# sql/lambdas.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

import inspect
import itertools
import operator
import sys
import types
import weakref

from . import coercions
from . import elements
from . import roles
from . import schema
from . import traversals
from . import type_api
from . import visitors
from .base import _clone
from .base import Options
from .operators import ColumnOperators
from .. import exc
from .. import inspection
from .. import util
from ..util import collections_abc
from ..util import compat

_closure_per_cache_key = util.LRUCache(1000)


class LambdaOptions(Options):
    enable_tracking = True
    track_closure_variables = True
    track_on = None
    global_track_bound_values = True
    track_bound_values = True
    lambda_cache = None


def lambda_stmt(
    lmb,
    enable_tracking=True,
    track_closure_variables=True,
    track_on=None,
    global_track_bound_values=True,
    track_bound_values=True,
    lambda_cache=None,
):
    """Produce a SQL statement that is cached as a lambda.

    The Python code object within the lambda is scanned for both Python
    literals that will become bound parameters as well as closure variables
    that refer to Core or ORM constructs that may vary.   The lambda itself
    will be invoked only once per particular set of constructs detected.

    E.g.::

        from sqlalchemy import lambda_stmt

        stmt = lambda_stmt(lambda: table.select())
        stmt += lambda s: s.where(table.c.id == 5)

        result = connection.execute(stmt)

    The object returned is an instance of :class:`_sql.StatementLambdaElement`.

    .. versionadded:: 1.4

    :param lmb: a Python function, typically a lambda, which takes no arguments
     and returns a SQL expression construct
    :param enable_tracking: when False, all scanning of the given lambda for
     changes in closure variables or bound parameters is disabled.  Use for
     a lambda that produces the identical results in all cases with no
     parameterization.
    :param track_closure_variables: when False, changes in closure variables
     within the lambda will not be scanned.   Use for a lambda where the
     state of its closure variables will never change the SQL structure
     returned by the lambda.
    :param track_bound_values: when False, bound parameter tracking will
     be disabled for the given lambda.  Use for a lambda that either does
     not produce any bound values, or where the initial bound values never
     change.
    :param global_track_bound_values: when False, bound parameter tracking
     will be disabled for the entire statement including additional links
     added via the :meth:`_sql.StatementLambdaElement.add_criteria` method.
    :param lambda_cache: a dictionary or other mapping-like object where
     information about the lambda's Python code as well as the tracked closure
     variables in the lambda itself will be stored.   Defaults
     to a global LRU cache.  This cache is independent of the "compiled_cache"
     used by the :class:`_engine.Connection` object.

    .. seealso::

        :ref:`engine_lambda_caching`


    """

    return StatementLambdaElement(
        lmb,
        roles.StatementRole,
        LambdaOptions(
            enable_tracking=enable_tracking,
            track_on=track_on,
            track_closure_variables=track_closure_variables,
            global_track_bound_values=global_track_bound_values,
            track_bound_values=track_bound_values,
            lambda_cache=lambda_cache,
        ),
    )


class LambdaElement(elements.ClauseElement):
    """A SQL construct where the state is stored as an un-invoked lambda.

    The :class:`_sql.LambdaElement` is produced transparently whenever
    passing lambda expressions into SQL constructs, such as::

        stmt = select(table).where(lambda: table.c.col == parameter)

    The :class:`_sql.LambdaElement` is the base of the
    :class:`_sql.StatementLambdaElement` which represents a full statement
    within a lambda.

    .. versionadded:: 1.4

    .. seealso::

        :ref:`engine_lambda_caching`

    """

    __visit_name__ = "lambda_element"

    _is_lambda_element = True

    _traverse_internals = [
        ("_resolved", visitors.InternalTraversal.dp_clauseelement)
    ]

    _transforms = ()

    parent_lambda = None

    def __repr__(self):
        return "%s(%r)" % (self.__class__.__name__, self.fn.__code__)

    def __init__(
        self, fn, role, opts=LambdaOptions, apply_propagate_attrs=None
    ):
        self.fn = fn
        self.role = role
        self.tracker_key = (fn.__code__,)
        self.opts = opts

        if apply_propagate_attrs is None and (role is roles.StatementRole):
            apply_propagate_attrs = self

        rec = self._retrieve_tracker_rec(fn, apply_propagate_attrs, opts)

        if apply_propagate_attrs is not None:
            propagate_attrs = rec.propagate_attrs
            if propagate_attrs:
                apply_propagate_attrs._propagate_attrs = propagate_attrs

    def _retrieve_tracker_rec(self, fn, apply_propagate_attrs, opts):
        lambda_cache = opts.lambda_cache
        if lambda_cache is None:
            lambda_cache = _closure_per_cache_key

