Workplane.rect: test and document negative lengths (#774)

Author: marcus7070

cadquery/cq.py

@@ -2491,10 +2491,8 @@ def rect(
         """
         Make a rectangle for each item on the stack.
 
-        :param xLen: length in xDirection ( in workplane coordinates )
-        :type xLen: float > 0
-        :param yLen: length in yDirection ( in workplane coordinates )
-        :type yLen: float > 0
+        :param xLen: length in the x direction (in workplane coordinates)
+        :param yLen: length in the y direction (in workplane coordinates)
         :param centered: If True, the rectangle will be centered around the reference
           point. If False, the corner of the rectangle will be on the reference point and
           it will extend in the positive x and y directions. Can also use a 2-tuple to
@@ -2511,6 +2509,9 @@ def rect(
 
         Creates 4 circles at the corners of a square centered on the origin.
 
+        Negative values for xLen and yLen are permitted, although they only have an effect when
+        centered is False.
+
         Future Enhancements:
             * project points not in the workplane plane onto the workplane plane
         """

tests/test_cadquery.py

@@ -434,6 +434,27 @@ def testRect(self):
             )
             self.assertTupleAlmostEquals(v0, v1, 3)
 
+        # test negative lengths
+        r0 = Workplane().rect(-x, -y, centered=False)
+        self.assertTupleAlmostEquals(
+            (0, 0, 0), r0.vertices(">X and >Y").val().toTuple(), 3
+        )
+        self.assertTupleAlmostEquals(
+            (-x, -y, 0), r0.vertices("<X and <Y").val().toTuple(), 3
+        )
+        # test move plus negative length
+        r1 = Workplane().move(x, y).rect(-x, -y, centered=False)
+        self.assertTupleAlmostEquals(
+            (x, y, 0), r1.vertices(">X and >Y").val().toTuple(), 3
+        )
+        self.assertTupleAlmostEquals(
+            (0, 0, 0), r1.vertices("<X and <Y").val().toTuple(), 3
+        )
+        # negative length should have no effect with centered=True
+        v2 = Workplane().rect(x, y).vertices(">X and >Y").val().toTuple()
+        v3 = Workplane().rect(-x, -y).vertices(">X and >Y").val().toTuple()
+        self.assertTupleAlmostEquals(v2, v3, 3)
+
     def testLoft(self):
         """
         Test making a lofted solid