core-prefs: typed snapshot access and nullableBooleanPref

CHANGELOG.md

@@ -30,6 +30,10 @@ are no binary releases; "version" tracks the shared `version` in the root build
 
 ### Added
 
+- **`core-prefs`** — `Preferences[pref]` and `MutablePreferences[pref] = value`,
+  so an app can read several prefs out of one `PrefStore.data` snapshot and
+  write several in one `PrefStore.edit` without dropping to raw keys. Plus
+  `nullableBooleanPref`, for a tri-state flag where unset differs from `false`.
 - **`components`** — picker-row helpers lifted from Calendula's pickers and
   settings, all additive. `GroupedRow` takes `checked` (default `false`): it
   implies `selected` and fills an empty trailing slot with `SelectedCheck`,

core-prefs/src/main/kotlin/de/jeanlucmakiola/floret/prefs/Pref.kt

@@ -54,10 +54,20 @@ fun stringSetPref(name: String, default: Set<String> = emptySet()): Pref<Set<Str
 fun nullableStringPref(name: String): Pref<String?> =
     nullablePref(stringPreferencesKey(name), name)
 
+/** Absent reads back as `null`; writing `null` removes the key. */
+fun nullableBooleanPref(name: String): Pref<Boolean?> =
+    nullablePref(booleanPreferencesKey(name), name)
+
 /** Absent reads back as `null`; writing `null` removes the key. */
 fun nullableLongPref(name: String): Pref<Long?> =
     nullablePref(longPreferencesKey(name), name)
 
+/** [pref]'s value in this snapshot, for reading several prefs in one `PrefStore.data` map. */
+operator fun <T> Preferences.get(pref: Pref<T>): T = pref.read(this)
+
+/** Writes [pref] inside a multi-key `PrefStore.edit`, with the same encoding as `PrefStore.set`. */
+operator fun <T> MutablePreferences.set(pref: Pref<T>, value: T) = pref.write(this, value)
+
 /** An absent key reads back as [default]; the value is stored under [key] verbatim. */
 private fun <T : Any> scalarPref(key: Preferences.Key<T>, name: String, default: T): Pref<T> =
     Pref(

core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefStoreTest.kt

@@ -281,4 +281,45 @@ class PrefStoreTest {
 
         assertThat(store.get(pref)).isFalse()
     }
+
+    @Test
+    fun `a nullable boolean keeps false apart from unset`(@TempDir tempDir: Path) = runTest {
+        val store = newStore(tempDir)
+        val pref = nullableBooleanPref("b")
+        assertThat(store.get(pref)).isNull()
+
+        store.set(pref, false)
+        assertThat(store.get(pref)).isFalse()
+
+        store.set(pref, null)
+        assertThat(store.get(pref)).isNull()
+    }
+
+    @Test
+    fun `several prefs read from one snapshot`(@TempDir tempDir: Path) = runTest {
+        val store = newStore(tempDir)
+        val count = intPref("count", 1)
+        val mode = enumPref("mode", ThemeMode.SYSTEM)
+        store.set(mode, ThemeMode.DARK)
+
+        val snapshot = store.data.first()
+
+        assertThat(snapshot[count] to snapshot[mode]).isEqualTo(1 to ThemeMode.DARK)
+    }
+
+    @Test
+    fun `a multi-key edit writes typed prefs with their codecs`(@TempDir tempDir: Path) = runTest {
+        val store = newStore(tempDir)
+        val mode = enumPref("mode", ThemeMode.SYSTEM)
+        val folder = nullableStringPref("folder")
+        store.set(folder, "content://x")
+
+        store.edit {
+            it[mode] = ThemeMode.BLACK
+            it[folder] = null
+        }
+
+        assertThat(store.data.first()[stringPreferencesKey("mode")]).isEqualTo("BLACK")
+        assertThat(store.get(folder)).isNull()
+    }
 }

core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefTest.kt

@@ -46,11 +46,11 @@ class PrefTest {
 
     @Test
     fun `the nullable factories default to null`() {
-        val prefs = listOf(nullableStringPref("s"), nullableLongPref("l"))
+        val prefs = listOf(nullableStringPref("s"), nullableLongPref("l"), nullableBooleanPref("b"))
 
         val defaults = prefs.map { it.default }
 
-        assertThat(defaults).containsExactly(null, null)
+        assertThat(defaults).containsExactly(null, null, null)
     }
 
     @Test