File.usingTemp util

pathikrit · Feb 2, 2017 · d3522e8 · d3522e8
1 parent 6f95055
commit d3522e8
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diff --git a/CHANGES.md b/CHANGES.md
@@ -1,5 +1,6 @@
 ## v3.0.0
 
+* [File.usingTemp]()
 * [Optional symbolic operations](https://github.com/pathikrit/better-files/issues/102)
 * [PR #100](https://github.com/pathikrit/better-files/pull/100): Fix issue in unzip of parents
 * [PR #101](https://github.com/pathikrit/better-files/pull/101): Removed File.Type

diff --git a/README.md b/README.md
@@ -19,6 +19,7 @@
   0. [Java compatibility](#java-interoperability)
   0. [Globbing](#globbing)
   0. [File system operations](#file-system-operations)
+  0. [Temporary files](#temporary-files)
   0. [UNIX DSL](#unix-dsl)
   0. [File attributes](#file-attributes)
   0. [File comparison](#file-comparison)
@@ -270,10 +271,29 @@ file.setGroup(group: String)     // chgrp group file
 Seq(file1, file2) `>:` file3     // same as cat file1 file2 > file3 (must import import better.files.Dsl.SymbolicOperations)
 Seq(file1, file2) >>: file3      // same as cat file1 file2 >> file3 (must import import better.files.Dsl.SymbolicOperations)
 file.isReadLocked; file.isWriteLocked; file.isLocked
-File.newTemporaryDirectory() / File.newTemporaryFile() // create temp dir/file
 File.numberOfOpenFileDescriptors        // number of open file descriptors
 ```
 
+### Temporary files
+Utils to create temporary files:
+```scala
+File.newTemporaryDirectory() 
+File.newTemporaryFile()
+```
+The above APIs allow optional specifications of `prefix`, `suffix` and `parentDir`. 
+These files are [not deleted automatically on exit by the JVM](http://stackoverflow.com/questions/16691437/when-are-java-temporary-files-deleted) (you have to set `deleteOnExit` which adds to `shutdownHook`).
+
+A cleaner alternative is to use self-deleting file contexts which deletes the file immediately when done:
+```scala
+File.usingTempFile() {tempFile =>
+  ...
+}
+
+// or equivalently:
+
+File.newTempFile().applyAndDelete(tempFile =>  ...)
+```
+
 ### UNIX DSL
 All the above can also be expressed using [methods](http://pathikrit.github.io/better-files/latest/api/better/files/Dsl$.html) reminiscent of the command line:
 ```scala

diff --git a/core/src/main/scala/better/files/File.scala b/core/src/main/scala/better/files/File.scala
@@ -759,6 +759,11 @@ class File private(val path: Path) {
     this
   }
 
+  def deleteOnExit(): this.type = {
+    toJava.deleteOnExit()
+    this
+  }
+
   override def hashCode =
     path.hashCode()
 
@@ -828,6 +833,20 @@ class File private(val path: Path) {
   def unzip(zipFilter: ZipEntry => Boolean = _ => true)(implicit codec: Codec): File =
     unzipTo(destination = File.newTemporaryDirectory(name), zipFilter)(codec)
 
+  /**
+    * Applies the given function on this and then deletes this file
+    *
+    * @param f
+    * @tparam U
+    * @return
+    */
+  def applyAndDelete[U](f: File => U): U =
+    try {
+      f(this)
+    } finally {
+      val _ = delete(swallowIOExceptions = true)
+    }
+
   //TODO: add features from https://github.com/sbt/io
 }
 
@@ -839,13 +858,19 @@ object File {
     }
   }
 
+  def usingTemporaryDirectory[U](prefix: String = "", parent: Option[File] = None, attributes: Attributes = Attributes.default)(f: File => U): U =
+    newTemporaryDirectory(prefix, parent)(attributes).applyAndDelete(f)
+
   def newTemporaryFile(prefix: String = "", suffix: String = "", parent: Option[File] = None)(implicit attributes: Attributes = Attributes.default): File = {
     parent match {
       case Some(dir) => Files.createTempFile(dir.path, prefix, suffix, attributes: _*)
       case _ => Files.createTempFile(prefix, suffix, attributes: _*)
     }
   }
 
+  def usingTemporaryFile[U](prefix: String = "", suffix: String = "", parent: Option[File] = None, attributes: Attributes = Attributes.default)(f: File => U): U =
+    newTemporaryFile(prefix, suffix, parent)(attributes).applyAndDelete(f)
+
   implicit def apply(path: Path): File =
     new File(path.toAbsolutePath.normalize())
 

diff --git a/core/src/test/scala/better/files/FileSpec.scala b/core/src/test/scala/better/files/FileSpec.scala
@@ -233,16 +233,17 @@ class FileSpec extends FlatSpec with BeforeAndAfterEach with Matchers {
   }
 
   it should "detect file locks" in {
-    val file = File.newTemporaryFile()
-    def lockInfo() = file.isReadLocked() -> file.isWriteLocked()
-    // TODO: Why is file.isReadLocked() should be false?
-    lockInfo() shouldBe (true -> false)
-    val channel = file.newRandomAccess(File.RandomAccessMode.readWrite).getChannel
-    val lock = channel.tryLock()
-    lockInfo() shouldBe (true -> true)
-    lock.release()
-    channel.close()
-    lockInfo() shouldBe (true -> false)
+    File.usingTemporaryFile() {file =>
+      def lockInfo() = file.isReadLocked() -> file.isWriteLocked()
+      // TODO: Why is file.isReadLocked() should be false?
+      lockInfo() shouldBe (true -> false)
+      val channel = file.newRandomAccess(File.RandomAccessMode.readWrite).getChannel
+      val lock = channel.tryLock()
+      lockInfo() shouldBe (true -> true)
+      lock.release()
+      channel.close()
+      lockInfo() shouldBe (true -> false)
+    }
   }
 
   it should "support ln/cp/mv" in {