Add future=True to create_engine/Session; unify select()

Several weeks of using the future_select() construct
has led to the proposal there be just one select() construct
again which features the new join() method, and otherwise accepts
both the 1.x and 2.x argument styles.   This would make
migration simpler and reduce confusion.

However, confusion may be increased by the fact that select().join()
is different  Current thinking is we may be better off
with a few hard behavioral changes to old and relatively unknown APIs
rather than trying to play both sides within two extremely similar
but subtly different APIs.  At the moment, the .join() thing seems
to be the only behavioral change that occurs without the user
taking any explicit steps.   Session.execute() will still
behave the old way as we are adding a future flag.

This change also adds the "future" flag to Session() and
session.execute(), so that interpretation of the incoming statement,
as well as that the new style result is returned, does not
occur for existing applications unless they add the use
of this flag.

The change in general is moving the "removed in 2.0" system
further along where we want the test suite to fully pass
even if the SQLALCHEMY_WARN_20 flag is set.

Get many tests to pass when SQLALCHEMY_WARN_20 is set; this
should be ongoing after this patch merges.

Improve the RemovedIn20 warning; these are all deprecated
"since" 1.4, so ensure that's what the messages read.
Make sure the inforamtion link is on all warnings.
Add deprecation warnings for parameters present and
add warnings to all FromClause.select() types of methods.

Fixes: #5379
Fixes: #5284
Change-Id: I765a0b912b3dcd0e995426427d8bb7997cbffd51
References: #5159

6 files changed, 86 insertions, 26 deletions

diff --git a/lib/sqlalchemy/orm/context.py b/lib/sqlalchemy/orm/context.py
index 09163d4e9..d5f001db1 100644
--- a/lib/sqlalchemy/orm/context.py
+++ b/lib/sqlalchemy/orm/context.py
@@ -25,6 +25,7 @@ from ..sql import expression
 from ..sql import roles
 from ..sql import util as sql_util
 from ..sql import visitors
+from ..sql.base import _entity_namespace_key
 from ..sql.base import _select_iterables
 from ..sql.base import CacheableOptions
 from ..sql.base import CompileState
@@ -241,8 +242,6 @@ class ORMCompileState(CompileState):
         # were passed to session.execute:
         # session.execute(legacy_select([User.id, User.name]))
         # see test_query->test_legacy_tuple_old_select
-        if not statement._is_future:
-            return result
 
         load_options = execution_options.get(
             "_sa_orm_load_options", QueryContext.default_load_options
@@ -399,6 +398,7 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
     compound_eager_adapter = None
 
     correlate = None
+    correlate_except = None
     _where_criteria = ()
     _having_criteria = ()
 
@@ -406,9 +406,6 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
     def create_for_statement(cls, statement, compiler, **kw):
         """compiler hook, we arrive here from compiler.visit_select() only."""
 
-        if not statement._is_future:
-            return SelectState(statement, compiler, **kw)
-
         if compiler is not None:
             toplevel = not compiler.stack
             compiler._rewrites_selected_columns = True
@@ -592,6 +589,13 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
                     for s in query._correlate
                 )
             )
+        elif query._correlate_except:
+            self.correlate_except = tuple(
+                util.flatten_iterator(
+                    sql_util.surface_selectables(s) if s is not None else None
+                    for s in query._correlate_except
+                )
+            )
         elif not query._auto_correlate:
             self.correlate = (None,)
 
@@ -827,6 +831,7 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
             hints=self.select_statement._hints,
             statement_hints=self.select_statement._statement_hints,
             correlate=self.correlate,
+            correlate_except=self.correlate_except,
             **self._select_args
         )
 
@@ -902,6 +907,7 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
             hints=self.select_statement._hints,
             statement_hints=self.select_statement._statement_hints,
             correlate=self.correlate,
+            correlate_except=self.correlate_except,
             **self._select_args
         )
 
@@ -921,6 +927,7 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
         hints,
         statement_hints,
         correlate,
+        correlate_except,
         limit_clause,
         offset_clause,
         distinct,
@@ -972,6 +979,11 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
         if correlate:
             statement.correlate.non_generative(statement, *correlate)
 
