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[EDIT] FILE: sqla_compat.py

from __future__ import annotations

import contextlib
import re
from typing import Any
from typing import Iterable
from typing import Iterator
from typing import Mapping
from typing import Optional
from typing import TYPE_CHECKING
from typing import TypeVar
from typing import Union

from sqlalchemy import __version__
from sqlalchemy import inspect
from sqlalchemy import schema
from sqlalchemy import sql
from sqlalchemy import types as sqltypes
from sqlalchemy.engine import url
from sqlalchemy.ext.compiler import compiles
from sqlalchemy.schema import CheckConstraint
from sqlalchemy.schema import Column
from sqlalchemy.schema import ForeignKeyConstraint
from sqlalchemy.sql import visitors
from sqlalchemy.sql.elements import BindParameter
from sqlalchemy.sql.elements import ColumnClause
from sqlalchemy.sql.elements import quoted_name
from sqlalchemy.sql.elements import TextClause
from sqlalchemy.sql.elements import UnaryExpression
from sqlalchemy.sql.visitors import traverse
from typing_extensions import TypeGuard

if TYPE_CHECKING:
    from sqlalchemy import Index
    from sqlalchemy import Table
    from sqlalchemy.engine import Connection
    from sqlalchemy.engine import Dialect
    from sqlalchemy.engine import Transaction
    from sqlalchemy.engine.reflection import Inspector
    from sqlalchemy.sql.base import ColumnCollection
    from sqlalchemy.sql.compiler import SQLCompiler
    from sqlalchemy.sql.dml import Insert
    from sqlalchemy.sql.elements import ColumnElement
    from sqlalchemy.sql.schema import Constraint
    from sqlalchemy.sql.schema import SchemaItem
    from sqlalchemy.sql.selectable import Select
    from sqlalchemy.sql.selectable import TableClause

_CE = TypeVar("_CE", bound=Union["ColumnElement[Any]", "SchemaItem"])

def _safe_int(value: str) -> Union[int, str]:
    try:
        return int(value)
    except:
        return value

_vers = tuple(
    [_safe_int(x) for x in re.findall(r"(\d+|[abc]\d)", __version__)]
)
sqla_13 = _vers >= (1, 3)
sqla_14 = _vers >= (1, 4)
# https://docs.sqlalchemy.org/en/latest/changelog/changelog_14.html#change-0c6e0cc67dfe6fac5164720e57ef307d
sqla_14_18 = _vers >= (1, 4, 18)
sqla_14_26 = _vers >= (1, 4, 26)
sqla_2 = _vers >= (2,)
sqlalchemy_version = __version__

try:
    from sqlalchemy.sql.naming import _NONE_NAME as _NONE_NAME
except ImportError:
    from sqlalchemy.sql.elements import _NONE_NAME as _NONE_NAME  # type: ignore  # noqa: E501

class _Unsupported:
    "Placeholder for unsupported SQLAlchemy classes"

try:
    from sqlalchemy import Computed
except ImportError:

class Computed(_Unsupported):  # type: ignore
        pass

has_computed = False
    has_computed_reflection = False
else:
    has_computed = True
    has_computed_reflection = _vers >= (1, 3, 16)

try:
    from sqlalchemy import Identity
except ImportError:

class Identity(_Unsupported):  # type: ignore
        pass

has_identity = False
else:
    # attributes common to Identity and Sequence
    _identity_options_attrs = (
        "start",
        "increment",
        "minvalue",
        "maxvalue",
        "nominvalue",
        "nomaxvalue",
        "cycle",
        "cache",
        "order",
    )
    # attributes of Identity
    _identity_attrs = _identity_options_attrs + ("on_null",)
    has_identity = True

if sqla_2:
    from sqlalchemy.sql.base import _NoneName
else:
    from sqlalchemy.util import symbol as _NoneName  # type: ignore[assignment]

_ConstraintName = Union[None, str, _NoneName]

_ConstraintNameDefined = Union[str, _NoneName]

def constraint_name_defined(
    name: _ConstraintName,
) -> TypeGuard[_ConstraintNameDefined]:
    return name is _NONE_NAME or isinstance(name, (str, _NoneName))

def constraint_name_string(
    name: _ConstraintName,
) -> TypeGuard[str]:
    return isinstance(name, str)

def constraint_name_or_none(
    name: _ConstraintName,
) -> Optional[str]:
    return name if constraint_name_string(name) else None

