additional testing for sea serpent visibility

src/kernel/unit.c

@@ -1218,9 +1218,11 @@ int invisible(const unit * target, const unit * viewer)
             if (hidden > target->number) hidden = target->number;
             if (viewer) {
                 const resource_type *rtype = get_resourcetype(R_AMULET_OF_TRUE_SEEING);
+                if (rtype) {
                     hidden -= i_get(viewer->items, rtype->itype);
                 }
             }
+        }
         return hidden;
     }
 }

src/laws.c

@@ -4032,11 +4032,16 @@ static enum cansee_t cansee_ex(const unit *u, const region *r, const unit *targe
     enum cansee_t result = CANSEE_HIDDEN;
     if (rings >= target->number) {
         const resource_type *rtype = get_resourcetype(R_AMULET_OF_TRUE_SEEING);
+        if (rtype) {
             int amulet = i_get(u->items, rtype->itype);
             if (amulet <= 0) {
                 return CANSEE_INVISIBLE;
             }
         }
+        else {
+            return CANSEE_INVISIBLE;
+        }
+    }
     if (skill_enabled(SK_PERCEPTION)) {
         int watch = effskill(u, SK_PERCEPTION, r);
         if (stealth > watch) {

src/laws.test.c

@@ -1967,6 +1967,42 @@ static void test_cansee_sphere(CuTest *tc) {
     test_teardown();
 }
 
+/**
+ * Hidden monsters are seen in oceans if they are big enough.
+ */
+static void test_cansee_monsters(CuTest *tc) {
+    unit *u, *u2;
+    race *rc;
+    const item_type *itype;
+
+    test_setup();
+    itype = test_create_itemtype("roi");
+    u = test_create_unit(test_create_faction(), test_create_ocean(0, 0));
+    u2 = test_create_unit(test_create_faction(), u->region);
+    rc = test_create_race("seaserpent");
+    rc->weight = 4999;
+    u_setrace(u2, rc);
+
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 0));
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 2));
+
+    set_level(u2, SK_STEALTH, 1);
+    CuAssertTrue(tc, !cansee(u->faction, u->region, u2, 0));
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 1));
+
+    rc->weight = 5000;
+    /* no stealth for fatties at sea */
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 0));
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 1));
+
+    /* rings still work */
+    i_change(&u2->items, itype, 1);
+    CuAssertTrue(tc, !cansee(u->faction, u->region, u2, 0));
+    CuAssertTrue(tc, !cansee(u->faction, u->region, u2, 2));
+
+    test_teardown();
+}
+
 static void test_nmr_timeout(CuTest *tc) {
     test_setup();
     CuAssertIntEquals(tc, 0, NMRTimeout());
@@ -2439,6 +2475,7 @@ CuSuite *get_laws_suite(void)
     SUITE_ADD_TEST(suite, test_cansee);
     SUITE_ADD_TEST(suite, test_cansee_ring);
     SUITE_ADD_TEST(suite, test_cansee_sphere);
+    SUITE_ADD_TEST(suite, test_cansee_monsters);
     SUITE_ADD_TEST(suite, test_nmr_timeout);
     SUITE_ADD_TEST(suite, test_long_orders);
     SUITE_ADD_TEST(suite, test_long_order_on_ocean);