From 1328b5e7da3f908be350ff101a0ec95140a74bca Mon Sep 17 00:00:00 2001
From: Sergey B Kirpichev <skirpichev@gmail.com>
Date: Sat, 6 Jul 2024 06:46:38 +0300
Subject: [PATCH] gh-121245: Refactor site.register_readline()

also initialize CAN_USE_PYREPL at import from _pyrepl.main
---
 Lib/_pyrepl/main.py                           | 39 +++++++++----------
 Lib/site.py                                   | 23 +++++------
 ...-07-13-06-23-24.gh-issue-121245.RfOgf4.rst |  3 ++
 3 files changed, 32 insertions(+), 33 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2024-07-13-06-23-24.gh-issue-121245.RfOgf4.rst

diff --git a/Lib/_pyrepl/main.py b/Lib/_pyrepl/main.py
index 041a4009f42ed8..aaa0763cc03b0b 100644
--- a/Lib/_pyrepl/main.py
+++ b/Lib/_pyrepl/main.py
@@ -7,10 +7,26 @@
 else:
     CAN_USE_PYREPL = sys.getwindowsversion().build >= 10586  # Windows 10 TH2
 
+FAIL_MSG = ""
+try:
+    import errno
+    if not os.isatty(sys.stdin.fileno()):
+        raise OSError(errno.ENOTTY, "tty required", "stdin")
+    from .simple_interact import check
+    if err := check():
+        raise RuntimeError(err)
+except Exception as e:
+    FAIL_MSG = f"warning: can't use pyrepl: {e}"
+    CAN_USE_PYREPL = False
+
 
 def interactive_console(mainmodule=None, quiet=False, pythonstartup=False):
-    global CAN_USE_PYREPL
+    global CAN_USE_PYREPL, FAIL_MSG
     if not CAN_USE_PYREPL:
+        if not os.environ.get('PYTHON_BASIC_REPL', None):
+            from .trace import trace
+            trace(FAIL_MSG)
+            print(FAIL_MSG, file=sys.stderr)
         return sys._baserepl()
 
     if mainmodule:
@@ -34,22 +50,5 @@ def interactive_console(mainmodule=None, quiet=False, pythonstartup=False):
     if not hasattr(sys, "ps2"):
         sys.ps2 = "... "
 
-    run_interactive = None
-    try:
-        import errno
-        if not os.isatty(sys.stdin.fileno()):
-            raise OSError(errno.ENOTTY, "tty required", "stdin")
-        from .simple_interact import check
-        if err := check():
-            raise RuntimeError(err)
-        from .simple_interact import run_multiline_interactive_console
-        run_interactive = run_multiline_interactive_console
-    except Exception as e:
-        from .trace import trace
-        msg = f"warning: can't use pyrepl: {e}"
-        trace(msg)
-        print(msg, file=sys.stderr)
-        CAN_USE_PYREPL = False
-    if run_interactive is None:
-        return sys._baserepl()
-    run_interactive(namespace)
+    from .simple_interact import run_multiline_interactive_console
+    run_multiline_interactive_console(namespace)
diff --git a/Lib/site.py b/Lib/site.py
index daa56e158949db..b54e9f22f5cad8 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -509,6 +509,10 @@ def register_readline():
         pass
 
     if readline.get_current_history_length() == 0:
+        try:
+            from _pyrepl.main import CAN_USE_PYREPL
+        except ImportError:
+            CAN_USE_PYREPL = False
         # If no history was loaded, default to .python_history,
         # or PYTHON_HISTORY.
         # The guard is necessary to avoid doubling history size at
@@ -516,25 +520,18 @@ def register_readline():
         # through a PYTHONSTARTUP hook, see:
         # http://bugs.python.org/issue5845#msg198636
         history = gethistoryfile()
+        if os.getenv("PYTHON_BASIC_REPL") or not CAN_USE_PYREPL:
+            my_readline = readline
+        else:
+            my_readline = _pyrepl.readline
         try:
-            if os.getenv("PYTHON_BASIC_REPL"):
-                readline.read_history_file(history)
-            else:
-                _pyrepl.readline.read_history_file(history)
+            my_readline.read_history_file(history)
         except (OSError,* _pyrepl.unix_console._error):
             pass
 
         def write_history():
             try:
-                from _pyrepl.main import CAN_USE_PYREPL
-            except ImportError:
-                CAN_USE_PYREPL = False
-
-            try:
-                if os.getenv("PYTHON_BASIC_REPL") or not CAN_USE_PYREPL:
-                    readline.write_history_file(history)
-                else:
-                    _pyrepl.readline.write_history_file(history)
+                my_readline.write_history_file(history)
             except (FileNotFoundError, PermissionError):
                 # home directory does not exist or is not writable
                 # https://bugs.python.org/issue19891
diff --git a/Misc/NEWS.d/next/Library/2024-07-13-06-23-24.gh-issue-121245.RfOgf4.rst b/Misc/NEWS.d/next/Library/2024-07-13-06-23-24.gh-issue-121245.RfOgf4.rst
new file mode 100644
index 00000000000000..1758f587157f36
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-07-13-06-23-24.gh-issue-121245.RfOgf4.rst
@@ -0,0 +1,3 @@
+Simplify handling of the history file in ``site.register_readline()``
+helper. The ``CAN_USE_PYREPL`` variable now will be initialized, when
+imported.  Patch by Sergey B Kirpichev.