fix: initialize stack frame params for all procedures

A previous change fixed compatibility with Scratch 2 removing 3's
unintentional scope leaking. This furthers that change so that
procedures with no parameters will also not accidentally use values in
other procedure stacks.

src/blocks/scratch3_procedures.js

@@ -38,6 +38,7 @@ class Scratch3ProcedureBlocks {
 
             const [paramNames, paramIds, paramDefaults] = paramNamesIdsAndDefaults;
 
+            util.initParams();
             for (let i = 0; i < paramIds.length; i++) {
                 if (args.hasOwnProperty(paramIds[i])) {
                     util.pushParam(paramNames[i], args[paramIds[i]]);

src/engine/block-utility.js

@@ -170,6 +170,13 @@ class BlockUtility {
         return this.thread.target.blocks.getProcedureParamNamesIdsAndDefaults(procedureCode);
     }
 
+    /**
+     * Initialize procedure parameters in the thread before pushing parameters.
+     */
+    initParams () {
+        this.thread.initParams();
+    }
+
     /**
      * Store a procedure parameter value by its name.
      * @param {string} paramName The procedure's parameter name.

src/engine/thread.js

@@ -321,6 +321,16 @@ class Thread {
         this.justReported = typeof value === 'undefined' ? null : value;
     }
 
+    /**
+     * Initialize procedure parameters on this stack frame.
+     */
+    initParams () {
+        const stackFrame = this.peekStackFrame();
+        if (stackFrame.params === null) {
+            stackFrame.params = {};
+        }
+    }
+
     /**
      * Add a parameter to the stack frame.
      * Use when calling a procedure with parameter values.
@@ -329,9 +339,6 @@ class Thread {
      */
     pushParam (paramName, value) {
         const stackFrame = this.peekStackFrame();
-        if (stackFrame.params === null) {
-            stackFrame.params = {};
-        }
         stackFrame.params[paramName] = value;
     }
 

test/unit/engine_thread.js

@@ -17,6 +17,7 @@ test('spec', t => {
     t.type(th.peekStackFrame, 'function');
     t.type(th.peekParentStackFrame, 'function');
     t.type(th.pushReportedValue, 'function');
+    t.type(th.initParams, 'function');
     t.type(th.pushParam, 'function');
     t.type(th.peekStack, 'function');
     t.type(th.getParam, 'function');
@@ -107,6 +108,7 @@ test('peekStack', t => {
 test('PushGetParam', t => {
     const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
+    th.initParams();
     th.pushParam('testParam', 'testValue');
     t.strictEquals(th.peekStackFrame().params.testParam, 'testValue');
     t.strictEquals(th.getParam('testParam'), 'testValue');