[3.13] gh-139289: Lazy import rlcompleter to fix the refleak (GH-139305) (#139357)

(cherry picked from commit 8288f3693f50058ad9b9fe04e01f5dad902d8bad)

diff --git a/Lib/pdb.py b/Lib/pdb.py
index 41735f4e249f5da75b4b72c31ce8ffef004acdcf..a990d60fe1c2fd8c1aec037d001afef31b649be7 100755 (executable)
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -332,14 +332,6 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         except ImportError:
             pass
 
-        # GH-138860
-        # We need to lazy-import rlcompleter to avoid deadlock
-        # We cannot import it during self.complete* methods because importing
-        # rlcompleter for the first time will overwrite readline's completer
-        # So we import it here and save the Completer class
-        from rlcompleter import Completer
-        self.RlCompleter = Completer
-
         self.allow_kbdint = False
         self.nosigint = nosigint
         # Consider these characters as part of the command so when the users type
@@ -918,6 +910,31 @@ class Pdb(bdb.Bdb, cmd.Cmd):
     # Generic completion functions.  Individual complete_foo methods can be
     # assigned below to one of these functions.
 
+    @property
+    def rlcompleter(self):
+        """Return the `Completer` class from `rlcompleter`, while avoiding the
+        side effects of changing the completer from `import rlcompleter`.
+
+        This is a compromise between GH-138860 and GH-139289. If GH-139289 is
+        fixed, then we don't need this and we can just `import rlcompleter` in
+        `Pdb.__init__`.
+        """
+        if not hasattr(self, "_rlcompleter"):
+            try:
+                import readline
+            except ImportError:
+                # readline is not available, just get the Completer
+                from rlcompleter import Completer
+                self._rlcompleter = Completer
+            else:
+                # importing rlcompleter could have side effect of changing
+                # the current completer, we need to restore it
+                prev_completer = readline.get_completer()
+                from rlcompleter import Completer
+                self._rlcompleter = Completer
+                readline.set_completer(prev_completer)
+        return self._rlcompleter
+
     def completenames(self, text, line, begidx, endidx):
         # Overwrite completenames() of cmd so for the command completion,
         # if no current command matches, check for expressions as well
@@ -996,7 +1013,7 @@ class Pdb(bdb.Bdb, cmd.Cmd):
 
         state = 0
         matches = []
-        completer = self.RlCompleter(self.curframe.f_globals | self.curframe.f_locals)
+        completer = self.rlcompleter(self.curframe.f_globals | self.curframe_locals)
         while (match := completer.complete(text, state)) is not None:
             matches.append(match)
             state += 1

diff --git a/Lib/test/test_pyclbr.py b/Lib/test/test_pyclbr.py
index a65705aaf53abc74d53b11717c45f21513d2dfa9..01f43ac1068df5d0b44690c3933f93d354c12324 100644 (file)
--- a/Lib/test/test_pyclbr.py
+++ b/Lib/test/test_pyclbr.py
@@ -225,7 +225,7 @@ class PyclbrTest(TestCase, ExtraAssertions):
         cm(
             'pdb',
             # pyclbr does not handle elegantly `typing` or properties
-            ignore=('Union', '_ModuleTarget', '_ScriptTarget', '_ZipTarget'),
+            ignore=('Union', '_ModuleTarget', '_ScriptTarget', '_ZipTarget', 'rlcompleter'),
         )
         cm('pydoc', ignore=('input', 'output',)) # properties
 

diff --git a/Misc/NEWS.d/next/Library/2025-09-24-14-17-34.gh-issue-139289.Vmk25k.rst b/Misc/NEWS.d/next/Library/2025-09-24-14-17-34.gh-issue-139289.Vmk25k.rst
new file mode 100644 (file)
index 0000000..0416261
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-09-24-14-17-34.gh-issue-139289.Vmk25k.rst
@@ -0,0 +1 @@
+Do a real lazy-import on :mod:`rlcompleter` in :mod:`pdb` and restore the existing completer after importing :mod:`rlcompleter`.