Preserve commas that are not part of a brace expansion

Author: nickiaconis

packages/ember-metal/lib/expand_properties.js

@@ -5,7 +5,6 @@ import { assert } from 'ember-metal/debug';
 @submodule ember-metal
 */
 
-var SPLIT_REGEX = /\{|\}/;
 var END_WITH_EACH_REGEX = /\.@each$/;
 
 /**
@@ -42,31 +41,46 @@ export default function expandProperties(pattern, callback) {
     pattern.indexOf(' ') === -1
   );
 
-  var parts = pattern.split(SPLIT_REGEX);
-  var properties = [parts];
+  let properties = [pattern];
 
-  for (let i = 0; i < parts.length; i++) {
-    let part = parts[i];
-    if (part.indexOf(',') >= 0) {
-      properties = duplicateAndReplace(properties, part.split(','), i);
+  // Iterating backward over the pattern makes dealing with indeces easier.
+  let bookmark;
+  let inside = false;
+  for (let i = pattern.length; i > 0; --i) {
+    let current = pattern[i - 1];
+
+    switch (current) {
+      // Closing curly brace will be the first character of the brace expansion we encounter.
+      // Bookmark its index so long as we're not already inside a brace expansion.
+      case '}':
+        if (!inside) {
+          bookmark = i - 1;
+          inside = true;
+        }
+        break;
+      // Opening curly brace will be the last character of the brace expansion we encounter.
+      // Apply the brace expansion so long as we've already seen a closing curly brace.
+      case '{':
+        if (inside) {
+          let expansion = pattern.slice(i, bookmark).split(',');
+          // Iterating backward allows us to push new properties w/out affecting our "cursor".
+          for (let j = properties.length; j > 0; --j) {
+            // Extract the unexpanded property from the array.
+            let property = properties.splice(j - 1, 1)[0];
+            // Iterate over the expansion, pushing the newly formed properties onto the array.
+            for (let k = 0; k < expansion.length; ++k) {
+              properties.push(property.slice(0, i - 1) +
+                              expansion[k] +
+                              property.slice(bookmark + 1));
+            }
+          }
+          inside = false;
+        }
+        break;
     }
   }
 
   for (let i = 0; i < properties.length; i++) {
-    callback(properties[i].join('').replace(END_WITH_EACH_REGEX, '.[]'));
+    callback(properties[i].replace(END_WITH_EACH_REGEX, '.[]'));
   }
 }
-
-function duplicateAndReplace(properties, currentParts, index) {
-  var all = [];
-
-  properties.forEach((property) => {
-    currentParts.forEach((part) => {
-      var current = property.slice(0);
-      current[index] = part;
-      all.push(current);
-    });
-  });
-
-  return all;
-}

packages/ember-metal/tests/expand_properties_test.js

@@ -75,6 +75,14 @@ QUnit.test('A property with only brace expansions expands correctly', function()
   deepEqual(expected.sort(), foundProperties.sort());
 });
 
+QUnit.test('A property with no braces does not expand', function() {
+  expect(1);
+
+  expandProperties('a,b,c.d.e,f', addProperty);
+
+  deepEqual(foundProperties, ['a,b,c.d.e,f']);
+});
+
 QUnit.test('A pattern must be a string', function() {
   expect(1);
 
@@ -87,6 +95,6 @@ QUnit.test('A pattern must not contain a space', function() {
   expect(1);
 
   expectAssertion(function() {
-    expandProperties('a, b', addProperty);
+    expandProperties('{a, b}', addProperty);
   }, /Brace expanded properties cannot contain spaces, e.g. "user.{firstName, lastName}" should be "user.{firstName,lastName}"/);
 });