Filesystem.exists and Filesystem.metadataOrNull

sneha1702 · Dec 27, 2020 · d3f0c32 · d3f0c32
1 parent 8a0a518
commit d3f0c32
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Showing 12 changed files with 102 additions and 27 deletions.
diff --git a/okio-testing/src/commonMain/kotlin/okio/FakeFilesystem.kt b/okio-testing/src/commonMain/kotlin/okio/FakeFilesystem.kt
@@ -79,10 +79,10 @@ class FakeFilesystem(
     return canonicalPath
   }
 
-  override fun metadata(path: Path): FileMetadata {
+  override fun metadataOrNull(path: Path): FileMetadata? {
     val canonicalPath = workingDirectory / path
-    val element = elements[canonicalPath] ?: throw IOException("no such file: $path")
-    return element.metadata
+    val element = elements[canonicalPath]
+    return element?.metadata
   }
 
   override fun list(dir: Path): List<Path> {

diff --git a/okio/src/appleMain/kotlin/okio/posixVariant.kt b/okio/src/appleMain/kotlin/okio/posixVariant.kt
@@ -18,17 +18,19 @@ package okio
 import kotlinx.cinterop.alloc
 import kotlinx.cinterop.memScoped
 import kotlinx.cinterop.ptr
+import platform.posix.ENOENT
 import platform.posix.S_IFDIR
 import platform.posix.S_IFMT
 import platform.posix.S_IFREG
 import platform.posix.errno
 import platform.posix.stat
 
 @ExperimentalFilesystem
-internal actual fun PosixSystemFilesystem.variantMetadata(path: Path): FileMetadata {
+internal actual fun PosixSystemFilesystem.variantMetadataOrNull(path: Path): FileMetadata? {
   return memScoped {
     val stat = alloc<stat>()
     if (platform.posix.lstat(path.toString(), stat.ptr) != 0) {
+      if (errno == ENOENT) return null
       throw IOException(errnoString(errno))
     }
     return@memScoped FileMetadata(

diff --git a/okio/src/commonMain/kotlin/okio/Filesystem.kt b/okio/src/commonMain/kotlin/okio/Filesystem.kt
@@ -31,8 +31,8 @@ package okio
  *
  *  * A remote filesystem could access files over the network.
  *
- *  * A decorating filesystem could apply monitoring, encryption, compression, or filtering to
- *    another filesystem implementation.
+ *  * A [decorating filesystem][ForwardingFilesystem] could apply monitoring, encryption,
+ *    compression, or filtering to another filesystem implementation.
  *
  * For improved capability and testability, consider structuring your classes to dependency inject
  * a `Filesystem` rather than using [SYSTEM] directly.
@@ -106,7 +106,30 @@ abstract class Filesystem {
    * @throws IOException if [path] does not exist or its metadata cannot be read.
    */
   @Throws(IOException::class)
-  abstract fun metadata(path: Path): FileMetadata
+  fun metadata(path: Path): FileMetadata {
+    return metadataOrNull(path) ?: throw IOException("no such file: $path")
+  }
+
+  /**
+   * Returns metadata of the file, directory, or object identified by [path]. This returns null if
+   * there is no file at [path].
+   *
+   * @throws IOException if [path] cannot be accessed due to a connectivity problem, permissions
+   *     problem, or other issue.
+   */
+  @Throws(IOException::class)
+  abstract fun metadataOrNull(path: Path): FileMetadata?
+
+  /**
+   * Returns true if [path] identifies an object on this filesystem.
+   *
+   * @throws IOException if [path] cannot be accessed due to a connectivity problem, permissions
+   *     problem, or other issue.
+   */
+  @Throws(IOException::class)
+  fun exists(path: Path): Boolean {
+    return metadataOrNull(path) != null
+  }
 
   /**
    * Returns the children of the directory identified by [dir].

diff --git a/okio/src/commonMain/kotlin/okio/ForwardingFilesystem.kt b/okio/src/commonMain/kotlin/okio/ForwardingFilesystem.kt
@@ -98,7 +98,8 @@ import kotlin.jvm.JvmName
  * non-abstract functions in the [Filesystem] interface.
  *
  * **This class forwards only the abstract functions;** non-abstract functions delegate to the
- * other functions of this class.
+ * other functions of this class. If desired, subclasses may override non-abstract functions to
+ * forward them.
  */
 @ExperimentalFilesystem
 abstract class ForwardingFilesystem(
@@ -121,7 +122,7 @@ abstract class ForwardingFilesystem(
    * file and once for the target file.
    *
    * @param path the path passed to any of the functions of this.
-   * @param functionName a string like "canonicalize", "metadata", or "appendingSink".
+   * @param functionName a string like "canonicalize", "metadataOrNull", or "appendingSink".
    * @param parameterName a string like "path", "file", "source", or "target".
    * @return the path to pass to [delegate] for the same parameter.
    */
@@ -150,9 +151,9 @@ abstract class ForwardingFilesystem(
   }
 
