refactor: prep for making MANAGE_EXTERNAL_STORAGE optional

AnkiDroid/src/main/java/com/ichi2/anki/InitialActivity.kt

@@ -243,8 +243,15 @@ internal fun selectStoragePermissions(
 }
 
 fun selectStoragePermissions(context: Context): PermissionSet {
+    // `false`: the collection is app-private, so it can be accessed without storage permissions
+    // `null`: no collection path is set
+    val currentFolderIsLegacy = isLegacyStorage(context, setCollectionPath = false)
+    if (currentFolderIsLegacy == false) {
+        return PermissionSet.APP_PRIVATE
+    }
+
     val canAccessLegacyStorage = Build.VERSION.SDK_INT < Build.VERSION_CODES.Q || Environment.isExternalStorageLegacy()
-    val currentFolderIsAccessibleAndLegacy = canAccessLegacyStorage && isLegacyStorage(context, setCollectionPath = false) == true
+    val currentFolderIsAccessibleAndLegacy = canAccessLegacyStorage && currentFolderIsLegacy == true
 
     return selectStoragePermissions(
         canManageExternalStorage = Permissions.canManageExternalStorage(context),

AnkiDroid/src/main/java/com/ichi2/anki/startup/SetupStorage.kt

@@ -107,6 +107,8 @@ fun ensureCollectionPathSet(context: Context) {
  * @param directoryName  The leaf folder name to use at the end of the returned path.
  *                       Defaults to `"AnkiDroid"` (the historical default-profile folder name).
  *                       Callers wanting a profile-specific layout can pass e.g. the profile id.
+ * @param folder  The storage location to return the default directory for.
+ *                Defaults to [selectAnkiDroidFolder].
  * @return Absolute Path to the default location starting location for the AnkiDroid directory
  *
  * @throws SystemStorageException if `getExternalFilesDir` returns null
@@ -116,14 +118,12 @@ fun ensureCollectionPathSet(context: Context) {
 fun getDefaultAnkiDroidDirectory(
     context: Context,
     directoryName: String = "AnkiDroid",
-): File {
-    val legacyStorage = selectAnkiDroidFolder(context) != AnkiDroidFolder.APP_PRIVATE
-    return if (legacyStorage) {
-        legacyAnkiDroidDirectory(directoryName)
-    } else {
-        File(getAppSpecificExternalAnkiDroidDirectory(context), directoryName)
+    folder: AnkiDroidFolder = selectAnkiDroidFolder(context),
+): File =
+    when (folder) {
+        AnkiDroidFolder.PUBLIC -> legacyAnkiDroidDirectory(directoryName)
+        AnkiDroidFolder.APP_PRIVATE -> File(getAppSpecificExternalAnkiDroidDirectory(context), directoryName)
     }
-}
 
 /**
  * Returns the absolute path to the AnkiDroid directory under the primary/shared external storage directory.

AnkiDroid/src/test/java/com/ichi2/anki/SelectStoragePermissionsTest.kt

@@ -3,16 +3,26 @@
 package com.ichi2.anki
 
 import android.annotation.SuppressLint
+import android.content.Context
 import android.os.Build
+import androidx.core.content.edit
+import androidx.test.core.app.ApplicationProvider
 import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.ichi2.anki.common.preferences.sharedPrefs
+import com.ichi2.anki.common.storage.CollectionHelper
 import com.ichi2.testutils.EmptyApplication
+import com.ichi2.utils.Permissions
+import io.mockk.every
+import io.mockk.mockkObject
+import io.mockk.unmockkObject
 import org.hamcrest.CoreMatchers.equalTo
 import org.hamcrest.MatcherAssert.assertThat
 import org.hamcrest.Matchers.contains
 import org.junit.Test
 import org.junit.experimental.categories.Category
 import org.junit.runner.RunWith
 import org.robolectric.annotation.Config
+import java.io.File
 import kotlin.test.assertTrue
 
 /**
@@ -95,6 +105,53 @@ class SelectStoragePermissionsTest {
         )
     }
 
+    @SuppressLint("NewApi") // EXTERNAL_MANAGER requires R, guaranteed by @Config
+    @Config(sdk = [R_OR_AFTER])
+    @Test // #13574: no collection path is set: permissions are based on device capabilities
+    fun `full build - screen is required while no collection path is set`() {
+        context.sharedPrefs().edit { remove(CollectionHelper.PREF_COLLECTION_PATH) }
+        withManageExternalStorageInManifest {
+            assertThat(selectStoragePermissions(context), equalTo(PermissionSet.EXTERNAL_MANAGER))
+        }
+    }
+
+    @SuppressLint("NewApi") // EXTERNAL_MANAGER requires R, guaranteed by @Config
+    @Config(sdk = [R_OR_AFTER])
+    @Test // #13574: public storage which the app cannot access: the screen is required
+    fun `full build - screen is required when access to public storage was revoked`() {
+        context.sharedPrefs().edit {
+            putString(CollectionHelper.PREF_COLLECTION_PATH, "/storage/emulated/0/AnkiDroid")
+        }
+        withManageExternalStorageInManifest {
+            assertThat(selectStoragePermissions(context), equalTo(PermissionSet.EXTERNAL_MANAGER))
+        }
+    }
+
+    @Config(sdk = [R_OR_AFTER])
+    @Test // #13574: app-private storage can be accessed without storage permissions
+    fun `app-private collection path requires no storage permissions`() {
+        context.sharedPrefs().edit {
+            putString(CollectionHelper.PREF_COLLECTION_PATH, File(context.filesDir, "AnkiDroid").path)
+        }
+        withManageExternalStorageInManifest {
+            assertThat(selectStoragePermissions(context), equalTo(PermissionSet.APP_PRIVATE))
+        }
+    }
+
+    private val context: Context
+        get() = ApplicationProvider.getApplicationContext()
+
+    /** a 'full' build: `MANAGE_EXTERNAL_STORAGE` is declared in the manifest */
+    private fun withManageExternalStorageInManifest(block: () -> Unit) {
+        mockkObject(Permissions)
+        every { Permissions.canManageExternalStorage(any()) } returns true
+        try {
+            block()
+        } finally {
+            unmockkObject(Permissions)
+        }
+    }
+
     /**
      * Helper for [com.ichi2.anki.selectStoragePermissions], making `currentFolderIsAccessibleAndLegacy` optional
      */