistency, structured concurrency and correctness (#1203, #1609, #2379, #1749, #1204, #1390, #1222, #1395, #1881, #1910, #1772, #1626, #1742, #2082, #2102, #2405, #2462
  ).
• The old API is deprecated for removal, but the new API is based on the similar concepts (README), and the migration path is designed to be graceful: migration guide

Dispatchers

• Introduced CoroutineDispatcher.limitedParallelism that allows obtaining a view of the original dispatcher with limited parallelism (#2919).
• Dispatchers.IO.limitedParallelism usages ignore the bound on the parallelism level of Dispatchers.IO itself to avoid starvation (#2943).
• Introduced new Dispatchers.shutdown method for containerized environments (#2558).
• newSingleThreadContext and newFixedThreadPoolContext are promoted to delicate API (#2919).

Breaking changes

• When racing with cancellation, the future builder no longer reports unhandled exceptions into the global CoroutineExceptionHandler. Thanks @vadimsemenov! (#2774, #2791).
• Mutex.onLock is deprecated for removal (#2794).
• Dispatchers.Main is now used as the default source of time for delay and withTimeout when present(#2972).
  • To opt-out from this behaviour, kotlinx.coroutines.main.delay system property can be set to false.
• Java target of coroutines build is now 8 instead of 6 (#1589).

Bug fixes and improvements

• Kotlin is updated to 1.6.0.
• Kotlin/Native new memory model is now supported in regular builds of coroutines conditionally depending on whether kotlin.native.binary.memoryModel is enabled (#2914).
• Introduced CopyableThreadContextElement for mutable context elements shared among multiple coroutines. Thanks @yorickhenning! (#2839 ).
• transformWhile, awaitClose, ProducerScope, merge, runningFold, runingReduce, and scan are promoted to stable API (#2971).
• SharedFlow.subscriptionCount no longer conflates incoming updates and gives all subscribers a chance to observe a short-lived subscription (#2488, #2863, #2871).
• Flow exception transparency mechanism is improved to be more exception-friendly (#3017, #2860).
• Cancellation from flat* operators that leverage multiple coroutines is no longer propagated upstream (#2964).
• SharedFlow.collect now returns Nothing (#2789, #2502).
• FlowCollector is now fun interface, and corresponding inline extension is removed (#2790).
• Deprecation level of all previously deprecated signatures is raised (#3024).
• The version file is shipped with each JAR as a resource (#2941).
• Unhandled exceptions on K/N are passed to the standard library function processUnhandledException (#2981).
• A direct executor is used for Task callbacks in kotlinx-coroutines-play-services (#2990).
• Metadata of coroutines artifacts leverages Gradle platform to have all versions of dependencies aligned (#2865).
• Default CoroutineExceptionHandler is loaded eagerly and does not invoke ServiceLoader on its exception-handling path (#2552).
• Fixed the R8 rules for ServiceLoader optimization (#2880).
• Fixed BlockHound integration false-positives (#2894, #2866, #2937).
• The exception recovery mechanism now uses ClassValue when available (#2997).
• JNA is updated to 5.9.0 to support Apple M1 (#3001).
• Obsolete method on internal Delay interface is deprecated (#2979).
• Support of deprecated CommonPool is removed.

1.5.2

• Kotlin is updated to 1.5.30.
• New native targets for Apple Silicon are introduced.
• Fixed a bug when onUndeliveredElement was incorrectly called on properly received elements on JS (#2826).
• Fixed Dispatchers.Default on React Native, it now fully relies on setTimeout instead of stub process.nextTick. Thanks to @Legion2 (#2843).
• Optimizations of Mutex implementation (#2581).
• Mutex implementation is made completely lock-free as stated (#2590).
• Various documentation and guides improvements. Thanks to @MasoodFallahpoor and @pihanya.