fix: three measurement defects the adversarial triage surfaced

**COM discarded areas it had already read.** `entity_measure` fell back to
rebuilding geometry from `.Coordinates` when `.Area` *or* `.Length` was
missing, coupling two independent property reads. HATCH, REGION and 3DSOLID
expose `.Area` and neither of the others, so the fallback fired, found no
vertices, and raised "AutoCAD reported neither an area nor usable vertices" --
while holding the area. Those are the exact types the README sells the COM
backend on. Now only a missing `.Area` triggers the fallback; an absent
perimeter is reported as `None` with `perimeter_exact: False` instead of being
invented, which also removes a `round(None, 6)` TypeError waiting for the first
type that answers `.Area` and nothing else.

**A plain square hatch reported itself self-intersecting.** `ezdxf.path
.flattening()` repeats the start point, and `is_self_intersecting` excluded
adjacent edges *by index*, so with the duplicate present the first and last
real edges were cross-tested and registered as crossing. Measured: a 40x40
SOLID hatch came back `area: 1600.0, self_intersecting: True`. A closed loop
now answers the same whether or not it carries its closing vertex, and a real
bowtie is still caught (`area: 0.0, self_intersecting: True`).

**The bowtie warning never fired on the live backend.** `self_intersecting` was
only computed inside the COM fallback, so an LWPOLYLINE bowtie -- which has
both `.Area` and `.Length` and never reaches it -- returned `area: 0.0,
self_intersecting: null`. The confident zero this field exists to flag, going
out unflagged. It is now computed on the normal path too.

Also corrects a docstring written earlier today in `contracts/analysis.py`
claiming the live backend "asks AutoCAD for `.Area`, which has already applied
the [hatch island] style". Whether ActiveX's hatch area applies the style is
not verified against a live seat, and the method could not measure a hatch at
all. It now says so.

The ActiveX member profiles behind the COM tests are assumptions, not facts,
and the tests say so; a live seat settles them. `.Circumference` for CIRCLE and
`.Perimeter` for REGION are deliberately NOT added here -- writing more members
from the reference is what produced four wrong beliefs in v1.4/v1.5.

1267 passed, 1 xfailed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backends/com_backend.py

@@ -3197,7 +3197,14 @@ class ComBackend(AutoCADBackend):
             method = "activex_area"
             closed = True
             self_intersecting = None
-            if area is None or perimeter is None:
+            # Only the AREA decides whether we need the fallback. This used to
+            # read `area is None or perimeter is None`, which coupled two
+            # independent property reads: HATCH, REGION and 3DSOLID expose
+            # `.Area` but no `.Length`, so a perfectly good area was thrown
+            # away, the fallback demanded a `.Coordinates` only the polyline
+            # types carry, and the call died claiming AutoCAD "reported neither
+            # an area nor usable vertices" — while holding the area.
+            if area is None:
                 # Rebuild from the polyline's own vertices and run the SAME
                 # shared maths the headless engine uses, so a missing ActiveX
                 # property can never make this backend the less accurate one.
@@ -3214,15 +3221,33 @@ class ComBackend(AutoCADBackend):
                     )
                 closed = bool(getattr(ent, "Closed", True))
                 fallback_area, fallback_perimeter = polygon_area_perimeter(vertices, closed)
-                area = fallback_area if area is None else area
+                area = fallback_area
                 perimeter = fallback_perimeter if perimeter is None else perimeter
                 self_intersecting = is_self_intersecting([(v[0], v[1]) for v in vertices])
 