   @Throws(IOException::class)
-  override fun metadata(path: Path): FileMetadata {
-    val path = onPathParameter(path, "metadata", "path")
-    return delegate.metadata(path)
+  override fun metadataOrNull(path: Path): FileMetadata? {
+    val path = onPathParameter(path, "metadataOrNull", "path")
+    return delegate.metadataOrNull(path)
   }
 
   @Throws(IOException::class)

diff --git a/okio/src/commonTest/kotlin/okio/AbstractFilesystemTest.kt b/okio/src/commonTest/kotlin/okio/AbstractFilesystemTest.kt
@@ -21,10 +21,12 @@ import okio.ByteString.Companion.toByteString
 import okio.Path.Companion.toPath
 import kotlin.random.Random
 import kotlin.test.BeforeTest
+import kotlin.test.Ignore
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
 import kotlin.test.assertFalse
+import kotlin.test.assertNull
 import kotlin.test.assertTrue
 import kotlin.time.ExperimentalTime
 import kotlin.time.seconds
@@ -432,6 +434,19 @@ abstract class AbstractFilesystemTest(
     assertInRange(metadata.lastAccessedAt, minTime, maxTime)
   }
 
+  @Test
+  fun absentMetadataOrNull() {
+    val path = base / "no-such-file"
+    assertNull(filesystem.metadataOrNull(path))
+  }
+
+  @Test
+  @Ignore
+  fun inaccessibleMetadata() {
+    // TODO(swankjesse): configure a test directory in CI that exists, but that this process doesn't
+    //     have permission to read metadata of. Perhaps a file in another user's /home directory?
+  }
+
   @Test
   fun absentMetadata() {
     val path = base / "no-such-file"
@@ -440,6 +455,22 @@ abstract class AbstractFilesystemTest(
     }
   }
 
+  @Test
+  fun fileExists() {
+    val path = base / "file-exists"
+    assertFalse(filesystem.exists(path))
+    path.writeUtf8("hello, world!")
+    assertTrue(filesystem.exists(path))
+  }
+
+  @Test
+  fun directoryExists() {
+    val path = base / "directory-exists"
+    assertFalse(filesystem.exists(path))
+    filesystem.createDirectory(path)
+    assertTrue(filesystem.exists(path))
+  }
+
   @Test
   fun deleteOpenForWritingFailsOnWindows() {
     val file = base / "file.txt"

diff --git a/okio/src/jsMain/kotlin/okio/NodeJsSystemFilesystem.kt b/okio/src/jsMain/kotlin/okio/NodeJsSystemFilesystem.kt
@@ -46,10 +46,11 @@ internal object NodeJsSystemFilesystem : Filesystem() {
     }
   }
 
-  override fun metadata(path: Path): FileMetadata {
+  override fun metadataOrNull(path: Path): FileMetadata? {
     val stat = try {
       statSync(path.toString())
     } catch (e: Throwable) {
+      if (e.errorCode == "ENOENT") return null // "No such file or directory".
       throw IOException(e.message)
     }
     return FileMetadata(
@@ -62,6 +63,16 @@ internal object NodeJsSystemFilesystem : Filesystem() {
     )
   }
 
+  /**
+   * Returns the error code on this `SystemError`. This uses `asDynamic()` because our JS bindings
+   * don't (yet) include the `SystemError` type.
+   *
+   * https://nodejs.org/dist/latest-v14.x/docs/api/errors.html#errors_class_systemerror
+   * https://nodejs.org/dist/latest-v14.x/docs/api/errors.html#errors_common_system_errors
+   */
+  private val Throwable.errorCode
+    get() = asDynamic().code
+
   override fun list(dir: Path): List<Path> {
     try {
       val opendir = opendirSync(dir.toString())

diff --git a/okio/src/jvmMain/kotlin/okio/JvmSystemFilesystem.kt b/okio/src/jvmMain/kotlin/okio/JvmSystemFilesystem.kt
@@ -29,7 +29,7 @@ internal open class JvmSystemFilesystem : Filesystem() {
     return canonicalFile.toOkioPath()
   }
 
-  override fun metadata(path: Path): FileMetadata {
+  override fun metadataOrNull(path: Path): FileMetadata? {
     val file = path.toFile()
     val isRegularFile = file.isFile
     val isDirectory = file.isDirectory
@@ -42,7 +42,7 @@ internal open class JvmSystemFilesystem : Filesystem() {
       size == 0L &&
       !file.exists()
     ) {
-      throw IOException("no such file")
+      return null
     }
 
