Minor refactoring in CachePolicy

Preparing the ground for TTLs

core-jvm/src/main/scala/coursier/core/MavenRepository.scala

@@ -80,7 +80,13 @@ case class MavenRepository(
         )
       }
 
-      EitherT(cachePolicy.saving(locally(localFile))(remote)(save))
+      EitherT(
+        cachePolicy[String \/ String](
+          _.isLeft )(
+          locally(localFile) )(
+          _ => CachePolicy.saving(remote)(save)
+        )
+      )
     }
   }
 

core/src/main/scala/coursier/core/Repository.scala

@@ -455,18 +455,18 @@ abstract class BaseMavenRepository(
 }
 
 sealed trait CachePolicy {
-  def apply[E,T](local: => Task[E \/ T])
-                (remote: => Task[E \/ T]): Task[E \/ T]
-
-  def saving[E,T](local: => Task[E \/ T])
-                 (remote: => Task[E \/ T])
-                 (save: => T => Task[Unit]): Task[E \/ T] =
-    apply(local)(CachePolicy.saving(remote)(save))
+  def apply[T](
+    tryRemote: T => Boolean )(
+    local: => Task[T] )(
+    remote: Option[T] => Task[T]
+  ): Task[T]
 }
 
 object CachePolicy {
-  def saving[E,T](remote: => Task[E \/ T])
-                 (save: T => Task[Unit]): Task[E \/ T] = {
+  def saving[E,T](
+    remote: => Task[E \/ T] )(
+    save: T => Task[Unit]
+  ): Task[E \/ T] = {
     for {
       res <- remote
       _ <- res.fold(_ => Task.now(()), t => save(t))
@@ -474,19 +474,28 @@ object CachePolicy {
   }
 
   case object Default extends CachePolicy {
-    def apply[E,T](local: => Task[E \/ T])
-                  (remote: => Task[E \/ T]): Task[E \/ T] =
+    def apply[T](
+      tryRemote: T => Boolean )(
+      local: => Task[T] )(
+      remote: Option[T] => Task[T]
+    ): Task[T] =
       local
-        .flatMap(res => if (res.isLeft) remote else Task.now(res))
+        .flatMap(res => if (tryRemote(res)) remote(Some(res)) else Task.now(res))
   }
   case object LocalOnly extends CachePolicy {
-    def apply[E,T](local: => Task[E \/ T])
-                  (remote: => Task[E \/ T]): Task[E \/ T] =
+    def apply[T](
+      tryRemote: T => Boolean )(
+      local: => Task[T] )(
+      remote: Option[T] => Task[T]
+    ): Task[T] =
       local
   }
   case object ForceDownload extends CachePolicy {
-    def apply[E,T](local: => Task[E \/ T])
-                  (remote: => Task[E \/ T]): Task[E \/ T] =
-      remote
+    def apply[T](
+      tryRemote: T => Boolean )(
+      local: => Task[T] )(
+      remote: Option[T] => Task[T]
+    ): Task[T] =
+      remote(None)
   }
 }

files/src/main/scala/coursier/Files.scala

@@ -143,8 +143,11 @@ case class Files(
     val tasks =
       for ((f, url) <- pairs if url != ("file:" + f) && url != ("file://" + f)) yield {
         val file = new File(f)
-        cachePolicy(locally(file))(remote(file, url))
-          .map(e => (file, url) -> e.map(_ => ()))
+        cachePolicy[FileError \/ File](
+          _.isLeft )(
+          locally(file) )(
+          _ => remote(file, url)
+        ).map(e => (file, url) -> e.map(_ => ()))
       }
 
     Nondeterminism[Task].gather(tasks)