AUTOINCREMENT_DEFAULT = "auto"

@contextlib.contextmanager
def _ensure_scope_for_ddl(
    connection: Optional[Connection],
) -> Iterator[None]:
    try:
        in_transaction = connection.in_transaction  # type: ignore[union-attr]
    except AttributeError:
        # catch for MockConnection, None
        in_transaction = None
        pass

# yield outside the catch
    if in_transaction is None:
        yield
    else:
        if not in_transaction():
            assert connection is not None
            with connection.begin():
                yield
        else:
            yield

def url_render_as_string(url, hide_password=True):
    if sqla_14:
        return url.render_as_string(hide_password=hide_password)
    else:
        return url.__to_string__(hide_password=hide_password)

def _safe_begin_connection_transaction(
    connection: Connection,
) -> Transaction:
    transaction = _get_connection_transaction(connection)
    if transaction:
        return transaction
    else:
        return connection.begin()

def _safe_commit_connection_transaction(
    connection: Connection,
) -> None:
    transaction = _get_connection_transaction(connection)
    if transaction:
        transaction.commit()

def _safe_rollback_connection_transaction(
    connection: Connection,
) -> None:
    transaction = _get_connection_transaction(connection)
    if transaction:
        transaction.rollback()

def _get_connection_in_transaction(connection: Optional[Connection]) -> bool:
    try:
        in_transaction = connection.in_transaction  # type: ignore
    except AttributeError:
        # catch for MockConnection
        return False
    else:
        return in_transaction()

def _idx_table_bound_expressions(idx: Index) -> Iterable[ColumnElement[Any]]:
    return idx.expressions  # type: ignore

def _copy(schema_item: _CE, **kw) -> _CE:
    if hasattr(schema_item, "_copy"):
        return schema_item._copy(**kw)  # type: ignore[union-attr]
    else:
        return schema_item.copy(**kw)  # type: ignore[union-attr]

def _get_connection_transaction(
    connection: Connection,
) -> Optional[Transaction]:
    if sqla_14:
        return connection.get_transaction()
    else:
        r = connection._root  # type: ignore[attr-defined]
        return r._Connection__transaction

def _create_url(*arg, **kw) -> url.URL:
    if hasattr(url.URL, "create"):
        return url.URL.create(*arg, **kw)
    else:
        return url.URL(*arg, **kw)

def _connectable_has_table(
    connectable: Connection, tablename: str, schemaname: Union[str, None]
) -> bool:
    if sqla_14:
        return inspect(connectable).has_table(tablename, schemaname)
    else:
        return connectable.dialect.has_table(
            connectable, tablename, schemaname
        )

def _exec_on_inspector(inspector, statement, **params):
    if sqla_14:
        with inspector._operation_context() as conn:
            return conn.execute(statement, params)
    else:
        return inspector.bind.execute(statement, params)

def _nullability_might_be_unset(metadata_column):
    if not sqla_14:
        return metadata_column.nullable
    else:
        from sqlalchemy.sql import schema

return (
            metadata_column._user_defined_nullable is schema.NULL_UNSPECIFIED
        )

def _server_default_is_computed(*server_default) -> bool:
    if not has_computed:
        return False
    else:
        return any(isinstance(sd, Computed) for sd in server_default)

def _server_default_is_identity(*server_default) -> bool:
    if not sqla_14:
        return False
    else:
        return any(isinstance(sd, Identity) for sd in server_default)

def _table_for_constraint(constraint: Constraint) -> Table:
    if isinstance(constraint, ForeignKeyConstraint):
        table = constraint.parent
        assert table is not None
        return table  # type: ignore[return-value]
    else:
        return constraint.table

def _columns_for_constraint(constraint):
    if isinstance(constraint, ForeignKeyConstraint):
        return [fk.parent for fk in constraint.elements]
    elif isinstance(constraint, CheckConstraint):
        return _find_columns(constraint.sqltext)
    else:
        return list(constraint.columns)

def _reflect_table(inspector: Inspector, table: Table) -> None:
    if sqla_14:
        return inspector.reflect_table(table, None)
    else:
        return inspector.reflecttable(  # type: ignore[attr-defined]
            table, None
        )

