Use typing.TYPE_CHECKING to avoid inner imports

src/backend/backend.py

@@ -13,9 +13,11 @@ from appdirs import AppDirs
 from . import __app_name__
 from .errors import MatrixError
 from .matrix_client import MatrixClient
+from .media_cache import MediaCache
 from .models import SyncId
 from .models.items import Account
 from .models.model_store import ModelStore
+from .user_files import Accounts, History, Theme, UISettings, UIState
 
 # Logging configuration
 log.getLogger().setLevel(log.INFO)
@@ -71,7 +73,6 @@ class Backend:
     def __init__(self) -> None:
         self.appdirs = AppDirs(appname=__app_name__, roaming=True)
 
-        from .user_files import Accounts, UISettings, UIState, History
         self.saved_accounts: Accounts   = Accounts(self)
         self.ui_settings:    UISettings = UISettings(self)
         self.ui_state:       UIState    = UIState(self)
@@ -87,7 +88,6 @@ class Backend:
         self.send_locks: DefaultDict[str, asyncio.Lock] = \
                 DefaultDict(asyncio.Lock)  # {room_id: lock}
 
-        from .media_cache import MediaCache
         cache_dir                    = Path(self.appdirs.user_cache_dir)
         self.media_cache: MediaCache = MediaCache(self, cache_dir)
 
@@ -247,7 +247,6 @@ class Backend:
     async def load_settings(self) -> tuple:
         """Return parsed user config files."""
 
-        from .user_files import Theme
         settings = await self.ui_settings.read()
         ui_state = await self.ui_state.read()
         history  = await self.history.read()

src/backend/matrix_client.py

@@ -14,19 +14,18 @@ from datetime import datetime
 from functools import partial
 from pathlib import Path
 from typing import (
-    Any, DefaultDict, Dict, List, NamedTuple, Optional, Set, Tuple, Type,
-    Union,
+    TYPE_CHECKING, Any, DefaultDict, Dict, List, NamedTuple, Optional, Set,
+    Tuple, Type, Union,
 )
 from urllib.parse import urlparse
 from uuid import UUID, uuid4
 
 import cairosvg
-from PIL import Image as PILImage
-from pymediainfo import MediaInfo
-
 import nio
 from nio.crypto import AsyncDataT as UploadData
 from nio.crypto import async_generator_from_data
+from PIL import Image as PILImage
+from pymediainfo import MediaInfo
 
 from . import __app_name__, __display_name__, utils
 from .errors import (
@@ -34,12 +33,15 @@ from .errors import (
     MatrixNotFound, UneededThumbnail,
 )
 from .html_markdown import HTML_PROCESSOR as HTML
-from .models.items import (
-    Event, Member, Room, TypeSpecifier, Upload, UploadStatus,
-)
+from .media_cache import Media, Thumbnail
+from .models.items import Event, Member, Room, Upload, UploadStatus
 from .models.model_store import ModelStore
+from .nio_callbacks import NioCallbacks
 from .pyotherside_events import AlertRequested
 
+if TYPE_CHECKING:
+    from .backend import Backend
+
 CryptDict = Dict[str, Any]
 
 
@@ -103,8 +105,7 @@ class MatrixClient(nio.AsyncClient):
             ),
         )
 
-        from .backend import Backend
-        self.backend: Backend    = backend
+        self.backend: "Backend"  = backend
         self.models:  ModelStore = self.backend.models
 
         self.profile_task:    Optional[asyncio.Future] = None
@@ -120,7 +121,6 @@ class MatrixClient(nio.AsyncClient):
 
         self.skipped_events: DefaultDict[str, int] = DefaultDict(lambda: 0)
 
-        from .nio_callbacks import NioCallbacks
         self.nio_callbacks = NioCallbacks(self)
 
 
@@ -292,11 +292,9 @@ class MatrixClient(nio.AsyncClient):
     ) -> None:
         """Monitorably upload a file + thumbnail and send the built event."""
 
