pdb: do not raise outcomes.Exit with quit in debug

changelog/4968.bugfix.rst

@@ -0,0 +1,3 @@
+The pdb ``quit`` command is handled properly when used after the ``debug`` command with `pdb++`_.
+
+.. _pdb++: https://pypi.org/project/pdbpp/

src/_pytest/debugging.py

@@ -152,8 +152,15 @@ def do_continue(self, arg):
                 do_c = do_cont = do_continue
 
                 def set_quit(self):
+                    """Raise Exit outcome when quit command is used in pdb.
+
+                    This is a bit of a hack - it would be better if BdbQuit
+                    could be handled, but this would require to wrap the
+                    whole pytest run, and adjust the report etc.
+                    """
                     super(_PdbWrapper, self).set_quit()
-                    outcomes.exit("Quitting debugger")
+                    if cls._recursive_debug == 0:
+                        outcomes.exit("Quitting debugger")
 
                 def setup(self, f, tb):
                     """Suspend on setup().

testing/test_pdb.py

@@ -519,16 +519,17 @@ def test_1():
         assert "1 failed" in rest
         self.flush(child)
 
-    def test_pdb_interaction_continue_recursive(self, testdir):
+    def test_pdb_with_injected_do_debug(self, testdir):
+        """Simulates pdbpp, which injects Pdb into do_debug, and uses
+        self.__class__ in do_continue.
+        """
         p1 = testdir.makepyfile(
             mytest="""
             import pdb
             import pytest
 
             count_continue = 0
 
-            # Simulates pdbpp, which injects Pdb into do_debug, and uses
-            # self.__class__ in do_continue.
             class CustomPdb(pdb.Pdb, object):
                 def do_debug(self, arg):
                     import sys
@@ -577,6 +578,14 @@ def test_1():
         child.expect("LEAVING RECURSIVE DEBUGGER")
         assert b"PDB continue" not in child.before
         assert b"print_from_foo" in child.before
+
+        # set_debug should not raise outcomes.Exit, if used recrursively.
+        child.sendline("debug 42")
+        child.sendline("q")
+        child.expect("LEAVING RECURSIVE DEBUGGER")
+        assert b"ENTERING RECURSIVE DEBUGGER" in child.before
+        assert b"Quitting debugger" not in child.before
+
         child.sendline("c")
         child.expect(r"PDB continue \(IO-capturing resumed\)")
         rest = child.read().decode("utf8")