From 14c9137a337893d63b589b3a8174868fa5183a57 Mon Sep 17 00:00:00 2001
From: Sam Judd <judds@google.com>
Date: Sun, 26 Nov 2017 19:15:22 -0800
Subject: [PATCH] Avoid IOExceptions in delete() when the cache dir is deleted
 externally.
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listFiles() will return null if the directory has been deleted. This
scenario isn’t totally far fetched because it’s fairly common for
Android developers to place their disk caches in the Android application
cache directory. The cache directory can be cleared at any time by the
system, including while the app is open, which in turn can cause
unexpected IOExceptions when delete() is called.

See https://github.com/bumptech/glide/issues/2465 for additional
context.
---
 .../com/jakewharton/disklrucache/Util.java    |  3 ++
 .../disklrucache/DiskLruCacheTest.java        | 37 +++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/src/main/java/com/jakewharton/disklrucache/Util.java b/src/main/java/com/jakewharton/disklrucache/Util.java
index 0a7dba9..cc61711 100644
--- a/src/main/java/com/jakewharton/disklrucache/Util.java
+++ b/src/main/java/com/jakewharton/disklrucache/Util.java
@@ -50,6 +50,9 @@ static String readFully(Reader reader) throws IOException {
    * could not be deleted, or if {@code dir} is not a readable directory.
    */
   static void deleteContents(File dir) throws IOException {
+    if (!dir.exists()) {
+      return;
+    }
     File[] files = dir.listFiles();
     if (files == null) {
       throw new IOException("not a readable directory: " + dir);
diff --git a/src/test/java/com/jakewharton/disklrucache/DiskLruCacheTest.java b/src/test/java/com/jakewharton/disklrucache/DiskLruCacheTest.java
index 6735179..553a434 100644
--- a/src/test/java/com/jakewharton/disklrucache/DiskLruCacheTest.java
+++ b/src/test/java/com/jakewharton/disklrucache/DiskLruCacheTest.java
@@ -21,6 +21,7 @@
 import java.io.FileReader;
 import java.io.FileWriter;
 import java.io.InputStream;
+import java.io.IOException;
 import java.io.Reader;
 import java.io.StringWriter;
 import java.io.Writer;
@@ -885,6 +886,42 @@ public final class DiskLruCacheTest {
     assertThat(cache.get("a")).isNull();
   }
 
+  @Test public void deleteAfterCacheDirectoryIsDeletedExternallyDoesNotThrow()
+      throws IOException {
+    FileUtils.deleteDirectory(cacheDir);
+    cache.delete();
+  }
+
+  @Test public void deleteWithNotReadableCacheDirectoryThowsIOException()
+      throws IOException {
+    try {
+      if (!cacheDir.setReadable(false)) {
+        fail("Unable to set writable on: " + cacheDir);
+      }
+      cache.delete();
+      fail("Expected delete to throw");
+    } catch (IOException e) {
+      // Expected.
+    } finally {
+       cacheDir.setReadable(true);
+    }
+  }
+
+  @Test public void deleteWithNotWritableCacheDirectoryThowsIOException()
+      throws IOException {
+    try {
+      if (!cacheDir.setWritable(false)) {
+        fail("Unable to set writable on: " + cacheDir);
+      }
+      cache.delete();
+      fail("Expected delete to throw");
+    } catch (IOException e) {
+      // Expected.
+    } finally {
+       cacheDir.setWritable(true);
+    }
+  }
+
   private void assertJournalEquals(String... expectedBodyLines) throws Exception {
     List<String> expectedLines = new ArrayList<String>();
     expectedLines.add(MAGIC);