Add type accessors for JSON indexed/pathed element access

Added new accessors to expressions of type :class:`.JSON` to allow for
specific datatype access and comparison, covering strings, integers,
numeric, boolean elements.   This revises the documented approach of
CASTing to string when comparing values, instead adding specific
functionality into the PostgreSQL, SQlite, MySQL dialects to reliably
deliver these basic types in all cases.

The change also delivers a new feature to the test exclusions
system so that combinations and exclusions can be used together.

Fixes: #4276
Change-Id: Ica5a926c060feb40a0a7cd60b9d6e061d7825728

1 files changed, 12 insertions, 2 deletions

diff --git a/lib/sqlalchemy/dialects/sqlite/base.py b/lib/sqlalchemy/dialects/sqlite/base.py
index 02d44a260..2685a9243 100644
--- a/lib/sqlalchemy/dialects/sqlite/base.py
+++ b/lib/sqlalchemy/dialects/sqlite/base.py
@@ -1012,13 +1012,23 @@ class SQLiteCompiler(compiler.SQLCompiler):
         )
 
     def visit_json_getitem_op_binary(self, binary, operator, **kw):
-        return "JSON_QUOTE(JSON_EXTRACT(%s, %s))" % (
+        if binary.type._type_affinity is sqltypes.JSON:
+            expr = "JSON_QUOTE(JSON_EXTRACT(%s, %s))"
+        else:
+            expr = "JSON_EXTRACT(%s, %s)"
+
+        return expr % (
             self.process(binary.left, **kw),
             self.process(binary.right, **kw),
         )
 
     def visit_json_path_getitem_op_binary(self, binary, operator, **kw):
-        return "JSON_QUOTE(JSON_EXTRACT(%s, %s))" % (
+        if binary.type._type_affinity is sqltypes.JSON:
+            expr = "JSON_QUOTE(JSON_EXTRACT(%s, %s))"
+        else:
+            expr = "JSON_EXTRACT(%s, %s)"
+
+        return expr % (
             self.process(binary.left, **kw),
             self.process(binary.right, **kw),
         )