Add an API function for reading the nominal skill level.

LUA_API.rst

@@ -918,6 +918,11 @@ Units module
   Returns the age of the unit in years as a floating-point value.
   If ``true_age`` is true, ignores false identities.
 
+* ``dfhack.units.getNominalSkill(unit, skill[, use_rust])``
+
+  Retrieves the nominal skill level for the given unit. If ``use_rust``
+  is *true*, subtracts the rust penalty.
+
 * ``dfhack.units.getEffectiveSkill(unit, skill)``
 
   Computes the effective rating for the given skill, taking into account exhaustion, pain etc.

library/LuaApi.cpp

@@ -828,6 +828,7 @@ static const LuaWrapper::FunctionReg dfhack_units_module[] = {
     WRAPM(Units, isDwarf),
     WRAPM(Units, isCitizen),
     WRAPM(Units, getAge),
+    WRAPM(Units, getNominalSkill),
     WRAPM(Units, getEffectiveSkill),
     WRAPM(Units, computeMovementSpeed),
     WRAPM(Units, getProfessionName),

library/include/modules/Units.h

@@ -233,6 +233,7 @@ DFHACK_EXPORT bool isDwarf(df::unit *unit);
 
 DFHACK_EXPORT double getAge(df::unit *unit, bool true_age = false);
 
+DFHACK_EXPORT int getNominalSkill(df::unit *unit, df::job_skill skill_id, bool use_rust = false);
 DFHACK_EXPORT int getEffectiveSkill(df::unit *unit, df::job_skill skill_id);
 DFHACK_EXPORT int computeMovementSpeed(df::unit *unit);
 

library/modules/Units.cpp

@@ -876,7 +876,7 @@ inline void adjust_skill_rating(int &rating, bool is_adventure, int value, int d
     }
 }
 
-int Units::getEffectiveSkill(df::unit *unit, df::job_skill skill_id)
+int Units::getNominalSkill(df::unit *unit, df::job_skill skill_id, bool use_rust)
 {
     CHECK_NULL_POINTER(unit);
 
@@ -892,9 +892,24 @@ int Units::getEffectiveSkill(df::unit *unit, df::job_skill skill_id)
     df::enum_field<df::job_skill,int16_t> key(skill_id);
     auto skill = binsearch_in_vector(unit->status.current_soul->skills, &df::unit_skill::id, key);
 
-    int rating = 0;
     if (skill)
-        rating = std::max(0, int(skill->rating) - skill->rusty);
+    {
+        int rating = int(skill->rating);
+        if (use_rust)
+            rating -= skill->rusty;
+        return std::max(0, rating);
+    }
+
+    return 0;
+}
+
+int Units::getEffectiveSkill(df::unit *unit, df::job_skill skill_id)
+{
+    /*
+     * This is 100% reverse-engineered from DF code.
+     */
+
+    int rating = getNominalSkill(unit, skill_id, true);
 
     // Apply special states