gh-119102: Fix REPL for dumb terminal

Move CAN_USE_PYREPL variable from _pyrepl.__main__ to _pyrepl and
rename it to _CAN_USE_PYREPL. Use the variable in the site module to
decide if _pyrepl.write_history_file() can be used.

Author: vstinner

Lib/_pyrepl/__init__.py

@@ -17,3 +17,7 @@
 # RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
 # CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 # CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+import sys
+
+_CAN_USE_PYREPL = sys.platform != "win32"

Lib/_pyrepl/__main__.py

@@ -1,12 +1,10 @@
 import os
 import sys
-
-CAN_USE_PYREPL = sys.platform != "win32"
+import _pyrepl
 
 
 def interactive_console(mainmodule=None, quiet=False, pythonstartup=False):
-    global CAN_USE_PYREPL
-    if not CAN_USE_PYREPL:
+    if not _pyrepl._CAN_USE_PYREPL:
         return sys._baserepl()
 
     startup_path = os.getenv("PYTHONSTARTUP")
@@ -38,7 +36,7 @@ def interactive_console(mainmodule=None, quiet=False, pythonstartup=False):
         msg = f"warning: can't use pyrepl: {e}"
         trace(msg)
         print(msg, file=sys.stderr)
-        CAN_USE_PYREPL = False
+        _pyrepl._CAN_USE_PYREPL = False
     if run_interactive is None:
         return sys._baserepl()
     return run_interactive(mainmodule)

Lib/site.py

@@ -523,8 +523,9 @@ def register_readline():
             pass
 
         def write_history():
+            import _pyrepl
             try:
-                if os.getenv("PYTHON_BASIC_REPL"):
+                if os.getenv("PYTHON_BASIC_REPL") or not _pyrepl._CAN_USE_PYREPL:
                     readline.write_history_file(history)
                 else:
                     _pyrepl.readline.write_history_file(history)