fix: insert_rows() accepts float column values as strings again (#824)

google/cloud/bigquery/_helpers.py

@@ -19,6 +19,7 @@
 import decimal
 import math
 import re
+from typing import Union
 
 from google.cloud._helpers import UTC
 from google.cloud._helpers import _date_from_iso8601_date
@@ -338,14 +339,15 @@ def _int_to_json(value):
     return value
 
 
-def _float_to_json(value):
+def _float_to_json(value) -> Union[None, str, float]:
     """Coerce 'value' to an JSON-compatible representation."""
     if value is None:
         return None
-    elif math.isnan(value) or math.isinf(value):
-        return str(value)
-    else:
-        return float(value)
+
+    if isinstance(value, str):
+        value = float(value)
+
+    return str(value) if (math.isnan(value) or math.isinf(value)) else float(value)
 
 
 def _decimal_to_json(value):

tests/unit/test__helpers.py

@@ -690,21 +690,45 @@ def _call_fut(self, value):
     def test_w_none(self):
         self.assertEqual(self._call_fut(None), None)
 
+    def test_w_non_numeric(self):
+        with self.assertRaises(TypeError):
+            self._call_fut(object())
+
+    def test_w_integer(self):
+        result = self._call_fut(123)
+        self.assertIsInstance(result, float)
+        self.assertEqual(result, 123.0)
+
     def test_w_float(self):
         self.assertEqual(self._call_fut(1.23), 1.23)
 
+    def test_w_float_as_string(self):
+        self.assertEqual(self._call_fut("1.23"), 1.23)
+
     def test_w_nan(self):
         result = self._call_fut(float("nan"))
         self.assertEqual(result.lower(), "nan")
 
+    def test_w_nan_as_string(self):
+        result = self._call_fut("NaN")
+        self.assertEqual(result.lower(), "nan")
+
     def test_w_infinity(self):
         result = self._call_fut(float("inf"))
         self.assertEqual(result.lower(), "inf")
 
+    def test_w_infinity_as_string(self):
+        result = self._call_fut("inf")
+        self.assertEqual(result.lower(), "inf")
+
     def test_w_negative_infinity(self):
         result = self._call_fut(float("-inf"))
         self.assertEqual(result.lower(), "-inf")
 
+    def test_w_negative_infinity_as_string(self):
+        result = self._call_fut("-inf")
+        self.assertEqual(result.lower(), "-inf")
+
 
 class Test_decimal_to_json(unittest.TestCase):
     def _call_fut(self, value):