After updating the ports tree to r509722 (including latest commit to the port in question), synth fails to build index on my system.
[/usr/home/dries]$ sudo synth just-build /root/portlist
Regenerating flavor index: this may take a while ...
Scanning entire ports tree.
Scan aborted because 'make' encounted an error in the Makefile.
print/harfbuzz-hb-view (return code = 1)
Flavor index generation failed: ports scan
CC: Latest committer.
There is a typo in revision 509716 (https://svnweb.freebsd.org/ports?view=revision&revision=509716):
harfbuzz-bh-view should be replaced with harfbuzz-hb-view
A commit references this bug:
Date: Sat Aug 24 20:37:19 UTC 2019
New revision: 509754
Fix typo in port directory name.
PR: 240071 
Reported by: jbeich@, Dries Michiels <firstname.lastname@example.org> 
thanks for reporting.