Fix "redundant async" for coroutines 1.*, forbid explicit scopes case

Related to KT-28504
#KT-28445 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/coroutines/RedundantAsyncInspection.kt

@@ -9,6 +9,7 @@ import com.intellij.codeInspection.ProblemHighlightType
 import com.intellij.codeInspection.ProblemsHolder
 import org.jetbrains.kotlin.idea.inspections.collections.AbstractCallChainChecker
 import org.jetbrains.kotlin.idea.inspections.collections.SimplifyCallChainFix
+import org.jetbrains.kotlin.psi.KtQualifiedExpression
 import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import org.jetbrains.kotlin.psi.qualifiedExpressionVisitor
 import org.jetbrains.kotlin.resolve.calls.model.DefaultValueArgument
@@ -18,21 +19,21 @@ class RedundantAsyncInspection : AbstractCallChainChecker() {
         qualifiedExpressionVisitor(fun(expression) {
             var defaultContext: Boolean? = null
             var defaultStart: Boolean? = null
-            var defaultParent: Boolean? = null
+            // Temporary forbid cases with explicit scope
+            if (expression.receiverExpression is KtQualifiedExpression) return
+
             val conversion = findQualifiedConversion(expression, conversionGroups) check@{ _, firstResolvedCall, _, _ ->
                 for ((parameterDescriptor, valueArgument) in firstResolvedCall.valueArguments) {
                     val default = valueArgument is DefaultValueArgument
                     when (parameterDescriptor.name.asString()) {
                         "context" -> defaultContext = default
                         "start" -> defaultStart = default
-                        "parent" -> defaultParent = default
                     }
                 }
                 true
             } ?: return
             defaultContext ?: return
             defaultStart ?: return
-            if (defaultParent != true) return
             if (defaultContext!! && !defaultStart!!) return
 
             var replacement = conversion.replacement
@@ -71,7 +72,7 @@ class RedundantAsyncInspection : AbstractCallChainChecker() {
             )
         )
 
-        private const val defaultAsyncArgument = "$COROUTINE_PACKAGE.DefaultDispatcher"
+        private const val defaultAsyncArgument = "$COROUTINE_PACKAGE.Dispatchers.Default"
 
         private const val defaultAsyncArgumentExperimental = "$COROUTINE_EXPERIMENTAL_PACKAGE.DefaultDispatcher"
     }

idea/testData/inspectionsLocal/coroutines/redundantAsync/coroutines.lib.kt

@@ -6,7 +6,9 @@ interface Deferred<T> {
 
 interface CoroutineContext
 
-object DefaultDispatcher : CoroutineContext
+object Dispatchers {
+    object Default : CoroutineContext
+}
 
 enum class CoroutineStart {
     DEFAULT,
@@ -15,30 +17,28 @@ enum class CoroutineStart {
     UNDISPATCHED
 }
 
-interface Job
+interface CoroutineScope {
-
+    val coroutineContext: CoroutineContext get() = Dispatchers.Default
-fun <T> async(
-    context: CoroutineContext = DefaultDispatcher,
-    start: CoroutineStart = CoroutineStart.DEFAULT,
-    parent: Job? = null,
-    f: suspend () -> T
-): Deferred<T> {
-    TODO()
 }
 
-fun <T> runBlocking(
+object GlobalScope : CoroutineScope
-    context: CoroutineContext = DefaultDispatcher,
+
-    f: suspend () -> T
+fun <T> CoroutineScope.async(
-) {
+    context: CoroutineContext = Dispatchers.Default,
+    start: CoroutineStart = CoroutineStart.DEFAULT,
+    block: suspend CoroutineScope.() -> T
+): Deferred<T> {
     TODO()
 }
 
 suspend fun <T> withContext(
     context: CoroutineContext,
     start: CoroutineStart = CoroutineStart.DEFAULT,
-    f: suspend () -> T
+    block: suspend CoroutineScope.() -> T
 ) {
     TODO()
 }
 
