From 1bbb98d9a4b7d83e422b14ae2429cb368eff5a13 Mon Sep 17 00:00:00 2001
From: Peter Inglesby <peter.inglesby@gmail.com>
Date: Mon, 18 Jan 2021 19:07:07 +0000
Subject: [PATCH] Fixed #32363 -- Ensured sys.__interactivehook__ is called in
 shell

By default, this means that readline is properly registered, so that
.python_history is used.

sys.__interactivehook__ may be set by a $PYTHONSTARTUP file.
---
 django/core/management/commands/shell.py | 40 +++++++++++++-----------
 docs/releases/4.0.txt                    |  5 +++
 2 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/django/core/management/commands/shell.py b/django/core/management/commands/shell.py
index 3e8a451e3e..fe24f4b3fb 100644
--- a/django/core/management/commands/shell.py
+++ b/django/core/management/commands/shell.py
@@ -42,25 +42,8 @@ class Command(BaseCommand):
     def python(self, options):
         import code
 
-        # Set up a dictionary to serve as the environment for the shell, so
-        # that tab completion works on objects that are imported at runtime.
+        # Set up a dictionary to serve as the environment for the shell.
         imported_objects = {}
-        try:  # Try activating rlcompleter, because it's handy.
-            import readline
-        except ImportError:
-            pass
-        else:
-            # We don't have to wrap the following import in a 'try', because
-            # we already know 'readline' was imported successfully.
-            import rlcompleter
-            readline.set_completer(rlcompleter.Completer(imported_objects).complete)
-            # Enable tab completion on systems using libedit (e.g. macOS).
-            # These lines are copied from Python's Lib/site.py.
-            readline_doc = getattr(readline, '__doc__', '')
-            if readline_doc is not None and 'libedit' in readline_doc:
-                readline.parse_and_bind("bind ^I rl_complete")
-            else:
-                readline.parse_and_bind("tab:complete")
 
         # We want to honor both $PYTHONSTARTUP and .pythonrc.py, so follow system
         # conventions and get $PYTHONSTARTUP first then .pythonrc.py.
@@ -79,6 +62,27 @@ class Command(BaseCommand):
                 except Exception:
                     traceback.print_exc()
 
+        # By default, this will set up readline to do tab completion and to read and
+        # write history to the .python_history file, but this can be overridden by
+        # $PYTHONSTARTUP or ~/.pythonrc.py.
+        try:
+            sys.__interactivehook__()
+        except Exception:
+            # Match the behavior of the cpython shell where an error in
+            # sys.__interactivehook__ prints a warning and the exception and continues.
+            print("Failed calling sys.__interactivehook__")
+            traceback.print_exc()
+
+        # Set up tab completion for objects imported by $PYTHONSTARTUP or
+        # ~/.pythonrc.py.
+        try:
+            import readline
+            import rlcompleter
+            readline.set_completer(rlcompleter.Completer(imported_objects).complete)
+        except ImportError:
+            pass
+
+        # Start the interactive interpreter.
         code.interact(local=imported_objects)
 
     def handle(self, **options):
diff --git a/docs/releases/4.0.txt b/docs/releases/4.0.txt
index a9e660f0f1..9b57a524aa 100644
--- a/docs/releases/4.0.txt
+++ b/docs/releases/4.0.txt
@@ -236,6 +236,11 @@ Management Commands
 
 * On PostgreSQL, :djadmin:`dbshell` now supports specifying a password file.
 
+* The :djadmin:`shell` command now respects :py:data:`sys.__interactivehook__`
+  at startup. This allows loading shell history between interactive sessions.
+  As a consequence, ``readline`` is no longer loaded if running in *isolated*
+  mode.
+
 Migrations
 ~~~~~~~~~~