fix(tokens): normalize inverted bbox in get_location instead of asserting

docling_core/types/doc/tokens.py

@@ -302,14 +302,20 @@ def get_location(
         ysize: int = 500,  # TODO review
         self_closing: bool = False,
     ):
-        """Get the location string give bbox and page-dim."""
-        assert bbox[0] <= bbox[2], f"bbox[0]<=bbox[2] => {bbox[0]}<={bbox[2]}"
-        assert bbox[1] <= bbox[3], f"bbox[1]<=bbox[3] => {bbox[1]}<={bbox[3]}"
-
-        x0 = bbox[0] / page_w
-        y0 = bbox[1] / page_h
-        x1 = bbox[2] / page_w
-        y1 = bbox[3] / page_h
+        """Get the location string given bbox and page-dim."""
+        # Normalize potentially inverted coordinates instead of asserting on
+        # them. Near-degenerate elements (e.g. a thin rule whose layout-model
+        # regression produced a slightly inverted bbox) can arrive with
+        # bbox[0] > bbox[2] or bbox[1] > bbox[3]. The min()/max() calls below
+        # already emit correctly-ordered tokens, so sorting here mirrors that
+        # normalization and avoids crashing export_to_doctags on valid output.
+        left, right = sorted((bbox[0], bbox[2]))
+        top, bottom = sorted((bbox[1], bbox[3]))
+
+        x0 = left / page_w
+        y0 = top / page_h
+        x1 = right / page_w
+        y1 = bottom / page_h
 
         x0_tok = DocumentToken.get_location_token(val=min(x0, x1), rnorm=xsize, self_closing=self_closing)
         y0_tok = DocumentToken.get_location_token(val=min(y0, y1), rnorm=ysize, self_closing=self_closing)

test/test_tokens.py

@@ -0,0 +1,51 @@
+"""Unit tests for document tokens."""
+
+from docling_core.types.doc.tokens import DocumentToken
+
+
+def test_get_location_normal_bbox():
+    """A well-ordered bbox produces correctly-ordered location tokens."""
+    loc = DocumentToken.get_location(
+        bbox=(100.0, 200.0, 300.0, 400.0),
+        page_w=1000.0,
+        page_h=1000.0,
+    )
+    assert loc == "<loc_50><loc_100><loc_150><loc_200>"
+
+
+def test_get_location_inverted_bbox_does_not_crash():
+    """A near-degenerate, slightly inverted bbox must not raise.
+
+    Regression test for #620: layout-model regression can emit a bbox with
+    bbox[1] > bbox[3] (or bbox[0] > bbox[2]) on thin/degenerate elements.
+    get_location already normalizes coordinates via min()/max() downstream,
+    so it should serialize such boxes instead of crashing export_to_doctags.
+    """
+    # bbox from the issue: y is inverted by 7.7pt (633.39 > 625.68).
+    inverted = DocumentToken.get_location(
+        bbox=(0.0, 633.3925132751465, 100.0, 625.6789665222168),
+        page_w=1000.0,
+        page_h=1000.0,
+    )
+    # The result must equal the same box with y-coordinates ordered correctly.
+    normalized = DocumentToken.get_location(
+        bbox=(0.0, 625.6789665222168, 100.0, 633.3925132751465),
+        page_w=1000.0,
+        page_h=1000.0,
+    )
+    assert inverted == normalized
+
+
+def test_get_location_fully_inverted_bbox():
+    """Both axes inverted still normalizes to the ordered box."""
+    inverted = DocumentToken.get_location(
+        bbox=(300.0, 400.0, 100.0, 200.0),
+        page_w=1000.0,
+        page_h=1000.0,
+    )
+    ordered = DocumentToken.get_location(
+        bbox=(100.0, 200.0, 300.0, 400.0),
+        page_w=1000.0,
+        page_h=1000.0,
+    )
+    assert inverted == ordered