Make creating DataStore files more resilient (#7440)

Prepare the DataStore files directly in the Sessions SDK, instead of
relying on DataStore to do it.

DataStore uses the old `File.mkdirs` api, which lacks any meaningful
error messages. This will use the better `Files.createDirectories` api
if available, which has proper error messages.

Also renamed the parent directory from `aqs` to `firebaseSessions` to
avoid any collision with any other libraries that might use DataStore
and a 3 letter file name. If there is an unexpected file where the
`firebaseSessions` directory should be, this will safely remove it.

Tested manually by creating the conflicting file and running the
Sessions Test App on both old and new api levels.

Author: mrober

firebase-crashlytics/CHANGELOG.md

@@ -1,5 +1,7 @@
 # Unreleased
 
+- [fixed] Made creating DataStore files more resilient [#7440]
+
 # 20.0.2
 
 - [changed] Bumped internal dependencies.

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/FirebaseSessionsComponent.kt

@@ -17,6 +17,7 @@
 package com.google.firebase.sessions
 
 import android.content.Context
+import android.os.Build
 import android.util.Log
 import androidx.datastore.core.DataMigration
 import androidx.datastore.core.DataStore
@@ -48,6 +49,8 @@ import dagger.Component
 import dagger.Module
 import dagger.Provides
 import java.io.File
+import java.io.IOException
+import java.nio.file.Files
 import javax.inject.Qualifier
 import javax.inject.Singleton
 import kotlin.coroutines.CoroutineContext
@@ -146,7 +149,11 @@ internal interface FirebaseSessionsComponent {
               SessionConfigsSerializer.defaultValue
             },
           scope = CoroutineScope(blockingDispatcher),
-          produceFile = { appContext.dataStoreFile("aqs/sessionConfigsDataStore.data") },
+          produceFile = {
+            appContext.dataStoreFile("firebaseSessions/sessionConfigsDataStore.data").also {
+              prepDataStoreFile(it)
+            }
+          },
         )
 
       @Provides
@@ -164,7 +171,11 @@ internal interface FirebaseSessionsComponent {
               sessionDataSerializer.defaultValue
             },
           scope = CoroutineScope(blockingDispatcher),
-          produceFile = { appContext.dataStoreFile("aqs/sessionDataStore.data") },
+          produceFile = {
+            appContext.dataStoreFile("firebaseSessions/sessionDataStore.data").also {
+              prepDataStoreFile(it)
+            }
+          },
         )
 
       private fun <T> createDataStore(
@@ -197,6 +208,43 @@ internal interface FirebaseSessionsComponent {
         } catch (_: SecurityException) {
           false
         }
+
+      /**
+       * Prepares the DataStore file by ensuring its parent directory exists. Throws [IOException]
+       * if the directory could not be created, or if a conflicting file could not be removed.
+       */
+      private fun prepDataStoreFile(dataStoreFile: File) {
+        val parentDir = dataStoreFile.parentFile ?: return
+
+        // Check if something exists at the path, but isn't a directory
+        if (parentDir.exists() && !parentDir.isDirectory) {
+          // Only delete it if it's the specific file we know we can safely remove
+          if (parentDir.name == "firebaseSessions") {
+            if (!parentDir.delete()) {
+              throw IOException("Failed to delete conflicting file: $parentDir")
+            }
+          }
+        }
+
+        if (parentDir.isDirectory) {
+          return
+        }
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+          try {
+            Files.createDirectories(parentDir.toPath())
+          } catch (ex: Exception) {
+            throw IOException("Failed to create directory: $parentDir", ex)
+          }
+        } else {
+          if (!parentDir.mkdirs()) {
+            // It's possible another thread created it in the meantime, so we double-check
+            if (!parentDir.isDirectory) {
+              throw IOException("Failed to create directory: $parentDir")
+            }
+          }
+        }
+      }
     }
   }
 }