Refuse read-only provider tables before the store check (#137)

The provider contract tests failed whenever Agendula ran on an external
provider: the store check fired first. Value checks still need the own store,
so those two tests now skip without it.

app/src/androidTest/java/de/jeanlucmakiola/agendula/data/tasks/provider/AgendulaTaskProviderTest.kt

@@ -124,6 +124,7 @@ class AgendulaTaskProviderTest {
 
     @Test
     fun aBadWriteReachesTheClientAsIllegalArgument() {
+        assumeTrue("Agendula is running on an external provider", ownStore())
         // No list has this id, so nothing in the app's real store is touched.
         val values = ContentValues().apply {
             put("list_id", Long.MAX_VALUE)
@@ -135,6 +136,7 @@ class AgendulaTaskProviderTest {
 
     @Test
     fun aFailingBatchWritesNothing() {
+        assumeTrue("Agendula is running on an external provider", ownStore())
         val missingList = Long.MAX_VALUE
         val operations = arrayListOf(
             ContentProviderOperation.newInsert(uri("tasks")).withValue("list_id", missingList).withValue("title", "a").build(),
@@ -145,6 +147,9 @@ class AgendulaTaskProviderTest {
             .use { assertThat(it.count).isEqualTo(0) }
     }
 
+    /** Whether the app's own store is active: only then does the provider take writes at all. */
+    private fun ownStore() = runCatching { resolver.delete(uri("tasks"), "_id = -1", null) }.isSuccess
+
     /** stdout and stderr of [command]; the denial lands on stderr. */
     private fun shell(command: String): String {
         val (stdout, stdin, stderr) = InstrumentationRegistry.getInstrumentation().uiAutomation

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/provider/ProviderWriter.kt

@@ -62,16 +62,15 @@ class ProviderWriter internal constructor(
     private var batchWrote = false
 
     /** Inserts one row and returns its published id. */
-    fun insert(table: ProviderTable, values: ProviderValues): Long = write {
+    fun insert(table: ProviderTable, values: ProviderValues): Long = writable(table, INSERTABLE_TABLES) {
         when (table) {
             ProviderTable.TASKS -> insertTask(values)
-            ProviderTable.PROPERTIES -> insertProperty(values)
-            else -> throw UnsupportedOperationException("${table.path} is read-only")
+            else -> insertProperty(values)
         }
     }
 
     /** Updates every row [selection] matches and returns how many changed. */
-    fun update(table: ProviderTable, values: ProviderValues, selection: String?, args: Array<out String>?): Int = write {
+    fun update(table: ProviderTable, values: ProviderValues, selection: String?, args: Array<out String>?): Int = writable(table, WRITABLE_TABLES) {
         when (table) {
             ProviderTable.TASKS -> {
                 val writable = ProviderTaskWriter.writable(table, values, WRITABLE_TASK_COLUMNS)
@@ -83,17 +82,17 @@ class ProviderWriter internal constructor(
                 instances(selection, args).count { updateInstance(it, writable) }
             }
             ProviderTable.PROPERTIES -> ids(table, selection, args).count { updateProperty(it, values) }
-            else -> throw UnsupportedOperationException("${table.path} is read-only")
+            else -> error("unreachable")
         }
     }
 
     /** Deletes every row [selection] matches and returns how many went. */
-    fun delete(table: ProviderTable, selection: String?, args: Array<out String>?): Int = write {
+    fun delete(table: ProviderTable, selection: String?, args: Array<out String>?): Int = writable(table, WRITABLE_TABLES) {
         when (table) {
             ProviderTable.TASKS -> ids(table, selection, args).count { deleteTask(it) }
             ProviderTable.INSTANCES -> instances(selection, args).count { deleteInstance(it) }
             ProviderTable.PROPERTIES -> ids(table, selection, args).count { deleteProperty(it) }
-            else -> throw UnsupportedOperationException("${table.path} is read-only")
+            else -> error("unreachable")
         }
     }
 
@@ -113,6 +112,12 @@ class ProviderWriter internal constructor(
         }
     }
 
+    /** A read-only table is refused as such, whichever store is active. */
+    private fun <T> writable(table: ProviderTable, allowed: Set<ProviderTable>, block: () -> T): T {
+        if (table !in allowed) throw UnsupportedOperationException("${table.path} is read-only")
+        return write(block)
+    }
+
     private fun <T> write(block: () -> T): T = source.locked {
         check(resolver.mode() == StorageMode.OWN) {
             "Agendula is working on top of an external tasks provider; write to that one instead"
@@ -435,3 +440,6 @@ class ProviderWriter internal constructor(
 
     private fun zone(): String = ZoneId.systemDefault().id
 }
+
+private val INSERTABLE_TABLES = setOf(ProviderTable.TASKS, ProviderTable.PROPERTIES)
+private val WRITABLE_TABLES = INSERTABLE_TABLES + ProviderTable.INSTANCES