path: root/lib/sqlalchemy/orm/evaluator.py

# orm/evaluator.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 __future__ import annotations

import operator

from .. import exc
from .. import inspect
from .. import util
from ..sql import and_
from ..sql import operators


class UnevaluatableError(exc.InvalidRequestError):
    pass


class _NoObject(operators.ColumnOperators):
    def operate(self, *arg, **kw):
        return None

    def reverse_operate(self, *arg, **kw):
        return None


_NO_OBJECT = _NoObject()


class EvaluatorCompiler:
    def __init__(self, target_cls=None):
        self.target_cls = target_cls

    def process(self, clause, *clauses):
        if clauses:
            clause = and_(clause, *clauses)

        meth = getattr(self, f"visit_{clause.__visit_name__}", None)
        if not meth:
            raise UnevaluatableError(
                f"Cannot evaluate {type(clause).__name__}"
            )
        return meth(clause)

    def visit_grouping(self, clause):
        return self.process(clause.element)

    def visit_null(self, clause):
        return lambda obj: None

    def visit_false(self, clause):
        return lambda obj: False

    def visit_true(self, clause):
        return lambda obj: True

    def visit_column(self, clause):
        if "parentmapper" in clause._annotations:
            parentmapper = clause._annotations["parentmapper"]
            if self.target_cls and not issubclass(
                self.target_cls, parentmapper.class_
            ):
                raise UnevaluatableError(
                    "Can't evaluate criteria against "
                    f"alternate class {parentmapper.class_}"
                )
            key = parentmapper._columntoproperty[clause].key
        else:
            key = clause.key
            if (
                self.target_cls
                and key in inspect(self.target_cls).column_attrs
            ):
                util.warn(
                    f"Evaluating non-mapped column expression '{clause}' onto "
                    "ORM instances; this is a deprecated use case.  Please "
                    "make use of the actual mapped columns in ORM-evaluated "
                    "UPDATE / DELETE expressions."
                )
            else:
                raise UnevaluatableError(f"Cannot evaluate column: {clause}")

        get_corresponding_attr = operator.attrgetter(key)
        return (
            lambda obj: get_corresponding_attr(obj)
            if obj is not None
            else _NO_OBJECT
        )

    def visit_tuple(self, clause):
        return self.visit_clauselist(clause)

    def visit_expression_clauselist(self, clause):
        return self.visit_clauselist(clause)

    def visit_clauselist(self, clause):
        evaluators = [self.process(clause) for clause in clause.clauses]

        dispatch = (
            f"visit_{clause.operator.__name__.rstrip('_')}_clauselist_op"
        )
        meth = getattr(self, dispatch, None)
        if meth:
            return meth(clause.operator, evaluators, clause)
        else:
            raise UnevaluatableError(
                f"Cannot evaluate clauselist with operator {clause.operator}"
            )

    def visit_binary(self, clause):
        eval_left = self.process(clause.left)
        eval_right = self.process(clause.right)

        dispatch = f"visit_{clause.operator.__name__.rstrip('_')}_binary_op"
        meth = getattr(self, dispatch, None)
        if meth:
            return meth(clause.operator, eval_left, eval_right)
        else:
            raise UnevaluatableError(
                f"Cannot evaluate {type(clause).__name__} with "
                f"operator {clause.operator}"
            )

    def visit_or_clauselist_op(self, operator, evaluators, clause):
        def evaluate(obj):
            has_null = False
            for sub_evaluate in evaluators:
                value = sub_evaluate(obj)
                if value:
                    return True
                has_null = has_null or value is None
            if has_null:
                return None
            return False

        return evaluate

    def visit_and_clauselist_op(self, operator, evaluators, clause):
        def evaluate(obj):
            for sub_evaluate in evaluators:
                value = sub_evaluate(obj)
                if not value:
                    if value is None or value is _NO_OBJECT:
                        return None
                    return False
            return True

        return evaluate

    def visit_comma_op_clauselist_op(self, operator, evaluators, clause):
        def evaluate(obj):
            values = []
            for sub_evaluate in evaluators:
                value = sub_evaluate(obj)
                if value is None or value is _NO_OBJECT:
                    return None
                values.append(value)
            return tuple(values)

        return evaluate

    def visit_custom_op_binary_op(self, operator, eval_left, eval_right):
        if operator.python_impl:
            return self._straight_evaluate(operator, eval_left, eval_right)
        else:
            raise UnevaluatableError(
                f"Custom operator {operator.opstring!r} can't be evaluated "
                "in Python unless it specifies a callable using "
                "`.python_impl`."
            )

    def visit_is_binary_op(self, operator, eval_left, eval_right):
        def evaluate(obj):
            return eval_left(obj) == eval_right(obj)

        return evaluate

    def visit_is_not_binary_op(self, operator, eval_left, eval_right):
        def evaluate(obj):
            return eval_left(obj) != eval_right(obj)

        return evaluate

    def _straight_evaluate(self, operator, eval_left, eval_right):
        def evaluate(obj):
            left_val = eval_left(obj)
            right_val = eval_right(obj)
            if left_val is None or right_val is None:
                return None
            return operator(eval_left(obj), eval_right(obj))

        return evaluate

    visit_add_binary_op = _straight_evaluate
    visit_mul_binary_op = _straight_evaluate
    visit_sub_binary_op = _straight_evaluate
    visit_mod_binary_op = _straight_evaluate
    visit_truediv_binary_op = _straight_evaluate
    visit_lt_binary_op = _straight_evaluate
    visit_le_binary_op = _straight_evaluate
    visit_ne_binary_op = _straight_evaluate
    visit_gt_binary_op = _straight_evaluate
    visit_ge_binary_op = _straight_evaluate
    visit_eq_binary_op = _straight_evaluate

    def visit_in_op_binary_op(self, operator, eval_left, eval_right):
        return self._straight_evaluate(
            lambda a, b: a in b if a is not _NO_OBJECT else None,
            eval_left,
            eval_right,
        )

    def visit_not_in_op_binary_op(self, operator, eval_left, eval_right):
        return self._straight_evaluate(
            lambda a, b: a not in b if a is not _NO_OBJECT else None,
            eval_left,
            eval_right,
        )

    def visit_concat_op_binary_op(self, operator, eval_left, eval_right):
        return self._straight_evaluate(
            lambda a, b: a + b, eval_left, eval_right
        )

    def visit_startswith_op_binary_op(self, operator, eval_left, eval_right):
        return self._straight_evaluate(
            lambda a, b: a.startswith(b), eval_left, eval_right
        )

    def visit_endswith_op_binary_op(self, operator, eval_left, eval_right):
        return self._straight_evaluate(
            lambda a, b: a.endswith(b), eval_left, eval_right
        )

    def visit_unary(self, clause):
        eval_inner = self.process(clause.element)
        if clause.operator is operators.inv:

            def evaluate(obj):
                value = eval_inner(obj)
                if value is None:
                    return None
                return not value

            return evaluate
        raise UnevaluatableError(
            f"Cannot evaluate {type(clause).__name__} "
            f"with operator {clause.operator}"
        )

    def visit_bindparam(self, clause):
        if clause.callable:
            val = clause.callable()
        else:
            val = clause.value
        return lambda obj: val