Support for IPython %magics, like %timeit

[giladbarnea]

Hi, thanks for pdbr!

Since IPython is already baked into RichPdb (if available), it itched me to unlock some IPython features, so I started with %magic commands.
This is something that I've wanted to do for some time now; pdbr stands for a lot of things I enjoy: terminal debuggers, IPython and rich library.

I've added 2 functions in _pdbr.py, wrote a test in test_pdbr.py, and added a description of the feature in the README.md.

I had trouble testing the actual magic functionality, because when trying to init a rich_pdb_klass(IPython.terminal.debugger.TerminalPdb) inside a test, it raises an exception, complaining about stdout not being a terminal. I couldn't get past that.

Additionally, some magics don't work out of the box, for example %lsmagic. This can be fixed by overriding onecmd(), but I wanted to know if you're at all interested in this PR's idea before adding more changes. Let me know if you want this fixed as well :)

Thanks,
Gilad

[cansarigol]

Great job @giladbarnea . I was planning to work on it especially for %env command. With your PR all magic will be real :). Thanks for your effort.

Because of pytest --pdb is activated in project, you can see the real error via -s like pytest tests/test_pdbr.py -s. And you also need to put ipython package in test func of the noxfile.

[cansarigol]

Suggested change

	return result or ""
	return self._print(result) or ""

this change will fix some commands like lsmagic

[cansarigol]

Suggested change

	return result or ""
	return self._print(result) or ""

[cansarigol]

@giladbarnea When i run a command and run magic secondly, i always see the last result with magic result. Can you have a look at it as well?

[giladbarnea]

@cansarigol thanks for the quick reply :)
It looks like we're dealing with more than 1 issue, what do you think about writing tests for individual magics? I'd be happy to do it. There are a few dozen, I guess we'll find out we're not interested in some, or that others are working weirdly and require a more comprehensive fix.

About that bug with the repeating output, maybe it has to do with self.cmdqueue in pdb.Pdb.precmd(), or cmd.Cmd.emptyline(). I'll have to check that.

By the way, maybe it's worth sharing, I've made a pseudocode gist of the main loop. It helps me sort out the inheritance / method overload mess (cmd.Cmd > pdb.Pdb > IPython.core.debugger.Pdb > IPython.terminal.debugger.TerminalPdb > RichPdb):

class IPython.terminal.debugger.TerminalPdb:
	def cmdloop():
		self.preloop()
		# pdb.Pdb.preloop() displays expressions set by `display` command
		
		stop = None
		while not stop:
			line = self.cmdqueue.pop(0)
			line = self.precmd(line)		
			# core.debugger.Pdb.precmd() does line="pinfo "+... if ends with ?, 
			# then calls super which is pdb.Pdb.precmd()
			# pdb.Pdb.precmd() handles self.aliases and appends to self.cmdqueue
			
			stop = self.onecmd(line)
			# pdb.Pdb.onecmd() calls cmd.Cmd.onecmd(), 
			# unless we're executing `commands`.
				cmd.Cmd.onecmd(line):
					cmd, arg, line = self.parseline(line)
					if not line:
						return self.onecmd(self.lastcmd) if self.lastcmd else None
					# pdb.Pdb.default() compiles and execs the line
					if not cmd:
						return self.default(line)
					if self.do_{cmd}:
						return self.do_{cmd}(arg)
					return self.default(line)
			
			stop = self.postcmd(stop, line)
			# cmd.Cmd.postcmd() just returns stop as-is

		self.postloop()
		# cmd.Cmd.postloop(): pass

Are there any magics that you don't want altogether?

[cansarigol]

@giladbarnea writing tests for individual magics and making out TerminalPdb class and overriding its cmdloop are great ideas, please go ahead. My only objection would be for the %pdb but I don't have too much experience with magics.

[cansarigol]

Hi @giladbarnea your PR looks great 👍. If you don't have time to put inherited TerminalPdb class, let's merge it as is and you can pursue with a new PR. Thanks for your effort btw

[giladbarnea]

Hi @giladbarnea your PR looks great +1. If you don't have time to put inherited TerminalPdb class, let's merge it as is and you can pursue with a new PR. Thanks for your effort btw

Hi @cansarigol, you're right, I couldn't find the time (had my first kid a week ago :))
Let me see what quick wins I can get us within the next 45 minutes, I'll prepare a good-enough commit and hopefully it'll be ok.

[giladbarnea]

@cansarigol, I've branched out to run-magic-through-ipython to continue work there on making more magics work (by capturing self.shell.run_cell(...)'s output), so you can merge the commit I just made f4294af8 if you want.
Thanks!

[cansarigol]

Hi @giladbarnea your PR looks great +1. If you don't have time to put inherited TerminalPdb class, let's merge it as is and you can pursue with a new PR. Thanks for your effort btw

Hi @cansarigol, you're right, I couldn't find the time (had my first kid a week ago :)) Let me see what quick wins I can get us within the next 45 minutes, I'll prepare a good-enough commit and hopefully it'll be ok.

congratulations 👏 👶 🎉 . hope everybody is doing fine.

[cansarigol]

For the latest version of Ipython, there is a bug that is about to get reverted.

Suggested change

	"IPython",
	"IPython==7.x",

[cansarigol]

@giladbarnea tests fail for me. Are they same for you as well?

[giladbarnea]

@giladbarnea tests fail for me. Are they same for you as well?

@cansarigol Yes, I think at the very least the session.install() statement in noxfile.test() should include a . to install pdbr itself, and session.run() should include a "--capture=no" arg.
This fixes some tests but others are still failing, I'll update when it's fixed

[giladbarnea]

@cansarigol That's it, f13020f succeeded through the CI pipeline.

[cansarigol]

@giladbarnea Great, thanks for your effort again. I am looking forward to using it myself first 😺

we can fix windows test errors later.