Support dots in identifiers

lib/sheet.js

@@ -25,6 +25,14 @@ const getValue = (target, prop) => {
   return target.handleUnknownIdentifier(prop, target);
 };
 
+const wrapValue = (target, prop) =>
+  new Proxy(target, {
+    get: (currentTarget, currentProp) => {
+      const targetProp = `${prop}.${currentProp}`;
+      return getValue(target, targetProp);
+    },
+  });
+
 const getCell = (target, prop) => {
   const { expressions, data } = target;
   const collection = expressions.has(prop) ? expressions : data;
@@ -40,9 +48,22 @@ const setCell = (target, prop, value) => {
     const options = { context: target.context };
     const script = metavm.createScript(prop, src, options);
     target.expressions.set(prop, { compute: script.exports, source: value });
-  } else {
+    return true;
+  }
+
+  if (prop.includes('.')) {
+    let nextDotIndex = prop.indexOf('.');
+    while (nextDotIndex !== -1) {
+      const key = prop.substring(0, nextDotIndex);
+      target.data.set(key, wrapValue(target, key));
+      nextDotIndex = prop.indexOf('.', nextDotIndex + 1);
+    }
+
     target.data.set(prop, value);
+    return true;
   }
+
+  target.data.set(prop, value);
   return true;
 };
 

test/unit.js

@@ -79,6 +79,53 @@ 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);
+
+  sheet.cells['item3.price'] = 300;
+  test.strictSame(sheet.values['total'], 600);
+
+  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);
+
+    sheet.cells['item.discount'] = 0.5;
+    test.strictSame(sheet.values['item.total'], 100);
+
+    test.end();
+  },
+);
+
+metatests.test('Read non-table expressions', async (test) => {
+  const sheet = new Sheet();
+  sheet.cells['item.basePrice'] = 100;
+  sheet.cells['item.discount'] = 0.5;
+  sheet.cells['item.price'] = '=item.basePrice * item.discount';
+  sheet.cells['item.quantity'] = 2;
+  sheet.cells['item.total'] = '=item.price * item.quantity';
+  test.strictSame(sheet.values['item.total'], 100);
+
+  test.end();
+});
+
 metatests.test('Prevent arbitrary js code execution', async (test) => {
   const sheet = new Sheet();