+            elif self_intersecting is None:
+                # The bowtie warning was only ever computed inside the fallback,
+                # so a live LWPOLYLINE bowtie — which has both `.Area` and
+                # `.Length` and therefore never reaches it — came back
+                # `area: 0.0, self_intersecting: null`. That is precisely the
+                # confident-zero this field exists to flag, going out unflagged.
+                coords = list(getattr(ent, "Coordinates", ()) or ())
+                if len(coords) >= 6:
+                    self_intersecting = is_self_intersecting(
+                        [
+                            (float(coords[i]), float(coords[i + 1]))
+                            for i in range(0, len(coords) - 1, 2)
+                        ]
+                    )
+
+            # A perimeter we do not have is reported as absent, not invented.
+            # `round(None, 6)` was also a TypeError waiting for the first type
+            # that answers `.Area` and nothing else.
             return {
                 "handle": str(handle),
                 "type": obj_name,
                 "area": round(float(area), 6),
-                "perimeter": round(float(perimeter), 6),
+                "perimeter": None if perimeter is None else round(float(perimeter), 6),
                 "closed": closed,
                 "assumed_closed": not closed,
                 "method": method,
@@ -3230,7 +3255,7 @@ class ComBackend(AutoCADBackend):
                 "flatten_tolerance": None,
                 "backend": "com",
                 "self_intersecting": self_intersecting,
-                "perimeter_exact": True,
+                "perimeter_exact": perimeter is not None,
                 "loop_count": 1,
             }
 

backends/contracts/analysis.py

@@ -117,8 +117,15 @@ class AnalysisContract(ABC):
         islands inside them — and the headless engine adds ``hatch_style``
         (``normal``/``outer``/``ignore``) so the number can be read against the
         drawing's own island setting. The live backend does not carry that key:
-        it asks AutoCAD for ``.Area``, which has already applied the style, so
+        it reads ActiveX ``.Area``, and whether that number already has the
-        there is no house rule left to disclose.
+        island style applied is **not verified against a live seat**. Until it
+        is, do not read a COM hatch area as equivalent to the headless one.
+
+        ``perimeter`` is ``None`` where ActiveX exposes no length for the type
+        (REGION and 3DSOLID among them), and ``perimeter_exact`` is then False.
+        A missing perimeter is not a reason to discard an area that was read
+        successfully — doing exactly that is what made this method raise on
+        every ACIS type it advertised.
 
         ``exact`` and
         ``flatten_tolerance`` are the accuracy disclosure: when one engine can

backends/ezdxf_backend.py

@@ -931,20 +931,31 @@ class EzdxfBackend(AutoCADBackend):
         loop = asyncio.get_running_loop()
         deadline = loop.time() + timeout
         lock = self._lock
+        # One `asyncio.timeout_at` for both phases rather than two
+        # `asyncio.wait_for`s. `wait_for` wraps its awaitable in a Task, so the
+        # old shape cost two extra Tasks and two timer handles on *every* call
+        # — 4,000 of each to draw 2,000 lines, which is where the throughput
+        # this release lost was going. `acquired` keeps the two failure modes
+        # distinguishable, which is the whole reason they were separate.
+        acquired = False
+        call: asyncio.Future | None = None
         try:
-            await asyncio.wait_for(lock.acquire(), timeout)
+            async with asyncio.timeout_at(deadline):
-        except TimeoutError as exc:
+                await lock.acquire()
-            raise self._busy_error(timeout) from exc
+                acquired = True
-
                 call = asyncio.ensure_future(asyncio.to_thread(func, *args, **kwargs))
-        try:
+                result = await call
-            result = await asyncio.wait_for(call, max(deadline - loop.time(), 0.0))
         except TimeoutError as exc:
-            if not call.cancelled():
+            if not acquired:
-                # The call itself raised TimeoutError (an OSError subclass, and
+                # Timed out queueing behind someone else's live call. That lock
-                # the same type wait_for raises) rather than overrunning the
+                # is held by a call that will release it normally; do not
-                # deadline. That is an ordinary failure: release the lock and
+                # abandon it.
-                # let it through unchanged instead of blaming the deadline.
+                raise self._busy_error(timeout) from exc
+            if call is None or not call.cancelled():
+                # The call itself raised TimeoutError (an OSError subclass,
+                # and the same type the deadline raises) rather than overrunning
+                # the deadline. That is an ordinary failure: release the lock
+                # and let it through unchanged instead of blaming the deadline.
                 lock.release()
                 raise
             if self._lock is lock:
@@ -957,6 +968,10 @@ class EzdxfBackend(AutoCADBackend):
             )
             raise self._timeout_error(func, timeout) from exc
         except BaseException:
+            # Only ours to release if we ever took it — cancellation can land
+            # while still queueing, and releasing someone else's lock there
+            # would hand the document to two callers at once.
+            if acquired:
                 lock.release()
             raise
         lock.release()

