Add a utility for giving blocks new IDs, use it for sharing blocks.

test/unit/util_new-block-ids.js

@@ -0,0 +1,64 @@
+const newBlockIds = require('../../src/util/new-block-ids');
+const simpleStack = require('../fixtures/simple-stack');
+const tap = require('tap');
+const test = tap.test;
+
+let originals;
+let newBlocks;
+
+tap.beforeEach(done => {
+    originals = simpleStack;
+    // Will be mutated so make a copy first
+    newBlocks = JSON.parse(JSON.stringify(simpleStack));
+    newBlockIds(newBlocks);
+    done();
+});
+
+
+/**
+ * The structure of the simple stack is:
+ *      moveTo (looks_size) -> stopAllSounds
+ * The list of blocks is
+ *      0: moveTo (TO input block: 1, shadow: 2)
+ *      1: looks_size (parent: 0)
+ *      2: obscured shadow for moveTo input (parent: 0)
+ *      3: stopAllSounds (parent: 0)
+ * Inspect fixtures/blocks for the full object.
+ */
+
+test('top-level block IDs have all changed', t => {
+    newBlocks.forEach((block, i) => {
+        t.notEqual(block.id, originals[i].id);
+    });
+    t.end();
+});
+
+test('input reference is maintained on parent for attached block', t => {
+    t.equal(newBlocks[0].inputs.TO.block, newBlocks[1].id);
+    t.end();
+});
+
+test('input reference is maintained on parent for obscured shadow', t => {
+    t.equal(newBlocks[0].inputs.TO.shadow, newBlocks[2].id);
+    t.end();
+});
+
+test('parent reference is maintained for attached input', t => {
+    t.equal(newBlocks[1].parent, newBlocks[0].id);
+    t.end();
+});
+
+test('parent reference is maintained for obscured shadow', t => {
+    t.equal(newBlocks[2].parent, newBlocks[0].id);
+    t.end();
+});
+
+test('parent reference is maintained for next block', t => {
+    t.equal(newBlocks[3].parent, newBlocks[0].id);
+    t.end();
+});
+
+test('next reference is maintained for previous block', t => {
+    t.equal(newBlocks[0].next, newBlocks[3].id);
+    t.end();
+});