gh-84995: Run sys.__interactivehook__() on asyncio REPL startup (#20517)

This makes the asyncio REPL (`python -m asyncio`) more usable
and similar to the regular REPL.

This exposes register_readline() as a top-level function in site.py,
but it's intentionally undocumented. 

Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
Co-authored-by: Itamar Oren <itamarost@gmail.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/Lib/asyncio/__main__.py b/Lib/asyncio/__main__.py
index 18bb87a5bc4..cbc1d7c93ef 100644
--- a/Lib/asyncio/__main__.py
+++ b/Lib/asyncio/__main__.py
@@ -3,6 +3,7 @@ import asyncio
 import code
 import concurrent.futures
 import inspect
+import site
 import sys
 import threading
 import types
@@ -109,6 +110,21 @@ if __name__ == '__main__':
     except ImportError:
         pass
 
+    interactive_hook = getattr(sys, "__interactivehook__", None)
+
+    if interactive_hook is not None:
+        interactive_hook()
+
+    if interactive_hook is site.register_readline:
+        # Fix the completer function to use the interactive console locals
+        try:
+            import rlcompleter
+        except:
+            pass
+        else:
+            completer = rlcompleter.Completer(console.locals)
+            readline.set_completer(completer.complete)
+
     repl_thread = REPLThread()
     repl_thread.daemon = True
     repl_thread.start()