Gracefully degrade for SQLite JSON receiving direct numeric value

Fixed issue to workaround SQLite's behavior of assigning "numeric" affinity
to JSON datatypes, first described at :ref:`change_3850`, which returns
scalar numeric JSON values as a number and not as a string that can be JSON
deserialized.  The SQLite-specific JSON deserializer now gracefully
degrades for this case as an exception and bypasses deserialization for
single numeric values, as from a JSON perspective they are already
deserialized.

Also adds a combinatoric fixture for JSON single values within
the dialect-general test suite.

Fixes: #5014
Change-Id: Id38221dce1271fec527ca198b23908547b25d8a0

1 files changed, 20 insertions, 1 deletions

diff --git a/lib/sqlalchemy/dialects/sqlite/base.py b/lib/sqlalchemy/dialects/sqlite/base.py
index 2685a9243..f228c151c 100644
--- a/lib/sqlalchemy/dialects/sqlite/base.py
+++ b/lib/sqlalchemy/dialects/sqlite/base.py
@@ -570,6 +570,7 @@ When using the per-:class:`.Engine` execution option, note that
 """  # noqa
 
 import datetime
+import numbers
 import re
 
 from .json import JSON
@@ -599,6 +600,24 @@ from ...types import TIMESTAMP  # noqa
 from ...types import VARCHAR  # noqa
 
 
+class _SQliteJson(JSON):
+    def result_processor(self, dialect, coltype):
+        default_processor = super(_SQliteJson, self).result_processor(
+            dialect, coltype
+        )
+
+        def process(value):
+            try:
+                return default_processor(value)
+            except TypeError:
+                if isinstance(value, numbers.Number):
+                    return value
+                else:
+                    raise
+
+        return process
+
+
 class _DateTimeMixin(object):
     _reg = None
     _storage_format = None
@@ -899,7 +918,7 @@ class TIME(_DateTimeMixin, sqltypes.Time):
 colspecs = {
     sqltypes.Date: DATE,
     sqltypes.DateTime: DATETIME,
-    sqltypes.JSON: JSON,
+    sqltypes.JSON: _SQliteJson,
     sqltypes.JSON.JSONIndexType: JSONIndexType,
     sqltypes.JSON.JSONPathType: JSONPathType,
     sqltypes.Time: TIME,