Cache classloader signatures

1 files changed, 9 insertions, 5 deletions

diff --git a/core/src/main/scala/mill/eval/Evaluator.scala b/core/src/main/scala/mill/eval/Evaluator.scala
index 63dd0813..c45f1744 100644
--- a/core/src/main/scala/mill/eval/Evaluator.scala
+++ b/core/src/main/scala/mill/eval/Evaluator.scala
@@ -1,6 +1,7 @@
 package mill.eval
 
 import java.net.URLClassLoader
+
 import ammonite.ops._
 import ammonite.runtime.SpecialClassLoader
 import mill.define.{Graph, Target, Task}
@@ -29,12 +30,14 @@ class Evaluator(workspacePath: Path,
 
     val evaluated = new OSet.Mutable[Task[_]]
     val results = mutable.LinkedHashMap.empty[Task[_], Result[Any]]
+    val classLoaderSignatureCache = mutable.Map.empty[ClassLoader, Seq[(Path, Long)]]
 
     for ((terminal, group)<- sortedGroups.items()){
       val (newResults, newEvaluated) = evaluateGroupCached(
         terminal,
         group,
-        results
+        results,
+        classLoaderSignatureCache
       )
       for(ev <- newEvaluated){
         evaluated.append(ev)
@@ -62,18 +65,19 @@ class Evaluator(workspacePath: Path,
 
   def evaluateGroupCached(terminal: Either[Task[_], LabelledTarget[_]],
                           group: OSet[Task[_]],
-                          results: collection.Map[Task[_], Result[Any]]): (collection.Map[Task[_], Result[Any]], Seq[Task[_]]) = {
+                          results: collection.Map[Task[_], Result[Any]],
+                          signatureCache: mutable.Map[ClassLoader, Seq[(Path, Long)]]): (collection.Map[Task[_], Result[Any]], Seq[Task[_]]) = {
 
 
     val externalInputs = group.items.flatMap(_.inputs).filter(!group.contains(_))
 
     // check if the build itself has changed
-    val classLoaderSig = group.toVector.map { task =>
-      task.getClass.getClassLoader match {
+    val classLoaderSig = group.toVector.map(_.getClass.getClassLoader).map { cl =>
+      signatureCache.getOrElseUpdate(cl, cl match {
         case scl: SpecialClassLoader => scl.classpathSignature
         case ucl: URLClassLoader => SpecialClassLoader.initialClasspathSignature(ucl)
         case _ => Nil
-      }
+      })
     }
 
     val inputsHash =