A parent project is throwing the following error when trying to integrate a child project.
Exception: < FILE > - can't integrate (already opened for delete)
Under what scenario does this occur?
When Perforce integrates changes, it tries to resolve the incoming changes in the files in the local workspace. This exception is basically saying that it can't attempt to resolve the changes for the given file, since the file has been marked as being deleted on the local workspace, so it has no place to resolve it.
There are flags you can pass to the integrate command to allow the integration to proceed anyway. However, I've found it's generally not a good idea to integrate changes on top of in-progress changes, so I would recommend finishing (or shelving) your in-progress changes, then attempting the integration.