Warning: reset() expects parameter 1 to be array, null given after upgrade to 7.x-1.15

I can confirm the issue

Setting this to Needs Work for a few issues but the general approach seems fine to me (though I don't really know why it's breaking for you but didn't cause problems for anyone involved with #2293537: Cart form attributes selects do not work with translated taxonomies/products).

field_get_items() is not guaranteed to return an array, so assuming it would return an array with an element 0 was incorrect.

That was done in several places so I think it should get fixed in multiple places, not just commerce_cart_add_to_cart_form().

-            $field_value = reset($field_items[0]);
+            if (!empty($field_items[0])){
+              $field_value = reset($field_items[0]);
+            }else{
+              $field_value = NULL;
+            }

There's a few changes necessary to meet the Drupal coding standards: https://www.drupal.org/docs/develop/standards

Use spaces between parentheses/braces - so if (!empty(...)){ would be if (!empty(...)) {.
put else on a new line, not in line with the closing brace of the if statement.

And to commit a patch it would be necessary to write a test that demonstrates the problem - which might require a sleuth to determine the root cause.

I haven't tried replicating the issue yet but I'd venture a guess that you have at least one attribute field on your product variation that has no value. Is that true?

We are experiencing this on a client site as well. We don't use the Commerce Sale Price module.

Going to apply the patch for now.

Patch at #9 works for me. Thank you @TynanFox.

I can confirm the issue when you have at least one attribute field on your product variation that has no value.

Thanks for the fix, @TynanFox! I was able to confirm it fixed the issue - we obviously didn't test the previous changes with optional attributes (and apparently never added full test coverage for them).

Also, re: @tbradbury's review, I did expand the patch to the 3 other places turning up reset() warnings for me in my test environment. Likely a factor of me having multiple types of attributes on the test product display turned up the other ones.

I saw a few more places where field values are assumed to be an array, but in context, it isn't clear to me that setting a default value to NULL in the absence of a response would be the right behavior, so I'm leaving them alone until we see bug reports. Committed!

I was still getting this warning to the point that my host charged me a $900 penalty for CPU overages. I was forced to put my site in maintenance mode until fixed.

All modules and core are up to date and I am using Commerce Kickstart.

Fixed with patch #14. I posted a notification in Commerce Kickstart issues... https://www.drupal.org/project/commerce_kickstart/issues/3108817#comment...

#14 has worked for me.

Good, because it's been committed for a while now. : D

Warning: reset() expects parameter 1 to be array, null given commerce_cart_add_to_cart_form()
/html/profiles/commerce_kickstart/modules/contrib/commerce/modules/cart/commerce_cart.module 2110
commerce_kickstart-7.x-2.66
Today I updated the

Also get many warnings after upgrade Commerce from 7.x-1.13 to 7.x-1.15

Warning: reset() expects parameter 1 to be array, null given in reset() (line 2141 of /home/www/com/sites/all/modules/commerce/modules/cart/commerce_cart.module).

line 2141, Should be the same error as above line 2110, As I have patched many other patches before.

Changing version to make it more easily identifiable that it's commited in 7.x-1.x-dev. No stable release exists yet to fix this issue.