Remove style layers and sources by object so they can come back

src/main/java/com/mapconductor/maptiler/MapTilerStyleMutationTarget.kt

@@ -118,9 +118,12 @@ internal class MapTilerStyleMutationTarget(
 
     override fun removeLayer(layerId: String) {
         val target = style() ?: return
-        // `removeLayerById` reaches the page without being checked against
-        // anything, and removing an absent layer there is a no-op.
-        target.removeLayerById(layerId)
+        // Remove it from MTStyle's record too: `removeLayerById` alone leaves
+        // the id recorded, and adding the same background layer again throws
+        // LayerAlreadyExists. A layer MTStyle never recorded falls back to
+        // `removeLayerById`, which reaches the page unchecked (a no-op when the
+        // layer is absent). See MapTilerStyleRemoval.kt.
+        target.removeLayerAndForget(MTBackgroundLayer(layerId))
         own(target) -= layerId
     }
 

src/main/java/com/mapconductor/maptiler/MapTilerStyleRemoval.kt

@@ -0,0 +1,31 @@
+package com.mapconductor.maptiler
+
+import com.mapconductor.core.InternalMapConductorApi
+import com.maptiler.maptilersdk.map.style.MTStyle
+import com.maptiler.maptilersdk.map.style.layer.MTLayer
+import com.maptiler.maptilersdk.map.style.source.MTSource
+
+/*
+ * MTStyle からレイヤ・ソースを外すときは、id ではなくオブジェクトで外す。
+ *
+ * MTStyle は addLayer / addSource したものを id で覚えていて、同じ id をもう一度足そうとすると
+ * LayerAlreadyExists / SourceAlreadyExists を投げる。ところが removeLayerById / removeSourceById は
+ * ページ（MapLibre GL JS）から消すだけで、この記録を消さない。id で外したポリゴン・円・ラスター等を
+ * 同じ id（= 同じ state.id）で戻すと add が投げて、地図に戻らなかった。
+ * removeLayer(layer) / removeSource(source) は記録も消してからページへ渡す。
+ *
+ * 記録に無いとき（add の記録は SDK のコルーチンで遅れて入る）は NotFound を投げるので、
+ * そのときは id でページから消す。
+ */
+
+@InternalMapConductorApi
+internal fun MTStyle.removeLayerAndForget(layer: MTLayer) {
+    runCatching { removeLayer(layer) }
+        .onFailure { runCatching { removeLayerById(layer.identifier) } }
+}
+
+@InternalMapConductorApi
+internal fun MTStyle.removeSourceAndForget(source: MTSource) {
+    runCatching { removeSource(source) }
+        .onFailure { runCatching { removeSourceById(source.identifier) } }
+}

src/main/java/com/mapconductor/maptiler/circle/MapTilerCircleOverlayRenderer.kt

@@ -6,6 +6,8 @@ import com.mapconductor.core.circle.CircleOverlayRendererInterface
 import com.mapconductor.core.circle.CircleState
 import com.mapconductor.core.geometry.OverlayGeoJson
 import com.mapconductor.core.geometry.circleToRing
+import com.mapconductor.maptiler.removeLayerAndForget
+import com.mapconductor.maptiler.removeSourceAndForget
 import com.maptiler.maptilersdk.map.MTMapViewController
 import com.maptiler.maptilersdk.map.style.dsl.PropertyValue
 import com.maptiler.maptilersdk.map.style.layer.MTLayerVisibility
@@ -141,9 +143,10 @@ class MapTilerCircleOverlayRenderer(
     private fun removeCircle(entity: CircleEntityInterface<MapTilerCircleHandle>) {
         val style = mtController.style ?: return
         val handle = entity.circle
-        runCatching { style.removeLayerById(handle.lineLayerId) }
-        runCatching { style.removeLayerById(handle.fillLayerId) }
-        runCatching { style.removeSourceById(handle.sourceId) }
+        // id で外すと MTStyle の記録が残り、同じ id で戻せなくなる（MapTilerStyleRemoval.kt）。
+        style.removeLayerAndForget(handle.lineLayer)
+        style.removeLayerAndForget(handle.fillLayer)
+        style.removeSourceAndForget(handle.source)
     }
 
     /**

src/main/java/com/mapconductor/maptiler/groundimage/MapTilerGroundImageOverlayRenderer.kt

