Clear out the blocks in dispose. Fixes #1758 where old monitored variables were getting kept across project loads

src/engine/runtime.js

@@ -1547,6 +1547,7 @@ class Runtime extends EventEmitter {
     dispose () {
         this.stopAll();
         this.targets.map(this.disposeTarget, this);
+        this.monitorBlocks = new Blocks(true);
         this._monitorState = OrderedMap({});
         // @todo clear out extensions? turboMode? etc.
 

test/integration/variable_monitor_reset.js

@@ -0,0 +1,43 @@
+const path = require('path');
+const test = require('tap').test;
+const makeTestStorage = require('../fixtures/make-test-storage');
+const readFileToBuffer = require('../fixtures/readProjectFile').readFileToBuffer;
+const VirtualMachine = require('../../src/index');
+
+const projectUri = path.resolve(__dirname, '../fixtures/monitored_variables.sb3');
+const project = readFileToBuffer(projectUri);
+
+const anotherProjectUri = path.resolve(__dirname, '../fixtures/default.sb2');
+const anotherProject = readFileToBuffer(anotherProjectUri);
+
+test('importing one project after the other resets monitored variables', t => {
+    const vm = new VirtualMachine();
+    vm.attachStorage(makeTestStorage());
+
+    // Start VM, load project, and run
+    vm.start();
+    vm.clear();
+    vm.setCompatibilityMode(false);
+    vm.setTurboMode(false);
+    vm.loadProject(project).then(() => {
+
+        const refSprite = vm.runtime.targets[1];
+        const refVarId = Object.keys(refSprite.variables)[0];
+        const refBlock = vm.runtime.monitorBlocks.getBlock(refVarId);
+        t.ok(refBlock);
+        const jamalSprite = vm.runtime.targets[2];
+        const jamalVarId = Object.keys(jamalSprite.variables)[0];
+        const jamalBlock = vm.runtime.monitorBlocks.getBlock(jamalVarId);
+        t.ok(jamalBlock);
+        vm.loadProject(anotherProject).then(() => {
+            // Blocks from the previously loaded project should be gone.
+            const refVarBlock = vm.runtime.monitorBlocks.getBlock(refVarId);
+            t.notOk(refVarBlock);
+            const jamalVarBlock = vm.runtime.monitorBlocks.getBlock(jamalVarId);
+            t.notOk(jamalVarBlock);
+
+            t.end();
+            process.nextTick(process.exit);
+        });
+    });
+});