retronym commented on a change in pull request #28463:
URL: https://github.com/apache/spark/pull/28463#discussion_r422014834
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File path: core/src/main/scala/org/apache/spark/util/ClosureCleaner.scala
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@@ -414,6 +434,284 @@ private[spark] object ClosureCleaner extends Logging {
}
}
+private[spark] object IndylambdaScalaClosures extends Logging {
+ // internal name of java.lang.invoke.LambdaMetafactory
+ val LambdaMetafactoryClassName = "java/lang/invoke/LambdaMetafactory"
+ // the method that Scala indylambda use for bootstrap method
+ val LambdaMetafactoryMethodName = "altMetafactory"
+ val LambdaMetafactoryMethodDesc = "(Ljava/lang/invoke/MethodHandles$Lookup;"
+
+ "Ljava/lang/String;Ljava/lang/invoke/MethodType;[Ljava/lang/Object;)" +
+ "Ljava/lang/invoke/CallSite;"
+
+ /**
+ * Check if the given reference is a indylambda style Scala closure.
+ * If so, return a non-empty serialization proxy (SerializedLambda) of the
closure;
+ * otherwise return None.
+ *
+ * @param maybeClosure the closure to check.
+ */
+ def getSerializationProxy(maybeClosure: AnyRef): Option[SerializedLambda] = {
+ val maybeClosureClass = maybeClosure.getClass
+
+ // shortcut the fast check:
+ // 1. indylambda closure classes are generated by Java's
LambdaMetafactory, and they're always
+ // synthetic.
+ // 2. We only care about Serializable closures, so let's check that as well
+ if (!maybeClosureClass.isSynthetic ||
!maybeClosure.isInstanceOf[Serializable]) return None
+
+ val implementedInterfaces =
ClassUtils.getAllInterfaces(maybeClosureClass).asScala
+ val isClosureCandidate =
implementedInterfaces.exists(_.getName.startsWith("scala.Function"))
+
+ if (isClosureCandidate) {
+ try {
+ val lambdaProxy = inspect(maybeClosure)
+ if (isIndylambdaScalaClosure(lambdaProxy)) Option(lambdaProxy)
+ else None
+ } catch {
+ case e: Exception =>
+ // no need to check if debug is enabled here the Spark logging api
covers this.
+ logDebug("The given reference is not an indylambda Scala closure.",
e)
+ None
+ }
+ } else {
+ None
+ }
+ }
+
+ def isIndylambdaScalaClosure(lambdaProxy: SerializedLambda): Boolean = {
+ lambdaProxy.getImplMethodKind == MethodHandleInfo.REF_invokeStatic &&
+ lambdaProxy.getImplMethodName.contains("$anonfun$")
+ }
+
+ def inspect(closure: AnyRef): SerializedLambda = {
+ val writeReplace = closure.getClass.getDeclaredMethod("writeReplace")
+ writeReplace.setAccessible(true)
+ writeReplace.invoke(closure).asInstanceOf[SerializedLambda]
+ }
+
+ /**
+ * Check if the handle represents the LambdaMetafactory that indylambda
Scala closures
+ * use for creating the lambda class and getting a closure instance.
+ */
+ def isLambdaMetafactory(bsmHandle: Handle): Boolean = {
+ bsmHandle.getOwner == LambdaMetafactoryClassName &&
+ bsmHandle.getName == LambdaMetafactoryMethodName &&
+ bsmHandle.getDesc == LambdaMetafactoryMethodDesc
+ }
+
+ /**
+ * Check if the handle represents a target method that is:
+ * - a STATIC method that implements a Scala lambda body in the indylambda
style
+ * - captures the enclosing `this`, i.e. the first argument is a reference
to the same type as
+ * the owning class.
+ * Returns true if both criteria above are met.
+ */
+ def isLambdaBodyCapturingOuter(handle: Handle, ownerInternalName: String):
Boolean = {
+ handle.getTag == H_INVOKESTATIC &&
+ handle.getName.contains("$anonfun$") &&
+ handle.getOwner == ownerInternalName &&
+ handle.getDesc.startsWith(s"(L$ownerInternalName;")
+ }
+
+ /**
+ * Check if the callee of a call site is a inner class constructor.
+ * - A constructor has to be invoked via INVOKESPECIAL
+ * - A constructor's internal name is "<init>" and the return type is "V"
(void)
+ * - An inner class' first argument in the signature has to be a reference
to the
+ * enclosing "this", aka `$outer` in Scala.
+ */
+ def isInnerClassCtorCapturingOuter(
+ op: Int, owner: String, name: String, desc: String, callerInternalName:
String): Boolean = {
+ op == INVOKESPECIAL && name == "<init>" &&
desc.startsWith(s"(L$callerInternalName;")
+ }
+
+ // scalastyle:off line.size.limit
+ /**
+ * Scans an indylambda Scala closure, along with its lexically nested
closures, and populate
+ * the accessed fields info on which fields on the outer object are accessed.
+ *
+ * Example: run the following code snippet in a Spark Shell w/ Scala 2.12+:
Review comment:
Looks good!
I'd appreciate if it if (as a followup task) you could update to [Scala
2.12.11](https://github.com/scala/scala/releases/tag/v2.12.11).
I'd hope you could turn on `-Yrepl-use-magic-imports` by default in the
Spark REPL. I tested those changes in the Spark build so I'm expecting things
should work fine.
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