feature: provide a way to specify an additional data source for configuration data

[mattkae]

Why?

In miracle (and probably other compositors), people may want to specify configuration options in a different format (e.g. a json file, a yaml file, etc.). To facilitate this, users should be able to specify a simple map that contains the key-value pairs that were parsed from another source.

What's new?

• Added a new class to miral called ConfigurationDataSource
• Added DefaultConfiguration::set_options_map (maybe this should be in the constructor, but the constructors were a bit large)
• Added DefaultConfiguration::parse_custom
• Added ProgramOption::parse_map
• Fixed the symbols map generator

To test

In your main runner function, do something like:

return runner.run_with(
        {
            ...
            ConfigurationDataSource([]()
            {
                return std::map<std::string, std::string>{
                    {"startup-apps", "gedit"}
                };
            }),
            ...
         });

[codecov]

Codecov Report

Attention: Patch coverage is 19.23077% with 21 lines in your changes missing coverage. Please review.

Project coverage is 76.94%. Comparing base (5557be6) to head (115394d).

Files	Patch %	Lines
src/platform/options/program_option.cpp	0.00%	9 Missing ⚠️
src/miral/configuration_data_source.cpp	0.00%	5 Missing ⚠️
src/server/server.cpp	33.33%	4 Missing ⚠️
src/platform/options/default_configuration.cpp	50.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3478      +/-   ##
==========================================
- Coverage   76.95%   76.94%   -0.02%     
==========================================
  Files        1080     1081       +1     
  Lines       69380    69405      +25     
==========================================
+ Hits        53394    53403       +9     
- Misses      15986    16002      +16     

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[AlanGriffiths]

In miracle (and probably other compositors), people may want to specify configuration options in a different format (e.g. a json file, a yaml file, etc.). To facilitate this, users should be able to specify a simple map that contains the key-value pairs that were parsed from another source.

I'm not convinced this is useful in this form.

This adds complexity to the current "configuration fixed at startup" options. As you know, I'm working to replace a lot of what "configuration fixed at startup" is currently used for with a way to dynamic configuration changes whilst running. I suspect a lot of what you want to source from "a json file, a yaml file, etc." is going to fall into the "dynamic configuration" category and is better built on that work.

[mattkae]

I'm not convinced this is useful in this form.

This adds complexity to the current "configuration fixed at startup" options. As you know, I'm working to replace a lot of what "configuration fixed at startup" is currently used for with a way to dynamic configuration changes whilst running. I suspect a lot of what you want to source from "a json file, a yaml file, etc." is going to fall into the "dynamic configuration" category and is better built on that work.

So long as I can set a Mir-defined configuration option from some external source (e.g. somehow set "--display-config" from a JSON file), I'd be happy. If that work will enable it, then I will close this one in favor 👍