ARDUINO_USER_AGENT environment variable not set

[PaulStoffregen]

Describe the problem

Arduino CLI 0.36.0-rc.1 is not setting the ARDUINO_USER_AGENT environment variable when running tools.

To reproduce

Using Linux x86-64:

1: Install Teensy package 0.59.4
2: Copy this modified teensy_size tool to ~/.arduino15/packages/teensy/tools/teensy-tools/0.59.4/
3: Compile any sketch with FQBN "teensy:avr:teensy40" and look for "ARDUINO_USER_AGENT = " in the output.

This copy of teensy_size prints the ARDUINO_USER_AGENT environment variable to stdout. When run, you will see it prints (null).

./arduino-cli compile -b teensy:avr:teensy40 ~/.arduino15/packages/teensy/hardware/avr/0.59.4/libraries/_Teensy/examples/Serial/EchoBoth/EchoBoth.ino 
ARDUINO_USER_AGENT = (null)

Used platform Version Path
teensy:avr    0.59.4  /home/paul/.arduino15/packages/teensy/hardware/avr/0.59.4

To install Teensy package 0.59.4 using Arduino IDE 2.2.1:

1: File - Preferences, add Teensy URL https://www.pjrc.com/teensy/td_download.html
2: In Boards Manager, search "teensy".
3: Select 0.59.4 from drop-down list and click install.

Expected behavior

The ARDUINO_USER_AGENT environment variable is supposed to be set, according to the Platform Specification, under "Environment variables":

https://arduino.github.io/arduino-cli/0.35/platform-specification/#environment-variables

Running this with Arduino CLI 0.34.2 prints a correct ARDUINO_USER_AGENT.

arduino-cli compile -b teensy:avr:teensy40 ~/.arduino15/packages/teensy/hardware/avr/0.59.4/libraries/_Teensy/examples/Serial/EchoBoth/EchoBoth.ino 
ARDUINO_USER_AGENT = arduino-cli/0.34.2

Used platform Version Path                                                     
teensy:avr    0.59.4  /home/paul/.arduino15/packages/teensy/hardware/avr/0.59.4

Arduino CLI version

arduino-cli Version: 0.36.0-rc.1 Commit: 31e0341 Date: 2024-01-11T12:36:53Z

Operating system

Linux

Operating system version

Ubuntu 22.04

Additional context

This problem also happens with recent Arduino IDE night builds.

arduino/arduino-ide#2318

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the nightly build
• My report contains all necessary details

[PaulStoffregen]

Teensy's software depends on ARDUINO_USER_AGENT.

Really hoping this can be fixed before the next IDE release, because without ARDUINO_USER_AGENT my software believes it is running from Arduino IDE 1.8.19.

[PaulStoffregen]

Tested 0.35.1 just now, can confirm it solves this issue.