The SuggestionsInfo record

Argument suggestion methods can accept a function which takes in a SuggestionsInfo object and returns a suitable format for suggestions. The SuggestionInfo class is a record which contains the following methods:

public record SuggestionInfo {
    CommandSender sender();
    Object[] previousArgs();
    String currentInput();
    String currentArg();
}

These methods can be used to aid with providing context-aware suggestions for users. The fields are as follows:

CommandSender sender();

sender() represents the command sender which is typing this command and requesting these suggestions. This is normally a Player, but can also be a console command sender if using a Paper server.

Object[] previousArgs();

previousArgs() represents a list of previously declared arguments, which are parsed and interpreted as if they were being used to execute the command. See this example on the string argument suggestions page for an idea of how to utilize this field.

String currentInput();

currentInput() represents the current input that the command sender has entered. This is effectively everything that they have typed, including the leading / symbol which is required to start a command. If a user is typing /mycommand hellowor¦, the result of currentInput() would be "/mycommand hellowor".

String currentArg();

currentArg() represents the current text which the command sender has entered for the argument which you're trying to provide suggestions for. If a user is typing /mycommand hellowor¦, the result of currentArg() would be "hellowor".