octave @4.4.1_2: Error message when starting Octave.app and broken online help using the doc function

[maehne (Torsten Maehne)]

When launching the Octave.app GUI, a message window pops up with the following error message:

Could not copy help collection to temporary file. Search capabilities may be affected. Cannot create index tables in file /opt/local/share/octave/4.4.1/doc/octave_interpreter.qhc

After clicking on OK, the Octave GUI opens. Octave primary functions seem to work without problem except for the doc function (which was hinted by the error message). Asking, e.g., for the documentation of the deg2rad function will only display two empty panes in the tab "Documentation" instead of the requested page from the online version of the manual. Related may be that the menu entry Help->Documentation->On Disk is not working as expected -- only the two empty panes from the Documentation tab are shown.Help->Documentation->Online opens the Octave manual from ​http://octave.org in a web browser.

When using octave from a regular shell, the above error message is not shown and the doc command works as expected displaying the online manual in the info browser. I am using the octave port already for several years every couple of weeks, but I never noticed the error message before. Therefore, I suspect that the error got introduced by one of the recent updates to the port.

The exact variant of the port, which is installed is:

$ port installed octave
The following ports are currently installed:
  octave @4.4.1_2+accelerate+app+docs+gfortran+graphicsmagick+qt5+sound+sundials (active)

My MacPorts installation is fully updated and runs on macOS High Sierra 10.13.6 on MacBook Pro 15-inch 2017.