IDEA-285792 implement main coroutine dispatcher

- subclass `MainCoroutineDispatcher` in `EdtCoroutineDispatcher`;
- register `EdtCoroutineDispatcher` as main via `MainDispatcherFactory`.

GitOrigin-RevId: 18101ad18c424bb51733fe78350eb7dba2c33d54

platform/core-impl/src/com/intellij/openapi/application/impl/EdtCoroutineDispatcher.kt

@@ -3,11 +3,15 @@ package com.intellij.openapi.application.impl
 
 import com.intellij.openapi.application.ApplicationManager
 import com.intellij.openapi.application.ModalityState
-import kotlinx.coroutines.CoroutineDispatcher
+import com.intellij.util.ui.EDT
+import kotlinx.coroutines.MainCoroutineDispatcher
+import kotlinx.coroutines.Runnable
 import kotlinx.coroutines.job
 import kotlin.coroutines.CoroutineContext
 
-internal object EdtCoroutineDispatcher : CoroutineDispatcher() {
+internal sealed class EdtCoroutineDispatcher : MainCoroutineDispatcher() {
+
+  override val immediate: MainCoroutineDispatcher get() = Immediate
 
   override fun dispatch(context: CoroutineContext, block: Runnable) {
     val state = context[ModalityStateElement]?.modalityState
@@ -20,4 +24,24 @@ internal object EdtCoroutineDispatcher : CoroutineDispatcher() {
     }
     ApplicationManager.getApplication().invokeLater(runnable, state)
   }
+
+  companion object : EdtCoroutineDispatcher() {
+
+    override fun toString() = "EDT"
+  }
+
+  object Immediate : EdtCoroutineDispatcher() {
+
+    override fun isDispatchNeeded(context: CoroutineContext): Boolean {
+      if (!EDT.isCurrentThreadEdt()) {
+        return true
+      }
+      // The current coroutine is executed with the correct modality state
+      // (the execution would be postponed otherwise)
+      // => there is no need to check modality state here.
+      return false
+    }
+
+    override fun toString() = "EDT.immediate"
+  }
 }

platform/core-impl/src/com/intellij/openapi/application/impl/EdtCoroutineDispatcherFactory.kt

@@ -0,0 +1,16 @@
+// Copyright 2000-2021 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.openapi.application.impl
+
+import kotlinx.coroutines.InternalCoroutinesApi
+import kotlinx.coroutines.MainCoroutineDispatcher
+import kotlinx.coroutines.internal.MainDispatcherFactory
+
+@InternalCoroutinesApi
+internal class EdtCoroutineDispatcherFactory : MainDispatcherFactory {
+
+  override val loadPriority: Int get() = 0
+
+  override fun createDispatcher(allFactories: List<MainDispatcherFactory>): MainCoroutineDispatcher {
+    return EdtCoroutineDispatcher
+  }
+}

platform/platform-impl/resources/META-INF/services/kotlinx.coroutines.internal.MainDispatcherFactory

@@ -0,0 +1,2 @@
+# Copyright 2000-2021 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+com.intellij.openapi.application.impl.EdtCoroutineDispatcherFactory