Move constants used by db backend into a separate module so we dont need to import the full backend everywhere else

src/calibre/db/backend.py

@@ -16,9 +16,7 @@ import sys
 import time
 import uuid
 from contextlib import closing, suppress
-from dataclasses import dataclass
 from functools import partial
-from typing import Sequence
 
 from calibre import as_unicode, force_unicode, isbytestring, prints
 from calibre.constants import (
@@ -26,6 +24,10 @@ from calibre.constants import (
 )
 from calibre.db import SPOOL_SIZE, FTSQueryError
 from calibre.db.annotations import annot_db_data, unicode_normalize
+from calibre.db.constants import (
+    BOOK_ID_PATH_TEMPLATE, COVER_FILE_NAME, DEFAULT_TRASH_EXPIRY_TIME_SECONDS,
+    METADATA_FILE_NAME, TRASH_DIR_NAME, TrashEntry,
+)
 from calibre.db.errors import NoSuchFormat
 from calibre.db.schema_upgrades import SchemaUpgrade
 from calibre.db.tables import (
@@ -56,27 +58,11 @@ from polyglot.builtins import (
 
 # }}}
 
-COVER_FILE_NAME = 'cover.jpg'
-METADATA_FILE_NAME = 'metadata.opf'
-DEFAULT_TRASH_EXPIRY_TIME_SECONDS = 14 * 86400
-TRASH_DIR_NAME =  '.caltrash'
-DATA_DIR_NAME = 'data'
-BOOK_ID_PATH_TEMPLATE = ' ({})'
 CUSTOM_DATA_TYPES = frozenset(('rating', 'text', 'comments', 'datetime',
     'int', 'float', 'bool', 'series', 'composite', 'enumeration'))
 WINDOWS_RESERVED_NAMES = frozenset('CON PRN AUX NUL COM1 COM2 COM3 COM4 COM5 COM6 COM7 COM8 COM9 LPT1 LPT2 LPT3 LPT4 LPT5 LPT6 LPT7 LPT8 LPT9'.split())
 
 
-@dataclass
-class TrashEntry:
-    book_id: int
-    title: str
-    author: str
-    cover_path: str
-    mtime: float
-    formats: Sequence[str] = ()
-
-
 class DynamicFilter:  # {{{
 
     'No longer used, present for legacy compatibility'

src/calibre/db/constants.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+# License: GPLv3 Copyright: 2023, Kovid Goyal <kovid at kovidgoyal.net>
+
+from dataclasses import dataclass
+from typing import Sequence
+
+COVER_FILE_NAME = 'cover.jpg'
+METADATA_FILE_NAME = 'metadata.opf'
+DEFAULT_TRASH_EXPIRY_TIME_SECONDS = 14 * 86400
+TRASH_DIR_NAME =  '.caltrash'
+DATA_DIR_NAME = 'data'
+BOOK_ID_PATH_TEMPLATE = ' ({})'
+
+
+@dataclass
+class TrashEntry:
+    book_id: int
+    title: str
+    author: str
+    cover_path: str
+    mtime: float
+    formats: Sequence[str] = ()

src/calibre/db/restore.py

@@ -17,7 +17,8 @@ from threading import Thread
 
 from calibre import force_unicode, isbytestring
 from calibre.constants import filesystem_encoding
-from calibre.db.backend import DB, METADATA_FILE_NAME, TRASH_DIR_NAME, DBPrefs
+from calibre.db.backend import DB, DBPrefs
+from calibre.db.constants import METADATA_FILE_NAME, TRASH_DIR_NAME
 from calibre.db.cache import Cache
 from calibre.ebooks.metadata.opf2 import OPF
 from calibre.ptempfile import TemporaryDirectory

src/calibre/db/tests/add_remove.py

@@ -12,7 +12,7 @@ from datetime import timedelta
 from io import BytesIO
 from tempfile import NamedTemporaryFile
 
-from calibre.db.backend import METADATA_FILE_NAME
+from calibre.db.constants import METADATA_FILE_NAME
 from calibre.db.tests.base import IMG, BaseTest
 from calibre.ptempfile import PersistentTemporaryFile
 from calibre.utils.date import UNDEFINED_DATE, now, utcnow

src/calibre/ebooks/metadata/book/render.py

@@ -10,7 +10,7 @@ from functools import partial
 
 from calibre import force_unicode, prepare_string_for_xml
 from calibre.constants import filesystem_encoding
-from calibre.db.backend import DATA_DIR_NAME
+from calibre.db.constants import DATA_DIR_NAME
 from calibre.ebooks.metadata import fmt_sidx, rating_to_stars
 from calibre.ebooks.metadata.search_internet import (
     DEFAULT_AUTHOR_SOURCE, name_for, qquote, url_for_author_search, url_for_book_search,

src/calibre/gui2/actions/view.py

@@ -12,7 +12,7 @@ from functools import partial
 from qt.core import QAction, QDialog, QIcon, pyqtSignal
 
 from calibre.constants import ismacos, iswindows
-from calibre.db.backend import DATA_DIR_NAME
+from calibre.db.constants import DATA_DIR_NAME
 from calibre.gui2 import (
     Dispatcher, config, elided_text, error_dialog, info_dialog, open_local_file,
     question_dialog,

src/calibre/gui2/book_details.py

@@ -15,7 +15,7 @@ from qt.core import (
 
 from calibre import fit_image, sanitize_file_name
 from calibre.constants import config_dir, iswindows
-from calibre.db.backend import DATA_DIR_NAME
+from calibre.db.constants import DATA_DIR_NAME
 from calibre.ebooks import BOOK_EXTENSIONS
 from calibre.ebooks.metadata.book.base import Metadata, field_metadata
 from calibre.ebooks.metadata.book.render import mi_to_html

src/calibre/gui2/comments_editor.py

@@ -19,7 +19,7 @@ from qt.core import (
 )
 
 from calibre import xml_replace_entities
-from calibre.db.backend import DATA_DIR_NAME
+from calibre.db.constants import DATA_DIR_NAME
 from calibre.ebooks.chardet import xml_to_unicode
 from calibre.gui2 import (
     NO_URL_FORMATTING, choose_dir, choose_files, error_dialog, gprefs, is_dark_theme,

src/calibre/gui2/trash.py

@@ -12,7 +12,7 @@ from qt.core import (
 from typing import Iterator, List
 
 from calibre import fit_image
-from calibre.db.backend import DEFAULT_TRASH_EXPIRY_TIME_SECONDS, TrashEntry
+from calibre.db.constants import DEFAULT_TRASH_EXPIRY_TIME_SECONDS, TrashEntry
 from calibre.gui2 import error_dialog
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.widgets import BusyCursor

src/calibre/library/check_library.py

@@ -12,7 +12,7 @@ import traceback
 
 from calibre import isbytestring
 from calibre.constants import filesystem_encoding
-from calibre.db.backend import (
+from calibre.db.constants import (
     COVER_FILE_NAME, DATA_DIR_NAME, METADATA_FILE_NAME, TRASH_DIR_NAME,
 )
 from calibre.ebooks import BOOK_EXTENSIONS