-        # TODO: this function is WAY TOO COMPLEX, and most of it should be
+        # TODO: this function is way too complex, and most of it should be
         # refactored into nio.
 
-        from .media_cache import Media, Thumbnail
-
         transaction_id = uuid4()
         path           = Path(path)
         encrypt        = room_id in self.encrypted_rooms

src/backend/media_cache.py

@@ -10,17 +10,18 @@ import shutil
 import sys
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Any, DefaultDict, Dict, Optional
+from typing import TYPE_CHECKING, Any, DefaultDict, Dict, Optional
 from urllib.parse import urlparse
 
 import aiofiles
+import nio
 from PIL import Image as PILImage
 
-import nio
-
-from .backend import Backend
 from .utils import Size
 
+if TYPE_CHECKING:
+    from .backend import Backend
+
 if sys.version_info < (3, 8):
     import pyfastcopy  # noqa
 
@@ -34,8 +35,8 @@ ACCESS_LOCKS: DefaultDict[str, asyncio.Lock] = DefaultDict(asyncio.Lock)
 class MediaCache:
     """Matrix downloaded media cache."""
 
-    backend:  Backend = field()
-    base_dir: Path    = field()
+    backend:  "Backend" = field()
+    base_dir: Path      = field()
 
 
     def __post_init__(self) -> None:

src/backend/models/model.py

@@ -1,13 +1,15 @@
 # SPDX-License-Identifier: LGPL-3.0-or-later
 
 from threading import Lock
-from typing import Any, Dict, Iterator, List, MutableMapping
+from typing import TYPE_CHECKING, Any, Dict, Iterator, List, MutableMapping
 
 from ..pyotherside_events import (
     ModelCleared, ModelItemDeleted, ModelItemInserted,
 )
 from . import SyncId
-from .model_item import ModelItem
+
+if TYPE_CHECKING:
+    from .model_item import ModelItem
 
 
 class Model(MutableMapping):
@@ -30,10 +32,10 @@ class Model(MutableMapping):
     """
 
     def __init__(self, sync_id: SyncId) -> None:
-        self.sync_id:      SyncId               = sync_id
-        self._data:        Dict[Any, ModelItem] = {}
-        self._sorted_data: List[ModelItem]      = []
-        self._write_lock:  Lock                 = Lock()
+        self.sync_id:      SyncId                 = sync_id
+        self._data:        Dict[Any, "ModelItem"] = {}
+        self._sorted_data: List["ModelItem"]      = []
+        self._write_lock:  Lock                   = Lock()
 
 
     def __repr__(self) -> str:
@@ -58,7 +60,7 @@ class Model(MutableMapping):
         return self._data[key]
 
 
-    def __setitem__(self, key, value: ModelItem) -> None:
+    def __setitem__(self, key, value: "ModelItem") -> None:
         """Merge new item with an existing one if possible, else add it.
 
         If an existing item with the passed `key` is found, its fields will be

src/backend/models/model_item.py

@@ -1,6 +1,12 @@
 # SPDX-License-Identifier: LGPL-3.0-or-later
 
-from typing import Any, Dict, Optional
+from typing import TYPE_CHECKING, Any, Dict, Optional
+
+from ..pyotherside_events import ModelItemFieldChanged
+from ..utils import serialize_value_for_qml
+
+if TYPE_CHECKING:
+    from .model import Model
 
 
 class ModelItem:
@@ -18,7 +24,6 @@ class ModelItem:
     """
 
     def __new__(cls, *_args, **_kwargs) -> "ModelItem":
-        from .model import Model
         cls.parent_model: Optional[Model] = None
         return super().__new__(cls)
 
@@ -39,7 +44,6 @@ class ModelItem:
         self.parent_model._sorted_data.sort()
         new_index = self.parent_model._sorted_data.index(self)
 
-        from ..pyotherside_events import ModelItemFieldChanged
         ModelItemFieldChanged(
             self.parent_model.sync_id, old_index, new_index, name, value,
         )
@@ -53,8 +57,6 @@ class ModelItem:
     def serialized(self) -> Dict[str, Any]:
         """Return this item as a dict ready to be passed to QML."""
 
-        from ..utils import serialize_value_for_qml
-
         return {
             name: serialize_value_for_qml(getattr(self, name), json_lists=True)
             for name in dir(self)

src/backend/nio_callbacks.py

@@ -6,16 +6,18 @@ import logging as log
 from contextlib import suppress
 from dataclasses import dataclass, field
 from datetime import datetime
-from typing import Optional, Tuple
+from typing import TYPE_CHECKING, Optional, Tuple
 from urllib.parse import quote
 
 import nio
 
 from . import utils
 from .html_markdown import HTML_PROCESSOR
-from .matrix_client import MatrixClient
 from .models.items import TypeSpecifier
 
+if TYPE_CHECKING:
+    from .matrix_client import MatrixClient
+
 
 @dataclass
 class NioCallbacks:
@@ -30,7 +32,7 @@ class NioCallbacks:
     These are processed from QML, to allow translations of the strings.
     """
 
-    client: MatrixClient = field()
+    client: "MatrixClient" = field()
 
 
     def __post_init__(self) -> None:

src/backend/pyotherside_events.py

@@ -2,14 +2,16 @@
 
 from abc import ABC
 from dataclasses import dataclass, field
-from typing import Any, Optional
+from typing import TYPE_CHECKING, Any, Optional
 
 import pyotherside
 
 from .models import SyncId
-from .models.model_item import ModelItem
 from .utils import serialize_value_for_qml
 
+if TYPE_CHECKING:
+    from .models.model_item import ModelItem
+
 
 @dataclass
 class PyOtherSideEvent:
@@ -69,9 +71,9 @@ class ModelEvent(ABC, PyOtherSideEvent):
 
 @dataclass
 class ModelItemInserted(ModelEvent):
-    sync_id: SyncId    = field()
-    index:   int       = field()
-    item:    ModelItem = field()
+    sync_id: SyncId      = field()
+    index:   int         = field()
+    item:    "ModelItem" = field()
 
 
 @dataclass

src/backend/user_files.py

@@ -7,14 +7,16 @@ import json
 import logging as log
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Any, ClassVar, Dict, Optional
+from typing import TYPE_CHECKING, Any, ClassVar, Dict, Optional
 
 import aiofiles
 
-from .backend import Backend
 from .theme_parser import convert_to_qml
 from .utils import dict_update_recursive
 
+if TYPE_CHECKING:
+    from .backend import Backend
+
 JsonData = Dict[str, Any]
 
 WRITE_LOCK = asyncio.Lock()
@@ -26,8 +28,8 @@ class DataFile:
 
     is_config: ClassVar[bool] = False
 
-    backend:  Backend = field(repr=False)
-    filename: str     = field()
+    backend:  "Backend" = field(repr=False)
+    filename: str       = field()
 
     _to_write: Optional[str] = field(init=False, default=None)
 

src/backend/utils.py

@@ -21,8 +21,6 @@ from aiofiles.threadpool.binary import AsyncBufferedReader
 from nio.crypto import AsyncDataT as File
 from nio.crypto import async_generator_from_data
 
-from .models.model_item import ModelItem
-
 Size = Tuple[int, int]
 auto = autostr
 
@@ -143,12 +141,12 @@ def serialize_value_for_qml(value: Any, json_lists: bool = False) -> Any:
     if json_lists and isinstance(value, list):
         return json.dumps(value)
 
+    if hasattr(value, "serialized"):
+        return value.serialized
+
     if hasattr(value, "__class__") and issubclass(value.__class__, Enum):
         return value.value
 
-    if isinstance(value, ModelItem):
-        return value.serialized
-
     if isinstance(value, Path):
         return f"file://{value!s}"