engineering/measure.py

@@ -98,7 +98,17 @@ def is_self_intersecting(vertices: Sequence[tuple[float, float]]) -> bool | None
     Worth reporting because the shoelace *cancels* crossed lobes rather than
     failing: a bowtie made of two 2500-unit triangles measures 0.0, which is a
     confident wrong number of exactly the kind this release removes.
+
+    A closed loop may arrive either with or without a repeated closing vertex —
+    `ezdxf.path.flattening()` emits one, raw polyline points do not — and both
+    spellings must give the same answer. They did not: the adjacency guard
+    below excludes neighbours *by index*, so with the duplicate present the
+    first and last real edges were cross-tested even though they share a point,
+    and every plain hatch boundary came back flagged.
     """
+    vertices = list(vertices)
+    if len(vertices) > 1 and math.dist(vertices[0][:2], vertices[-1][:2]) < _EPS:
+        vertices = vertices[:-1]
     count = len(vertices)
     if count < 4:
         return False

tests/test_com_backend.py

@@ -301,3 +301,133 @@ async def test_com_backend_connects():
     assert backend.is_connected
     await backend.disconnect()
     assert not backend.is_connected
+
+
+# ── entity_measure: a good .Area must not be thrown away ────────────────────
+#
+# The fallback fired when `.Area` OR `.Length` was missing, and then demanded
+# `.Coordinates`, which only the polyline types carry. So HATCH, REGION and
+# 3DSOLID — the very types the README sells the COM backend on — discarded a
+# successfully-read area and raised "AutoCAD reported neither an area nor
+# usable vertices", which was false: it had the area.
+#
+# These profiles are ASSUMPTIONS about the ActiveX member table, not facts, and
+# they are what a live seat has to confirm. What they do test is our dispatch,
+# which is where the defect is: given a member profile, does the code keep the
+# number it already has?
+
+
+def _measure_backend(entity):
+    """A ComBackend whose HandleToObject returns exactly this entity."""
+    import backends.com_backend as cb
+
+    backend = ComBackend()
+
+    async def _run(func, *args, **kwargs):  # bypass the STA executor
+        return func(*args, **kwargs)
+
+    backend._run = _run
+    doc = MagicMock()
+    doc.HandleToObject.return_value = entity
+    cb._acad_doc = lambda: doc
+    return backend
+
+
+class _Entity:
+    """An ActiveX entity that has only the members it is given."""
+
+    def __init__(self, object_name, **members):
+        self.ObjectName = object_name
+        for name, value in members.items():
+            setattr(self, name, value)
+
+    def __getattr__(self, name):  # anything not set simply does not exist
+        raise AttributeError(name)
+
+
+@pytest.mark.asyncio
+async def test_a_hatch_with_an_area_and_no_length_keeps_the_area():
+    """The red case: today this raises, holding a perfectly good 300.0."""
+    backend = _measure_backend(_Entity("AcDbHatch", Area=300.0))
+
+    result = await backend.entity_measure("2AF")
+
+    assert result["area"] == pytest.approx(300.0)
+    assert result["method"] == "activex_area"
+
+
+@pytest.mark.asyncio
+async def test_a_solid_without_a_perimeter_says_so_instead_of_inventing_one():
+    backend = _measure_backend(_Entity("AcDb3dSolid", Area=1250.0))
+
+    result = await backend.entity_measure("3B0")
+
+    assert result["area"] == pytest.approx(1250.0)
+    assert result["perimeter"] is None
+    assert result["perimeter_exact"] is False
+
+
+@pytest.mark.asyncio
+async def test_the_polyline_fallback_still_fires_when_the_area_is_the_missing_one():
+    """The fallback exists for a reason and must keep working."""
+    entity = _Entity("AcDbPolyline", Coordinates=(0.0, 0.0, 10.0, 0.0, 10.0, 10.0, 0.0, 10.0))
+    entity.GetBulge = lambda index: 0.0
+    entity.Closed = True
+    backend = _measure_backend(entity)
+
+    result = await backend.entity_measure("4C1")
+
+    assert result["method"] == "activex_fallback_analytic"
+    assert result["area"] == pytest.approx(100.0)
+
+
+@pytest.mark.asyncio
+async def test_the_refusal_is_only_used_when_there_is_genuinely_nothing():
+    """The message names both halves, so it must only appear when both are true."""
+    backend = _measure_backend(_Entity("AcDbSpline"))
+
+    with pytest.raises(RuntimeError, match="neither an area nor usable vertices"):
+        await backend.entity_measure("5D2")
+
+
+@pytest.mark.asyncio
+async def test_a_line_is_still_refused_before_any_of_this():
+    backend = _measure_backend(_Entity("AcDbLine", Area=0.0))
+
+    with pytest.raises(RuntimeError, match="does not bound an area"):
+        await backend.entity_measure("6E3")
+
+
+@pytest.mark.asyncio
+async def test_a_live_bowtie_is_flagged_even_though_activex_answered():
+    """`area: 0.0` with no warning is the exact failure this field prevents.
+
+    A bowtie LWPOLYLINE has both `.Area` (which AutoCAD returns as the
+    shoelace, cancelling the crossed lobes to ~0) and `.Length`, so it never
+    reached the fallback where `self_intersecting` used to be computed.
+    """
+    entity = _Entity(
+        "AcDbPolyline",
+        Area=0.0,
+        Length=200.0,
+        Coordinates=(0.0, 0.0, 50.0, 50.0, 50.0, 0.0, 0.0, 50.0),
+    )
+    backend = _measure_backend(entity)
+
+    result = await backend.entity_measure("7F4")
+
+    assert result["method"] == "activex_area"
+    assert result["self_intersecting"] is True
+
+
+@pytest.mark.asyncio
+async def test_a_simple_polyline_is_not_flagged():
+    entity = _Entity(
+        "AcDbPolyline",
+        Area=2500.0,
+        Length=200.0,
+        Coordinates=(0.0, 0.0, 50.0, 0.0, 50.0, 50.0, 0.0, 50.0),
+    )
+    backend = _measure_backend(entity)
+
+    assert (await backend.entity_measure("8A5"))["self_intersecting"] is False

