Modify ThreadedHistory example(s) for new API

Author: Bob Hyman

examples/prompts/history/slow-history.py

@@ -5,6 +5,7 @@
 By wrapping it in `ThreadedHistory`, the history will load in the background
 without blocking any user interaction.
 """
+import asyncio
 import time
 
 from prompt_toolkit import PromptSession
@@ -32,11 +33,22 @@ def main():
  "Even when the input is accepted, loading will continue in the "
  "background and when the next prompt is displayed.\n"
  )
- our_history = ThreadedHistory(SlowHistory())
+
+ my_loop = asyncio.get_event_loop() # creates loop if needed
+
+ # Inform ThreadedHistory which event loop to use
+ # when passing lines of history to the prompt.
+
+ our_history = ThreadedHistory(SlowHistory(), my_loop)
 
  # The history needs to be passed to the `PromptSession`. It can't be passed
  # to the `prompt` call because only one history can be used during a
  # session.
+ # Note that PromptSession runs on the thread's current event loop because
+ # it was created above and is therefore in synch with ThreadedHistory.
+ # PromptSession would create and event loop if it didn't find one
+ # already running, but then ThreadedHistory would not work.
+
  session = PromptSession(history=our_history)
 
  while True:

prompt_toolkit/history.py

@@ -10,10 +10,10 @@
 import datetime
 import os
 import time
+import warnings
 from abc import ABCMeta, abstractmethod
 from threading import Thread
 from typing import Callable, Iterable, List, Optional
-import warnings
 
 __all__ = [
  "History",
@@ -40,7 +40,10 @@ def __init__(self) -> None:
  # Methods expected by `Buffer`.
  #
 
- def load(self, item_loaded_callback: Callable[[str], None],) -> None:
+ def load(
+ self,
+ item_loaded_callback: Callable[[str], None],
+ ) -> None:
  """
  Load the history and call the callback for every entry in the history.
  This one assumes the callback is only called from same thread as `Buffer` is using.
@@ -103,13 +106,13 @@ class ThreadedHistory(History):
  """
 
  def __init__(
- self, history: History, event_loop: asyncio.BaseEventLoop = None
+ self, history: History, event_loop: Optional[asyncio.AbstractEventLoop] = None
  ) -> None:
  """Create instance of ThreadedHistory
 
  Args:
  history (History): Instance of History intended to run on a background thread.
- event_loop (asyncio.BaseEventLoop, optional): The event loop on which prompt toolkit is running.
+ event_loop (asyncio.AbstractEventLoop, optional): The event loop on which prompt toolkit is running.
  (Deprecated) Defaults to ``asyncio.get_event_loop(), which may *create* the event loop. Caller should provide an explicit value.
  """
  self.history = history
@@ -151,7 +154,10 @@ def call_all_callbacks(item: str) -> None:
  self._load_thread.daemon = True
  self._load_thread.start()
 
- def bg_loader(self, item_loaded_callback: Callable[[str], None],) -> None:
+ def bg_loader(
+ self,
+ item_loaded_callback: Callable[[str], None],
+ ) -> None:
  """
  Load the history and schedule the callback for every entry in the history.
  TODO: extend the callback so it can take a batch of lines in one event_loop dispatch.