+        if correlate_except:
+            statement.correlate_except.non_generative(
+                statement, *correlate_except
+            )
+
         return statement
 
     def _adapt_polymorphic_element(self, element):
@@ -1222,7 +1234,7 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
                 # string given, e.g. query(Foo).join("bar").
                 # we look to the left entity or what we last joined
                 # towards
-                onclause = sql.util._entity_namespace_key(
+                onclause = _entity_namespace_key(
                     inspect(self._joinpoint_zero()), onclause
                 )
 
@@ -1243,9 +1255,7 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
                 info = inspect(jp0)
 
                 if getattr(info, "mapper", None) is onclause._parententity:
-                    onclause = sql.util._entity_namespace_key(
-                        info, onclause.key
-                    )
+                    onclause = _entity_namespace_key(info, onclause.key)
             # legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
             if isinstance(onclause, interfaces.PropComparator):
diff --git a/lib/sqlalchemy/orm/loading.py b/lib/sqlalchemy/orm/loading.py
index abb8ce32d..55c2b79f5 100644
--- a/lib/sqlalchemy/orm/loading.py
+++ b/lib/sqlalchemy/orm/loading.py
@@ -431,6 +431,7 @@ def load_on_pk_identity(
             params=load_options._params,
             execution_options={"_sa_orm_load_options": load_options},
             bind_arguments=bind_arguments,
+            future=True,
         )
         .unique()
         .scalars()
diff --git a/lib/sqlalchemy/orm/persistence.py b/lib/sqlalchemy/orm/persistence.py
index cbe7bde33..0cc16b96e 100644
--- a/lib/sqlalchemy/orm/persistence.py
+++ b/lib/sqlalchemy/orm/persistence.py
@@ -29,17 +29,17 @@ from .. import future
 from .. import sql
 from .. import util
 from ..engine import result as _result
-from ..future import select as future_select
 from ..sql import coercions
 from ..sql import expression
 from ..sql import operators
 from ..sql import roles
+from ..sql import select
+from ..sql.base import _entity_namespace_key
 from ..sql.base import CompileState
 from ..sql.base import Options
 from ..sql.dml import DeleteDMLState
 from ..sql.dml import UpdateDMLState
 from ..sql.elements import BooleanClauseList
-from ..sql.util import _entity_namespace_key
 
 
 def _bulk_insert(
@@ -887,7 +887,7 @@ def _emit_update_statements(
                 )
             )
 
-        stmt = table.update(clauses)
+        stmt = table.update().where(clauses)
         return stmt
 
     cached_stmt = base_mapper._memo(("update", table), update_stmt)
@@ -1280,7 +1280,7 @@ def _emit_post_update_statements(
                 )
             )
 
-        stmt = table.update(clauses)
+        stmt = table.update().where(clauses)
 
         if mapper.version_id_col is not None:
             stmt = stmt.return_defaults(mapper.version_id_col)
@@ -1394,7 +1394,7 @@ def _emit_delete_statements(
                 )
             )
 
-        return table.delete(clauses)
+        return table.delete().where(clauses)
 
     statement = base_mapper._memo(("delete", table), delete_stmt)
     for connection, recs in groupby(delete, lambda rec: rec[1]):  # connection
@@ -1940,7 +1940,7 @@ class BulkUDCompileState(CompileState):
             for k, v in iterator:
                 if mapper:
                     if isinstance(k, util.string_types):
-                        desc = sql.util._entity_namespace_key(mapper, k)
+                        desc = _entity_namespace_key(mapper, k)
                         values.extend(desc._bulk_update_tuples(v))
                     elif "entity_namespace" in k._annotations:
                         k_anno = k._annotations
@@ -1989,7 +1989,7 @@ class BulkUDCompileState(CompileState):
     ):
         mapper = update_options._subject_mapper
 