def _resolve_for_variant(type_, dialect):
    if _type_has_variants(type_):
        base_type, mapping = _get_variant_mapping(type_)
        return mapping.get(dialect.name, base_type)
    else:
        return type_

if hasattr(sqltypes.TypeEngine, "_variant_mapping"):

def _type_has_variants(type_):
        return bool(type_._variant_mapping)

def _get_variant_mapping(type_):
        return type_, type_._variant_mapping

else:

def _type_has_variants(type_):
        return type(type_) is sqltypes.Variant

def _get_variant_mapping(type_):
        return type_.impl, type_.mapping

def _fk_spec(constraint):
    source_columns = [
        constraint.columns[key].name for key in constraint.column_keys
    ]

source_table = constraint.parent.name
    source_schema = constraint.parent.schema
    target_schema = constraint.elements[0].column.table.schema
    target_table = constraint.elements[0].column.table.name
    target_columns = [element.column.name for element in constraint.elements]
    ondelete = constraint.ondelete
    onupdate = constraint.onupdate
    deferrable = constraint.deferrable
    initially = constraint.initially
    return (
        source_schema,
        source_table,
        source_columns,
        target_schema,
        target_table,
        target_columns,
        onupdate,
        ondelete,
        deferrable,
        initially,
    )

def _fk_is_self_referential(constraint: ForeignKeyConstraint) -> bool:
    spec = constraint.elements[0]._get_colspec()  # type: ignore[attr-defined]
    tokens = spec.split(".")
    tokens.pop(-1)  # colname
    tablekey = ".".join(tokens)
    assert constraint.parent is not None
    return tablekey == constraint.parent.key

def _is_type_bound(constraint: Constraint) -> bool:
    # this deals with SQLAlchemy #3260, don't copy CHECK constraints
    # that will be generated by the type.
    # new feature added for #3260
    return constraint._type_bound  # type: ignore[attr-defined]

def _find_columns(clause):
    """locate Column objects within the given expression."""

cols = set()
    traverse(clause, {}, {"column": cols.add})
    return cols

def _remove_column_from_collection(
    collection: ColumnCollection, column: Union[Column[Any], ColumnClause[Any]]
) -> None:
    """remove a column from a ColumnCollection."""

# workaround for older SQLAlchemy, remove the
    # same object that's present
    assert column.key is not None
    to_remove = collection[column.key]

# SQLAlchemy 2.0 will use more ReadOnlyColumnCollection
    # (renamed from ImmutableColumnCollection)
    if hasattr(collection, "_immutable") or hasattr(collection, "_readonly"):
        collection._parent.remove(to_remove)
    else:
        collection.remove(to_remove)

def _textual_index_column(
    table: Table, text_: Union[str, TextClause, ColumnElement[Any]]
) -> Union[ColumnElement[Any], Column[Any]]:
    """a workaround for the Index construct's severe lack of flexibility"""
    if isinstance(text_, str):
        c = Column(text_, sqltypes.NULLTYPE)
        table.append_column(c)
        return c
    elif isinstance(text_, TextClause):
        return _textual_index_element(table, text_)
    elif isinstance(text_, _textual_index_element):
        return _textual_index_column(table, text_.text)
    elif isinstance(text_, sql.ColumnElement):
        return _copy_expression(text_, table)
    else:
        raise ValueError("String or text() construct expected")

def _copy_expression(expression: _CE, target_table: Table) -> _CE:
    def replace(col):
        if (
            isinstance(col, Column)
            and col.table is not None
            and col.table is not target_table
        ):
            if col.name in target_table.c:
                return target_table.c[col.name]
            else:
                c = _copy(col)
                target_table.append_column(c)
                return c
        else:
            return None

return visitors.replacement_traverse(  # type: ignore[call-overload]
        expression, {}, replace
    )

class _textual_index_element(sql.ColumnElement):
    """Wrap around a sqlalchemy text() construct in such a way that
    we appear like a column-oriented SQL expression to an Index
    construct.

The issue here is that currently the Postgresql dialect, the biggest
    recipient of functional indexes, keys all the index expressions to
    the corresponding column expressions when rendering CREATE INDEX,
    so the Index we create here needs to have a .columns collection that
    is the same length as the .expressions collection.  Ultimately
    SQLAlchemy should support text() expressions in indexes.

