Fix Dice.roll() ValueError for sides=0, matching ROM's dice()

area_reader/__init__.py

@@ -761,9 +761,15 @@ def read(cls, reader, **kwargs):
 		return cls(number=number, sides=sides, bonus=bonus, **kwargs)
 
 	def roll(self):
+		# ROM's dice() (src/db.c) returns 0 for size 0, and its
+		# number_range() clamps a degenerate range to the low bound,
+		# so negative sides roll 1 per die.
+		if self.sides == 0:
+			return self.bonus
 		score = 0
+		sides = max(self.sides, 1)
 		for roll in range(self.number):
-			score += random.randrange(1, self.sides + 1)
+			score += random.randrange(1, sides + 1)
 		score += self.bonus
 		return score
 

test_area_reader.py

@@ -29,6 +29,16 @@ def test_dice_roll_includes_the_maximum_face(monkeypatch):
 	assert area_reader.Dice(number=2, sides=1, bonus=3).roll() == 5
 
 
+def test_dice_roll_zero_sides_contributes_zero():
+	assert area_reader.Dice(number=2, sides=0, bonus=0).roll() == 0
+	assert area_reader.Dice(number=5, sides=0, bonus=7).roll() == 7
+	assert area_reader.Dice().roll() == 0
+
+
+def test_dice_roll_negative_sides_rolls_one_per_die():
+	assert area_reader.Dice(number=3, sides=-4, bonus=2).roll() == 5
+
+
 reset_command = st.sampled_from(["M", "O", "P", "G", "E", "D", "R"])
 small_int = st.integers(min_value=0, max_value=9999)
 rom_source_dir = Path(r"C:\Users\Q\src\Rom24b6\area")