GH-111744: Make breakpoint() enter the debugger immediately (GH-118579)

Author: gaogaotiantian

Doc/library/bdb.rst

@@ -289,6 +289,10 @@ The :mod:`bdb` module also defines two classes:
       Start debugging from *frame*.  If *frame* is not specified, debugging
       starts from caller's frame.
 
+      .. versionchanged:: 3.13
+         :func:`set_trace` will enter the debugger immediately, rather than
+         on the next line of code to be executed.
+
    .. method:: set_continue()
 
       Stop only at breakpoints or when finished.  If there are no breakpoints,

Doc/library/pdb.rst

@@ -62,8 +62,8 @@ running without the debugger using the :pdbcmd:`continue` command.
 
 The debugger's prompt is ``(Pdb)``, which is the indicator that you are in debug mode::
 
-   > ...(3)double()
-   -> return x * 2
+   > ...(2)double()
+   -> breakpoint()
    (Pdb) p x
    3
    (Pdb) continue
@@ -164,6 +164,9 @@ slightly different way:
    .. versionchanged:: 3.7
       The keyword-only argument *header*.
 
+   .. versionchanged:: 3.13
+      :func:`set_trace` will enter the debugger immediately, rather than
+      on the next line of code to be executed.
 
 .. function:: post_mortem(traceback=None)
 

Doc/whatsnew/3.13.rst

@@ -715,6 +715,12 @@ pdb
 * :mod:`zipapp` is supported as a debugging target.
   (Contributed by Tian Gao in :gh:`118501`.)
 
+* ``breakpoint()`` and ``pdb.set_trace()`` now enter the debugger immediately
+  rather than on the next line of code to be executed. This change prevents the
+  debugger from breaking outside of the context when ``breakpoint()`` is positioned
+  at the end of the context.
+  (Contributed by Tian Gao in :gh:`118579`.)
+
 queue
 -----
 

Lib/bdb.py

@@ -378,7 +378,7 @@ def set_trace(self, frame=None):
             # We need f_trace_lines == True for the debugger to work
             frame.f_trace_lines = True
             frame = frame.f_back
-        self.set_step()
+        self.set_stepinstr()
         sys.settrace(self.trace_dispatch)
 
     def set_continue(self):

Lib/pdb.py

@@ -431,6 +431,8 @@ def user_line(self, frame):
         if self.bp_commands(frame):
             self.interaction(frame, None)
 
+    user_opcode = user_line
+
     def bp_commands(self, frame):
         """Call every command that was set for the current active breakpoint
         (if there is one).

Lib/test/test_doctest/test_doctest.py

@@ -2056,8 +2056,7 @@ def test_pdb_set_trace():
 
           >>> try: runner.run(test)
           ... finally: sys.stdin = real_stdin
-          --Return--
-          > <doctest foo-bar@baz[2]>(1)<module>()->None
+          > <doctest foo-bar@baz[2]>(1)<module>()
           -> import pdb; pdb.set_trace()
           (Pdb) print(x)
           42
@@ -2087,8 +2086,7 @@ def test_pdb_set_trace():
           ...     runner.run(test)
           ... finally:
           ...     sys.stdin = real_stdin
-          --Return--
-          > <doctest test.test_doctest.test_doctest.test_pdb_set_trace[9]>(3)calls_set_trace()->None
+          > <doctest test.test_doctest.test_doctest.test_pdb_set_trace[9]>(3)calls_set_trace()
           -> import pdb; pdb.set_trace()
           (Pdb) print(y)
           2
@@ -2114,6 +2112,7 @@ def test_pdb_set_trace():
           >>> test = parser.get_doctest(doc, globals(), "foo-bar@baz", "foo-bar@baz.py", 0)
           >>> real_stdin = sys.stdin
           >>> sys.stdin = FakeInput([
+          ...    'step',     # return event of g
           ...    'list',     # list source from example 2
           ...    'next',     # return from g()
           ...    'list',     # list source from example 1
@@ -2124,6 +2123,9 @@ def test_pdb_set_trace():
           >>> try: runner.run(test)
           ... finally: sys.stdin = real_stdin
           ... # doctest: +NORMALIZE_WHITESPACE
+          > <doctest foo-bar@baz[1]>(3)g()
+          -> import pdb; pdb.set_trace()
+          (Pdb) step
           --Return--
           > <doctest foo-bar@baz[1]>(3)g()->None
           -> import pdb; pdb.set_trace()
@@ -2188,6 +2190,7 @@ def test_pdb_set_trace_nested():
         >>> test = parser.get_doctest(doc, globals(), "foo-bar@baz", "foo-bar@baz.py", 0)
         >>> real_stdin = sys.stdin
         >>> sys.stdin = FakeInput([
+        ...    'step',
         ...    'print(y)',  # print data defined in the function
         ...    'step', 'step', 'step', 'step', 'step', 'step', 'print(z)',
         ...    'up', 'print(x)',
@@ -2201,6 +2204,9 @@ def test_pdb_set_trace_nested():
         ... finally:
         ...     sys.stdin = real_stdin
         ... # doctest: +REPORT_NDIFF
+        > <doctest test.test_doctest.test_doctest.test_pdb_set_trace_nested[0]>(4)calls_set_trace()
+        -> import pdb; pdb.set_trace()
+        (Pdb) step
         > <doctest test.test_doctest.test_doctest.test_pdb_set_trace_nested[0]>(5)calls_set_trace()
         -> self.f1()
         (Pdb) print(y)