[.87 Bug] Can't upgrade hammer to lightning hammer

i think lightning hammers got changed recently (from+1 att per level to a flat +2). maybe they messed up something when they made that change? 

Had similar problem in last beta- it was solved by redoing the design as weapon stats changing screws up the autoupgrade.

My problem was entirely on .87.  I deleted all old unit types (and shut off Steam synch) and designed this one from scratch within the .87 game.  So it must be a bug.

Are warhammers two-handed

Did you originally have a staff?  My second guess is this is some sort of 1h/2h-bug with the weapon class changes introduced.

there was a similar bug with longswords not upgrading to boreal blades a few patches ago. might just be an oversight that they haven't fixed the same(?) issue with warhammer -> lightning hammer. as i said, lightning hammers got nerfed recently, so it's also possible that this change somehow reverted the original fix.

If you want it to upgrade to a vareity of things you might consider changing that .xml code to read

        <EquipmentUpgradeDef>
            <SelectionCriterion>MaximizeSum</SelectionCriterion>
            <ComparisonAttribute>UnitStat_Attack_Pierce</ComparisonAttribute>
            <ComparisonAttribute>UnitStat_Attack_Lightning</ComparisonAttribute>
            <ComparisonAttribute>UnitStat_Attack_Fire</ComparisonAttribute>
            <ComparisonAttribute>UnitStat_Attack_Poison</ComparisonAttribute>
             <WeaponUpgradeType>Blunt</WeaponUpgradeType>
            <EquipmentSlot>Weapon</EquipmentSlot>
            <ForUpgradeActionOnly>0</ForUpgradeActionOnly>
        </EquipmentUpgradeDef>

Both the hammer and the lightning hammer are one handed.  The unit equips both a hammer and shield.

Ah, I think I see.  The base weapon damage of the lightning hammer (9) is the same as the base damage of the warhammer.  I guess the additional lightning damage isn't accounted for in the upgrade calculation.

Correct.

I designed two units, one carrying an Ice Staff and the other carrying an Incineration Staff.  Here's the upgrade XML for the first:

        <EquipmentUpgradeDef>
            <SelectionCriterion>MaximizeBest</SelectionCriterion>
            <ComparisonAttribute>UnitStat_Attack_Cold</ComparisonAttribute>
            <ComparisonAttribute>UnitStat_Attack_Fire</ComparisonAttribute>
            <ComparisonAttribute>UnitStat_Attack_Lightning</ComparisonAttribute>
            <ComparisonAttribute>UnitStat_Attack_Poison</ComparisonAttribute>
            <WeaponUpgradeType>ColdStaff</WeaponUpgradeType>
            <EquipmentSlot>Weapon</EquipmentSlot>
            <EquipmentSlot>Defense</EquipmentSlot>
            <ForUpgradeActionOnly>0</ForUpgradeActionOnly>
        </EquipmentUpgradeDef>

and here's the XML for the second:

        <EquipmentUpgradeDef>
            <SelectionCriterion>MaximizeBest</SelectionCriterion>
            <ComparisonAttribute>UnitStat_Attack_Cold</ComparisonAttribute>
            <ComparisonAttribute>UnitStat_Attack_Fire</ComparisonAttribute>
            <ComparisonAttribute>UnitStat_Attack_Lightning</ComparisonAttribute>
            <ComparisonAttribute>UnitStat_Attack_Poison</ComparisonAttribute>
            <WeaponUpgradeType>FireStaff</WeaponUpgradeType>
            <EquipmentSlot>Weapon</EquipmentSlot>
            <EquipmentSlot>Defense</EquipmentSlot>
            <ForUpgradeActionOnly>0</ForUpgradeActionOnly>
        </EquipmentUpgradeDef>

Having now researched the appropriate tech, the first unit now upgrades from the Ice Staff to the Hailstone Staff (expected), while the second upgrades from the Incineration Staff to the Leht Staff instead of to the Hellfire Staff (not expected).  I'm guessing that this is because both the Leht Staff and the Hellfire staff are classified as FireStaff, despite the Leht Staff doing lightning damage rather than fire.

And, indeed, the Leht Staff is listed as an Enchanted Fire Staff in the unit design window:

If units that are vulnerable to fire damage (ice elementals, for example) are also vulnerable to lightning damage, then this is not a problem and I should stop thinking about it.  Otherwise, the inability to upgrade to a HellFire Staff could present a reason not to upgrade and to design and train a new unit type instead.

Yes, but the real problem is that there is only 1 lightning staff. So it is rather pointless to give it's own staff classification. I would just suggest that you mod the .xml yourself and remove the lightning portion on the fire staff and it will never upgrade to that other staff.