bpo-32206: Pdb can now run modules (GH-4752)

Add a new argument "-m" to the pdb module to allow
users to run `python -m pdb -m my_module_name`.

This relies on private APIs in the runpy module to work,
but we can get away with that since they're both part of
the standard library and can be updated together if
the runpy internals get refactored.

1 files changed, 29 insertions, 4 deletions

diff --git a/Lib/pdb.py b/Lib/pdb.py
index 8dd4ded..d1a74bb 100755
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -1521,6 +1521,24 @@ class Pdb(bdb.Bdb, cmd.Cmd):
                 return fullname
         return None
 
+    def _runmodule(self, module_name):
+        self._wait_for_mainpyfile = True
+        self._user_requested_quit = False
+        import runpy
+        mod_name, mod_spec, code = runpy._get_module_details(module_name)
+        self.mainpyfile = self.canonic(code.co_filename)
+        import __main__
+        __main__.__dict__.clear()
+        __main__.__dict__.update({
+            "__name__": "__main__",
+            "__file__": self.mainpyfile,
+            "__package__": module_name,
+            "__loader__": mod_spec.loader,
+            "__spec__": mod_spec,
+            "__builtins__": __builtins__,
+        })
+        self.run(code)
+
     def _runscript(self, filename):
         # The script has to run in __main__ namespace (or imports from
         # __main__ will break).
@@ -1635,29 +1653,33 @@ To let the script run up to a given line X in the debugged file, use
 def main():
     import getopt
 
-    opts, args = getopt.getopt(sys.argv[1:], 'hc:', ['--help', '--command='])
+    opts, args = getopt.getopt(sys.argv[1:], 'mhc:', ['--help', '--command='])
 
     if not args:
         print(_usage)
         sys.exit(2)
 
     commands = []
+    run_as_module = False
     for opt, optarg in opts:
         if opt in ['-h', '--help']:
             print(_usage)
             sys.exit()
         elif opt in ['-c', '--command']:
             commands.append(optarg)
+        elif opt in ['-m']:
+            run_as_module = True
 
     mainpyfile = args[0]     # Get script filename
-    if not os.path.exists(mainpyfile):
+    if not run_as_module and not os.path.exists(mainpyfile):
         print('Error:', mainpyfile, 'does not exist')
         sys.exit(1)
 
     sys.argv[:] = args      # Hide "pdb.py" and pdb options from argument list
 
     # Replace pdb's dir with script's dir in front of module search path.
-    sys.path[0] = os.path.dirname(mainpyfile)
+    if not run_as_module:
+        sys.path[0] = os.path.dirname(mainpyfile)
 
     # Note on saving/restoring sys.argv: it's a good idea when sys.argv was
     # modified by the script being debugged. It's a bad idea when it was
@@ -1667,7 +1689,10 @@ def main():
     pdb.rcLines.extend(commands)
     while True:
         try:
-            pdb._runscript(mainpyfile)
+            if run_as_module:
+                pdb._runmodule(mainpyfile)
+            else:
+                pdb._runscript(mainpyfile)
             if pdb._user_requested_quit:
                 break
             print("The program finished and will be restarted")