From 80dbf17b3a1e060c43191788747a1ac536465895 Mon Sep 17 00:00:00 2001
From: Mhayk Whandson <hi@mhayk.com>
Date: Wed, 15 Jul 2026 15:34:46 +0100
Subject: [PATCH] Fix removeSource throwing TypeError in Terrain.update under
 globe projection

Style#_createTerrain left terrain.properties uninitialised until the first
Style#update ran from Map#_render. Under globe projection, the draping
terrain created on style load could therefore be consumed by Terrain#update
(via Map#removeSource -> Map#_updateTerrain) before the properties were
evaluated, throwing 'TypeError: Cannot read properties of undefined
(reading get)'.

Evaluate the terrain properties synchronously in Style#_createTerrain so
they are always available to consumers.

Fixes #13665
Fixes #13703
---
 src/style/style.ts                | 4 ++++
 test/unit/terrain/terrain.test.ts | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/src/style/style.ts b/src/style/style.ts
index b73c5904e7b..8e607eefbd6 100644
--- a/src/style/style.ts
+++ b/src/style/style.ts
@@ -4306,6 +4306,10 @@ class Style extends Evented<MapEvents> {
         this._force3DLayerUpdate();
         const parameters = this._getTransitionParameters({duration: 0});
         terrain.updateTransitions(parameters);
+        // Evaluate the terrain properties synchronously so that consumers such as
+        // Terrain#update can access them before the next Style#update runs (#13665).
+        const evaluationParameters = new EvaluationParameters(this.z || 0, {...parameters, worldview: this.map.getWorldview()});
+        terrain.recalculate(evaluationParameters);
     }
 
     _force3DLayerUpdate() {
diff --git a/test/unit/terrain/terrain.test.ts b/test/unit/terrain/terrain.test.ts
index 390d4a90481..8062451d6c7 100644
--- a/test/unit/terrain/terrain.test.ts
+++ b/test/unit/terrain/terrain.test.ts
@@ -163,6 +163,13 @@ describe('Elevation', () => {
         });
     });
 
+    test('mapbox-gl-js#13665: removeSource before the first render under globe projection does not throw', async () => {
+        const map = createMap({projection: 'globe'});
+        await waitFor(map, 'style.load');
+        map.addSource('repro-src', {type: 'geojson', data: {type: 'FeatureCollection', features: []}});
+        expect(() => map.removeSource('repro-src')).not.toThrowError();
+    });
+
     test('style diff=false removes dem source', async () => {
         const map = createMap();
         await waitFor(map, "style.load");