Provide toString implementation for limitedParallelism

Author: qwwdfsad

kotlinx-coroutines-core/common/src/internal/LimitedDispatcher.kt

@@ -95,6 +95,8 @@ internal class LimitedDispatcher(
         }
     }
 
+    override fun toString() = "$dispatcher.limitedParallelism($parallelism)"
+
     /**
      * A worker that polls the queue and runs tasks until there are no more of them.
      *
@@ -125,5 +127,4 @@ internal class LimitedDispatcher(
     }
 }
 
-// Save a few bytecode ops
 internal fun Int.checkParallelism() = require(this >= 1) { "Expected positive parallelism level, but got $this" }

kotlinx-coroutines-core/jvm/src/DefaultExecutor.kt

@@ -184,6 +184,11 @@ internal actual object DefaultExecutor : EventLoopImplBase(), Runnable {
         (this as Object).notifyAll()
     }
 
+    // User only for testing and nothing else
     internal val isThreadPresent
         get() = _thread != null
+
+    override fun toString(): String {
+        return "DefaultExecutor"
+    }
 }

kotlinx-coroutines-core/jvm/src/scheduling/Dispatcher.kt

@@ -49,6 +49,11 @@ private object UnlimitedIoScheduler : CoroutineDispatcher() {
         if (parallelism >= MAX_POOL_SIZE) return this
         return super.limitedParallelism(parallelism)
     }
+
+    // This name only leaks to user code as part of .limitedParallelism machinery
+    override fun toString(): String {
+        return "Dispatchers.IO"
+    }
 }
 
 // Dispatchers.IO

kotlinx-coroutines-core/jvm/test/DispatchersToStringTest.kt

@@ -11,4 +11,12 @@ class DispatchersToStringTest {
         assertEquals("Dispatchers.Main[missing]", Dispatchers.Main.toString())
         assertEquals("Dispatchers.Main[missing]", Dispatchers.Main.immediate.toString())
     }
+
+    @Test
+    fun testLimitedParallelism() {
+        assertEquals("Dispatchers.IO.limitedParallelism(1)", Dispatchers.IO.limitedParallelism(1).toString())
+        assertEquals("Dispatchers.Default.limitedParallelism(2)", Dispatchers.Default.limitedParallelism(2).toString())
+        // Not overridden at all, limited parallelism returns `this`
+        assertEquals("DefaultExecutor", (DefaultDelay as CoroutineDispatcher).limitedParallelism(42).toString())
+    }
 }