Expand and Fix PDB skip.

This expand and fix the logic arround PBD skip.

1) it should support nested decorators, as long as they are all marked.
2) it will stop into breakpoints if those are set even in debuggerskip.
3) Documentation mentioned those facts.

IPython/core/debugger.py

@@ -24,8 +24,12 b' By default, frames from readonly files will be hidden, frames containing'
 Frames containing ``__debuggerskip__`` will be stepped over, frames who's parent
 frames value of ``__debuggerskip__`` is ``True`` will be skipped.
 
-    >>> def helper_1():
+    >>> def helpers_helper():
+    ...     pass
+    ...
+    ... def helper_1():
     ...     print("don't step in me")
+    ...     helpers_helpers() # will be stepped over unless breakpoint set.
     ...
     ...
     ... def helper_2():
@@ -44,6 +48,7 b' One can define a decorator that wraps a function between the two helpers:'
     ...         result = function(*args, **kwargs)
     ...         __debuggerskip__ = True
     ...         helper_2()
+    ...         # setting __debuggerskip__ to False again is not necessary
     ...         return result
     ...
     ...     return wrapped_fn
@@ -902,12 +907,16 b' class Pdb(OldPdb):'
         stop at any point inside the function
 
         """
+
+        sup = super().break_anywhere(frame)
+        if sup:
+            return sup
         if self._predicates["debuggerskip"]:
             if DEBUGGERSKIP in frame.f_code.co_varnames:
                 return True
             if frame.f_back and self._get_frame_locals(frame.f_back).get(DEBUGGERSKIP):
                 return True
-        return super().break_anywhere(frame)
+        return False
 
     @skip_doctest
     def _is_in_decorator_internal_and_should_skip(self, frame):
@@ -926,8 +935,12 b' class Pdb(OldPdb):'
         if DEBUGGERSKIP in frame.f_code.co_varnames:
             return True
 
-        # if parent frame value set to True skip as well.
-        if frame.f_back and self._get_frame_locals(frame.f_back).get(DEBUGGERSKIP):
+        # if one of the parent frame value set to True skip as well.
+
+        cframe = frame
+        while getattr(cframe, "f_back", None):
+            cframe = cframe.f_back
+            if self._get_frame_locals(cframe).get(DEBUGGERSKIP):
             return True
 
         return False

IPython/core/tests/test_debugger.py

@@ -12,6 +12,7 b' import subprocess'
 import sys
 import time
 import warnings
+
 from subprocess import PIPE, CalledProcessError, check_output
 from tempfile import NamedTemporaryFile
 from textwrap import dedent
@@ -325,14 +326,30 b' def test_xmode_skip():'
 
 skip_decorators_blocks = (
     """
+    def helpers_helper():
+        pass # should not stop here except breakpoint
+    """,
+    """
     def helper_1():
-        pass # should not stop here
+        helpers_helper() # should not stop here
     """,
     """
     def helper_2():
         pass # should not stop here
     """,
     """
+    def pdb_skipped_decorator2(function):
+        def wrapped_fn(*args, **kwargs):
+            __debuggerskip__ = True
+            helper_2()
+            __debuggerskip__ = False
+            result = function(*args, **kwargs)
+            __debuggerskip__ = True
+            helper_2()
+            return result
+        return wrapped_fn
+    """,
+    """
     def pdb_skipped_decorator(function):
         def wrapped_fn(*args, **kwargs):
             __debuggerskip__ = True
@@ -346,6 +363,7 b' skip_decorators_blocks = ('
     """,
     """
     @pdb_skipped_decorator
+    @pdb_skipped_decorator2
     def bar(x, y):
         return x * y
     """,
@@ -423,7 +441,7 b' def test_decorator_skip_disabled():'
         ("step", "----> 3         __debuggerskip__"),
         ("step", "----> 4         helper_1()"),
         ("step", "---> 1 def helper_1():"),
-        ("next", "----> 2     pass"),
+        ("next", "----> 2     helpers_helper()"),
         ("next", "--Return--"),
         ("next", "----> 5         __debuggerskip__ = False"),
     ]:
@@ -436,6 +454,62 b' def test_decorator_skip_disabled():'
 
 
 @skip_win32
+def test_decorator_skip_with_breakpoint():
+    """test that decorator frame skipping can be disabled"""
+
+    import pexpect
+
+    env = os.environ.copy()
+    env["IPY_TEST_SIMPLE_PROMPT"] = "1"
+
+    child = pexpect.spawn(
+        sys.executable, ["-m", "IPython", "--colors=nocolor"], env=env
+    )
+    child.timeout = 5 * IPYTHON_TESTING_TIMEOUT_SCALE
+
+    child.expect("IPython")
+    child.expect("\n")
+
+    ### we need a filename, so we need to exec the full block with a filename
+    with NamedTemporaryFile(suffix=".py", dir=".", delete=True) as tf:
+
+        name = tf.name[:-3].split("/")[-1]
+        tf.write("\n".join([dedent(x) for x in skip_decorators_blocks[:-1]]).encode())
+        tf.flush()
+        codeblock = f"from {name} import f"
+
+        dedented_blocks = [
+            codeblock,
+            "f()",
+        ]
+
+        in_prompt_number = 1
+        for cblock in dedented_blocks:
+            child.expect_exact(f"In [{in_prompt_number}]:")
+            in_prompt_number += 1
+            for line in cblock.splitlines():
+                child.sendline(line)
+                child.expect_exact(line)
+            child.sendline("")
+
+        # as the filename does not exists, we'll rely on the filename prompt
+        child.expect_exact("47     bar(3, 4)")
+
+        for input_, expected in [
+            (f"b {name}.py:3", ""),
+            ("step", "1---> 3     pass # should not stop here except"),
+            ("step", "---> 38 @pdb_skipped_decorator"),
+            ("continue", ""),
+        ]:
+            child.expect("ipdb>")
+            child.sendline(input_)
+            child.expect_exact(input_)
+            child.expect_exact(expected)
+
+    child.close()
+
+
+@skip_win32
 def test_where_erase_value():
     """Test that `where` does not access f_locals and erase values."""
     import pexpect