loader choice in preferences.txt is ignored

[banana-string-theory]

Bug Report

Current behavior

$ arduino-cli board details SparkFun:apollo3:sfe_artemis_nano

It always shows the first .menu.loader.option_* entry listed in boards.txt, despite the environment having been configured to use a different choice (second menu entry) via the IDE. No indication of why the contrary choice is selected, or how it can be corrected, is provided. In my case this rendered the tool completely unable to upload sketches.

Expected behavior

The tool should reflect the user-selected preference (custom_loader=) in Arduino15/preferences.txt.
The upload command should support a command-line option for explicitly choosing the loader.

Environment

$ arduino-cli version
arduino-cli alpha Version: 0.14.0 Commit: a86b21d Date:

MacOS Big Sur 11.1

Additional context

n/a

[per1234]

Arduino CLI doesn't use preferences.txt. That file is only used by Arduino IDE. So your configuration in preferences.txt has no effect on Arduino CLI.

In Arduino CLI, custom board options such as the one shown in the Arduino IDE's Tools > Uploader menu when the "RedBoard Artemis Nano" board is selected are configured via the FQBN. So if you wanted to set the loader custom board option to option_svl, you would use this FQBN in your Arduino CLI commands: SparkFun:apollo3:sfe_artemis_nano:loader=option_svl

There's a more detailed explanation here: #591

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Related: #355