After a long hiatus and several upgrades (Arduino IDE to 1.8.5 and macOS to 10.13.1) I noticed the IDE listing only /dev/cu-Bluetooth.Incoming.Port under the Tools>Port menu, which is not good. The time it took me to figure out how to get the IDE to connect to the board over USB warrants writing it down here. (The Internet seems littered with threads on this topic, most of which date from the pre-macOS High Sierra days.)
First, download the USB to UART Bridge Virtual COM Port (VCP) driver from the Silicon Labs web site. At the time of this writing the driver’s version was 5.0.2, released on October 12, 2017.
Next in System Preferences go to Security & Privacy and allow apps downloaded from “App Store and identified developers.”
Once you install the driver and connect the Huzzah Feather you should see the SLAB devices:
% ls -l /dev/*SLAB* crw-rw-rw- 1 root wheel 21, 3 Nov 23 07:12 /dev/cu.SLAB_USBtoUART crw-rw-rw- 1 root wheel 21, 2 Nov 23 07:10 /dev/tty.SLAB_USBtoUART
The USB tree under Hardware>USB in System Information should also show the Silicon Labs controller:
With that in place select /dev/cu.SLAB_USBtoUART in the IDE’s port selector (alongside appropriate values for Board, CPU Frequency and Upload Speed) and you should be all set.