Backport PR #12453: Allow spaces when using debug magic

IPython/core/magics/execution.py

@@ -467,7 +467,13 b' python-profiler package from non-free.""")'
 
         if not (args.breakpoint or args.statement or cell):
             self._debug_post_mortem()
+        elif not (args.breakpoint or cell):
+            # If there is no breakpoints, the line is just code to execute
+            self._debug_exec(line, None)
         else:
+            # Here we try to reconstruct the code from the output of
+            # parse_argstring. This might not work if the code has spaces
+            # For example this fails for `print("a b")`
             code = "\n".join(args.statement)
             if cell:
                 code += "\n" + cell

IPython/core/tests/test_magic.py

@@ -32,6 +32,7 b' from IPython.utils.io import capture_output'
 from IPython.utils.tempdir import (TemporaryDirectory,
                                     TemporaryWorkingDirectory)
 from IPython.utils.process import find_cmd
+from .test_debugger import PdbTestInput
 
 
 @magic.magics_class
@@ -622,6 +623,18 b' def doctest_precision():'
     Out[5]: '3.141593e+00'
     """
 
+def test_debug_magic():
+    """Test debugging a small code with %debug
+    
+    In [1]: with PdbTestInput(['c']):
+       ...:     %debug print("a b") #doctest: +ELLIPSIS
+       ...:
+    ...
+    ipdb> c
+    a b
+    In [2]:
+    """
+
 def test_psearch():
     with tt.AssertPrints("dict.fromkeys"):
         _ip.run_cell("dict.fr*?")