+suspend fun <R> coroutineScope(block: suspend CoroutineScope.() -> R): R = GlobalScope.block()
+
 

idea/testData/inspectionsLocal/coroutines/redundantAsync/explicitScope.kt

@@ -0,0 +1,9 @@
+// WITH_RUNTIME
+// PROBLEM: none
+
+package kotlinx.coroutines
+
+suspend fun test(ctx: CoroutineContext, scope: CoroutineScope) {
+    // Does not work yet (1.3.11)
+    scope.<caret>async(ctx) { 42 }.await()
+}

idea/testData/inspectionsLocal/coroutines/redundantAsync/globalScope.kt

@@ -1,8 +1,9 @@
-// PROBLEM: none
 // WITH_RUNTIME
+// PROBLEM: none
 
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    <caret>async(parent = null) { 42 }.await()
+    // Does not work yet (1.3.11)
+    GlobalScope.<caret>async(ctx) { 42 }.await()
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/simple.kt

@@ -4,5 +4,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    <caret>async(ctx) { 42 }.await()
+    coroutineScope {
+        <caret>async(ctx) { 42 }.await()
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/simple.kt.after

@@ -4,5 +4,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    withContext(ctx) { 42 }
+    coroutineScope {
+        withContext(ctx) { 42 }
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/simplest.kt

@@ -1,8 +1,10 @@
 // WITH_RUNTIME
-// FIX: Merge call chain to 'withContext(DefaultDispatcher)'
+// FIX: Merge call chain to 'withContext(Default)'
 
 package kotlinx.coroutines
 
 suspend fun test() {
-    <caret>async { 42 }.await()
+    coroutineScope {
+        <caret>async { 42 }.await()
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/simplest.kt.after

@@ -1,8 +1,10 @@
 // WITH_RUNTIME
-// FIX: Merge call chain to 'withContext(DefaultDispatcher)'
+// FIX: Merge call chain to 'withContext(Default)'
 
 package kotlinx.coroutines
 
 suspend fun test() {
-    withContext(DefaultDispatcher) { 42 }
+    coroutineScope {
+        withContext(Dispatchers.Default) { 42 }
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/withStartAndContext.kt

@@ -3,5 +3,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    <caret>async(ctx, CoroutineStart.LAZY) { 42 }.await()
+    coroutineScope {
+        <caret>async(ctx, CoroutineStart.LAZY) { 42 }.await()
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/withStartAndContext.kt.after

@@ -3,5 +3,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    withContext(ctx, CoroutineStart.LAZY) { 42 }
+    coroutineScope {
+        withContext(ctx, CoroutineStart.LAZY) { 42 }
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/withStartNoContext.kt

@@ -4,5 +4,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    <caret>async(start = CoroutineStart.LAZY) { 42 }.await()
+    coroutineScope {
+        <caret>async(start = CoroutineStart.LAZY) { 42 }.await()
+    }
 }

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -2007,6 +2007,16 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
                 runTest("idea/testData/inspectionsLocal/coroutines/redundantAsync/experimental.kt");
             }
 
+            @TestMetadata("explicitScope.kt")
+            public void testExplicitScope() throws Exception {
+                runTest("idea/testData/inspectionsLocal/coroutines/redundantAsync/explicitScope.kt");
+            }
+
+            @TestMetadata("globalScope.kt")
+            public void testGlobalScope() throws Exception {
+                runTest("idea/testData/inspectionsLocal/coroutines/redundantAsync/globalScope.kt");
+            }
+
             @TestMetadata("simple.kt")
             public void testSimple() throws Exception {
                 runTest("idea/testData/inspectionsLocal/coroutines/redundantAsync/simple.kt");
@@ -2017,11 +2027,6 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
                 runTest("idea/testData/inspectionsLocal/coroutines/redundantAsync/simplest.kt");
             }
 
-            @TestMetadata("withParent.kt")
-            public void testWithParent() throws Exception {
-                runTest("idea/testData/inspectionsLocal/coroutines/redundantAsync/withParent.kt");
-            }
-
             @TestMetadata("withStartAndContext.kt")
             public void testWithStartAndContext() throws Exception {
                 runTest("idea/testData/inspectionsLocal/coroutines/redundantAsync/withStartAndContext.kt");