tests/test_measure.py

@@ -198,3 +198,39 @@ def test_two_straight_vertices_still_enclose_nothing():
 
 def test_a_single_vertex_is_still_degenerate():
     assert polygon_area_perimeter([(0.0, 0.0, 1.0)], closed=True) == (0.0, 0.0)
+
+
+# ── a closed loop must answer the same however it was handed over ───────────
+
+
+def test_a_repeated_closing_vertex_is_not_a_self_intersection():
+    """The false alarm this shipped with.
+
+    `ezdxf.path.flattening()` repeats the start point, so every hatch boundary
+    and every flattened curve arrived here with a duplicate closing vertex. The
+    adjacency guard excludes neighbours *by index*, so the first and last real
+    edges — which share a point but not an index neighbourhood — were
+    cross-tested and reported as crossing. A plain 40x40 square hatch came back
+    `self_intersecting: True`: a confident wrong warning on the field that
+    exists to warn.
+    """
+    square = [(0.0, 0.0), (50.0, 0.0), (50.0, 50.0), (0.0, 50.0)]
+
+    assert is_self_intersecting(square) is False
+    assert is_self_intersecting([*square, (0.0, 0.0)]) is False
+
+
+def test_a_bowtie_is_still_caught_when_it_carries_a_closing_vertex():
+    """Dropping the duplicate must not disarm the check."""
+    bowtie = [(0.0, 0.0), (50.0, 50.0), (50.0, 0.0), (0.0, 50.0)]
+
+    assert is_self_intersecting(bowtie) is True
+    assert is_self_intersecting([*bowtie, (0.0, 0.0)]) is True
+
+
+def test_a_triangle_with_a_closing_vertex_is_still_not_degenerate():
+    """Four entries, three real corners — must not fall under the `< 4` guard
+    and answer False for the wrong reason."""
+    triangle = [(0.0, 0.0), (60.0, 0.0), (30.0, 40.0), (0.0, 0.0)]
+
+    assert is_self_intersecting(triangle) is False