        tracker_key = self.tracker_key

        fn = self.fn
        closure = fn.__closure__
        tracker = AnalyzedCode.get(
            fn,
            self,
            opts,
        )

        self._resolved_bindparams = bindparams = []

        if self.parent_lambda is not None:
            parent_closure_cache_key = self.parent_lambda.closure_cache_key
        else:
            parent_closure_cache_key = ()

        if parent_closure_cache_key is not traversals.NO_CACHE:
            anon_map = traversals.anon_map()
            cache_key = tuple(
                [
                    getter(closure, opts, anon_map, bindparams)
                    for getter in tracker.closure_trackers
                ]
            )

            if traversals.NO_CACHE not in anon_map:
                cache_key = parent_closure_cache_key + cache_key

                self.closure_cache_key = cache_key

                try:
                    rec = lambda_cache[tracker_key + cache_key]
                except KeyError:
                    rec = None
            else:
                cache_key = traversals.NO_CACHE
                rec = None

        else:
            cache_key = traversals.NO_CACHE
            rec = None

        self.closure_cache_key = cache_key

        if rec is None:
            if cache_key is not traversals.NO_CACHE:
                rec = AnalyzedFunction(
                    tracker, self, apply_propagate_attrs, fn
                )
                rec.closure_bindparams = bindparams
                lambda_cache[tracker_key + cache_key] = rec
            else:
                rec = NonAnalyzedFunction(self._invoke_user_fn(fn))

        else:
            bindparams[:] = [
                orig_bind._with_value(new_bind.value, maintain_key=True)
                for orig_bind, new_bind in zip(
                    rec.closure_bindparams, bindparams
                )
            ]

        self._rec = rec

        if cache_key is not traversals.NO_CACHE:
            if self.parent_lambda is not None:
                bindparams[:0] = self.parent_lambda._resolved_bindparams

            lambda_element = self
            while lambda_element is not None:
                rec = lambda_element._rec
                if rec.bindparam_trackers:
                    tracker_instrumented_fn = rec.tracker_instrumented_fn
                    for tracker in rec.bindparam_trackers:
                        tracker(
                            lambda_element.fn,
                            tracker_instrumented_fn,
                            bindparams,
                        )
                lambda_element = lambda_element.parent_lambda

        return rec

    def __getattr__(self, key):
        return getattr(self._rec.expected_expr, key)

    @property
    def _is_sequence(self):
        return self._rec.is_sequence

    @property
    def _select_iterable(self):
        if self._is_sequence:
            return itertools.chain.from_iterable(
                [element._select_iterable for element in self._resolved]
            )

        else:
            return self._resolved._select_iterable

    @property
    def _from_objects(self):
        if self._is_sequence:
            return itertools.chain.from_iterable(
                [element._from_objects for element in self._resolved]
            )

        else:
            return self._resolved._from_objects

    def _param_dict(self):
        return {b.key: b.value for b in self._resolved_bindparams}

    def _setup_binds_for_tracked_expr(self, expr):
        bindparam_lookup = {b.key: b for b in self._resolved_bindparams}

        def replace(thing):
            if isinstance(thing, elements.BindParameter):

                if thing.key in bindparam_lookup:
                    bind = bindparam_lookup[thing.key]
                    if thing.expanding:
                        bind.expanding = True
                        bind.expand_op = thing.expand_op
                        bind.type = thing.type
                    return bind

        if self._rec.is_sequence:
            expr = [
                visitors.replacement_traverse(sub_expr, {}, replace)
                for sub_expr in expr
            ]
        elif getattr(expr, "is_clause_element", False):
            expr = visitors.replacement_traverse(expr, {}, replace)

        return expr

    def _copy_internals(
        self, clone=_clone, deferred_copy_internals=None, **kw
    ):
        # TODO: this needs A LOT of tests
        self._resolved = clone(
            self._resolved,
            deferred_copy_internals=deferred_copy_internals,
            **kw
        )

    @util.memoized_property
    def _resolved(self):
        expr = self._rec.expected_expr

        if self._resolved_bindparams:
            expr = self._setup_binds_for_tracked_expr(expr)

        return expr

    def _gen_cache_key(self, anon_map, bindparams):
        if self.closure_cache_key is traversals.NO_CACHE:
            anon_map[traversals.NO_CACHE] = True
            return None

        cache_key = (
            self.fn.__code__,
            self.__class__,
        ) + self.closure_cache_key

        parent = self.parent_lambda
        while parent is not None:
            cache_key = (
                (parent.fn.__code__,) + parent.closure_cache_key + cache_key
            )

            parent = parent.parent_lambda

        if self._resolved_bindparams:
            bindparams.extend(self._resolved_bindparams)
        return cache_key

    def _invoke_user_fn(self, fn, *arg):
        return fn()


class DeferredLambdaElement(LambdaElement):
    """A LambdaElement where the lambda accepts arguments and is
    invoked within the compile phase with special context.

