fix: error using empty array of structs parameter (#474)

* fix: error using empty array of structs parameter

* Add QueryParameterType classes

* Use query parameter types with ArrayQueryParameter

* Adjust system test to changed ArrayQueryParameter

* Clarify a comment about an assertion

Co-authored-by: Tim Swast <swast@google.com>

* Clarify when name/descr. is omitted from API repr

* Rename subtypes to fields

* Add fields property to StructQueryParameterType

* Add a check for empty struct fields

* Define scalar SQL parameter types as type objects

Co-authored-by: Tim Swast <swast@google.com>

google/cloud/bigquery/__init__.py

@@ -66,8 +66,11 @@
 from google.cloud.bigquery.model import Model
 from google.cloud.bigquery.model import ModelReference
 from google.cloud.bigquery.query import ArrayQueryParameter
+from google.cloud.bigquery.query import ArrayQueryParameterType
 from google.cloud.bigquery.query import ScalarQueryParameter
+from google.cloud.bigquery.query import ScalarQueryParameterType
 from google.cloud.bigquery.query import StructQueryParameter
+from google.cloud.bigquery.query import StructQueryParameterType
 from google.cloud.bigquery.query import UDFResource
 from google.cloud.bigquery.retry import DEFAULT_RETRY
 from google.cloud.bigquery.routine import DeterminismLevel
@@ -93,6 +96,9 @@
     "ArrayQueryParameter",
     "ScalarQueryParameter",
     "StructQueryParameter",
+    "ArrayQueryParameterType",
+    "ScalarQueryParameterType",
+    "StructQueryParameterType",
     # Datasets
     "Dataset",
     "DatasetReference",

google/cloud/bigquery/enums.py

@@ -18,6 +18,7 @@
 import itertools
 
 from google.cloud.bigquery_v2 import types as gapic_types
+from google.cloud.bigquery.query import ScalarQueryParameterType
 
 
 class Compression(object):
@@ -215,6 +216,26 @@ class SqlTypeNames(str, enum.Enum):
     DATETIME = "DATETIME"
 
 
+class SqlParameterScalarTypes:
+    """Supported scalar SQL query parameter types as type objects."""
+
+    STRING = ScalarQueryParameterType("STRING")
+    BYTES = ScalarQueryParameterType("BYTES")
+    INTEGER = ScalarQueryParameterType("INT64")
+    INT64 = ScalarQueryParameterType("INT64")
+    FLOAT = ScalarQueryParameterType("FLOAT64")
+    FLOAT64 = ScalarQueryParameterType("FLOAT64")
+    NUMERIC = ScalarQueryParameterType("NUMERIC")
+    BIGNUMERIC = ScalarQueryParameterType("BIGNUMERIC")
+    BOOLEAN = ScalarQueryParameterType("BOOL")
+    BOOL = ScalarQueryParameterType("BOOL")
+    GEOGRAPHY = ScalarQueryParameterType("GEOGRAPHY")
+    TIMESTAMP = ScalarQueryParameterType("TIMESTAMP")
+    DATE = ScalarQueryParameterType("DATE")
+    TIME = ScalarQueryParameterType("TIME")
+    DATETIME = ScalarQueryParameterType("DATETIME")
+
+
 class WriteDisposition(object):
     """Specifies the action that occurs if destination table already exists.