make url optional and add example for LinkPreview widget

example/link_preview.py

@@ -0,0 +1,95 @@
+from aiogram import Bot, Dispatcher
+from aiogram.filters import Command
+from aiogram.filters.state import State, StatesGroup
+from aiogram.fsm.storage.memory import MemoryStorage
+from aiogram.types import Message
+
+from aiogram_dialog import (
+    Dialog,
+    DialogManager,
+    StartMode,
+    Window,
+    setup_dialogs,
+)
+from aiogram_dialog.widgets.kbd import SwitchTo
+from aiogram_dialog.widgets.link_preview import LinkPreview
+from aiogram_dialog.widgets.text import Const, Format
+
+
+async def photo_getter(**_):
+    return {"photo_url": "https://nplus1.ru/news/2024/05/23/voyager-1-science-data"}
+
+
+class SG(StatesGroup):
+    MAIN = State()
+    IS_DISABLED = State()
+    SMALL_MEDIA = State()
+    LARGE_MEDIA = State()
+    SHOW_ABOVE_TEXT = State()
+
+
+BACK = SwitchTo(Const("back"), "_back", SG.MAIN)
+
+
+dialog = Dialog(
+    Window(
+        Format("Default\n{photo_url}"),
+        SwitchTo(
+            Const("disable"), "_disable", SG.IS_DISABLED,
+        ),
+        SwitchTo(
+            Const("prefer small media"), "_prefer_small_media", SG.SMALL_MEDIA,
+        ),
+        SwitchTo(
+            Const("prefer large media"), "_prefer_large_media", SG.LARGE_MEDIA,
+        ),
+        SwitchTo(
+            Const("show above text"), "_show_above_text", SG.SHOW_ABOVE_TEXT,
+        ),
+        getter=photo_getter,
+        state=SG.MAIN,
+    ),
+    Window(
+        Format("{photo_url}"),
+        LinkPreview(is_disabled=True),
+        BACK,
+        state=SG.IS_DISABLED,
+        getter=photo_getter,
+    ),
+    Window(
+        Const("prefer small media"),
+        LinkPreview(Format("{photo_url}"), prefer_small_media=True),
+        BACK,
+        state=SG.SMALL_MEDIA,
+        getter=photo_getter,
+    ),
+    Window(
+        Const("prefer large media"),
+        LinkPreview(Format("{photo_url}"), prefer_large_media=True),
+        BACK,
+        state=SG.LARGE_MEDIA,
+        getter=photo_getter,
+    ),
+    Window(
+        Const("show above text"),
+        LinkPreview(Format("{photo_url}"), show_above_text=True),
+        BACK,
+        state=SG.SHOW_ABOVE_TEXT,
+        getter=photo_getter,
+    ),
+)
+
+storage = MemoryStorage()
+bot = Bot("token")
+dp = Dispatcher(storage=storage)
+dp.include_router(dialog)
+setup_dialogs(dp)
+
+
+@dp.message(Command("start"))
+async def start(message: Message, dialog_manager: DialogManager):
+    await dialog_manager.start(SG.MAIN, mode=StartMode.RESET_STACK)
+
+
+if __name__ == "__main__":
+    dp.run_polling(bot, skip_updates=True)

src/aiogram_dialog/widgets/link_preview/base.py

@@ -27,7 +27,7 @@ async def _render_link_preview(
 class LinkPreview(LinkPreviewBase):
     def __init__(
             self,
-            url: TextWidget,
+            url: Optional[TextWidget] = None,
             is_disabled: bool = False,
             prefer_small_media: bool = False,
             prefer_large_media: bool = False,
@@ -51,9 +51,8 @@ async def render_link_preview(
     async def _render_link_preview(
             self, data: dict, manager: DialogManager,
     ) -> Optional[LinkPreviewOptions]:
-        url = await self.url.render_text(data, manager)
         return LinkPreviewOptions(
-            url=url,
+            url=await self.url.render_text(data, manager) if self.url else None,
             is_disabled=self.is_disabled,
             prefer_small_media=self.prefer_small_media,
             prefer_large_media=self.prefer_large_media,