gh-93696: Locate frozen module source with __file__

Lib/pdb.py

@@ -1332,6 +1332,10 @@ def do_list(self, arg):
         if last is None:
             last = first + 10
         filename = self.curframe.f_code.co_filename
+        # gh-93696: stdlib frozen modules provide a useful __file__ (see also gh-89815)
+        if filename.startswith("<frozen"):
+            if "__file__" in self.curframe.f_globals:
+                filename = self.curframe.f_globals["__file__"]
         breaklist = self.get_file_breaks(filename)
         try:
             lines = linecache.getlines(filename, self.curframe.f_globals)

Lib/test/test_pdb.py

@@ -2104,6 +2104,52 @@ def inner(v): pass
         stdout, stderr = self.run_pdb_script(script, commands)
         self.assertFalse(stderr)
 
+    def test_gh_93696_frozen_list(self):
+        frozen_src = """
+        def func():
+            x = "Sentinel string for gh-93696"
+            print(x)
+        """
+        host_program = """
+        import os
+        import sys
+
+        def _create_fake_frozen_module():
+            with open('gh93696.py') as f:
+                src = f.read()
+
+            # this function has a co_filename as if it were in a frozen module
+            dummy_mod = compile(src, "<frozen gh93696>", "exec")
+            func_code = dummy_mod.co_consts[0]
+
+            mod = type(sys)("gh93696")
+            mod.func = type(lambda: None)(func_code, mod.__dict__)
+            mod.__file__ = 'gh93696.py'
+
+            return mod
+
+        mod = _create_fake_frozen_module()
+        mod.func()
+        """
+        commands = """
+            break 20
+            continue
+            step
+            list
+            quit
+        """
+        with open('gh93696.py', 'w') as f:
+            f.write(textwrap.dedent(frozen_src))
+
+        with open('gh93696_host.py', 'w') as f:
+            f.write(textwrap.dedent(host_program))
+
+        self.addCleanup(os_helper.unlink, 'gh93696.py')
+        self.addCleanup(os_helper.unlink, 'gh93696_host.py')
+        stdout, stderr = self._run_pdb(["gh93696_host.py"], commands)
+        # verify that pdb found the source of the "frozen" function
+        self.assertIn('x = "Sentinel string for gh-93696"', stdout, "Sentinel statement not found")
+
 class ChecklineTests(unittest.TestCase):
     def setUp(self):
         linecache.clearcache()  # Pdb.checkline() uses linecache.getline()

Misc/NEWS.d/next/Core and Builtins/2022-06-10-16-37-44.gh-issue-93696.65BI2R.rst

@@ -0,0 +1 @@
+Allow :mod:`pdb` to locate source for frozen modules in the standard library.