-        select_stmt = future_select(
+        select_stmt = select(
             *(mapper.primary_key + (mapper.select_identity_token,))
         )
         select_stmt._where_criteria = statement._where_criteria
@@ -2007,6 +2007,7 @@ class BulkUDCompileState(CompileState):
             execution_options,
             bind_arguments,
             _add_event=skip_for_full_returning,
+            future=True,
         )
         matched_rows = result.fetchall()
 
diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index 1ca65c733..acc76094b 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -45,12 +45,13 @@ from .. import inspection
 from .. import log
 from .. import sql
 from .. import util
-from ..future.selectable import Select as FutureSelect
 from ..sql import coercions
 from ..sql import expression
 from ..sql import roles
+from ..sql import Select
 from ..sql import util as sql_util
 from ..sql.annotation import SupportsCloneAnnotations
+from ..sql.base import _entity_namespace_key
 from ..sql.base import _generative
 from ..sql.base import Executable
 from ..sql.selectable import _SelectFromElements
@@ -61,7 +62,6 @@ from ..sql.selectable import HasSuffixes
 from ..sql.selectable import LABEL_STYLE_NONE
 from ..sql.selectable import LABEL_STYLE_TABLENAME_PLUS_COL
 from ..sql.selectable import SelectStatementGrouping
-from ..sql.util import _entity_namespace_key
 from ..sql.visitors import InternalTraversal
 from ..util import collections_abc
 
@@ -419,7 +419,7 @@ class Query(
             stmt._propagate_attrs = self._propagate_attrs
         else:
             # Query / select() internal attributes are 99% cross-compatible
-            stmt = FutureSelect.__new__(FutureSelect)
+            stmt = Select.__new__(Select)
             stmt.__dict__.update(self.__dict__)
             stmt.__dict__.update(
                 _label_style=self._label_style,
@@ -2836,6 +2836,7 @@ class Query(
             statement,
             params,
             execution_options={"_sa_orm_load_options": self.load_options},
+            future=True,
         )
 
         # legacy: automatically set scalars, unique
@@ -3209,6 +3210,7 @@ class Query(
             delete_,
             self.load_options._params,
             execution_options={"synchronize_session": synchronize_session},
+            future=True,
         )
         bulk_del.result = result
         self.session.dispatch.after_bulk_delete(bulk_del)
@@ -3363,6 +3365,7 @@ class Query(
             upd,
             self.load_options._params,
             execution_options={"synchronize_session": synchronize_session},
+            future=True,
         )
         bulk_ud.result = result
         self.session.dispatch.after_bulk_update(bulk_ud)
diff --git a/lib/sqlalchemy/orm/relationships.py b/lib/sqlalchemy/orm/relationships.py
index bedc54153..0be15260e 100644
--- a/lib/sqlalchemy/orm/relationships.py
+++ b/lib/sqlalchemy/orm/relationships.py
@@ -1352,12 +1352,18 @@ class RelationshipProperty(StrategizedProperty):
             crit = j & sql.True_._ifnone(criterion)
 
             if secondary is not None:
-                ex = sql.exists(
-                    [1], crit, from_obj=[dest, secondary]
-                ).correlate_except(dest, secondary)
+                ex = (
+                    sql.exists(1)
+                    .where(crit)
+                    .select_from(dest, secondary)
+                    .correlate_except(dest, secondary)
+                )
             else:
-                ex = sql.exists([1], crit, from_obj=dest).correlate_except(
-                    dest
+                ex = (
+                    sql.exists(1)
+                    .where(crit)
+                    .select_from(dest)
+                    .correlate_except(dest)
                 )
             return ex
 
diff --git a/lib/sqlalchemy/orm/session.py b/lib/sqlalchemy/orm/session.py
index abc990f7b..f4f7374e4 100644
--- a/lib/sqlalchemy/orm/session.py
+++ b/lib/sqlalchemy/orm/session.py
@@ -118,6 +118,7 @@ class ORMExecuteState(util.MemoizedSlots):
         "_compile_state_cls",
         "_starting_event_idx",
         "_events_todo",
+        "_future",
     )
 
     def __init__(
@@ -129,6 +130,7 @@ class ORMExecuteState(util.MemoizedSlots):
         bind_arguments,
         compile_state_cls,
         events_todo,
+        future,
     ):
         self.session = session
         self.statement = statement
@@ -137,6 +139,7 @@ class ORMExecuteState(util.MemoizedSlots):
         self.bind_arguments = bind_arguments
         self._compile_state_cls = compile_state_cls
         self._events_todo = list(events_todo)
+        self._future = future
 
     def _remaining_events(self):
         return self._events_todo[self._starting_event_idx + 1 :]
@@ -212,6 +215,7 @@ class ORMExecuteState(util.MemoizedSlots):
             _execution_options,
             _bind_arguments,
             _parent_execute_state=self,
+            future=self._future,
         )
 
