Positive, when the event EVENT_UNIT_ATTACKED or EVENT_PLAYER_UNIT_ATTACKED fires, the unit is in fulfilling its order and on a quite critical point, a marginal one. So overlapping the order with a new one is not very secure.
The same happens with the similar EVENT_UNIT_TARGET_IN_RANGE.
I could not reconstruct the problem yet when pausing/unpausing the unit before reordering, although this also seems risky:
Code:
public function Attack takes nothing returns nothing
local unit lanceur = GetAttacker()
local unit cible = GetTriggerUnit()
local integer lvl = GetUnitAbilityLevel(lanceur,spellid1)
call PauseUnit(lanceur, true)
call PauseUnit(lanceur, false)
if GetUnitState(lanceur,UNIT_STATE_MANA)>=manacost1+manacostperlvl1*lvl then
if IssueTargetOrderById(lanceur,OrderId("carrionswarm"),cible)==true then
//call ReOrderDelayed(lanceur,1)
endif
endif
set lanceur = null
set cible = null
endfunction
Else you might add a timer like Troll-Brain suggested or going with another event. For example, you could give the unit an instant attack and capture an EVENT_UNIT_DAMAGED for its targets. To cast active spells on attack you might also use an orb ability that channels the desired spell through itself.
Afaik orb effects only react when the unit is actively using the "attack" order and not if the target was automatically chosen to attack by AI, so you might have to reorder the attack.
JASS: