initial reorganize for static typing

start applying foundational annotations to key
elements.

two main elements addressed here:

1. removal of public_factory() and replacement with
   explicit functions.  this just works much better with
   typing.

2. typing support for column expressions and operators.
   The biggest part of this involves stubbing out all the
   ColumnOperators methods under ColumnElement in a
   TYPE_CHECKING section.  Took me a while to see this
   method vs. much more complicated things I thought
   I needed.

Also for this version implementing #7519, ColumnElement
types against the Python type and not TypeEngine.  it is
hoped this leads to easier transferrence between ORM/Core
as well as eventual support for result set typing.
Not clear yet how well this approach will work and what
new issues it may introduce.

given the current approach we now get full, rich typing for
scenarios like this:

from sqlalchemy import column, Integer, String, Boolean

c1 = column('a', String)

c2 = column('a', Integer)

expr1 = c2.in_([1, 2, 3])

expr2 = c2 / 5

expr3 = -c2

expr4_a = ~(c2 == 5)

expr4_b = ~column('q', Boolean)

expr5 = c1 + 'x'

expr6 = c2 + 10

Fixes: #7519
Fixes: #6810
Change-Id: I078d9f57955549f6f7868314287175f6c61c44cb

1 files changed, 467 insertions, 0 deletions

diff --git a/lib/sqlalchemy/sql/_selectable_constructors.py b/lib/sqlalchemy/sql/_selectable_constructors.py
new file mode 100644
index 000000000..4b67c12f0
--- /dev/null
+++ b/lib/sqlalchemy/sql/_selectable_constructors.py
@@ -0,0 +1,467 @@
+# sql/_selectable_constructors.py
+# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
+# <see AUTHORS file>
+#
+# This module is part of SQLAlchemy and is released under
+# the MIT License: https://www.opensource.org/licenses/mit-license.php
+
+from typing import Any
+from typing import Type
+from typing import Union
+
+from . import coercions
+from . import roles
+from .elements import ColumnClause
+from .selectable import Alias
+from .selectable import CompoundSelect
+from .selectable import Exists
+from .selectable import Join
+from .selectable import Lateral
+from .selectable import Select
+from .selectable import TableClause
+from .selectable import TableSample
+from .selectable import Values
+
+
+def alias(selectable, name=None, flat=False):
+    """Return an :class:`_expression.Alias` object.
+
+    An :class:`_expression.Alias` represents any
+    :class:`_expression.FromClause`
+    with an alternate name assigned within SQL, typically using the ``AS``
+    clause when generated, e.g. ``SELECT * FROM table AS aliasname``.
+
+    Similar functionality is available via the
+    :meth:`_expression.FromClause.alias`
+    method available on all :class:`_expression.FromClause` subclasses.
+    In terms of
+    a SELECT object as generated from the :func:`_expression.select`
+    function, the :meth:`_expression.SelectBase.alias` method returns an
+    :class:`_expression.Alias` or similar object which represents a named,
+    parenthesized subquery.
+
+    When an :class:`_expression.Alias` is created from a
+    :class:`_schema.Table` object,
+    this has the effect of the table being rendered
+    as ``tablename AS aliasname`` in a SELECT statement.
+
+    For :func:`_expression.select` objects, the effect is that of
+    creating a named subquery, i.e. ``(select ...) AS aliasname``.
+
+    The ``name`` parameter is optional, and provides the name
+    to use in the rendered SQL.  If blank, an "anonymous" name
+    will be deterministically generated at compile time.
+    Deterministic means the name is guaranteed to be unique against
+    other constructs used in the same statement, and will also be the
+    same name for each successive compilation of the same statement
+    object.
+
+    :param selectable: any :class:`_expression.FromClause` subclass,
+        such as a table, select statement, etc.
+
+    :param name: string name to be assigned as the alias.
+        If ``None``, a name will be deterministically generated
+        at compile time.
+
+    :param flat: Will be passed through to if the given selectable
+     is an instance of :class:`_expression.Join` - see
+     :meth:`_expression.Join.alias`
+     for details.
+
+    """
+    return Alias._factory(selectable, name=name, flat=flat)
+
+
+def cte(selectable, name=None, recursive=False):
+    r"""Return a new :class:`_expression.CTE`,
+    or Common Table Expression instance.
+
+    Please see :meth:`_expression.HasCTE.cte` for detail on CTE usage.
+
+    """
+    return coercions.expect(roles.HasCTERole, selectable).cte(
+        name=name, recursive=recursive
+    )
+
+
+def except_(*selects):
+    r"""Return an ``EXCEPT`` of multiple selectables.
+
+    The returned object is an instance of
+    :class:`_expression.CompoundSelect`.
+
+    :param \*selects:
+      a list of :class:`_expression.Select` instances.
+
+    """
+    return CompoundSelect._create_except(*selects)
+
+
+def except_all(*selects):
+    r"""Return an ``EXCEPT ALL`` of multiple selectables.
+
+    The returned object is an instance of
+    :class:`_expression.CompoundSelect`.
+
+    :param \*selects:
+      a list of :class:`_expression.Select` instances.
+
+    """
+    return CompoundSelect._create_except_all(*selects)
+
+
+def exists(__argument=None):
+    """Construct a new :class:`_expression.Exists` construct.
+
+    The :func:`_sql.exists` can be invoked by itself to produce an
+    :class:`_sql.Exists` construct, which will accept simple WHERE
+    criteria::
+
+        exists_criteria = exists().where(table1.c.col1 == table2.c.col2)
+
+    However, for greater flexibility in constructing the SELECT, an
+    existing :class:`_sql.Select` construct may be converted to an
+    :class:`_sql.Exists`, most conveniently by making use of the
+    :meth:`_sql.SelectBase.exists` method::
+
+        exists_criteria = (
+            select(table2.c.col2).
+            where(table1.c.col1 == table2.c.col2).
+            exists()
+        )
+
+    The EXISTS criteria is then used inside of an enclosing SELECT::
+
+        stmt = select(table1.c.col1).where(exists_criteria)
+
+    The above statement will then be of the form::
+
+        SELECT col1 FROM table1 WHERE EXISTS
+        (SELECT table2.col2 FROM table2 WHERE table2.col2 = table1.col1)
+
+    .. seealso::
+
+        :ref:`tutorial_exists` - in the :term:`2.0 style` tutorial.
+
+        :meth:`_sql.SelectBase.exists` - method to transform a ``SELECT`` to an
+        ``EXISTS`` clause.
+
+    """  # noqa E501
+
+    return Exists(__argument)
+
+
+def intersect(*selects):
+    r"""Return an ``INTERSECT`` of multiple selectables.
+
+    The returned object is an instance of
+    :class:`_expression.CompoundSelect`.
+
+    :param \*selects:
+      a list of :class:`_expression.Select` instances.
+
+    """
+    return CompoundSelect._create_intersect(*selects)
+
+
+def intersect_all(*selects):
+    r"""Return an ``INTERSECT ALL`` of multiple selectables.
+
+    The returned object is an instance of
+    :class:`_expression.CompoundSelect`.
+
+    :param \*selects:
+      a list of :class:`_expression.Select` instances.
+
+
+    """
+    return CompoundSelect._create_intersect_all(*selects)
+
+
+def join(left, right, onclause=None, isouter=False, full=False):
+    """Produce a :class:`_expression.Join` object, given two
+    :class:`_expression.FromClause`
+    expressions.
+
+    E.g.::
+
+        j = join(user_table, address_table,
+                 user_table.c.id == address_table.c.user_id)
+        stmt = select(user_table).select_from(j)
+
+    would emit SQL along the lines of::
+
+        SELECT user.id, user.name FROM user
+        JOIN address ON user.id = address.user_id
+
+    Similar functionality is available given any
+    :class:`_expression.FromClause` object (e.g. such as a
+    :class:`_schema.Table`) using
+    the :meth:`_expression.FromClause.join` method.
+
+    :param left: The left side of the join.
+
+    :param right: the right side of the join; this is any
+     :class:`_expression.FromClause` object such as a
+     :class:`_schema.Table` object, and
+     may also be a selectable-compatible object such as an ORM-mapped
+     class.
+
+    :param onclause: a SQL expression representing the ON clause of the
+     join.  If left at ``None``, :meth:`_expression.FromClause.join`
+     will attempt to
+     join the two tables based on a foreign key relationship.
+
+    :param isouter: if True, render a LEFT OUTER JOIN, instead of JOIN.
+
+    :param full: if True, render a FULL OUTER JOIN, instead of JOIN.
+
+     .. versionadded:: 1.1
+
+    .. seealso::
+
+        :meth:`_expression.FromClause.join` - method form,
+        based on a given left side.
+
+        :class:`_expression.Join` - the type of object produced.
+
+    """
+
+    return Join(left, right, onclause, isouter, full)
+
+
+def lateral(selectable, name=None):
+    """Return a :class:`_expression.Lateral` object.
+
+    :class:`_expression.Lateral` is an :class:`_expression.Alias`
+    subclass that represents
+    a subquery with the LATERAL keyword applied to it.
+
+    The special behavior of a LATERAL subquery is that it appears in the
+    FROM clause of an enclosing SELECT, but may correlate to other
+    FROM clauses of that SELECT.   It is a special case of subquery
+    only supported by a small number of backends, currently more recent
+    PostgreSQL versions.
+
+    .. versionadded:: 1.1
+
+    .. seealso::
+
+        :ref:`lateral_selects` -  overview of usage.
+
+    """
+    return Lateral._factory(selectable, name=name)
+
+
+def outerjoin(left, right, onclause=None, full=False):
+    """Return an ``OUTER JOIN`` clause element.
+
+    The returned object is an instance of :class:`_expression.Join`.
+
+    Similar functionality is also available via the
+    :meth:`_expression.FromClause.outerjoin` method on any
+    :class:`_expression.FromClause`.
+
+    :param left: The left side of the join.
+
+    :param right: The right side of the join.
+
+    :param onclause:  Optional criterion for the ``ON`` clause, is
+      derived from foreign key relationships established between
+      left and right otherwise.
+
+    To chain joins together, use the :meth:`_expression.FromClause.join`
+    or
+    :meth:`_expression.FromClause.outerjoin` methods on the resulting
+    :class:`_expression.Join` object.
+
+    """
+    return Join(left, right, onclause, isouter=True, full=full)
+
+
+def select(*entities: Union[roles.ColumnsClauseRole, Type]) -> "Select":
+    r"""Construct a new :class:`_expression.Select`.
+
+
+    .. versionadded:: 1.4 - The :func:`_sql.select` function now accepts
+       column arguments positionally.   The top-level :func:`_sql.select`
+       function will automatically use the 1.x or 2.x style API based on
+       the incoming arguments; using :func:`_future.select` from the
+       ``sqlalchemy.future`` module will enforce that only the 2.x style
+       constructor is used.
+
+    Similar functionality is also available via the
+    :meth:`_expression.FromClause.select` method on any
+    :class:`_expression.FromClause`.
+
+    .. seealso::
+
+        :ref:`coretutorial_selecting` - Core Tutorial description of
+        :func:`_expression.select`.
+
+    :param \*entities:
+      Entities to SELECT from.  For Core usage, this is typically a series
+      of :class:`_expression.ColumnElement` and / or
+      :class:`_expression.FromClause`
+      objects which will form the columns clause of the resulting
+      statement.   For those objects that are instances of
+      :class:`_expression.FromClause` (typically :class:`_schema.Table`
+      or :class:`_expression.Alias`
+      objects), the :attr:`_expression.FromClause.c`
+      collection is extracted
+      to form a collection of :class:`_expression.ColumnElement` objects.
+
+      This parameter will also accept :class:`_expression.TextClause`
+      constructs as
+      given, as well as ORM-mapped classes.
+
+    """
+
+    return Select(*entities)
+
+
+def table(name: str, *columns: ColumnClause, **kw: Any) -> "TableClause":
+    """Produce a new :class:`_expression.TableClause`.
+
+    The object returned is an instance of
+    :class:`_expression.TableClause`, which
+    represents the "syntactical" portion of the schema-level
+    :class:`_schema.Table` object.
+    It may be used to construct lightweight table constructs.
+
+    .. versionchanged:: 1.0.0 :func:`_expression.table` can now
+       be imported from the plain ``sqlalchemy`` namespace like any
+       other SQL element.
+
+
