Apply java.nio.file.Files.createDirectories for Android SDK 26 or later to surface more error info

gradle/dependencies.gradle

@@ -52,11 +52,12 @@ def androidx = [
 ]
 
 def test = [
+        concurrentunit      : 'net.jodah:concurrentunit:0.4.6',
         junit      : 'junit:junit:4.13.1',
         junitX     : 'androidx.test.ext:junit:1.0.0',
         truth      : 'com.google.truth:truth:1.1',
         truthX   : 'androidx.test.ext:truth:1.5.0',
-        robolectric: 'org.robolectric:robolectric:4.4',
+        robolectric: 'org.robolectric:robolectric:4.5.1',
         espresso   : 'androidx.test.espresso:espresso-core:3.5.1',
         runner     : 'androidx.test:runner:1.5.2',
         rules      : 'androidx.test:rules:1.5.0',

simplestore/build.gradle

@@ -23,6 +23,9 @@ android {
 
     testOptions {
         execution 'ANDROIDX_TEST_ORCHESTRATOR'
+        unitTests {
+            includeAndroidResources = true
+        }
     }
 
     defaultConfig {
@@ -45,6 +48,7 @@ dependencies {
     testImplementation deps.test.junitX
     testImplementation deps.test.truth
     testImplementation deps.test.truthX
+    testImplementation deps.test.concurrentunit
     testImplementation deps.test.robolectric
 
     androidTestImplementation deps.test.runner

simplestore/src/main/java/com/uber/simplestore/impl/AtomicFile.java

@@ -21,6 +21,9 @@
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
 import org.jetbrains.annotations.Nullable;
 
 /*
@@ -93,10 +96,7 @@ public FileOutputStream startWrite() throws IOException {
     try {
       return new FileOutputStream(mNewName);
     } catch (FileNotFoundException e) {
-      File parent = mNewName.getParentFile();
-      if (!parent.mkdirs()) {
-        throw new IOException("Failed to create directory for " + mNewName);
-      }
+      resolveParentFolder(e);
       try {
         return new FileOutputStream(mNewName);
       } catch (FileNotFoundException e2) {
@@ -105,6 +105,22 @@ public FileOutputStream startWrite() throws IOException {
     }
   }
 
+  private void resolveParentFolder(FileNotFoundException rawError) throws IOException {
+    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
+      Path parentPath = mNewName.toPath().getParent();
+      if (parentPath != null && !Files.exists(parentPath)) {
+        Files.createDirectories(parentPath);
+      } else {
+        throw rawError;
+      }
+    } else {
+      File parent = mNewName.getParentFile();
+      if (!parent.mkdirs()) {
+        throw rawError;
+      }
+    }
+  }
+
   /**
    * Call when you have successfully finished writing to the stream returned by {@link
    * #startWrite()}. This will close, sync, and commit the new data. The next attempt to read the

simplestore/src/test/java/com/uber/simplestore/impl/AtomicFileConcurrentTest.kt

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2019. Uber Technologies
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.uber.simplestore.impl
+
+import android.app.Application
+import androidx.test.core.app.ApplicationProvider
+import com.google.common.truth.Truth.assertThat
+import com.uber.simplestore.impl.ConcurrentTestUtil.executeConcurrent
+import org.junit.Ignore
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import java.io.File
+import java.io.FileNotFoundException
+
+
+@RunWith(RobolectricTestRunner::class)
+class AtomicFileConcurrentTest {
+
+    @Test(expected = FileNotFoundException::class)
+    fun `case 0 when parent folder is absent will trigger FileNotFoundException`() {
+        //arrange
+        //makeParentFolder()
+        val targetFile = createTargetFile()
+        //act
+        val target = targetFile.outputStream()
+        //assert
+        assertThat(target).isNotNull()
+    }
+
+    @Test
+    fun `case 1 when parent folder is present will not trigger FileNotFoundException`() {
+        //arrange
+        makeParentFolder()
+        val targetFile = createTargetFile()
+        //act
+        val target = targetFile.outputStream()
+        //assert
+        assertThat(target).isNotNull()
+    }
+
+
+    /**
+     * This represents a typical file that stores a value for a random key.
+     */
+    private fun createTargetFile(): File {
+        return File(app().dataDir, "files/simplestore/657b3cd7-f689-451b-aca0-628de60aa234/random_key")
+    }
+
+    /**
+     * This presents a typical simple store folder scoped with under an `uuid`.
+     */
+    private fun makeParentFolder() {
+        val parent = File(app().dataDir, "files/simplestore/657b3cd7-f689-451b-aca0-628de60aa234")
+        parent.mkdirs()
+    }
+
+    private fun app(): Application {
+        return ApplicationProvider.getApplicationContext()
+    }
+}

simplestore/src/test/java/com/uber/simplestore/impl/ConcurrentTestUtil.kt

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2019. Uber Technologies
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.uber.simplestore.impl
+
+import net.jodah.concurrentunit.Waiter
+import java.util.concurrent.Executors
+
+
+/**
+ * A utility class to execute a given action concurrently.
+ * It will trigger [Waiter.fail] if the action throws an exception during the whole concurrent execution process.
+ * It will trigger [Waiter.resume] if the action is concluded successfully for the whole concurrent execution.
+ */
+object ConcurrentTestUtil {
+    /**
+     * The maximum number of threads to be executed concurrently.
+     */
+    private const val MAX_THREAD = 5
+
+
+    /**
+     * Executes the given action concurrently.
+     * It will trigger [Waiter.fail] if the action throws an exception during the whole concurrent execution process.
+     * It will trigger [Waiter.resume] if the action is concluded successfully for the whole concurrent execution.
+     */
+    fun executeConcurrent(action: () -> Unit) {
+        val waiter = Waiter()
+        for (i in 0 until 1000) {
+            val service = Executors.newFixedThreadPool(MAX_THREAD)
+            for (j in 0 until 10) {
+                service.submit {
+                    executeConcurrentInternally(action, waiter)
+                }
+            }
+        }
+        waiter.await(1000L * MAX_THREAD)
+    }
+
+    private fun executeConcurrentInternally(action: () -> Unit, waiter: Waiter) {
+        try {
+            run(action)
+        } catch (e: Exception) {
+            waiter.fail(e)
+        } finally {
+            waiter.resume()
+        }
+    }
+
+
+}