@@ -4,6 +4,8 @@ import com.mapconductor.core.features.GeoRectBounds
 import com.mapconductor.core.groundimage.GroundImageEntityInterface
 import com.mapconductor.core.groundimage.GroundImageOverlayRendererInterface
 import com.mapconductor.core.groundimage.GroundImageState
+import com.mapconductor.maptiler.removeLayerAndForget
+import com.mapconductor.maptiler.removeSourceAndForget
 import com.maptiler.maptilersdk.map.LngLat
 import com.maptiler.maptilersdk.map.MTMapViewController
 import com.maptiler.maptilersdk.map.style.dsl.PropertyValue
@@ -132,8 +134,9 @@ class MapTilerGroundImageOverlayRenderer(
     private fun removeGroundImage(entity: GroundImageEntityInterface<MapTilerGroundImageHandle>) {
         val style = mtController.style ?: return
         val handle = entity.groundImage
-        runCatching { style.removeLayerById(handle.layerId) }
-        runCatching { style.removeSourceById(handle.sourceId) }
+        // id で外すと MTStyle の記録が残り、同じ id で戻せなくなる（MapTilerStyleRemoval.kt）。
+        style.removeLayerAndForget(handle.layer)
+        style.removeSourceAndForget(handle.source)
     }
 
     /**

src/main/java/com/mapconductor/maptiler/polygon/MapTilerPolygonOverlayRenderer.kt

@@ -7,6 +7,8 @@ import com.mapconductor.core.polygon.PolygonEntityInterface
 import com.mapconductor.core.polygon.PolygonOverlayRendererInterface
 import com.mapconductor.core.polygon.PolygonState
 import com.mapconductor.core.polygon.unionHoles
+import com.mapconductor.maptiler.removeLayerAndForget
+import com.mapconductor.maptiler.removeSourceAndForget
 import com.maptiler.maptilersdk.map.MTMapViewController
 import com.maptiler.maptilersdk.map.style.dsl.PropertyValue
 import com.maptiler.maptilersdk.map.style.layer.MTLayerVisibility
@@ -164,9 +166,10 @@ class MapTilerPolygonOverlayRenderer(
     private fun removePolygon(entity: PolygonEntityInterface<MapTilerPolygonHandle>) {
         val style = mtController.style ?: return
         val handle = entity.polygon
-        runCatching { style.removeLayerById(handle.lineLayerId) }
-        runCatching { style.removeLayerById(handle.fillLayerId) }
-        runCatching { style.removeSourceById(handle.sourceId) }
+        // id で外すと MTStyle の記録が残り、同じ id で戻せなくなる（MapTilerStyleRemoval.kt）。
+        style.removeLayerAndForget(handle.lineLayer)
+        style.removeLayerAndForget(handle.fillLayer)
+        style.removeSourceAndForget(handle.source)
     }
 
     /**

src/main/java/com/mapconductor/maptiler/polyline/MapTilerPolylineOverlayRenderer.kt

@@ -6,6 +6,8 @@ import com.mapconductor.core.geometry.buildUnwrappedPolylinePath
 import com.mapconductor.core.polyline.PolylineEntityInterface
 import com.mapconductor.core.polyline.PolylineOverlayRendererInterface
 import com.mapconductor.core.polyline.PolylineState
+import com.mapconductor.maptiler.removeLayerAndForget
+import com.mapconductor.maptiler.removeSourceAndForget
 import com.maptiler.maptilersdk.map.MTMapViewController
 import com.maptiler.maptilersdk.map.style.dsl.PropertyValue
 import com.maptiler.maptilersdk.map.style.layer.MTLayerVisibility
@@ -141,8 +143,9 @@ class MapTilerPolylineOverlayRenderer(
     private fun removeLine(entity: PolylineEntityInterface<MapTilerPolylineHandle>) {
         val style = mtController.style ?: return
         val handle = entity.polyline
-        runCatching { style.removeLayerById(handle.layerId) }
-        runCatching { style.removeSourceById(handle.sourceId) }
+        // id で外すと MTStyle の記録が残り、同じ id で戻せなくなる（MapTilerStyleRemoval.kt）。
+        style.removeLayerAndForget(handle.layer)
+        style.removeSourceAndForget(handle.source)
     }
 
     /**

src/main/java/com/mapconductor/maptiler/raster/MapTilerRasterLayerOverlayRenderer.kt

