Problem: when attempting to create an Arduino project (Blink LED on anything else) using VisualGDB-5.4r7 and Visual Studio 2017, New Arduino Project Wizard displays “Invalid URI” message instead of a list of Arduino target boards in Arduino Device page of the wizard (second page).
Solution: there is apparently a stray semicolon character in the end of the in the “Package index URLs” setting value. To fix the problem, close the wizard, go to the Visual Studio main menu, go to Tools -> VisualGDB -> Arduino Settings and change “Package Index URLs” setting value from “http://downloads.arduino.cc/packages/package_index.json;” to “http://downloads.arduino.cc/packages/package_index.json” (remove trailing semicolon). Go back to File -> New -> Project -> VisualGDB -> Arduino Project Wizard, the list will now populate correctly on the Arduino Device page of the wizard (Internet connection required).
This wrong setting came right out of the box (version 5.4r7), would be nice if the next release ships with correct setting.
As we wanted to minimize the amount of users affected by the broken Arduino downloads, we released the R8 installer in a very short timeframe with minimal changes required to resolve the package download issue (properly skipping the empty URLs in the package downloading logic). The stray semicolon is indeed shown in the default settings for R8, however it no longer causes any problems.