make ordered serialization stable across compilations (#1664)

* ordered serialization - fix `knownDirectSubclasses` indeterminism * remove special handling for hierarchies with <= 4 elements
twitter · May 16, 2017 · 0f95484 · 0f95484
1 parent b1bf1be
commit 0f95484
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Showing 3 changed files with 22 additions and 3 deletions.
diff --git a/...ing/serialization/macros/impl/ordered_serialization/providers/SealedTraitOrderedBuf.scala b/...ing/serialization/macros/impl/ordered_serialization/providers/SealedTraitOrderedBuf.scala
@@ -34,7 +34,7 @@ object SealedTraitOrderedBuf {
     import c.universe._
     def freshT(id: String) = newTermName(c.fresh(s"$id"))
 
-    val knownDirectSubclasses = outerType.typeSymbol.asClass.knownDirectSubclasses
+    val knownDirectSubclasses = StableKnownDirectSubclasses(c)(outerType)
 
     if (knownDirectSubclasses.isEmpty)
       c.abort(c.enclosingPosition, s"Unable to access any knownDirectSubclasses for $outerType , a bug in scala 2.10/2.11 makes this unreliable.")

diff --git a/...rialization/macros/impl/ordered_serialization/providers/StableKnownDirectSubclasses.scala b/...rialization/macros/impl/ordered_serialization/providers/StableKnownDirectSubclasses.scala
@@ -0,0 +1,18 @@
+package com.twitter.scalding.serialization.macros.impl.ordered_serialization.providers
+
+import scala.reflect.macros.whitebox.Context
+
+/**
+ * The `knownDirectSubclasses` method doesn't provide stable ordering
+ * since it returns an unordered `Set` and the `Type` AST nodes don't
+ * override the `hashCode` method, relying on the default identity
+ * `hashCode`.
+ *
+ * This function makes the ordering stable using a list ordered by the
+ * full name of the types.
+ */
+object StableKnownDirectSubclasses {
+
+  def apply(c: Context)(tpe: c.Type): List[c.universe.TypeSymbol] = 
+    tpe.typeSymbol.asClass.knownDirectSubclasses.map(_.asType).toList.sortBy(_.fullName)
+}
diff --git a/...om/twitter/scalding/thrift/macros/impl/ordered_serialization/ScroogeUnionOrderedBuf.scala b/...om/twitter/scalding/thrift/macros/impl/ordered_serialization/ScroogeUnionOrderedBuf.scala
@@ -15,6 +15,7 @@
  */
 package com.twitter.scalding.thrift.macros.impl.ordered_serialization
 
+import com.twitter.scalding.serialization.macros.impl.ordered_serialization.providers.StableKnownDirectSubclasses
 import com.twitter.scalding.serialization.macros.impl.ordered_serialization._
 import com.twitter.scrooge.ThriftUnion
 
@@ -39,8 +40,8 @@ object ScroogeUnionOrderedBuf {
 
     val dispatcher = buildDispatcher
 
-    val subClasses: List[Type] = outerType.typeSymbol.asClass.knownDirectSubclasses.map(_.asType.toType).toList
-
+    val subClasses: List[Type] = StableKnownDirectSubclasses(c)(outerType).map(_.toType)
+    
     val subData: List[(Int, Type, Option[TreeOrderedBuf[c.type]])] = subClasses.map { t =>
       if (t.typeSymbol.name.toString == "UnknownUnionField") {
         (t, None)