Favor previous anchor only when still available

src/symbol/placement.js

@@ -344,7 +344,7 @@ export class Placement {
                     // anchor to the front of the anchor list.
                     if (this.prevPlacement && this.prevPlacement.variableOffsets[symbolInstance.crossTileID]) {
                         const prevOffsets = this.prevPlacement.variableOffsets[symbolInstance.crossTileID];
-                        if (anchors[0] !== prevOffsets.anchor) {
+                        if (anchors[0] !== prevOffsets.anchor && anchors.indexOf(prevOffsets.anchor) >= 0) {
                             anchors = anchors.filter(anchor => anchor !== prevOffsets.anchor);
                             anchors.unshift(prevOffsets.anchor);
                         }

test/integration/render-tests/runtime-styling/layout-property-text-variable-anchor/style.json

@@ -0,0 +1,73 @@
+{
+    "version": 8,
+    "metadata": {
+      "test": {
+        "width": 64,
+        "height": 64,
+        "operations": [
+          [
+            "setLayoutProperty",
+            "symbol",
+            "text-variable-anchor",
+            ["bottom"]
+          ],
+          [
+            "wait"
+          ]
+        ]
+      }
+    },
+    "transition": {
+      "duration": 0
+    },
+    "sources": {
+      "geojson": {
+        "type": "geojson",
+        "data": {
+          "type": "FeatureCollection",
+          "features": [
+            {
+              "type": "Feature",
+              "geometry": {
+                "type": "Point",
+                "coordinates": [
+                  0,
+                  0
+                ]
+              }
+            }
+          ]
+        }
+      }
+    },
+    "glyphs": "local://glyphs/{fontstack}/{range}.pbf",
+    "layers": [
+      {
+        "id": "symbol",
+        "type": "symbol",
+        "source": "geojson",
+        "layout": {
+            "text-variable-anchor": ["left"],
+            "text-field": "ABC",
+            "text-font": [
+                "Open Sans Semibold",
+                "Arial Unicode MS Bold"
+              ],
+              "symbol-placement": "point"
+        },
+        "paint": {
+            "text-color": "red"
+        }
+      },
+      {
+          "id" : "dot",
+          "type": "circle",
+          "source": "geojson",
+          "paint": {
+              "circle-color": "red"
+          }
+
+      }
+    ]
+  }
+