    This lambda doesn't normally produce its real SQL expression outside of the
    compile phase.  It is passed a fixed set of initial arguments
    so that it can generate a sample expression.

    """

    def __init__(self, fn, role, opts=LambdaOptions, lambda_args=()):
        self.lambda_args = lambda_args
        super(DeferredLambdaElement, self).__init__(fn, role, opts)

    def _invoke_user_fn(self, fn, *arg):
        return fn(*self.lambda_args)

    def _resolve_with_args(self, *lambda_args):
        tracker_fn = self._rec.tracker_instrumented_fn
        expr = tracker_fn(*lambda_args)

        expr = coercions.expect(self.role, expr)

        expr = self._setup_binds_for_tracked_expr(expr)

        # this validation is getting very close, but not quite, to achieving
        # #5767.  The problem is if the base lambda uses an unnamed column
        # as is very common with mixins, the parameter name is different
        # and it produces a false positive; that is, for the documented case
        # that is exactly what people will be doing, it doesn't work, so
        # I'm not really sure how to handle this right now.
        # expected_binds = [
        #    b._orig_key
        #    for b in self._rec.expr._generate_cache_key()[1]
        #    if b.required
        # ]
        # got_binds = [
        #    b._orig_key for b in expr._generate_cache_key()[1] if b.required
        # ]
        # if expected_binds != got_binds:
        #    raise exc.InvalidRequestError(
        #        "Lambda callable at %s produced a different set of bound "
        #        "parameters than its original run: %s"
        #        % (self.fn.__code__, ", ".join(got_binds))
        #    )

        # TODO: TEST TEST TEST, this is very out there
        for deferred_copy_internals in self._transforms:
            expr = deferred_copy_internals(expr)

        return expr

    def _copy_internals(
        self, clone=_clone, deferred_copy_internals=None, **kw
    ):
        super(DeferredLambdaElement, self)._copy_internals(
            clone=clone,
            deferred_copy_internals=deferred_copy_internals,  # **kw
            opts=kw,
        )

        # TODO: A LOT A LOT of tests.   for _resolve_with_args, we don't know
        # our expression yet.   so hold onto the replacement
        if deferred_copy_internals:
            self._transforms += (deferred_copy_internals,)


class StatementLambdaElement(roles.AllowsLambdaRole, LambdaElement):
    """Represent a composable SQL statement as a :class:`_sql.LambdaElement`.

    The :class:`_sql.StatementLambdaElement` is constructed using the
    :func:`_sql.lambda_stmt` function::


        from sqlalchemy import lambda_stmt

        stmt = lambda_stmt(lambda: select(table))

    Once constructed, additional criteria can be built onto the statement
    by adding subsequent lambdas, which accept the existing statement
    object as a single parameter::

        stmt += lambda s: s.where(table.c.col == parameter)


    .. versionadded:: 1.4

    .. seealso::

        :ref:`engine_lambda_caching`

    """

    def __add__(self, other):
        return self.add_criteria(other)

    def add_criteria(
        self,
        other,
        enable_tracking=True,
        track_on=None,
        track_closure_variables=True,
        track_bound_values=True,
    ):
        """Add new criteria to this :class:`_sql.StatementLambdaElement`.

        E.g.::

            >>> def my_stmt(parameter):
            ...     stmt = lambda_stmt(
            ...         lambda: select(table.c.x, table.c.y),
            ...     )
            ...     stmt = stmt.add_criteria(
            ...         lambda: table.c.x > parameter
            ...     )
            ...     return stmt

        The :meth:`_sql.StatementLambdaElement.add_criteria` method is
        equivalent to using the Python addition operator to add a new
        lambda, except that additional arguments may be added including
        ``track_closure_values`` and ``track_on``::

            >>> def my_stmt(self, foo):
            ...     stmt = lambda_stmt(
            ...         lambda: select(func.max(foo.x, foo.y)),
            ...         track_closure_variables=False
            ...     )
            ...     stmt = stmt.add_criteria(
            ...         lambda: self.where_criteria,
            ...         track_on=[self]
            ...     )
            ...     return stmt

        See :func:`_sql.lambda_stmt` for a description of the parameters
        accepted.

        """

        opts = self.opts + dict(
            enable_tracking=enable_tracking,
            track_closure_variables=track_closure_variables,
            global_track_bound_values=self.opts.global_track_bound_values,
            track_on=track_on,
            track_bound_values=track_bound_values,
        )

        return LinkedLambdaElement(other, parent_lambda=self, opts=opts)

    def _execute_on_connection(
        self, connection, multiparams, params, execution_options
    ):
        if self._rec.expected_expr.supports_execution:
            return connection._execute_clauseelement(
                self, multiparams, params, execution_options
            )
        else:
            raise exc.ObjectNotExecutableError(self)

    @property
    def _with_options(self):
        return self._rec.expected_expr._with_options

    @property
    def _effective_plugin_target(self):
        return self._rec.expected_expr._effective_plugin_target

    @property
    def _execution_options(self):
        return self._rec.expected_expr._execution_options

    def spoil(self):
        """Return a new :class:`.StatementLambdaElement` that will run
        all lambdas unconditionally each time.

        """
        return NullLambdaStatement(self.fn())


class NullLambdaStatement(roles.AllowsLambdaRole, elements.ClauseElement):
    """Provides the :class:`.StatementLambdaElement` API but does not
    cache or analyze lambdas.

    the lambdas are instead invoked immediately.

    The intended use is to isolate issues that may arise when using
    lambda statements.

    """

    __visit_name__ = "lambda_element"

    _is_lambda_element = True

    _traverse_internals = [
        ("_resolved", visitors.InternalTraversal.dp_clauseelement)
    ]

    def __init__(self, statement):
        self._resolved = statement
        self._propagate_attrs = statement._propagate_attrs

    def __getattr__(self, key):
        return getattr(self._resolved, key)

    def __add__(self, other):
        statement = other(self._resolved)

        return NullLambdaStatement(statement)

    def add_criteria(self, other, **kw):
        statement = other(self._resolved)

        return NullLambdaStatement(statement)

    def _execute_on_connection(
        self, connection, multiparams, params, execution_options
    ):
        if self._resolved.supports_execution:
            return connection._execute_clauseelement(
                self, multiparams, params, execution_options
            )
        else:
            raise exc.ObjectNotExecutableError(self)


class LinkedLambdaElement(StatementLambdaElement):
    """Represent subsequent links of a :class:`.StatementLambdaElement`."""

    role = None

    def __init__(self, fn, parent_lambda, opts):
        self.opts = opts
        self.fn = fn
        self.parent_lambda = parent_lambda

        self.tracker_key = parent_lambda.tracker_key + (fn.__code__,)
        self._retrieve_tracker_rec(fn, self, opts)
        self._propagate_attrs = parent_lambda._propagate_attrs

    def _invoke_user_fn(self, fn, *arg):
        return fn(self.parent_lambda._resolved)


class AnalyzedCode(object):
    __slots__ = (
        "track_closure_variables",
        "track_bound_values",
        "bindparam_trackers",
        "closure_trackers",
        "build_py_wrappers",
    )
    _fns = weakref.WeakKeyDictionary()

    @classmethod
    def get(cls, fn, lambda_element, lambda_kw, **kw):
        try:
            # TODO: validate kw haven't changed?
            return cls._fns[fn.__code__]
        except KeyError:
            pass
        cls._fns[fn.__code__] = analyzed = AnalyzedCode(
            fn, lambda_element, lambda_kw, **kw
        )
        return analyzed

    def __init__(self, fn, lambda_element, opts):
        if inspect.ismethod(fn):
            raise exc.ArgumentError(
                "Method %s may not be passed as a SQL expression" % fn
            )
        closure = fn.__closure__

        self.track_bound_values = (
            opts.track_bound_values and opts.global_track_bound_values
        )
        enable_tracking = opts.enable_tracking
        track_on = opts.track_on
        track_closure_variables = opts.track_closure_variables

        self.track_closure_variables = track_closure_variables and not track_on

        # a list of callables generated from _bound_parameter_getter_*
        # functions.  Each of these uses a PyWrapper object to retrieve
        # a parameter value
        self.bindparam_trackers = []

        # a list of callables generated from _cache_key_getter_* functions
        # these callables work to generate a cache key for the lambda
        # based on what's inside its closure variables.
        self.closure_trackers = []

        self.build_py_wrappers = []

        if enable_tracking:
            if track_on:
                self._init_track_on(track_on)

            self._init_globals(fn)

            if closure:
                self._init_closure(fn)

        self._setup_additional_closure_trackers(fn, lambda_element, opts)

    def _init_track_on(self, track_on):
        self.closure_trackers.extend(
            self._cache_key_getter_track_on(idx, elem)
            for idx, elem in enumerate(track_on)
        )

    def _init_globals(self, fn):
        build_py_wrappers = self.build_py_wrappers
        bindparam_trackers = self.bindparam_trackers
        track_bound_values = self.track_bound_values

        for name in fn.__code__.co_names:
            if name not in fn.__globals__:
                continue

            _bound_value = self._roll_down_to_literal(fn.__globals__[name])

            if coercions._deep_is_literal(_bound_value):
                build_py_wrappers.append((name, None))
                if track_bound_values:
                    bindparam_trackers.append(
                        self._bound_parameter_getter_func_globals(name)
                    )

    def _init_closure(self, fn):
        build_py_wrappers = self.build_py_wrappers
        closure = fn.__closure__

        track_bound_values = self.track_bound_values
        track_closure_variables = self.track_closure_variables
        bindparam_trackers = self.bindparam_trackers
        closure_trackers = self.closure_trackers

        for closure_index, (fv, cell) in enumerate(
            zip(fn.__code__.co_freevars, closure)
        ):
            _bound_value = self._roll_down_to_literal(cell.cell_contents)

            if coercions._deep_is_literal(_bound_value):
                build_py_wrappers.append((fv, closure_index))
                if track_bound_values:
                    bindparam_trackers.append(
                        self._bound_parameter_getter_func_closure(
                            fv, closure_index
                        )
                    )
            else:
                # for normal cell contents, add them to a list that
                # we can compare later when we get new lambdas.  if
                # any identities have changed, then we will
                # recalculate the whole lambda and run it again.

                if track_closure_variables:
                    closure_trackers.append(
                        self._cache_key_getter_closure_variable(
                            fn, fv, closure_index, cell.cell_contents
                        )
                    )

    def _setup_additional_closure_trackers(self, fn, lambda_element, opts):
        # an additional step is to actually run the function, then
        # go through the PyWrapper objects that were set up to catch a bound
        # parameter.   then if they *didn't* make a param, oh they're another
        # object in the closure we have to track for our cache key.  so
        # create trackers to catch those.

        analyzed_function = AnalyzedFunction(
            self,
            lambda_element,
            None,
            fn,
        )

        closure_trackers = self.closure_trackers

        for pywrapper in analyzed_function.closure_pywrappers:
            if not pywrapper._sa__has_param:
                closure_trackers.append(
                    self._cache_key_getter_tracked_literal(fn, pywrapper)
                )

    @classmethod
    def _roll_down_to_literal(cls, element):
        is_clause_element = hasattr(element, "__clause_element__")

        if is_clause_element:
            while not isinstance(
                element, (elements.ClauseElement, schema.SchemaItem, type)
            ):
                try:
                    element = element.__clause_element__()
                except AttributeError:
                    break

        if not is_clause_element:
            insp = inspection.inspect(element, raiseerr=False)
            if insp is not None:
                try:
                    return insp.__clause_element__()
                except AttributeError:
                    return insp

            # TODO: should we coerce consts None/True/False here?
            return element
        else:
            return element

    def _bound_parameter_getter_func_globals(self, name):
        """Return a getter that will extend a list of bound parameters
        with new entries from the ``__globals__`` collection of a particular
        lambda.

        """

        def extract_parameter_value(
            current_fn, tracker_instrumented_fn, result
        ):
            wrapper = tracker_instrumented_fn.__globals__[name]
            object.__getattribute__(wrapper, "_extract_bound_parameters")(
                current_fn.__globals__[name], result
            )

        return extract_parameter_value

    def _bound_parameter_getter_func_closure(self, name, closure_index):
        """Return a getter that will extend a list of bound parameters
        with new entries from the ``__closure__`` collection of a particular
        lambda.

        """

        def extract_parameter_value(
            current_fn, tracker_instrumented_fn, result
        ):
            wrapper = tracker_instrumented_fn.__closure__[
                closure_index
            ].cell_contents
            object.__getattribute__(wrapper, "_extract_bound_parameters")(
                current_fn.__closure__[closure_index].cell_contents, result
            )

        return extract_parameter_value

    def _cache_key_getter_track_on(self, idx, elem):
        """Return a getter that will extend a cache key with new entries
        from the "track_on" parameter passed to a :class:`.LambdaElement`.

        """

        if isinstance(elem, tuple):
            # tuple must contain hascachekey elements
            def get(closure, opts, anon_map, bindparams):
                return tuple(
                    tup_elem._gen_cache_key(anon_map, bindparams)
                    for tup_elem in opts.track_on[idx]
                )

        elif isinstance(elem, traversals.HasCacheKey):

            def get(closure, opts, anon_map, bindparams):
                return opts.track_on[idx]._gen_cache_key(anon_map, bindparams)

        else:

            def get(closure, opts, anon_map, bindparams):
                return opts.track_on[idx]

        return get

    def _cache_key_getter_closure_variable(
        self,
        fn,
        variable_name,
        idx,
        cell_contents,
        use_clause_element=False,
        use_inspect=False,
    ):
        """Return a getter that will extend a cache key with new entries
        from the ``__closure__`` collection of a particular lambda.

        """

        if isinstance(cell_contents, traversals.HasCacheKey):

            def get(closure, opts, anon_map, bindparams):

                obj = closure[idx].cell_contents
                if use_inspect:
                    obj = inspection.inspect(obj)
                elif use_clause_element:
                    while hasattr(obj, "__clause_element__"):
                        if not getattr(obj, "is_clause_element", False):
                            obj = obj.__clause_element__()

                return obj._gen_cache_key(anon_map, bindparams)

        elif isinstance(cell_contents, types.FunctionType):

            def get(closure, opts, anon_map, bindparams):
                return closure[idx].cell_contents.__code__

        elif isinstance(cell_contents, collections_abc.Sequence):

            def get(closure, opts, anon_map, bindparams):
                contents = closure[idx].cell_contents

                try:
                    return tuple(
                        elem._gen_cache_key(anon_map, bindparams)
                        for elem in contents
                    )
                except AttributeError as ae:
                    self._raise_for_uncacheable_closure_variable(
                        variable_name, fn, from_=ae
                    )

        else:
            # if the object is a mapped class or aliased class, or some
            # other object in the ORM realm of things like that, imitate
            # the logic used in coercions.expect() to roll it down to the
            # SQL element
            element = cell_contents
            is_clause_element = False
            while hasattr(element, "__clause_element__"):
                is_clause_element = True
                if not getattr(element, "is_clause_element", False):
                    element = element.__clause_element__()
                else:
                    break

            if not is_clause_element:
                insp = inspection.inspect(element, raiseerr=False)
                if insp is not None:
                    return self._cache_key_getter_closure_variable(
                        fn, variable_name, idx, insp, use_inspect=True
                    )
            else:
                return self._cache_key_getter_closure_variable(
                    fn, variable_name, idx, element, use_clause_element=True
                )

            self._raise_for_uncacheable_closure_variable(variable_name, fn)

        return get

    def _raise_for_uncacheable_closure_variable(
        self, variable_name, fn, from_=None
    ):
        util.raise_(
            exc.InvalidRequestError(
                "Closure variable named '%s' inside of lambda callable %s "
                "does not refer to a cacheable SQL element, and also does not "
                "appear to be serving as a SQL literal bound value based on "
                "the default "
                "SQL expression returned by the function.   This variable "
                "needs to remain outside the scope of a SQL-generating lambda "
                "so that a proper cache key may be generated from the "
                "lambda's state.  Evaluate this variable outside of the "
                "lambda, set track_on=[<elements>] to explicitly select "
                "closure elements to track, or set "
                "track_closure_variables=False to exclude "
                "closure variables from being part of the cache key."
                % (variable_name, fn.__code__),
            ),
            from_=from_,
        )

    def _cache_key_getter_tracked_literal(self, fn, pytracker):
        """Return a getter that will extend a cache key with new entries
        from the ``__closure__`` collection of a particular lambda.

        this getter differs from _cache_key_getter_closure_variable
        in that these are detected after the function is run, and PyWrapper
        objects have recorded that a particular literal value is in fact
        not being interpreted as a bound parameter.

        """

        elem = pytracker._sa__to_evaluate
        closure_index = pytracker._sa__closure_index
        variable_name = pytracker._sa__name

        return self._cache_key_getter_closure_variable(
            fn, variable_name, closure_index, elem
        )


class NonAnalyzedFunction(object):
    __slots__ = ("expr",)

    closure_bindparams = None
    bindparam_trackers = None

    def __init__(self, expr):
        self.expr = expr

    @property
    def expected_expr(self):
        return self.expr


class AnalyzedFunction(object):
    __slots__ = (
        "analyzed_code",
        "fn",
        "closure_pywrappers",
        "tracker_instrumented_fn",
        "expr",
        "bindparam_trackers",
        "expected_expr",
        "is_sequence",
        "propagate_attrs",
        "closure_bindparams",
    )

    def __init__(
        self,
        analyzed_code,
        lambda_element,
        apply_propagate_attrs,
        fn,
    ):
        self.analyzed_code = analyzed_code
        self.fn = fn

        self.bindparam_trackers = analyzed_code.bindparam_trackers

        self._instrument_and_run_function(lambda_element)

        self._coerce_expression(lambda_element, apply_propagate_attrs)

    def _instrument_and_run_function(self, lambda_element):
        analyzed_code = self.analyzed_code

        fn = self.fn
        self.closure_pywrappers = closure_pywrappers = []

        build_py_wrappers = analyzed_code.build_py_wrappers

        if not build_py_wrappers:
            self.tracker_instrumented_fn = tracker_instrumented_fn = fn
            self.expr = lambda_element._invoke_user_fn(tracker_instrumented_fn)
        else:
            track_closure_variables = analyzed_code.track_closure_variables
            closure = fn.__closure__

            # will form the __closure__ of the function when we rebuild it
            if closure:
                new_closure = {
                    fv: cell.cell_contents
                    for fv, cell in zip(fn.__code__.co_freevars, closure)
                }
            else:
                new_closure = {}

            # will form the __globals__ of the function when we rebuild it
            new_globals = fn.__globals__.copy()

            for name, closure_index in build_py_wrappers:
                if closure_index is not None:
                    value = closure[closure_index].cell_contents
                    new_closure[name] = bind = PyWrapper(
                        fn,
                        name,
                        value,
                        closure_index=closure_index,
                        track_bound_values=(
                            self.analyzed_code.track_bound_values
                        ),
                    )
                    if track_closure_variables:
                        closure_pywrappers.append(bind)
                else:
                    value = fn.__globals__[name]
                    new_globals[name] = bind = PyWrapper(fn, name, value)

            # rewrite the original fn.   things that look like they will
            # become bound parameters are wrapped in a PyWrapper.
            self.tracker_instrumented_fn = (
                tracker_instrumented_fn
            ) = self._rewrite_code_obj(
                fn,
                [new_closure[name] for name in fn.__code__.co_freevars],
                new_globals,
            )

            # now invoke the function.  This will give us a new SQL
            # expression, but all the places that there would be a bound
            # parameter, the PyWrapper in its place will give us a bind
            # with a predictable name we can match up later.

            # additionally, each PyWrapper will log that it did in fact
            # create a parameter, otherwise, it's some kind of Python
            # object in the closure and we want to track that, to make
            # sure it doesn't change to something else, or if it does,
            # that we create a different tracked function with that
            # variable.
            self.expr = lambda_element._invoke_user_fn(tracker_instrumented_fn)

    def _coerce_expression(self, lambda_element, apply_propagate_attrs):
        """Run the tracker-generated expression through coercion rules.

        After the user-defined lambda has been invoked to produce a statement
        for re-use, run it through coercion rules to both check that it's the
        correct type of object and also to coerce it to its useful form.

        """

        parent_lambda = lambda_element.parent_lambda
        expr = self.expr

        if parent_lambda is None:
            if isinstance(expr, collections_abc.Sequence):
                self.expected_expr = [
                    coercions.expect(
                        lambda_element.role,
                        sub_expr,
                        apply_propagate_attrs=apply_propagate_attrs,
                    )
                    for sub_expr in expr
                ]
                self.is_sequence = True
            else:
                self.expected_expr = coercions.expect(
                    lambda_element.role,
                    expr,
                    apply_propagate_attrs=apply_propagate_attrs,
                )
                self.is_sequence = False
        else:
            self.expected_expr = expr
            self.is_sequence = False

        if apply_propagate_attrs is not None:
            self.propagate_attrs = apply_propagate_attrs._propagate_attrs
        else:
            self.propagate_attrs = util.EMPTY_DICT

    def _rewrite_code_obj(self, f, cell_values, globals_):
        """Return a copy of f, with a new closure and new globals

        yes it works in pypy :P

        """

        argrange = range(len(cell_values))

        code = "def make_cells():\n"
        if cell_values:
            code += "    (%s) = (%s)\n" % (
                ", ".join("i%d" % i for i in argrange),
                ", ".join("o%d" % i for i in argrange),
            )
        code += "    def closure():\n"
        code += "        return %s\n" % ", ".join("i%d" % i for i in argrange)
        code += "    return closure.__closure__"
        vars_ = {"o%d" % i: cell_values[i] for i in argrange}
        compat.exec_(code, vars_, vars_)
        closure = vars_["make_cells"]()

        func = type(f)(
            f.__code__, globals_, f.__name__, f.__defaults__, closure
        )
        if sys.version_info >= (3,):
            func.__annotations__ = f.__annotations__
            func.__kwdefaults__ = f.__kwdefaults__
        func.__doc__ = f.__doc__
        func.__module__ = f.__module__

        return func


class PyWrapper(ColumnOperators):
    """A wrapper object that is injected into the ``__globals__`` and
    ``__closure__`` of a Python function.

    When the function is instrumented with :class:`.PyWrapper` objects, it is
    then invoked just once in order to set up the wrappers.  We look through
    all the :class:`.PyWrapper` objects we made to find the ones that generated
    a :class:`.BindParameter` object, e.g. the expression system interpreted
    something as a literal.   Those positions in the globals/closure are then
    ones that we will look at, each time a new lambda comes in that refers to
    the same ``__code__`` object.   In this way, we keep a single version of
    the SQL expression that this lambda produced, without calling upon the
    Python function that created it more than once, unless its other closure
    variables have changed.   The expression is then transformed to have the
    new bound values embedded into it.

    """

    def __init__(
        self,
        fn,
        name,
        to_evaluate,
        closure_index=None,
        getter=None,
        track_bound_values=True,
    ):
        self.fn = fn
        self._name = name
        self._to_evaluate = to_evaluate
        self._param = None
        self._has_param = False
        self._bind_paths = {}
        self._getter = getter
        self._closure_index = closure_index
        self.track_bound_values = track_bound_values

    def __call__(self, *arg, **kw):
        elem = object.__getattribute__(self, "_to_evaluate")
        value = elem(*arg, **kw)
        if (
            self._sa_track_bound_values
            and coercions._deep_is_literal(value)
            and not isinstance(
                # TODO: coverage where an ORM option or similar is here
                value,
                traversals.HasCacheKey,
            )
        ):
            name = object.__getattribute__(self, "_name")
            raise exc.InvalidRequestError(
                "Can't invoke Python callable %s() inside of lambda "
                "expression argument at %s; lambda SQL constructs should "
                "not invoke functions from closure variables to produce "
                "literal values since the "
                "lambda SQL system normally extracts bound values without "
                "actually "
                "invoking the lambda or any functions within it.  Call the "
                "function outside of the "
                "lambda and assign to a local variable that is used in the "
                "lambda as a closure variable, or set "
                "track_bound_values=False if the return value of this "
                "function is used in some other way other than a SQL bound "
                "value." % (name, self._sa_fn.__code__)
            )
        else:
            return value

    def operate(self, op, *other, **kwargs):
        elem = object.__getattribute__(self, "__clause_element__")()
        return op(elem, *other, **kwargs)

    def reverse_operate(self, op, other, **kwargs):
        elem = object.__getattribute__(self, "__clause_element__")()
        return op(other, elem, **kwargs)

    def _extract_bound_parameters(self, starting_point, result_list):
        param = object.__getattribute__(self, "_param")
        if param is not None:
            param = param._with_value(starting_point, maintain_key=True)
            result_list.append(param)
        for pywrapper in object.__getattribute__(self, "_bind_paths").values():
            getter = object.__getattribute__(pywrapper, "_getter")
            element = getter(starting_point)
            pywrapper._sa__extract_bound_parameters(element, result_list)

    def __clause_element__(self):
        param = object.__getattribute__(self, "_param")
        to_evaluate = object.__getattribute__(self, "_to_evaluate")
        if param is None:
            name = object.__getattribute__(self, "_name")
            self._param = param = elements.BindParameter(
                name, required=False, unique=True
            )
            self._has_param = True
            param.type = type_api._resolve_value_to_type(to_evaluate)
        return param._with_value(to_evaluate, maintain_key=True)

    def __bool__(self):
        to_evaluate = object.__getattribute__(self, "_to_evaluate")
        return bool(to_evaluate)

    def __nonzero__(self):
        to_evaluate = object.__getattribute__(self, "_to_evaluate")
        return bool(to_evaluate)

    def __getattribute__(self, key):
        if key.startswith("_sa_"):
            return object.__getattribute__(self, key[4:])
        elif key in (
            "__clause_element__",
            "operate",
            "reverse_operate",
            "__class__",
            "__dict__",
        ):
            return object.__getattribute__(self, key)

        if key.startswith("__"):
            elem = object.__getattribute__(self, "_to_evaluate")
            return getattr(elem, key)
        else:
            return self._sa__add_getter(key, operator.attrgetter)

    def __iter__(self):
        elem = object.__getattribute__(self, "_to_evaluate")
        return iter(elem)

    def __getitem__(self, key):
        elem = object.__getattribute__(self, "_to_evaluate")
        if not hasattr(elem, "__getitem__"):
            raise AttributeError("__getitem__")

        if isinstance(key, PyWrapper):
            # TODO: coverage
            raise exc.InvalidRequestError(
                "Dictionary keys / list indexes inside of a cached "
                "lambda must be Python literals only"
            )
        return self._sa__add_getter(key, operator.itemgetter)

    def _add_getter(self, key, getter_fn):

        bind_paths = object.__getattribute__(self, "_bind_paths")

        bind_path_key = (key, getter_fn)
        if bind_path_key in bind_paths:
            return bind_paths[bind_path_key]

        getter = getter_fn(key)
        elem = object.__getattribute__(self, "_to_evaluate")
        value = getter(elem)

        rolled_down_value = AnalyzedCode._roll_down_to_literal(value)

        if coercions._deep_is_literal(rolled_down_value):
            wrapper = PyWrapper(self._sa_fn, key, value, getter=getter)
            bind_paths[bind_path_key] = wrapper
            return wrapper
        else:
            return value


@inspection._inspects(LambdaElement)
def insp(lmb):
    return inspection.inspect(lmb._resolved)
