Ensure _.set passes strict mode tests.

lodash.src.js

@@ -9964,11 +9964,10 @@
      * // => 5
      */
     function set(object, path, value) {
-      if (object == null) {
-        return object;
-      }
       if (isKey(path, object)) {
-        object[path] = value;
+        if (isObject(object)) {
+          object[path] = value;
+        }
         return object;
       }
       path = toPath(path);
@@ -9978,12 +9977,14 @@
           endIndex = length - 1,
           nested = object;
 
-      while (++index < length) {
+      while (nested != null && ++index < length) {
         var key = path[index];
-        if (index == endIndex) {
-          nested[key] = value;
-        } else if (nested[key] == null) {
-          nested[key] = isIndex(path[index + 1]) ? [] : {};
+        if (isObject(nested)) {
+          if (index == endIndex) {
+            nested[key] = value;
+          } else if (nested[key] == null) {
+            nested[key] = isIndex(path[index + 1]) ? [] : {};
+          }
         }
         nested = nested[key];
       }

test/test.js

@@ -13261,7 +13261,7 @@
 
     test('should follow `path` over non-plain objects', 2, function() {
       _.set(0, 'constructor.prototype.a', 'ok');
-      strictEqual(1..a, 'ok');
+      strictEqual(0..a, 'ok');
       delete numberProto.a;
 
       var object = { 'a': '' };
@@ -13269,6 +13269,21 @@
       strictEqual(stringProto.replace.b, 1);
       delete stringProto.replace.b;
     });
+
+    test('should not error on paths over primitive values in strict mode', 2, function() {
+      numberProto.a = 0;
+
+      _.each(['a', 'a.a.a'], function(path) {
+        try {
+          _.set(0, path, 1);
+          strictEqual(0..a, 0);
+        } catch(e) {
+          ok(false, e.message);
+        }
+      });
+
+      delete numberProto.a;
+    });
   }());
 
   /*--------------------------------------------------------------------------*/