From 7844490e0b338c923b88218e6563c7c903b2ea50 Mon Sep 17 00:00:00 2001
From: LloydZ <35182391+cocolato@users.noreply.github.com>
Date: Tue, 25 Nov 2025 13:34:47 +0000
Subject: [PATCH 1/6] fix incorrectly pdb break

---
 Lib/pdb.py                                    |  4 ++-
 Lib/test/test_pdb.py                          | 25 +++++++++++++++++++
 ...5-11-25-16-00-29.gh-issue-59000.YtOyJy.rst |  1 +
 3 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2025-11-25-16-00-29.gh-issue-59000.YtOyJy.rst

diff --git a/Lib/pdb.py b/Lib/pdb.py
index 60b713ebaf3d1a..18cee7e9ae60e1 100644
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -1487,7 +1487,9 @@ def lineinfo(self, identifier):
             f = self.lookupmodule(parts[0])
             if f:
                 fname = f
-            item = parts[1]
+                item = parts[1]
+            else:
+                return failed
         answer = find_function(item, self.canonic(fname))
         return answer or failed
 
diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index 34dfc220c7ed73..99a69ba493a2c3 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -4587,6 +4587,31 @@ def bar():
             ]))
             self.assertIn('break in bar', stdout)
 
+    def test_issue_59000(self):
+        script = """
+            def foo():
+                pass
+
+            class C:
+                def c_foo(self):
+                    pass
+                def foo(self):
+                    pass
+
+            foo()
+        """
+        commands = """
+            break foo
+            break C.foo
+            break C.c_foo
+            break 10
+            continue
+            break C.foo
+            quit
+        """
+        stdout, stderr = self.run_pdb_script(script, commands)
+        self.assertIn("The specified object 'C.c_foo' is not a function", stdout)
+
 
 class ChecklineTests(unittest.TestCase):
     def setUp(self):
diff --git a/Misc/NEWS.d/next/Library/2025-11-25-16-00-29.gh-issue-59000.YtOyJy.rst b/Misc/NEWS.d/next/Library/2025-11-25-16-00-29.gh-issue-59000.YtOyJy.rst
new file mode 100644
index 00000000000000..33ab8a0659e4a2
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-11-25-16-00-29.gh-issue-59000.YtOyJy.rst
@@ -0,0 +1 @@
+Fix :mod:`pdb` breakpoint resolution for class methods when the module defining the class is not imported.

From 7b8fe202fbac415c8a851c0226ecc508e1ebecfe Mon Sep 17 00:00:00 2001
From: LloydZ <35182391+cocolato@users.noreply.github.com>
Date: Sun, 30 Nov 2025 05:07:45 +0000
Subject: [PATCH 2/6] fix test

---
 Lib/test/test_pdb.py | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index 99a69ba493a2c3..460945c1971dbf 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -4590,27 +4590,32 @@ def bar():
     def test_issue_59000(self):
         script = """
             def foo():
-                pass
+                test_str = "break foo"
 
             class C:
-                def c_foo(self):
-                    pass
                 def foo(self):
-                    pass
+                    test_str = "break C.foo"
 
             foo()
+            C().foo()
         """
         commands = """
             break foo
             break C.foo
-            break C.c_foo
-            break 10
             continue
             break C.foo
+            continue
             quit
         """
         stdout, stderr = self.run_pdb_script(script, commands)
-        self.assertIn("The specified object 'C.c_foo' is not a function", stdout)
+        res_lines = [x.strip() for x in stdout.splitlines()]
+        print(res_lines)
+        # can't set breakpoint before class C is defined, and gives an error
+        self.assertIn("The specified object 'C.foo' is not a function", res_lines[3])
+        # can set correctly after the class C is defined
+        self.assertRegex(res_lines[6], r"Breakpoint 2 at .*main\.py:7")
+        self.assertIn('test_str = "break C.foo"', res_lines[8])
+
 
 
 class ChecklineTests(unittest.TestCase):

From 25c88198c7a448fccd94422fe183782d9288fc64 Mon Sep 17 00:00:00 2001
From: LloydZ <35182391+cocolato@users.noreply.github.com>
Date: Sun, 30 Nov 2025 11:29:08 +0000
Subject: [PATCH 3/6] fix test

---
 Lib/test/test_pdb.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index 460945c1971dbf..ecb21f330ee772 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -4609,7 +4609,6 @@ def foo(self):
         """
         stdout, stderr = self.run_pdb_script(script, commands)
         res_lines = [x.strip() for x in stdout.splitlines()]
-        print(res_lines)
         # can't set breakpoint before class C is defined, and gives an error
         self.assertIn("The specified object 'C.foo' is not a function", res_lines[3])
         # can set correctly after the class C is defined

From df885343569b6b539fbdfa65a34d77b73c83b3f3 Mon Sep 17 00:00:00 2001
From: LloydZ <35182391+cocolato@users.noreply.github.com>
Date: Mon, 1 Dec 2025 03:24:31 +0000
Subject: [PATCH 4/6] fix test

---
 Lib/test/test_pdb.py | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index ecb21f330ee772..281bb0600dc9b3 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -4595,26 +4595,13 @@ def foo():
             class C:
                 def foo(self):
                     test_str = "break C.foo"
-
-            foo()
-            C().foo()
         """
         commands = """
-            break foo
-            break C.foo
-            continue
             break C.foo
-            continue
             quit
         """
         stdout, stderr = self.run_pdb_script(script, commands)
-        res_lines = [x.strip() for x in stdout.splitlines()]
-        # can't set breakpoint before class C is defined, and gives an error
-        self.assertIn("The specified object 'C.foo' is not a function", res_lines[3])
-        # can set correctly after the class C is defined
-        self.assertRegex(res_lines[6], r"Breakpoint 2 at .*main\.py:7")
-        self.assertIn('test_str = "break C.foo"', res_lines[8])
-
+        self.assertIn("The specified object 'C.foo' is not a function", stdout)
 
 
 class ChecklineTests(unittest.TestCase):

From b59d79aa4a21009d33da23c188e9230f1084e4c9 Mon Sep 17 00:00:00 2001
From: LloydZ <35182391+cocolato@users.noreply.github.com>
Date: Mon, 1 Dec 2025 03:51:27 +0000
Subject: [PATCH 5/6] fix test

---
 Lib/test/test_pdb.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index 281bb0600dc9b3..848a58b0d01a5f 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -4590,7 +4590,7 @@ def bar():
     def test_issue_59000(self):
         script = """
             def foo():
-                test_str = "break foo"
+                pass
 
             class C:
                 def foo(self):

From 53ac2601975bdb6d3c5ff1c89172f9a5a7ab301a Mon Sep 17 00:00:00 2001
From: LloydZ <35182391+cocolato@users.noreply.github.com>
Date: Mon, 1 Dec 2025 07:23:54 +0000
Subject: [PATCH 6/6] fix test

---
 Lib/test/test_pdb.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index 848a58b0d01a5f..8d582742499815 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -4594,7 +4594,7 @@ def foo():
 
             class C:
                 def foo(self):
-                    test_str = "break C.foo"
+                    pass
         """
         commands = """
             break C.foo