fix: add error if geometry is unfixable

.pre-commit-config.yaml

@@ -15,7 +15,7 @@ repos:
   - repo: https://github.com/charliermarsh/ruff-pre-commit
     rev: v0.14.6
     hooks:
-      - id: ruff
+      - id: ruff-check
         types_or: [python, pyi, jupyter]
       - id: ruff-format
         types_or: [python, pyi, jupyter]

src/antimeridian/_implementation.py

@@ -358,10 +358,19 @@ def fix_polygon(
         if shapely.is_ccw(polygon.exterior):
             return polygon
         else:
-            return Polygon(
+            pole_covering_polygon = Polygon(
                 [(-180, 90), (-180, -90), (180, -90), (180, 90)],
                 [polygon.exterior.coords],
             )
+            if shapely.is_valid(pole_covering_polygon):
+                return pole_covering_polygon
+            else:
+                raise ValueError(
+                    "Fixed polygon is invalid, check your input polygon for validity. "
+                    "Reason your polygon is invalid: "
+                    + shapely.is_valid_reason(polygon)
+                )
+
     else:
         return MultiPolygon(polygons)
 

tests/data/input/issues-182.json

@@ -0,0 +1,28 @@
+{
+  "coordinates": [
+    [
+      [41.701686, 27.555683],
+      [41.677091, 27.556499],
+      [41.701686, 27.555683],
+      [41.701676, 27.552681],
+      [41.694555, 27.537487],
+      [41.69456, 27.536652],
+      [41.684332, 27.538833],
+      [41.683195, 27.539543],
+      [41.674979, 27.541187],
+      [41.672853, 27.540324],
+      [41.671549, 27.538989],
+      [41.671067, 27.537625],
+      [41.665152, 27.538274],
+      [41.664217, 27.538102],
+      [41.661835, 27.538401],
+      [41.66299, 27.541284],
+      [41.667426, 27.54781],
+      [41.67182, 27.554058],
+      [41.674274, 27.555888],
+      [41.677091, 27.556499],
+      [41.701686, 27.555683]
+    ]
+  ],
+  "type": "Polygon"
+}

tests/test_polygon.py

@@ -18,8 +18,9 @@
         "complex-split",
         "crossing-latitude",
         "extra-crossing",
-        "issues-81",
         "issues-171",
+        "issues-187",
+        "issues-81",
         "latitude-band",
         "north-pole",
         "one-hole",
@@ -30,7 +31,6 @@
         "south-pole",
         "split",
         "two-holes",
-        "issues-187",
     ],
 )
 @pytest.mark.parametrize(
@@ -253,3 +253,10 @@ def test_great_circle(
     output = read_output("great-circle", subdirectory)
     fixed = antimeridian.fix_polygon(input, great_circle=great_circle)
     assert fixed.normalize() == output.normalize()
+
+
+def test_invalid_polygon(read_input: Reader) -> None:
+    input = read_input("issues-182")
+    with pytest.warns(FixWindingWarning):
+        with pytest.raises(ValueError):
+            antimeridian.fix_polygon(input)