[Problem] When ran in a directory without write access, MPF.Check will not create a config in the known-good location

[InternalLoss]

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• Remember to try the latest WIP build to see if the issue has already been addressed.
• Is it copy protection related? If so, report the issue here instead.
• Check multiple discs to help narrow down the issue
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If all of those fail, then continue...

Version
What version are you using?

• Stable release 3.6.0
• WIP release (version here)

Build
What runtime version are you using?

• .NET 10 running on macOS 26.3

Describe the issue
When MPF.Check is placed in a read-only directory (such as /usr/local/bin), it does not create a config.json at ~/.config/mpf/config.json as expected.

Furthermore, if a config.json is manually generated and placed either in the same directory as the executable or in the shared configuration directory with just a RedumpUsername/RedumpPassword, the Redump credentials are not used.

To Reproduce

1. Place MPF.Check binary in /usr/local/bin or similar on-PATH but not writable directory.
2. Run MPF.Check (I specifically ran MPF.Check xbone xxx.log
3. Observe no config.json is created in the ~/.config/mpf/ folder
4. Place a config.json (see below for my example) in ~/.config/mpf/
5. Run MPF.Check again
6. Observe the Redump credentials are not used - no Options will be loaded from found configuration file! is shown.

{
"RedumpUsername": "Billy",
"RedumpPassword": "hunter2"
}

Expected behavior

1. MPF creates a config.json in the ~/.config/mpf/ folder, if it can't write locally.
2. MPF uses the Redump credentials if only those two variables are set.

Additional context
I also noticed that the config.json made when MPF.Check is running in a directory that's writeable (such as ~/Downloads/) is blank.

[mnadareski]

For the part of the issue regarding partial configs is very much expected. The configuration files are not expected to be partial as they are generated by both MPF.UI and MPF.CLI. One of the configuration items, FirstRun, is used as an indicator for a lot of stuff to ensure new users have a different experience. I do not currently consider adding support for partial configs as something I would like to support.

The remainder of the issue is valid and will be investigated when there is time.

[mnadareski]

According to a StackOverflow post, the location for configuration files should be in ~/Library/Application Support/<appname>/<appname>.cfg. This is a significant departure from the current OS-agnostic setup and may mean that Windows changes to %APPDATA% in the process as well. I was hoping to avoid this, to be entirely honest.

Addendum: This enforcement of directory rules may also explain the blank configuration file being generated. I have no idea how, but this may mean that macOS will always require a centralized configuration file.