From 0dcccc351dc23fc875b8ebfd01933067d64ed413 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adam=20Urba=C5=84czyk?=
 <adam-urbanczyk@users.noreply.github.com>
Date: Mon, 15 Feb 2021 21:18:09 +0100
Subject: [PATCH] tangentAt fix (#641)

* tangentAt fix

* Better testTangengAt

* Change default to length

* tests fix
---
 cadquery/occ_impl/shapes.py |  4 ++--
 tests/test_cadquery.py      | 17 +++++++++++++++--
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/cadquery/occ_impl/shapes.py b/cadquery/occ_impl/shapes.py
index 4e133d06..6fdc01c3 100644
--- a/cadquery/occ_impl/shapes.py
+++ b/cadquery/occ_impl/shapes.py
@@ -1117,7 +1117,7 @@ class Mixin1D(object):
     def tangentAt(
         self: Mixin1DProtocol,
         locationParam: float = 0.5,
-        mode: Literal["length", "parameter"] = "parameter",
+        mode: Literal["length", "parameter"] = "length",
     ) -> Vector:
         """
         Compute tangent vector at the specified location.
@@ -1137,7 +1137,7 @@ class Mixin1D(object):
         else:
             param = locationParam
 
-        curve.D1(self.paramAt(param), tmp, res)
+        curve.D1(param, tmp, res)
 
         return Vector(gp_Dir(res))
 
diff --git a/tests/test_cadquery.py b/tests/test_cadquery.py
index ad0b103b..e992b1a9 100644
--- a/tests/test_cadquery.py
+++ b/tests/test_cadquery.py
@@ -3999,8 +3999,21 @@ class TestCadQuery(BaseTest):
 
         path = Workplane("XZ").spline(pts, tangents=((0, 1), (1, 0))).val()
 
-        self.assertTrue(path.tangentAt(0.5) == path.tangentAt(0.5))
-        self.assertFalse(path.tangentAt(0.5) == path.tangentAt(0.5, mode="length"))
+        self.assertTrue(
+            path.tangentAt(0.0, mode="parameter") == path.tangentAt(0.0, mode="length")
+        )
+        self.assertFalse(
+            path.tangentAt(0.5, mode="parameter") == path.tangentAt(0.5, mode="length")
+        )
+
+        arc = Workplane().radiusArc((2, 0), 1).val()
+
+        self.assertTupleAlmostEquals(
+            arc.tangentAt(math.pi / 2, "parameter").toTuple(), (1, 0, 0), 6
+        )
+        self.assertTupleAlmostEquals(
+            arc.tangentAt(0.5, "length").toTuple(), (1, 0, 0), 6
+        )
 
     def testEnd(self):