Fix BasicCommand suggestion arg count (#11241)

patches/server/0971-Brigadier-based-command-API.patch

@@ -686,10 +686,10 @@ index 0000000000000000000000000000000000000000..1b1642f306771f029e6214a2e2ebebb6
 +}
 diff --git a/src/main/java/io/papermc/paper/command/brigadier/PaperCommands.java b/src/main/java/io/papermc/paper/command/brigadier/PaperCommands.java
 new file mode 100644
-index 0000000000000000000000000000000000000000..da50ca4c6524e4f99ea4de2157d7ef900178d0f1
+index 0000000000000000000000000000000000000000..95d3b42cbe2184b0a04d941f27f7a6e643ef59be
 --- /dev/null
 +++ b/src/main/java/io/papermc/paper/command/brigadier/PaperCommands.java
-@@ -0,0 +1,198 @@
+@@ -0,0 +1,204 @@
 +package io.papermc.paper.command.brigadier;
 +
 +import com.google.common.base.Preconditions;
@@ -711,6 +711,7 @@ index 0000000000000000000000000000000000000000..da50ca4c6524e4f99ea4de2157d7ef90
 +import java.util.Locale;
 +import java.util.Set;
 +import net.minecraft.commands.CommandBuildContext;
++import org.apache.commons.lang3.ArrayUtils;
 +import org.apache.commons.lang3.StringUtils;
 +import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 +import org.checkerframework.checker.nullness.qual.NonNull;
@@ -868,7 +869,12 @@ index 0000000000000000000000000000000000000000..da50ca4c6524e4f99ea4de2157d7ef90
 +            .then(
 +                Commands.argument("args", StringArgumentType.greedyString())
 +                    .suggests((context, suggestionsBuilder) -> {
-+                        final String[] args = StringUtils.split(suggestionsBuilder.getRemaining());
++                        String[] args = StringUtils.split(suggestionsBuilder.getRemaining());
++                        if (suggestionsBuilder.getRemaining().endsWith(" ")) {
++                            // if there is trailing whitespace, we should add an empty argument to signify
++                            // that there may be more, but no characters have been typed yet
++                            args = ArrayUtils.add(args, "");
++                        }
 +                        final SuggestionsBuilder offsetSuggestionsBuilder = suggestionsBuilder.createOffset(suggestionsBuilder.getInput().lastIndexOf(' ') + 1);
 +
 +                        final Collection<String> suggestions = basicCommand.suggest(context.getSource(), args);