gh-80744: do not read .pdbrc twice when cwd == $home

Lib/pdb.py

@@ -378,11 +378,12 @@ def __init__(self, completekey='tab', stdin=None, stdout=None, skip=None,
                     self.rcLines.extend(rcFile)
             except OSError:
                 pass
-            try:
-                with open(".pdbrc", encoding='utf-8') as rcFile:
-                    self.rcLines.extend(rcFile)
-            except OSError:
-                pass
+            if os.path.abspath(".pdbrc") != os.path.expanduser("~/.pdbrc"):
+                try:
+                    with open(".pdbrc", encoding='utf-8') as rcFile:
+                        self.rcLines.extend(rcFile)
+                except OSError:
+                    pass
 
         self.commands = {} # associates a command list to breakpoint numbers
         self.commands_defining = False # True while in the process of defining

Lib/test/test_pdb.py

@@ -3935,6 +3935,23 @@ def test_readrc_homedir(self):
                     f.write("invalid")
                 self.assertEqual(pdb.Pdb().rcLines[0], "invalid")
 
+    def test_readrc_current_dir(self):
+        with os_helper.temp_cwd() as cwd:
+            rc_path = os.path.join(cwd, ".pdbrc")
+            with open(rc_path, "w") as f:
+                f.write("invalid")
+            self.assertEqual(pdb.Pdb().rcLines[-1], "invalid")
+
+    def test_readrc_cwd_is_home(self):
+        with os_helper.EnvironmentVarGuard() as env:
+            env.unset("HOME")
+            with os_helper.temp_cwd() as cwd, patch("os.path.expanduser"):
+                rc_path = os.path.join(cwd, ".pdbrc")
+                os.path.expanduser.return_value = rc_path
+                with open(rc_path, "w") as f:
+                    f.write("invalid")
+                self.assertEqual(pdb.Pdb().rcLines, ["invalid"])
+
     def test_header(self):
         stdout = StringIO()
         header = 'Nobody expects... blah, blah, blah'