CAM: Add tests loading a helical path created with v0.21

This demonstrates a regression introduced with PR #14364, where documents
containing helix operations cannot be recomputed any more (see #15643).
This is in preparation for a fix and to ensure we don't break it again.
The fixture has been created with the official mac build of FreeCAD-0.21.1

src/Mod/CAM/CAMTests/PathTestUtils.py

@@ -185,3 +185,14 @@ class PathTestBase(unittest.TestCase):
         self.assertEqual(len(pts0), len(pts1))
         for i in range(len(pts0)):
             self.assertCoincide(pts0[i], pts1[i])
+
+    def assertSuccessfulRecompute(self, doc, *objs, msg=None):
+        """Asserts that the given objects can be successfully recomputed."""
+        if len(objs) == 0:
+            doc.recompute()
+            objs = doc.Objects
+        else:
+            doc.recompute(objs)
+        failed_objects = [o.Name for o in objs if "Invalid" in o.State]
+        if len(failed_objects) > 0:
+            self.fail(msg or f"Recompute failed for {failed_objects}")

src/Mod/CAM/CAMTests/TestPathHelix.py

@@ -20,6 +20,8 @@
 # *                                                                         *
 # ***************************************************************************
 
+import pathlib
+
 import Draft
 import FreeCAD
 import Path
@@ -27,6 +29,8 @@ import Path.Main.Job as PathJob
 import Path.Op.Helix as PathHelix
 import CAMTests.PathTestUtils as PathTestUtils
 
+FIXTURE_PATH = pathlib.Path(__file__).parent / "Fixtures"
+
 Path.Log.setLevel(Path.Log.Level.INFO, Path.Log.thisModule())
 # Path.Log.trackModule(Path.Log.thisModule())
 
@@ -126,3 +130,47 @@ class TestPathHelix(PathTestUtils.PathTestBase):
                     self.assertRoughly(
                         round(pos.Length / 10, 0), proxy.holeDiameter(op, model, sub)
                     )
+
+    def testRecomputeHelixFromV021(self):
+        """Verify that we can still open and recompute a Helix created with older FreeCAD"""
+        self.tearDown()
+        self.doc = FreeCAD.openDocument(str(FIXTURE_PATH / "OpHelix_v0-21.FCStd"))
+        created_with = f"created with {self.doc.getProgramVersion()}"
+
+        def check(helix, direction, start_side, cut_mode):
+            with self.subTest(f"{helix.Name}: {direction}, {start_side}, {cut_mode}"):
+                # no recompute yet, i.e. check original as precondition
+                self.assertEqual(
+                    helix.Direction,
+                    direction,
+                    msg=f"Direction does not match fixture for helix {created_with}",
+                )
+                self.assertEqual(
+                    helix.StartSide,
+                    start_side,
+                    msg=f"StartSide does not match fixture for helix {created_with}",
+                )
+
+                # now see whether we can recompute the object from the old document
+                helix.enforceRecompute()
+                self.assertSuccessfulRecompute(
+                    self.doc, helix, msg=f"Cannot recompute helix {created_with}"
+                )
+                self.assertEqual(
+                    helix.Direction,
+                    direction,
+                    msg=f"Direction changed after recomputing helix {created_with}",
+                )
+                self.assertEqual(
+                    helix.StartSide,
+                    start_side,
+                    msg=f"StartSide changed after recomputing helix {created_with}",
+                )
+                # self.assertEqual(helix.CutMode, cut_mode,
+                #    msg=f"CutMode not correctly derived for helix {created_with}")
+
+        # object names and expected values defined in the fixture
+        check(self.doc.Helix, "CW", "Inside", "Conventional")
+        check(self.doc.Helix001, "CW", "Outside", "Climb")
+        check(self.doc.Helix002, "CCW", "Inside", "Climb")
+        check(self.doc.Helix003, "CCW", "Outside", "Conventional")

src/Mod/CAM/CMakeLists.txt

@@ -349,6 +349,10 @@ SET(Tests_SRCS
     CAMTests/Tools/Shape/test-path-tool-bit-shape-00.fcstd
 )
 
+SET(Tests_Fixtures
+    CAMTests/Fixtures/OpHelix_v0-21.FCStd
+)
+
 SET(PathImages_Ops
     Images/Ops/chamfer.svg
 )
@@ -411,6 +415,7 @@ ADD_CUSTOM_TARGET(PathScripts ALL
 SET(test_files
   ${Path_Scripts}
   ${Tests_SRCS}
+  ${Tests_Fixtures}
 )
 
 ADD_CUSTOM_TARGET(Tests ALL
@@ -536,6 +541,13 @@ INSTALL(
         Mod/CAM/CAMTests
 )
 
+INSTALL(
+    FILES
+        ${Tests_Fixtures}
+    DESTINATION
+        Mod/CAM/CAMTests/Fixtures
+)
+
 INSTALL(
   DIRECTORY
       CAMTests/Tools