     return FileMetadata(

diff --git a/okio/src/jvmMain/kotlin/okio/NioSystemFilesystem.kt b/okio/src/jvmMain/kotlin/okio/NioSystemFilesystem.kt
@@ -18,6 +18,7 @@ package okio
 import org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement
 import java.nio.file.Files
 import java.nio.file.LinkOption
+import java.nio.file.NoSuchFileException
 import java.nio.file.StandardCopyOption.ATOMIC_MOVE
 import java.nio.file.StandardCopyOption.REPLACE_EXISTING
 import java.nio.file.attribute.BasicFileAttributes
@@ -30,14 +31,18 @@ import java.nio.file.attribute.FileTime
 @ExperimentalFilesystem
 @IgnoreJRERequirement // Only used on platforms that support java.nio.file.
 internal class NioSystemFilesystem : JvmSystemFilesystem() {
-  override fun metadata(path: Path): FileMetadata {
+  override fun metadataOrNull(path: Path): FileMetadata? {
     val nioPath = path.toNioPath()
 
-    val attributes = Files.readAttributes(
-      nioPath,
-      BasicFileAttributes::class.java,
-      LinkOption.NOFOLLOW_LINKS
-    )
+    val attributes = try {
+      Files.readAttributes(
+        nioPath,
+        BasicFileAttributes::class.java,
+        LinkOption.NOFOLLOW_LINKS
+      )
+    } catch (_: NoSuchFileException) {
+      return null
+    }
 
     return FileMetadata(
       isRegularFile = attributes.isRegularFile,
@@ -53,7 +58,6 @@ internal class NioSystemFilesystem : JvmSystemFilesystem() {
    * Returns this time as a epoch millis. If this is 0L this returns null, because epoch time 0L is
    * a special value that indicates the requested time was not available.
    */
-  @IgnoreJRERequirement
   private fun FileTime.zeroToNull(): Long? {
     return toMillis().takeIf { it != 0L }
   }

diff --git a/okio/src/linuxX64Main/kotlin/okio/posixVariant.kt b/okio/src/linuxX64Main/kotlin/okio/posixVariant.kt
@@ -18,17 +18,19 @@ package okio
 import kotlinx.cinterop.alloc
 import kotlinx.cinterop.memScoped
 import kotlinx.cinterop.ptr
+import platform.posix.ENOENT
 import platform.posix.S_IFDIR
 import platform.posix.S_IFMT
 import platform.posix.S_IFREG
 import platform.posix.errno
 import platform.posix.stat
 
 @ExperimentalFilesystem
-internal actual fun PosixSystemFilesystem.variantMetadata(path: Path): FileMetadata {
+internal actual fun PosixSystemFilesystem.variantMetadataOrNull(path: Path): FileMetadata? {
   return memScoped {
     val stat = alloc<stat>()
     if (platform.posix.lstat(path.toString(), stat.ptr) != 0) {
+      if (errno == ENOENT) return null
       throw IOException(errnoString(errno))
     }
     return@memScoped FileMetadata(

diff --git a/okio/src/mingwX64Main/kotlin/okio/posixVariant.kt b/okio/src/mingwX64Main/kotlin/okio/posixVariant.kt
@@ -71,10 +71,11 @@ internal actual fun PosixSystemFilesystem.variantCanonicalize(path: Path): Path
 }
 
 @ExperimentalFilesystem
-internal actual fun PosixSystemFilesystem.variantMetadata(path: Path): FileMetadata {
+internal actual fun PosixSystemFilesystem.variantMetadataOrNull(path: Path): FileMetadata? {
   return memScoped {
     val stat = alloc<_stat64>()
     if (_stat64(path.toString(), stat.ptr) != 0) {
+      if (errno == ENOENT) return null
       throw IOException(errnoString(errno))
     }
     return@memScoped FileMetadata(

diff --git a/okio/src/nativeMain/kotlin/okio/PosixSystemFilesystem.kt b/okio/src/nativeMain/kotlin/okio/PosixSystemFilesystem.kt
@@ -35,8 +35,8 @@ internal object PosixSystemFilesystem : Filesystem() {
 
   override fun canonicalize(path: Path) = variantCanonicalize(path)
 
-  override fun metadata(path: Path): FileMetadata {
-    return variantMetadata(path)
+  override fun metadataOrNull(path: Path): FileMetadata? {
+    return variantMetadataOrNull(path)
   }
 
   override fun list(dir: Path): List<Path> {

diff --git a/okio/src/nativeMain/kotlin/okio/posixVariant.kt b/okio/src/nativeMain/kotlin/okio/posixVariant.kt
@@ -27,7 +27,7 @@ internal expect fun PosixSystemFilesystem.variantMkdir(dir: Path): Int
 internal expect fun PosixSystemFilesystem.variantCanonicalize(path: Path): Path
 
 @ExperimentalFilesystem
-internal expect fun PosixSystemFilesystem.variantMetadata(path: Path): FileMetadata
+internal expect fun PosixSystemFilesystem.variantMetadataOrNull(path: Path): FileMetadata?
 
 @ExperimentalFilesystem
 internal expect fun PosixSystemFilesystem.variantMove(source: Path, target: Path)