+    :param name: Name of the table.
+
+    :param columns: A collection of :func:`_expression.column` constructs.
+
+    :param schema: The schema name for this table.
+
+        .. versionadded:: 1.3.18 :func:`_expression.table` can now
+           accept a ``schema`` argument.
+    """
+
+    return TableClause(name, *columns, **kw)
+
+
+def tablesample(selectable, sampling, name=None, seed=None):
+    """Return a :class:`_expression.TableSample` object.
+
+    :class:`_expression.TableSample` is an :class:`_expression.Alias`
+    subclass that represents
+    a table with the TABLESAMPLE clause applied to it.
+    :func:`_expression.tablesample`
+    is also available from the :class:`_expression.FromClause`
+    class via the
+    :meth:`_expression.FromClause.tablesample` method.
+
+    The TABLESAMPLE clause allows selecting a randomly selected approximate
+    percentage of rows from a table. It supports multiple sampling methods,
+    most commonly BERNOULLI and SYSTEM.
+
+    e.g.::
+
+        from sqlalchemy import func
+
+        selectable = people.tablesample(
+                    func.bernoulli(1),
+                    name='alias',
+                    seed=func.random())
+        stmt = select(selectable.c.people_id)
+
+    Assuming ``people`` with a column ``people_id``, the above
+    statement would render as::
+
+        SELECT alias.people_id FROM
+        people AS alias TABLESAMPLE bernoulli(:bernoulli_1)
+        REPEATABLE (random())
+
+    .. versionadded:: 1.1
+
+    :param sampling: a ``float`` percentage between 0 and 100 or
+        :class:`_functions.Function`.
+
+    :param name: optional alias name
+
+    :param seed: any real-valued SQL expression.  When specified, the
+     REPEATABLE sub-clause is also rendered.
+
+    """
+    return TableSample._factory(selectable, sampling, name=name, seed=seed)
+
+
+def union(*selects, **kwargs):
+    r"""Return a ``UNION`` of multiple selectables.
+
+    The returned object is an instance of
+    :class:`_expression.CompoundSelect`.
+
+    A similar :func:`union()` method is available on all
+    :class:`_expression.FromClause` subclasses.
+
+    :param \*selects:
+      a list of :class:`_expression.Select` instances.
+
+    :param \**kwargs:
+      available keyword arguments are the same as those of
+      :func:`select`.
+
+    """
+    return CompoundSelect._create_union(*selects, **kwargs)
+
+
+def union_all(*selects):
+    r"""Return a ``UNION ALL`` of multiple selectables.
+
+    The returned object is an instance of
+    :class:`_expression.CompoundSelect`.
+
+    A similar :func:`union_all()` method is available on all
+    :class:`_expression.FromClause` subclasses.
+
+    :param \*selects:
+      a list of :class:`_expression.Select` instances.
+
+    """
+    return CompoundSelect._create_union_all(*selects)
+
+
+def values(*columns, name=None, literal_binds=False) -> "Values":
+    r"""Construct a :class:`_expression.Values` construct.
+
+    The column expressions and the actual data for
+    :class:`_expression.Values` are given in two separate steps.  The
+    constructor receives the column expressions typically as
+    :func:`_expression.column` constructs,
+    and the data is then passed via the
+    :meth:`_expression.Values.data` method as a list,
+    which can be called multiple
+    times to add more data, e.g.::
+
+        from sqlalchemy import column
+        from sqlalchemy import values
+
+        value_expr = values(
+            column('id', Integer),
+            column('name', String),
+            name="my_values"
+        ).data(
+            [(1, 'name1'), (2, 'name2'), (3, 'name3')]
+        )
+
+    :param \*columns: column expressions, typically composed using
+     :func:`_expression.column` objects.
+
+    :param name: the name for this VALUES construct.  If omitted, the
+     VALUES construct will be unnamed in a SQL expression.   Different
+     backends may have different requirements here.
+
+    :param literal_binds: Defaults to False.  Whether or not to render
+     the data values inline in the SQL output, rather than using bound
+     parameters.
+
+    """
+    return Values(*columns, literal_binds=literal_binds, name=name)