From b42a665b2fc3010622994c4548842463bad4a1d9 Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Tue, 13 Mar 2018 17:27:48 -0700
Subject: [PATCH] Fix race condition in VectorTileWorkerSource#reloadTile

---
 src/source/vector_tile_worker_source.js       |  24 ++---
 .../source/vector_tile_worker_source.test.js  | 101 ++++++++++++++++++
 2 files changed, 112 insertions(+), 13 deletions(-)

diff --git a/src/source/vector_tile_worker_source.js b/src/source/vector_tile_worker_source.js
index 46d08ec96f3..b02cdf4d94b 100644
--- a/src/source/vector_tile_worker_source.js
+++ b/src/source/vector_tile_worker_source.js
@@ -147,22 +147,20 @@ class VectorTileWorkerSource implements WorkerSource {
             const workerTile = loaded[uid];
             workerTile.showCollisionBoxes = params.showCollisionBoxes;
 
+            const done = (err, data) => {
+                const reloadCallback = workerTile.reloadCallback;
+                if (reloadCallback) {
+                    delete workerTile.reloadCallback;
+                    workerTile.parse(workerTile.vectorTile, vtSource.layerIndex, vtSource.actor, reloadCallback);
+                }
+                callback(err, data);
+            };
+
             if (workerTile.status === 'parsing') {
-                workerTile.reloadCallback = callback;
+                workerTile.reloadCallback = done;
             } else if (workerTile.status === 'done') {
-                workerTile.parse(workerTile.vectorTile, this.layerIndex, this.actor, done.bind(workerTile));
-            }
-
-        }
-
-        function done(err, data) {
-            if (this.reloadCallback) {
-                const reloadCallback = this.reloadCallback;
-                delete this.reloadCallback;
-                this.parse(this.vectorTile, vtSource.layerIndex, vtSource.actor, reloadCallback);
+                workerTile.parse(workerTile.vectorTile, this.layerIndex, this.actor, done);
             }
-
-            callback(err, data);
         }
     }
 
diff --git a/test/unit/source/vector_tile_worker_source.test.js b/test/unit/source/vector_tile_worker_source.test.js
index 5814a6cb1d9..90787a68bc7 100644
--- a/test/unit/source/vector_tile_worker_source.test.js
+++ b/test/unit/source/vector_tile_worker_source.test.js
@@ -51,6 +51,107 @@ test('VectorTileWorkerSource#removeTile removes loaded tile', (t) => {
     t.end();
 });
 
+test('VectorTileWorkerSource#reloadTile reloads a previously-loaded tile', (t) => {
+    const source = new VectorTileWorkerSource(null, new StyleLayerIndex());
+    const parse = t.spy();
+
+    source.loaded = {
+        '0': {
+            status: 'done',
+            parse
+        }
+    };
+
+    const callback = t.spy();
+    source.reloadTile({ uid: 0 }, callback);
+    t.equal(parse.callCount, 1);
+
+    parse.firstCall.args[3]();
+    t.equal(callback.callCount, 1);
+
+    t.end();
+});
+
+test('VectorTileWorkerSource#reloadTile queues a reload when parsing is in progress', (t) => {
+    const source = new VectorTileWorkerSource(null, new StyleLayerIndex());
+    const parse = t.spy();
+
+    source.loaded = {
+        '0': {
+            status: 'done',
+            parse
+        }
+    };
+
+    const callback1 = t.spy();
+    const callback2 = t.spy();
+    source.reloadTile({ uid: 0 }, callback1);
+    t.equal(parse.callCount, 1);
+
+    source.loaded[0].status = 'parsing';
+    source.reloadTile({ uid: 0 }, callback2);
+    t.equal(parse.callCount, 1);
+
+    parse.firstCall.args[3]();
+    t.equal(parse.callCount, 2);
+    t.equal(callback1.callCount, 1);
+    t.equal(callback2.callCount, 0);
+
+    parse.secondCall.args[3]();
+    t.equal(callback1.callCount, 1);
+    t.equal(callback2.callCount, 1);
+
+    t.end();
+});
+
+test('VectorTileWorkerSource#reloadTile handles multiple pending reloads', (t) => {
+    // https://github.com/mapbox/mapbox-gl-js/issues/6308
+    const source = new VectorTileWorkerSource(null, new StyleLayerIndex());
+    const parse = t.spy();
+
+    source.loaded = {
+        '0': {
+            status: 'done',
+            parse
+        }
+    };
+
+    const callback1 = t.spy();
+    const callback2 = t.spy();
+    const callback3 = t.spy();
+    source.reloadTile({ uid: 0 }, callback1);
+    t.equal(parse.callCount, 1);
+
+    source.loaded[0].status = 'parsing';
+    source.reloadTile({ uid: 0 }, callback2);
+    t.equal(parse.callCount, 1);
+
+    parse.firstCall.args[3]();
+    t.equal(parse.callCount, 2);
+    t.equal(callback1.callCount, 1);
+    t.equal(callback2.callCount, 0);
+    t.equal(callback3.callCount, 0);
+
+    source.reloadTile({ uid: 0 }, callback3);
+    t.equal(parse.callCount, 2);
+    t.equal(callback1.callCount, 1);
+    t.equal(callback2.callCount, 0);
+    t.equal(callback3.callCount, 0);
+
+    parse.secondCall.args[3]();
+    t.equal(parse.callCount, 3);
+    t.equal(callback1.callCount, 1);
+    t.equal(callback2.callCount, 1);
+    t.equal(callback3.callCount, 0);
+
+    parse.thirdCall.args[3]();
+    t.equal(callback1.callCount, 1);
+    t.equal(callback2.callCount, 1);
+    t.equal(callback3.callCount, 1);
+
+    t.end();
+});
+
 test('VectorTileWorkerSource provides resource timing information', (t) => {
     const rawTileData = fs.readFileSync(path.join(__dirname, '/../../fixtures/mbsv5-6-18-23.vector.pbf'));