String xsd:double value crash toRdf()

.gitignore

@@ -14,3 +14,9 @@ lib/PyLD.egg-info
 profiler
 tests/test_caching.py
 tests/data/test_caching.json
+
+# JetBrains IDEs
+.idea
+
+# pyenv
+.python-version

lib/pyld/jsonld.py

@@ -3661,12 +3661,33 @@ def _object_to_rdf(self, item, issuer, triples, rdfDirection):
             elif _is_bool(value):
                 object['value'] = 'true' if value else 'false'
                 object['datatype'] = datatype or XSD_BOOLEAN
-            elif _is_double(value) or datatype == XSD_DOUBLE:
-                # canonical double representation
-                object['value'] = re.sub(
-                    r'(\d)0*E\+?0*(\d)', r'\1E\2',
-                    ('%1.15E' % value))
-                object['datatype'] = datatype or XSD_DOUBLE
+
+            elif _is_double(value):
+                return {
+                    **object,
+                    'value': _canonicalize_double(value),
+                    'datatype': datatype or XSD_DOUBLE,
+                }
+
+            elif datatype == XSD_DOUBLE:
+                # Since the previous branch did not activate, we know that `value` is not a float number.
+                try:
+                    float_value = float(value)
+                except (ValueError, TypeError):
+                    # If `value` is not convertible to float, we will return it as-is.
+                    return {
+                        **object,
+                        'value': value,
+                        'datatype': XSD_DOUBLE,
+                    }
+                else:
+                    # We have a float, and canonicalization may proceed.
+                    return {
+                        **object,
+                        'value': _canonicalize_double(float_value),
+                        'datatype': XSD_DOUBLE,
+                    }
+
             elif _is_integer(value):
                 object['value'] = str(value)
                 object['datatype'] = datatype or XSD_INTEGER
@@ -6390,6 +6411,13 @@ def _is_double(v):
     return not isinstance(v, Integral) and isinstance(v, Real)
 
 
+def _canonicalize_double(value: float) -> str:
+    """Convert a float value to canonical lexical form of `xsd:double`."""
+    return re.sub(
+        r'(\d)0*E\+?0*(\d)', r'\1E\2',
+        ('%1.15E' % value))
+
+
 def _is_numeric(v):
     """
     Returns True if the given value is numeric.

tests/test_double_to_rdf.py

@@ -0,0 +1,69 @@
+"""
+Tests for to_rdf functionality, specifically focusing on double/float handling bugs.
+"""
+
+import json
+import sys
+import os
+import unittest
+
+# Add the lib directory to the path so we can import pyld
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', 'lib'))
+
+import pyld.jsonld
+
+
+class TestDoubleToRdf(unittest.TestCase):
+    """Test cases for to_rdf functionality with double/float values."""
+
+    def test_offline_pyld_bug_reproduction(self):
+        """Test reproducing the PyLD bug with captured Wikidata data structure."""
+        # This is the exact problematic data structure captured from Wikidata Q399
+        # The bug occurs when PyLD tries to convert this to RDF
+        data = {
+            "@context": {
+                "xsd": "http://www.w3.org/2001/XMLSchema#",
+                "geoLongitude": "http://www.w3.org/2003/01/geo/wgs84_pos#longitude"
+            },
+            "@graph": [
+                {
+                    "@id": "http://www.wikidata.org/entity/Q399",
+                    "geoLongitude": {
+                        "@type": "xsd:double",
+                        "@value": "45"  # This string number causes the PyLD bug
+                    }
+                }
+            ]
+        }
+
+        # This should work now that the bug is fixed
+        # The bug was in PyLD's _object_to_rdf method where string values
+        # with @type: "xsd:double" were not being converted to float
+        result = pyld.jsonld.to_rdf(data)
+
+        # Expected result after bug fix
+        expected = {
+            "@default": [
+                {
+                    "subject": {
+                        "type": "IRI",
+                        "value": "http://www.wikidata.org/entity/Q399"
+                    },
+                    "predicate": {
+                        "type": "IRI",
+                        "value": "http://www.w3.org/2003/01/geo/wgs84_pos#longitude"
+                    },
+                    "object": {
+                        "type": "literal",
+                        "value": "4.5E1",
+                        "datatype": "http://www.w3.org/2001/XMLSchema#double"
+                    }
+                }
+            ]
+        }
+
+        self.assertEqual(result, expected)
+
+
+if __name__ == '__main__':
+    unittest.main()