Bug Report

Current behavior

The --config-file global command line option currently only defines the directory containing the configuration file. It does not allow configuring the specific configuration file within that directory.

arduino-cli expects the path specified via --config-file to contain a file named with the prefix arduino-cli followed by a file extension associated with one of the supported formats.

$ ./arduino-cli config dump --verbose --config-file ./config
INFO[0000] Using config file: /home/per/ArduinoIDE/arduino-cli_nightly/config/arduino-cli.json

Even if you specify a filename, it will be ignored:

$ ./arduino-cli config dump --verbose --config-file ./config/foo.json
INFO[0000] Using config file: /home/per/ArduinoIDE/arduino-cli_nightly/config/arduino-cli.json

Unless the file doesn't exist:

$ ./arduino-cli config dump --verbose --config-file ./config/nonexistent.json
INFO[0000] Config file not found, using default values  

If the configuration directory contains multiple configuration files, there is a specific order of precedence that determines which one is used, regardless of the filename provided to the --config-file option:

$ ./arduino-cli config dump --verbose --config-file ./config/arduino-cli.toml
INFO[0000] Using config file: /home/per/ArduinoIDE/arduino-cli_nightly/config/arduino-cli.json 

(note that I specified the .toml file, but the .json file was used instead)
The order of precedence:

• JSON
• TOML
• YAML
• Java properties file
• HCL
• envfile
• INI

Expected behavior

The --config-file option's documentation seems somewhat misleading to me:

--config-file string        The custom config file (if not specified the default will be used).

From reading that, I would expect to be able to specify any arbitrary filename (with the appropriate file extension for the file's format).

I don't have a problem with the current behavior of arduino-cli regarding custom configuration file locations, it's just not the behavior I expect from the option name and command line help. I don't think requiring a specific filename (arduino-cli) is onerous, and I don't think it likely the user will ever have configuration files of multiple formats in the configuration directory (I only discovered this because I was verifying support for all the formats). So a simple solution for this would be keep the current behavior, but change the option name to something like --config-dir (hopefully keeping --config-file as an undocumented alias for backwards compatibility), and update the command line help accordingly.

Environment

• CLI version (output of arduino-cli version): 0.11.0-rc1 Commit: 5373961
• OS and platform: Ubuntu 20.04, Windows 10