A wire that lost two edges still called itself done

An extrude built a solid the user never drew: three sides of the handle plus the arc
that bulges outside the outline, with the bowl's second arc and the left edge missing.

Two faults met. entities_to_wires added edges in ENTITY-CREATION order, so a partial
wire rejects the next edge even when the sketch closes perfectly; and one joint of the
reported sketch is open by 2.28e-5 mm, wider than OCCT's 1e-7 vertex tolerance and
wider than this function's own EPS of 1e-6, so that edge was refused on geometry too.

Neither showed up, because BRepLib_MakeWire::Add DROPS a disconnected edge
(BRepLib_DisconnectedWire + NotDone) while every successful Add ends with
BRepLib_WireDone + Done() — overwriting the failure. `if (!wm.IsDone()) return {}`
was therefore asking only whether the LAST edge connected. Six edges in, four out,
IsDone() true.

Endpoints now weld into shared nodes at one tolerance (kSketchWeldTol) used by BOTH
the union-find grouping and the wire build — they disagreed before, which is how a
joint gets united into a loop and then refused by the builder. Each node becomes ONE
TopoDS_Vertex, so the builder matches on identity instead of proximity, with the
vertex tolerance widened because BRepLib_MakeEdge::Init projects a vertex onto the
curve within that tolerance and a welded node sits up to the weld gap off its
neighbour's curve. Members are then walked in traversal order. Finally the result is
counted: IsDone() alone is not evidence, edge_count == members.size() is.

Arc geometry is untouched — the midpoint from (start_angle+end_angle)/2 and the
solver's angle reflow both measured correct and were never part of this.

The regression case carries the reported sketch verbatim, open joint included. It
fails 4 == 6 without the fix, which was measured, not assumed. Kernel 66092
assertions / 604 cases green.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011FbJKJAJxxkhDTs9XdZzKA

tests/libslic3r/test_sketchedit.cpp

@@ -1,6 +1,8 @@
 #include <catch2/catch_all.hpp>   // mainline OrcaSlicer ships Catch2 v3 (v2 was catch2/catch.hpp)
 #include "libslic3r/CAD/SketchEngine.hpp"
 #include <cmath>
+#include <TopExp_Explorer.hxx>
+#include <TopAbs.hxx>
 
 using namespace Slic3r;
 
@@ -499,3 +501,57 @@ TEST_CASE("Trim arc with no crossing returns false", "[SketchEdit]")
 
     REQUIRE_FALSE(SketchEngine::trim_entity(e, {cut}, Vec2d(5 * std::cos(M_PI/4), 5 * std::sin(M_PI/4))));
 }
+
+// Regression guard: BEFORE the weld fix this test failed with 4 edges instead of 6.
+// BRepLib_MakeWire::Add silently DROPS a disconnected edge (BRepLib_DisconnectedWire + NotDone)
+// yet every successful Add ends with BRepLib_WireDone + Done(), so IsDone() reported only whether
+// the LAST edge connected. This sketch is a real user loop (2 arcs + 4 lines) given in
+// creation order, which is NOT traversal order, and its joint between the 3rd and 4th entity
+// below is open by 2.28e-5 mm — larger than OCCT's default vertex tolerance.
+TEST_CASE("entities_to_wires keeps every edge of a loop drawn out of order", "[SketchEngine]")
+{
+    std::vector<SketchEntity> ents(6);
+
+    ents[0].type = SketchEntity::Type::Line;
+    ents[0].p0   = Vec2d(-0.537697713190522, -0.0009077462579133498);
+    ents[0].p1   = Vec2d(99.46230228680926, -0.0009141694814321626);
+
+    ents[1].type        = SketchEntity::Type::Arc;
+    ents[1].p0          = Vec2d(-0.537697713190522, -0.0009077462579133498);
+    ents[1].p1          = Vec2d(-100.14602636660666, -0.27673132181233495);
+    ents[1].center      = Vec2d(-50.313868583115394, -10.248112903179617);
+    ents[1].radius      = 50.81999999999999;
+    ents[1].start_angle = 0.20302922018398933;
+    ents[1].end_angle   = 2.944101582158999;
+
+    ents[2].type = SketchEntity::Type::Line;
+    ents[2].p0   = Vec2d(99.46228668626469, -39.22091416947833);
+    ents[2].p1   = Vec2d(-0.537864366432629, -39.22420589376945);
+
+    ents[3].type        = SketchEntity::Type::Arc;
+    ents[3].p0          = Vec2d(-100.14602636694521, -38.94673132181234);
+    ents[3].p1          = Vec2d(-0.5378420354900413, -39.22421049164698);
+    ents[3].center      = Vec2d(-50.31377078666179, -28.975499083790503);
+    ents[3].radius      = 50.82006659345552;
+    ents[3].start_angle = -2.944104841286737;
+    ents[3].end_angle   = -0.20305921095748136;
+
+    ents[4].type = SketchEntity::Type::Line;
+    ents[4].p0   = Vec2d(99.46228668626469, -39.22091416947833);
+    ents[4].p1   = Vec2d(99.46230228680926, -0.0009141694814321626);
+
+    ents[5].type = SketchEntity::Type::Line;
+    ents[5].p0   = Vec2d(-100.14602636694521, -38.94673132181234);
+    ents[5].p1   = Vec2d(-100.14602636660666, -0.27673132181233495);
+
+    auto wires = SketchEngine::entities_to_wires(ents, SketchPlane::XY());
+
+    REQUIRE(wires.size() == 1);
+
+    int edge_count = 0;
+    for (TopExp_Explorer ex(wires[0], TopAbs_EDGE); ex.More(); ex.Next())
+        ++edge_count;
+    REQUIRE(edge_count == 6);
+
+    REQUIRE(wires[0].Closed());
+}