Fatal error when bw_trace2 function not defined

[bobbingwide]

While upgrading oik and oik-bwtrace in a WordPress Multisite installation ( oik-plugins.eu ) I got a Fatal error; produced when oik-types attempted to call bw_trace2.

Expected output

No fatal error.
Oik-types is dependent upon oik and oik-fields so should not be using functions until it’s safe to do so.

Actual output

Fatal error: Uncaught Error: Call to undefined function bw_trace2() in oik-types/oik-types.php:460

Explanation

During an upgrade to the latest version of oik-bwtrace and oik I'd deactivated oik-bwtrace to avoid a compatibility problem between non-final versions. But somehow the oik plugin had also become deactivated. This was unexpected. So bw_trace2 was not being loaded by either of these plugins.

Workaround

Deactivate oik-types prior to updating oik.

Proposed solution

• Remove the offending call(s) to bw_trace2
• Implement test cases for Respond to the 'register_post_type_args' filter function in WordPress 4.4 #3

It’s an unexpected situation leading to an unexpected result.
It should be tested in both WPMS and straight WordPress.