std/settings

An application's settings, as editors keep them: a JSON Schema says what each setting is; the user's settings file and the workspace's, each JSON with comments, lie over the schema's defaults; changes are told to whoever listens; and the settings model lists them for a settings page. For settings from the environment and files in any number of layers, see std/config.

import "std/settings"

Settings s = open_settings(schema, config_dir() + "/app/settings.json", ".app/settings.json")?
print(s.number("editor.fontSize"))
s.on_change("editor.fontSize", func(str key, Json value) do
    print(f"{key} is now {to_json(value)}")
end)
s.set("editor.fontSize", Json.NUMBER(16.0))?          // in the user's file

Settings have flat keys, as "editor.fontSize", in the schema's properties and in the files.

Function or method
`open_settings(schema, user_file, workspace_file)`	the settings; a file that is not there has none
`s.get(key)`, `s.text(key)`, `s.number(key)`, `s.flag(key)`	a setting's value: the workspace's, the user's, or the schema's default
`s.source(key)`	where it comes from: `"workspace"`, `"user"`, or `"default"`
`s.set(key, value, layer)`	sets it in the `"user"` (the default) or `"workspace"` file; a value the schema does not allow is an `ERROR` of kind `"invalid_setting"`. Only the setting's member of the file changes, so comments and layout stay
`s.reset(key, layer)`	takes it out of a file, so the value below shows
`s.on_change(key, changed)`	`changed` gets the key and the new value each time it changes; `""` listens to every setting
`s.reload()`, `s.watch_files()`, `s.stop_watching()`	reads the files again, now or each time they change while the event loop runs, and tells the listeners
`s.model()`	a `SettingInfo` for each setting of the schema, then each the files give that it does not know: `key`, `title` (the schema's, or made from the key, as "Font Size"), `description`, `type`, `default_value`, `value`, `source`, `choices`, and `problem`
`s.problems()`	what is wrong, as `key: problem`