@@ -6,6 +6,8 @@ import com.mapconductor.core.raster.RasterLayerOverlayRendererInterface
 import com.mapconductor.core.raster.RasterLayerSource
 import com.mapconductor.core.raster.RasterLayerState
 import com.mapconductor.core.raster.TileScheme
+import com.mapconductor.maptiler.removeLayerAndForget
+import com.mapconductor.maptiler.removeSourceAndForget
 import com.maptiler.maptilersdk.map.MTMapViewController
 import com.maptiler.maptilersdk.map.style.MTTileScheme
 import com.maptiler.maptilersdk.map.style.dsl.PropertyValue
@@ -121,8 +123,10 @@ class MapTilerRasterLayerOverlayRenderer(
     private fun removeLayer(entity: RasterLayerEntityInterface<MapTilerRasterLayerHandle>) {
         val style = mtController.style ?: return
         val handle = entity.layer
-        runCatching { style.removeLayerById(handle.layerId) }
-        runCatching { style.removeSourceById(handle.sourceId) }
+        // id で外すと MTStyle の記録が残り、同じ id で戻せなくなる（MapTilerStyleRemoval.kt）。
+        // ソースを替えるとき（onChange）も同じ id で足し直すので、ここで記録まで消す。
+        style.removeLayerAndForget(handle.layer)
+        style.removeSourceAndForget(handle.source)
     }
 
     private fun buildSource(

src/test/java/com/mapconductor/maptiler/MapTilerStyleRemovalTest.kt

@@ -0,0 +1,73 @@
+package com.mapconductor.maptiler
+
+import com.mapconductor.core.InternalMapConductorApi
+import com.maptiler.maptilersdk.bridge.MTBridge
+import com.maptiler.maptilersdk.bridge.MTBridgeReturnType
+import com.maptiler.maptilersdk.bridge.MTCommand
+import com.maptiler.maptilersdk.bridge.MTCommandExecutable
+import com.maptiler.maptilersdk.map.style.MTMapReferenceStyle
+import com.maptiler.maptilersdk.map.style.MTStyle
+import com.maptiler.maptilersdk.map.style.MTStyleError
+import com.maptiler.maptilersdk.map.style.source.MTGeoJSONSource
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertThrows
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+
+/**
+ * 外したソースを同じ id で足し直せること（ポリゴン・円・ラスター等が「一度外すと戻らない」不具合）。
+ *
+ * 実物の [MTStyle] に、ページ（WebView）の代わりにコマンドを記録するだけの実行器をつないで確かめる。
+ */
+@OptIn(InternalMapConductorApi::class)
+class MapTilerStyleRemovalTest {
+    private val commands = mutableListOf<String>()
+    private lateinit var style: MTStyle
+
+    @Before
+    fun setUp() {
+        val executor =
+            object : MTCommandExecutable {
+                override suspend fun execute(command: MTCommand): MTBridgeReturnType {
+                    commands += command.javaClass.simpleName
+                    return MTBridgeReturnType.BoolValue(true)
+                }
+            }
+        style = MTStyle(MTMapReferenceStyle.STREETS)
+        // initWorker は SDK の internal。地図の ready で SDK 自身が呼ぶものを、ここでは反射で呼ぶ。
+        MTStyle::class.java
+            .declaredMethods
+            .single { it.name.startsWith("initWorker") }
+            .apply { isAccessible = true }
+            .invoke(style, MTBridge(executor), CoroutineScope(Dispatchers.Unconfined))
+    }
+
+    private fun source() = MTGeoJSONSource.fromJsonString("polygon-source-PG", """{"type":"FeatureCollection","features":[]}""")
+
+    /** 不具合の原因: id で外しても MTStyle の記録が残り、同じ id の add が投げる。 */
+    @Test
+    fun removeSourceById_leavesTheIdRecorded() {
+        style.addSource(source())
+        style.removeSourceById("polygon-source-PG")
+        assertThrows(MTStyleError.SourceAlreadyExists::class.java) { style.addSource(source()) }
+    }
+
+    @Test
+    fun removeSourceAndForget_letsTheSameIdBeAddedAgain() {
+        val first = source()
+        style.addSource(first)
+        style.removeSourceAndForget(first)
+        style.addSource(source())
+        assertEquals(listOf("AddSource", "RemoveSource", "AddSource"), commands.filter { it.contains("Source") })
+    }
+
+    /** 記録に無いもの（足していない・記録が遅れている）は id でページから消す。 */
+    @Test
+    fun removeSourceAndForget_fallsBackToTheIdWhenNotRecorded() {
+        style.removeSourceAndForget(source())
+        assertTrue(commands.toString(), commands.contains("RemoveSourceById"))
+    }
+}