See SQLAlchemy issue 3174.

"""

__visit_name__ = "_textual_idx_element"

def __init__(self, table: Table, text: TextClause) -> None:
        self.table = table
        self.text = text
        self.key = text.text
        self.fake_column = schema.Column(self.text.text, sqltypes.NULLTYPE)
        table.append_column(self.fake_column)

def get_children(self):
        return [self.fake_column]

@compiles(_textual_index_element)
def _render_textual_index_column(
    element: _textual_index_element, compiler: SQLCompiler, **kw
) -> str:
    return compiler.process(element.text, **kw)

class _literal_bindparam(BindParameter):
    pass

@compiles(_literal_bindparam)
def _render_literal_bindparam(
    element: _literal_bindparam, compiler: SQLCompiler, **kw
) -> str:
    return compiler.render_literal_bindparam(element, **kw)

def _get_index_expressions(idx):
    return list(idx.expressions)

def _get_index_column_names(idx):
    return [getattr(exp, "name", None) for exp in _get_index_expressions(idx)]

def _column_kwargs(col: Column) -> Mapping:
    if sqla_13:
        return col.kwargs
    else:
        return {}

def _get_constraint_final_name(
    constraint: Union[Index, Constraint], dialect: Optional[Dialect]
) -> Optional[str]:
    if constraint.name is None:
        return None
    assert dialect is not None
    if sqla_14:
        # for SQLAlchemy 1.4 we would like to have the option to expand
        # the use of "deferred" names for constraints as well as to have
        # some flexibility with "None" name and similar; make use of new
        # SQLAlchemy API to return what would be the final compiled form of
        # the name for this dialect.
        return dialect.identifier_preparer.format_constraint(
            constraint, _alembic_quote=False
        )
    else:

# prior to SQLAlchemy 1.4, work around quoting logic to get at the
        # final compiled name without quotes.
        if hasattr(constraint.name, "quote"):
            # might be quoted_name, might be truncated_name, keep it the
            # same
            quoted_name_cls: type = type(constraint.name)
        else:
            quoted_name_cls = quoted_name

new_name = quoted_name_cls(str(constraint.name), quote=False)
        constraint = constraint.__class__(name=new_name)

if isinstance(constraint, schema.Index):
            # name should not be quoted.
            d = dialect.ddl_compiler(dialect, None)  # type: ignore[arg-type]
            return d._prepared_index_name(  # type: ignore[attr-defined]
                constraint
            )
        else:
            # name should not be quoted.
            return dialect.identifier_preparer.format_constraint(constraint)

def _constraint_is_named(
    constraint: Union[Constraint, Index], dialect: Optional[Dialect]
) -> bool:
    if sqla_14:
        if constraint.name is None:
            return False
        assert dialect is not None
        name = dialect.identifier_preparer.format_constraint(
            constraint, _alembic_quote=False
        )
        return name is not None
    else:
        return constraint.name is not None

def _is_mariadb(mysql_dialect: Dialect) -> bool:
    if sqla_14:
        return mysql_dialect.is_mariadb  # type: ignore[attr-defined]
    else:
        return bool(
            mysql_dialect.server_version_info
            and mysql_dialect._is_mariadb  # type: ignore[attr-defined]
        )

def _mariadb_normalized_version_info(mysql_dialect):
    return mysql_dialect._mariadb_normalized_version_info

def _insert_inline(table: Union[TableClause, Table]) -> Insert:
    if sqla_14:
        return table.insert().inline()
    else:
        return table.insert(inline=True)  # type: ignore[call-arg]

if sqla_14:
    from sqlalchemy import create_mock_engine
    from sqlalchemy import select as _select
else:
    from sqlalchemy import create_engine

def create_mock_engine(url, executor, **kw):  # type: ignore[misc]
        return create_engine(
            "postgresql://", strategy="mock", executor=executor
        )

def _select(*columns, **kw) -> Select:  # type: ignore[no-redef]
        return sql.select(list(columns), **kw)  # type: ignore[call-overload]

def is_expression_index(index: Index) -> bool:
    expr: Any
    for expr in index.expressions:
        while isinstance(expr, UnaryExpression):
            expr = expr.element
        if not isinstance(expr, ColumnClause) or expr.is_literal:
            return True
    return False

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