feat: introduce FileSystem.unjarOnce

`specs2-html` currently copies all of its html resources (41 files) for each specification (executed with html output), reading and traversing the `specs2-html.jar` four times in the process, overwriting its own previously copied files over and over. This is inefficient and causes unnecessary strain on the disk usage. The newly introduced `unjarOnce` method is used by `specs2-html` to only unjar its resources once for each target location and filter criteria.

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
  strategy:
  matrix:
  os: [ubuntu-latest]
- scala: [3.4.2]
+ scala: [3.3.3]
  java: [temurin@18]
  runs-on: ${{ matrix.os }}
  steps:
@@ -56,7 +56,7 @@ jobs:
  strategy:
  matrix:
  os: [ubuntu-latest]
- scala: [3.4.2]
+ scala: [3.3.3]
  java: [temurin@18]
  runs-on: ${{ matrix.os }}
  steps:

common/shared/src/main/scala/org/specs2/io/FileSystem.scala

@@ -58,6 +58,40 @@ case class FileSystem(logger: Logger) extends FilePathReader:
  def mkdirs(path: FilePath): Operation[Unit] =
  mkdirs(path.dir)
 
+ /** Unjaring the same thing over and over is inefficient. LRU cache to keep track of what was already done. */
+ private object UnjarLRUCache:
+ private var unjarLRUCache: Map[(URL, DirectoryPath, String), Long] = Map.empty
+ private val maxSize = 1000
+
+ /** Checks if the given parameters were already processed; if not immediately adds them to the cache. */
+ def alreadyUnjared(params: (URL, DirectoryPath, String)): Boolean =
+ UnjarLRUCache.synchronized:
+ val alreadyUnjared = unjarLRUCache.contains(params)
+ unjarLRUCache += params -> System.nanoTime
+ if !alreadyUnjared then clean()
+ alreadyUnjared
+
+ /** Clean up LRU entries until cache is at most max size. */
+ private def clean(): Unit = while unjarLRUCache.size > maxSize do unjarLRUCache -= unjarLRUCache.minBy(_._2)._1
+
+ /** Unjar the jar (or zip file) specified by "path" to the "dest" directory. Filters files which shouldn't be
+ * extracted with a regular expression. This is only done once per argument list (unless eventually evicted from LRU
+ * cache).
+ * @param jarUrl
+ * path of the jar file
+ * @param dest
+ * destination directory path
+ * @param regexFilter
+ * regular expression filtering files which shouldn't be extracted; the expression must capture the path of an
+ * entry as group 1 which will then be used relative to dirPath as target path for that entry
+ *
+ * @see
+ * [[unjar]]
+ */
+ def unjarOnce(jarUrl: URL, dest: DirectoryPath, regexFilter: String): Operation[Unit] =
+ if UnjarLRUCache.alreadyUnjared((jarUrl, dest, regexFilter)) then Operation.ok(())
+ else unjar(jarUrl, dest, regexFilter)
+
  /** Unjar the jar (or zip file) specified by "path" to the "dest" directory. Filters files which shouldn't be
  * extracted with a regular expression.
  * @param jarUrl
@@ -67,6 +101,9 @@ case class FileSystem(logger: Logger) extends FilePathReader:
  * @param regexFilter
  * regular expression filtering files which shouldn't be extracted; the expression must capture the path of an
  * entry as group 1 which will then be used relative to dirPath as target path for that entry
+ *
+ * @see
+ * [[unjarOnce]]
  */
  def unjar(jarUrl: URL, dest: DirectoryPath, regexFilter: String): Operation[Unit] =
  val regex = compile(regexFilter)

html/src/main/scala/org/specs2/reporter/HtmlPrinter.scala

@@ -187,7 +187,7 @@ case class HtmlPrinter(env: Env, searchPage: SearchPage, logger: Logger = Consol
  case Some(url) =>
  val fs = env.fileSystem
  if url.getProtocol.equalsIgnoreCase("jar") then
- fs.unjar(jarOf(url), outputDir, s"^${quote(base.path)}(/${quote(src.path)}/.*)$$")
+ fs.unjarOnce(jarOf(url), outputDir, s"^${quote(base.path)}(/${quote(src.path)}/.*)$$")
  else fs.copyDir(DirectoryPath.unsafe(url.toURI), outputDir / src)
  case _ =>
  val message = s"no resource found for path ${(base / src).path}"