"Error: poppler cannot be built while another version of poppler is active." Why?

[Joshua Root]

On 2019-10-30 12:49 , Thomas R. Murphy wrote:
> Is there a reason poppler is setup to disallow in-place updating? This
> essentially makes port upgrade outdatedrequire manual intervention when
> a rev-bump of poppler comes by. The end of the build log indicates that
> this is an intentional prebuild check:
> 
> :debug:configure Executing proc-pre-org.macports.configure-configure-0
> :error:configure poppler cannot be built while another version of
> poppler is active.
> :error:configure Please forcibly deactivate the existing copy of
> poppler, e.g. by running:
> :error:configure     sudo port -f deactivate poppler
> :error:configure Then try again.
> :error:configure Failed to configure poppler: poppler is active
> :debug:configure Error code: NONE

Short answer, because the build system is broken and searches include
directories in the wrong order (external ones before internal).

- Josh