Shulker bullets follow players who changed game mode from survival mode to creative mode

Confirmed in 1.16-pre5. Please, change the reporter to me so I can keep the ticket up-to-date.

You can't change the reporter

Can reproduce in 20w45a

Can confirm in 20w48a.

Can confirm in 20w51a.

Can confirm in 1.19.

Can confirm in 1.19.2.

Can confirm in latest snapshot, 26.1-snapshot-1

Can confirm in 1.21.11.

This issue likely stems from ShulkerBullet.class, where within the tick() method, the code only checks if the target is in spectator (confirmed ingame - Shulker bullets do NOT target the player when initially in Survival, then switching to Spectator).

public void tick() {
        super.tick();
        Entity finalTarget = !this.level().isClientSide() ? EntityReference.getEntity(this.finalTarget, this.level()) : null;
        HitResult hitResult = null;
        if (!this.level().isClientSide()) {
            if (finalTarget == null) {
                this.finalTarget = null;
            }

            if (finalTarget == null || !finalTarget.isAlive() || finalTarget instanceof Player && finalTarget.isSpectator()) {
                this.applyGravity();
            } else {
                // other code
        }

The if statement only checks finalTarget.isSpectator(), whereas Mob.class has a method called asValidTarget, which has checks for both spectator mode and a player.isCreative() check, on line 267 in the deobfuscated code:

protected @Nullable LivingEntity asValidTarget(final @Nullable LivingEntity target) {
        if (target instanceof Player player) {
            if (player.isCreative() || player.isSpectator()) {
                return null;
            }
        }