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Refactor page management to a PagesManager class (#8639)
## Describe your changes Migrates pages are primarily managed in the `source_util` module to a `PagesManager` class. Because V2 can have a dynamic set of pages per session, the Pages Manager instance will live on the `AppSession`. For V1, we will leverage static variables/methods for page watching. ## Testing Plan - Original Unit tests are applied (with patches adjusted) - Unit tests are applied for the PagesManager component --- **Contribution License Agreement** By submitting this pull request you agree that all contributions to this project are made under the Apache 2.0 license.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,148 @@ | ||
| # Copyright (c) Streamlit Inc. (2018-2022) Snowflake Inc. (2022-2024) | ||
| # | ||
| # Licensed under the Apache License, Version 2.0 (the "License"); | ||
| # you may not use this file except in compliance with the License. | ||
| # You may obtain a copy of the License at | ||
| # | ||
| # http://www.apache.org/licenses/LICENSE-2.0 | ||
| # | ||
| # Unless required by applicable law or agreed to in writing, software | ||
| # distributed under the License is distributed on an "AS IS" BASIS, | ||
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| # See the License for the specific language governing permissions and | ||
| # limitations under the License. | ||
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| from __future__ import annotations | ||
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| import threading | ||
| from pathlib import Path | ||
| from typing import Callable, Final | ||
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| from blinker import Signal | ||
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| from streamlit.logger import get_logger | ||
| from streamlit.source_util import PageInfo, get_pages | ||
| from streamlit.util import calc_md5 | ||
| from streamlit.watcher import watch_dir | ||
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| _LOGGER: Final = get_logger(__name__) | ||
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| class PagesManagerV1: | ||
| is_watching_pages_dir: bool = False | ||
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| # This is a static method because we only want to watch the pages directory | ||
| # once on initial load. | ||
| @staticmethod | ||
| def watch_pages_dir(pages_manager: PagesManager): | ||
| lock = threading.Lock() | ||
| with lock: | ||
| if PagesManagerV1.is_watching_pages_dir: | ||
| return | ||
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| def _on_pages_changed(_path: str) -> None: | ||
| pages_manager.invalidate_pages_cache() | ||
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| main_script_path = Path(pages_manager.main_script_path) | ||
| pages_dir = main_script_path.parent / "pages" | ||
| watch_dir( | ||
| str(pages_dir), | ||
| _on_pages_changed, | ||
| glob_pattern="*.py", | ||
| allow_nonexistent=True, | ||
| ) | ||
| PagesManagerV1.is_watching_pages_dir = True | ||
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| class PagesManager: | ||
| def __init__(self, main_script_path, **kwargs): | ||
| self._cached_pages: dict[str, PageInfo] | None = None | ||
| self._pages_cache_lock = threading.RLock() | ||
| self._on_pages_changed = Signal(doc="Emitted when the set of pages has changed") | ||
| self._main_script_path: str = main_script_path | ||
| self._main_script_hash: str = calc_md5(main_script_path) | ||
| self._current_page_hash: str = self._main_script_hash | ||
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| if kwargs.get("setup_watcher", True): | ||
| PagesManagerV1.watch_pages_dir(self) | ||
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| @property | ||
| def main_script_path(self) -> str: | ||
| return self._main_script_path | ||
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| def get_main_page(self) -> PageInfo: | ||
| return { | ||
| "script_path": self._main_script_path, | ||
| "page_script_hash": self._main_script_hash, | ||
| } | ||
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| def get_current_page_script_hash(self) -> str: | ||
| return self._current_page_hash | ||
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| def set_current_page_script_hash(self, page_hash: str) -> None: | ||
| self._current_page_hash = page_hash | ||
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| def get_active_script(self, page_script_hash: str, page_name: str): | ||
| pages = self.get_pages() | ||
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| if page_script_hash: | ||
| return pages.get(page_script_hash, None) | ||
| elif not page_script_hash and page_name: | ||
| # If a user navigates directly to a non-main page of an app, we get | ||
| # the first script run request before the list of pages has been | ||
| # sent to the frontend. In this case, we choose the first script | ||
| # with a name matching the requested page name. | ||
| return next( | ||
| filter( | ||
| # There seems to be this weird bug with mypy where it | ||
| # thinks that p can be None (which is impossible given the | ||
| # types of pages), so we add `p and` at the beginning of | ||
| # the predicate to circumvent this. | ||
| lambda p: p and (p["page_name"] == page_name), | ||
| pages.values(), | ||
| ), | ||
| None, | ||
| ) | ||
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| # If no information about what page to run is given, default to | ||
| # running the main page. | ||
| # Safe because pages will at least contain the app's main page. | ||
| main_page_info = list(pages.values())[0] | ||
| return main_page_info | ||
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| def get_pages(self) -> dict[str, PageInfo]: | ||
| # Avoid taking the lock if the pages cache hasn't been invalidated. | ||
| pages = self._cached_pages | ||
| if pages is not None: | ||
| return pages | ||
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| with self._pages_cache_lock: | ||
| # The cache may have been repopulated while we were waiting to grab | ||
| # the lock. | ||
| if self._cached_pages is not None: | ||
| return self._cached_pages | ||
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| pages = get_pages(self.main_script_path) | ||
| self._cached_pages = pages | ||
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| return pages | ||
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| def invalidate_pages_cache(self) -> None: | ||
| _LOGGER.debug("Set of pages have changed. Invalidating cache.") | ||
| with self._pages_cache_lock: | ||
| self._cached_pages = None | ||
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| self._on_pages_changed.send() | ||
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| def register_pages_changed_callback( | ||
| self, | ||
| callback: Callable[[str], None], | ||
| ) -> Callable[[], None]: | ||
| def disconnect(): | ||
| self._on_pages_changed.disconnect(callback) | ||
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| # weak=False so that we have control of when the pages changed | ||
| # callback is deregistered. | ||
| self._on_pages_changed.connect(callback, weak=False) | ||
|
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| return disconnect |
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