Problem/Motivation
When disabling modules that create fields this error is sometimes displayed. The message does not make it clear what caused the issue or how to fix it which is frustrating for users.
If you want to fix the underlying issue that causes this message check out #943772: field_delete_field() and others fail for inactive fields
The reason the fields are not deleted immediately on uninstall is that the database could be very, very large, and deleting all fields at the same time might time out the request, leaving the database in an unknown state. That's why cron is used to delete the fields.
Proposed resolution
Change message to be more descriptive and more helpful in resolving the issue
There are Fields pending deletion that were created by a module you just tried to disable. Delete offending fields now or try running cron, it might fix this issue.
The error message is produced by field_system_info_alter() in core/modules/field/field.module.
Also, give the user a report of how many such field entries exist, and if there are more than some arbitrary threshold, don't allow the user to try to delete them all at once.
Remaining tasks
Finalize the message text- Write a patch
Original report by [joachim]
I saw this message in my modules list and it completely baffled me.
I only found out I had to run cron thanks to a comment buried in an issue on a contrib module somewhere.
When this text appears in the module admin page it should be linked to further help.