Use safe stringify from -gui for visual reports

Fixes stringifying -0, objects, arrays

Author: GarboMuffin

src/engine/runtime.js

@@ -23,6 +23,7 @@ const ScratchLinkWebSocket = require('../util/scratch-link-websocket');
 const FontManager = require('./tw-font-manager');
 const fetchWithTimeout = require('../util/fetch-with-timeout');
 const platform = require('./tw-platform.js');
+const safeStringify = require('../util/tw-safe-stringify.js');
 
 // Virtual I/O devices.
 const Clock = require('../io/clock');
@@ -3084,7 +3085,10 @@ class Runtime extends EventEmitter {
      */
     visualReport (target, blockId, value) {
         if (target === this.getEditingTarget()) {
-            this.emit(Runtime.VISUAL_REPORT, {id: blockId, value: String(value)});
+            this.emit(Runtime.VISUAL_REPORT, {
+                id: blockId,
+                value: safeStringify(value)
+            });
         }
     }
 

src/util/tw-safe-stringify.js

@@ -0,0 +1,30 @@
+const circularReplacer = () => {
+    const seen = new WeakSet();
+    return (_, value) => {
+        if (typeof value === 'object' && value !== null) {
+            if (seen.has(value)) {
+                return Array.isArray(value) ? '[...]' : '{...}';
+            }
+            seen.add(value);
+        }
+        return value;
+    };
+};
+
+/**
+ * Safely stringify, properly handling circular relations and -0.
+ * @param {unknown} input Any value
+ * @returns {string} A stringified version of the input.
+ */
+const safeStringify = input => {
+    if (typeof input === 'object' && input !== null) {
+        return JSON.stringify(input, circularReplacer());
+    }
+    // -0 stringifies as "0" by default.
+    if (Object.is(input, -0)) {
+        return '-0';
+    }
+    return `${input}`;
+};
+
+module.exports = safeStringify;

test/unit/engine_runtime_tw.js

@@ -2,6 +2,7 @@ const tap = require('tap');
 const Runtime = require('../../src/engine/runtime');
 const {Map} = require('immutable');
 const makeTestStorage = require('../fixtures/make-test-storage');
+const Target = require('../../src/engine/target');
 
 const test = tap.test;
 
@@ -253,3 +254,21 @@ test('convertToPackagedRuntime and attachStorage call order', t => {
     rt2.attachStorage(makeTestStorage());
     t.end();
 });
+
+test('visual report -0', t => {
+    t.plan(1);
+
+    const rt = new Runtime();
+    const target = new Target();
+    rt.setEditingTarget(target);
+
+    rt.on(Runtime.VISUAL_REPORT, report => {
+        t.same(report, {
+            id: 'blockid',
+            value: '-0'
+        });
+    });
+    rt.visualReport(target, 'blockid', -0);
+
+    t.end();
+});

test/unit/tw_safe_stringify.js

@@ -0,0 +1,32 @@
+const {test} = require('tap');
+const safeStringify = require('../../src/util/tw-safe-stringify');
+
+test('safeStringify', t => {
+    t.equal(safeStringify(''), '');
+    t.equal(safeStringify('a'), 'a');
+
+    t.equal(safeStringify(true), 'true');
+    t.equal(safeStringify(false), 'false');
+
+    t.equal(safeStringify(0), '0');
+    t.equal(safeStringify(-0), '-0');
+    t.equal(safeStringify(1), '1');
+    t.equal(safeStringify(Infinity), 'Infinity');
+    t.equal(safeStringify(-Infinity), '-Infinity');
+    t.equal(safeStringify(NaN), 'NaN');
+
+    t.equal(safeStringify(null), 'null');
+    t.equal(safeStringify(undefined), 'undefined');
+
+    t.equal(safeStringify({}), '{}');
+    t.equal(safeStringify({a: 'b'}), '{"a":"b"}');
+
+    t.equal(safeStringify([]), '[]');
+    t.equal(safeStringify([1, 2, 3]), '[1,2,3]');
+
+    const circular = {};
+    circular.circular = circular;
+    t.equal(safeStringify(circular), '{"circular":"{...}"}');
+
+    t.end();
+});