     @property
@@ -924,6 +928,7 @@ class Session(_SessionClassMethods):
         self,
         bind=None,
         autoflush=True,
+        future=False,
         expire_on_commit=True,
         autocommit=False,
         twophase=False,
@@ -1039,6 +1044,26 @@ class Session(_SessionClassMethods):
            so that all attribute/object access subsequent to a completed
            transaction will load from the most recent database state.
 
+        :param future: if True, use 2.0 style behavior for the
+          :meth:`_orm.Session.execute` method.  This includes that the
+          :class:`_engine.Result` object returned will return new-style
+          tuple rows, as well as that Core constructs such as
+          :class:`_sql.Select`,
+          :class:`_sql.Update` and :class:`_sql.Delete` will be interpreted
+          in an ORM context if they are made against ORM entities rather than
+          plain :class:`.Table` metadata objects.
+
+          The "future" flag is also available on a per-execution basis
+          using the :paramref:`_orm.Session.execute.future` flag.
+
+          .. versionadded:: 1.4
+
+          .. seealso::
+
+            :ref:`migration_20_toplevel`
+
+            :ref:`migration_20_result_rows`
+
         :param info: optional dictionary of arbitrary data to be associated
            with this :class:`.Session`.  Is available via the
            :attr:`.Session.info` attribute.  Note the dictionary is copied at
@@ -1071,6 +1096,7 @@ class Session(_SessionClassMethods):
         self._flushing = False
         self._warn_on_events = False
         self._transaction = None
+        self.future = future
         self.hash_key = _new_sessionid()
         self.autoflush = autoflush
         self.autocommit = autocommit
@@ -1387,6 +1413,7 @@ class Session(_SessionClassMethods):
         params=None,
         execution_options=util.immutabledict(),
         bind_arguments=None,
+        future=False,
         _parent_execute_state=None,
         _add_event=None,
         **kw
@@ -1493,6 +1520,14 @@ class Session(_SessionClassMethods):
          Contents of this dictionary are passed to the
          :meth:`.Session.get_bind` method.
 
+        :param future:
+            Use future style execution for this statement.  This is
+            the same effect as the :paramref:`_orm.Session.future` flag,
+            except at the level of this single statement execution.  See
+            that flag for details.
+
+            .. versionadded:: 1.4
+
         :param mapper:
           deprecated; use the bind_arguments dictionary
 
@@ -1518,15 +1553,18 @@ class Session(_SessionClassMethods):
         """
         statement = coercions.expect(roles.CoerceTextStatementRole, statement)
 
+        future = future or self.future
+
         if not bind_arguments:
             bind_arguments = kw
         elif kw:
             bind_arguments.update(kw)
 
-        if (
+        if future and (
             statement._propagate_attrs.get("compile_state_plugin", None)
             == "orm"
         ):
+            # note that even without "future" mode, we need
             compile_state_cls = CompileState._get_plugin_class_for_plugin(
                 statement, "orm"
             )
@@ -1547,7 +1585,7 @@ class Session(_SessionClassMethods):
             )
         else:
             bind_arguments.setdefault("clause", statement)
-            if statement._is_future:
+            if future:
                 execution_options = util.immutabledict().merge_with(
                     execution_options, {"future_result": True}
                 )
@@ -1568,6 +1606,7 @@ class Session(_SessionClassMethods):
                 bind_arguments,
                 compile_state_cls,
                 events_todo,
+                future,
             )
             for idx, fn in enumerate(events_todo):
                 orm_exec_state._starting_event_idx = idx