Only convert Range for sqlalchemy Range object

Refined the new approach to range objects described at :ref:`change_7156`
to accommodate driver-specific range and multirange objects, to better
accommodate both legacy code as well as when passing results from raw SQL
result sets back into new range or multirange expressions.

Fixes: #8690
Change-Id: I7e62c47067f695c6380ad0fe2fe19deaf33594d1

3 files changed, 19 insertions, 23 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/asyncpg.py b/lib/sqlalchemy/dialects/postgresql/asyncpg.py
index 96bac59d9..cd161d28e 100644
--- a/lib/sqlalchemy/dialects/postgresql/asyncpg.py
+++ b/lib/sqlalchemy/dialects/postgresql/asyncpg.py
@@ -293,13 +293,11 @@ class AsyncpgCHAR(sqltypes.CHAR):
 
 class _AsyncpgRange(ranges.AbstractRangeImpl):
     def bind_processor(self, dialect):
-        Range = dialect.dbapi.asyncpg.Range
-
-        NoneType = type(None)
+        asyncpg_Range = dialect.dbapi.asyncpg.Range
 
         def to_range(value):
-            if not isinstance(value, (str, NoneType)):
-                value = Range(
+            if isinstance(value, ranges.Range):
+                value = asyncpg_Range(
                     value.lower,
                     value.upper,
                     lower_inc=value.bounds[0] == "[",
@@ -328,7 +326,7 @@ class _AsyncpgRange(ranges.AbstractRangeImpl):
 
 class _AsyncpgMultiRange(ranges.AbstractMultiRangeImpl):
     def bind_processor(self, dialect):
-        Range = dialect.dbapi.asyncpg.Range
+        asyncpg_Range = dialect.dbapi.asyncpg.Range
 
         NoneType = type(None)
 
@@ -337,8 +335,8 @@ class _AsyncpgMultiRange(ranges.AbstractMultiRangeImpl):
                 return value
 
             def to_range(value):
-                if not isinstance(value, (str, NoneType)):
-                    value = Range(
+                if isinstance(value, ranges.Range):
+                    value = asyncpg_Range(
                         value.lower,
                         value.upper,
                         lower_inc=value.bounds[0] == "[",
diff --git a/lib/sqlalchemy/dialects/postgresql/psycopg.py b/lib/sqlalchemy/dialects/postgresql/psycopg.py
index 7ca274e2c..400c3186e 100644
--- a/lib/sqlalchemy/dialects/postgresql/psycopg.py
+++ b/lib/sqlalchemy/dialects/postgresql/psycopg.py
@@ -164,13 +164,11 @@ class _PGBoolean(sqltypes.Boolean):
 
 class _PsycopgRange(ranges.AbstractRangeImpl):
     def bind_processor(self, dialect):
-        Range = cast(PGDialect_psycopg, dialect)._psycopg_Range
-
-        NoneType = type(None)
+        psycopg_Range = cast(PGDialect_psycopg, dialect)._psycopg_Range
 
         def to_range(value):
-            if not isinstance(value, (str, NoneType)):
-                value = Range(
+            if isinstance(value, ranges.Range):
+                value = psycopg_Range(
                     value.lower, value.upper, value.bounds, value.empty
                 )
             return value
@@ -193,18 +191,20 @@ class _PsycopgRange(ranges.AbstractRangeImpl):
 
 class _PsycopgMultiRange(ranges.AbstractMultiRangeImpl):
     def bind_processor(self, dialect):
-        Range = cast(PGDialect_psycopg, dialect)._psycopg_Range
-        Multirange = cast(PGDialect_psycopg, dialect)._psycopg_Multirange
+        psycopg_Range = cast(PGDialect_psycopg, dialect)._psycopg_Range
+        psycopg_Multirange = cast(
+            PGDialect_psycopg, dialect
+        )._psycopg_Multirange
 
         NoneType = type(None)
 
         def to_range(value):
-            if isinstance(value, (str, NoneType)):
+            if isinstance(value, (str, NoneType, psycopg_Multirange)):
                 return value
 
-            return Multirange(
+            return psycopg_Multirange(
                 [
-                    Range(
+                    psycopg_Range(
                         element.lower,
                         element.upper,
                         element.bounds,
diff --git a/lib/sqlalchemy/dialects/postgresql/psycopg2.py b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
index 350f4b616..4a8df5b5e 100644
--- a/lib/sqlalchemy/dialects/postgresql/psycopg2.py
+++ b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
@@ -503,16 +503,14 @@ class _Psycopg2Range(ranges.AbstractRangeImpl):
     _psycopg2_range_cls = "none"
 
     def bind_processor(self, dialect):
-        Range = getattr(
+        psycopg2_Range = getattr(
             cast(PGDialect_psycopg2, dialect)._psycopg2_extras,
             self._psycopg2_range_cls,
         )
 
-        NoneType = type(None)
-
         def to_range(value):
-            if not isinstance(value, (str, NoneType)):
-                value = Range(
+            if isinstance(value, ranges.Range):
+                value = psycopg2_Range(
                     value.lower, value.upper, value.bounds, value.empty
                 )
             return value