Implement fixes for #1870 - undo the Module.toDummy that happens when replacing a module, but the new module doesn't fit. And shuffle around the logic that dictates if a module / item fits onto a particular ship to allow us to ask a fit if a base item can fit based on low-level attributes that don't change

eos/saveddata/fit.py

@@ -384,6 +384,32 @@ class Fit(object):
         else:
             return val
 
+    def canFit(self, item):
+        # Whereas Module.fits() deals with current state of the fit in order to determine if somethign fits (for example maxGroupFitted which can be modified by effects),
+        # this function should be used against Items to see if the item is even allowed on the fit with rules that don't change
+
+        fitsOnType = set()
+        fitsOnGroup = set()
+
+        shipType = item.attributes.get("fitsToShipType", None)
+        if shipType is not None:
+            fitsOnType.add(shipType.value)
+
+        fitsOnType.update([item.attributes[attr].value for attr in item.attributes if attr.startswith("canFitShipType")])
+        fitsOnGroup.update([item.attributes[attr].value for attr in item.attributes if attr.startswith("canFitShipGroup")])
+
+        if (len(fitsOnGroup) > 0 or len(fitsOnType) > 0) \
+                and self.ship.item.group.ID not in fitsOnGroup \
+                and self.ship.item.ID not in fitsOnType:
+            return False
+
+        # Citadel modules are now under a new category, so we can check this to ensure only structure modules can fit on a citadel
+        if isinstance(self.ship, Citadel) and item.category.name != "Structure Module" or \
+                not isinstance(self.ship, Citadel) and item.category.name == "Structure Module":
+            return False
+
+        return True
+
     def clear(self, projected=False, command=False):
         self.__effectiveTank = None
         self.__weaponDpsMap = {}

eos/saveddata/module.py

@@ -539,34 +539,8 @@ class Module(HandledItem, HandledCharge, ItemAttrShortcut, ChargeAttrShortcut):
         return fits
 
     def __fitRestrictions(self, fit, hardpointLimit=True):
-        # Check ship type restrictions
-        fitsOnType = set()
-        fitsOnGroup = set()
 
-        shipType = self.getModifiedItemAttr("fitsToShipType", None)
-        if shipType is not None:
-            fitsOnType.add(shipType)
-
-        for attr in list(self.itemModifiedAttributes.keys()):
-            if attr.startswith("canFitShipType"):
-                shipType = self.getModifiedItemAttr(attr, None)
-                if shipType is not None:
-                    fitsOnType.add(shipType)
-
-        for attr in list(self.itemModifiedAttributes.keys()):
-            if attr.startswith("canFitShipGroup"):
-                shipGroup = self.getModifiedItemAttr(attr, None)
-                if shipGroup is not None:
-                    fitsOnGroup.add(shipGroup)
-
-        if (len(fitsOnGroup) > 0 or len(fitsOnType) > 0) \
-                and fit.ship.item.group.ID not in fitsOnGroup \
-                and fit.ship.item.ID not in fitsOnType:
-            return False
-
-        # Citadel modules are now under a new category, so we can check this to ensure only structure modules can fit on a citadel
-        if isinstance(fit.ship, Citadel) and self.item.category.name != "Structure Module" or \
-                not isinstance(fit.ship, Citadel) and self.item.category.name == "Structure Module":
+        if not fit.canFit(self.item):
             return False
 
         # EVE doesn't let capital modules be fit onto subcapital hulls. Confirmed by CCP Larrikin that this is dictated