Tab completion for first argument does not work correctly using SimpleCommand

Hello Velocity-Team,

I just migrated from waterfall to Velocity 3.3.0-SNAPSHOT-b389 and found that the first argument of an SimpleCommand isn't tab-completed correctly after I rewrote my plugins commands from waterfall to velocity.

In my command I used the following code to check what's the cause.

@Override
public CompletableFuture<List<String>> suggestAsync(Invocation invocation)
{
    CommandSource sender = invocation.source();
    String label = invocation.alias();
    String[] args = invocation.arguments();
    System.out.println("COMMAND | " + sender + " | " + label + " | " + String.join(", ", args) + " | " + args.length);
    if(args.length == 1)
        // tab completion here
}

I got these outputs:

Input: /mycommand (note the space at the end)
Output: COMMAND | [connected player] EvilJavaSkill (/ip) | mycommand | | 0

Input: /mycommand E
Output: COMMAND | [connected player] EvilJavaSkill (/ip) | mycommand | E | 1

Input: /mycommand (note the 2 spaces at the end)
Output: COMMAND | [connected player] EvilJavaSkill (/ip) | mycommand | , | 2

Inputting two spaces sets the args.length to 2 (output nr. 3) but inputting only one does set it to 0 (output nr. 1). The player has to enter a character first before the args length says that the player is trying to tab-complete the first argument.

In my code I check for an args.length equals 1 to make sure the player is tab-completing the first argument. But somehow when the player hasn't entered any letter no tab-completion will be done due to invocation.arguments(); returning an empty array. I would say that invocation.arguments(); should return an array with an empty string in it.

I consider this is a bug if there is no special reason why velocity does not provide an array length of 1.

If there are any questions, let me know and I will help as much as I can.

Kind regards

EvilJavaSkill

Start by tracing the command suggestion path around Invocation.arguments() and SimpleCommand, using the reported inputs /mycommand , /mycommand E, and /mycommand to reproduce the differing argument arrays. Done means first-argument completion receives a consistent representation when the command ends with one space, with regression coverage for the reported cases.