Support dots in identifiers

lib/sheet.js

@@ -12,6 +12,17 @@ const wrap = (target) =>
     },
   });
 
+const wrapValue = (target, path, prop) =>
+  new Proxy(target, {
+    get: (currentTarget, currentProp) => {
+      const targetProp = `${prop}.${currentProp}`;
+      if (target.data.has(targetProp)) return target.data.get(targetProp);
+      if (!path.startsWith(targetProp)) return undefined;
+
+      return wrapValue(currentTarget, path, targetProp);
+    },
+  });
+
 const math = wrap(Math);
 
 const getValue = (target, prop) => {
@@ -37,6 +48,11 @@ const setCell = (target, prop, value) => {
     const options = { context: target.context };
     const script = metavm.createScript(prop, src, options);
     target.expressions.set(prop, script.exports);
+  } else if (prop.includes('.')) {
+    const rootKey = prop.substring(0, prop.indexOf('.'));
+    const proxyValue = wrapValue(target, prop, rootKey);
+    target.data.set(rootKey, proxyValue);
+    target.data.set(prop, value);
   } else {
     target.data.set(prop, value);
   }

test/unit.js

@@ -70,6 +70,35 @@ metatests.test('Correct cell values', async (test) => {
   test.end();
 });
 
+metatests.test('Non-table identifiers', async (test) => {
+  const sheet = new Sheet();
+  sheet.cells['item1.price'] = 100;
+  sheet.cells['item2.price'] = 200;
+  sheet.cells['item3.price'] = 300;
+  sheet.cells['total'] = '=item1.price + item2.price + item3.price';
+  test.strictSame(sheet.values['total'], 600);
+
+  sheet.cells['item3'] = 42;
+  test.strictSame(sheet.values['item3'], 42);
+  test.strictSame(sheet.values['total'], NaN);
+
+  test.end();
+});
+
+metatests.test(
+  'Read undefined property in non-table identifier',
+  async (test) => {
+    const sheet = new Sheet();
+    sheet.cells['item.price'] = 100;
+    sheet.cells['item.quantity'] = 2;
+    sheet.cells['item.total'] =
+      '=item.price * item.quantity * (item.discount ?? 1)';
+    test.strictSame(sheet.values['item.total'], 200);
+
+    test.end();
+  },
+);
+
 metatests.test('Prevent arbitrary js code execution', async (test) => {
   const sheet = new Sheet();