Allow starting debugger while running

[GoogleCodeExporter]

What steps will reproduce the problem?

Attempting to run the one-line debugger call: `import pdb; pdb.set_trace()` 
does not start the debugger.

It results in an exception like this:

>   File 
"/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/bdb.py",
 line 48, in trace_dispatch
>    return self.dispatch_line(frame)
>  File 
"/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/bdb.py",
 line 67, in dispatch_line
>    if self.quitting: raise BdbQuit
>BdbQuit

What is the expected output? What do you see instead?

It would be very handy if this would start the debugger in the/a console that 
started the devappserver2 process.

What version of the product are you using? On what operating system?

0.5.2/Mac OS X 10.8

Cheers

Original issue reported on code.google.com by brianmh...@gmail.com on 28 Jan 2013 at 3:36

[GoogleCodeExporter]

Are you trying to debug the development server or your application? Where did 
you insert those code lines that you mentioned?

Original comment by brian.k....@gmail.com on 28 Jan 2013 at 8:55

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I think that I understand better: you entered the pdb comments in the 
interactive console with the idea that you could step through your applications 
code from there?

Original comment by brian.k....@gmail.com on 28 Jan 2013 at 8:57

[GoogleCodeExporter]

Hi Brian, thanks for the reply and sorry I wasn't clear.

The `import pdb; ...` is in application code, and it starts an interactive 
console allowing one to step through the code. There's no reason it couldn't 
"step up" into the debugger, but that wasn't my intention when posting the 
question so much as debugging a thread of an application.

I hope that clarifies!

Original comment by brianmh...@gmail.com on 28 Jan 2013 at 10:18

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Yes, I understand what you want to do now. But it isn't going to work due to 
the design of the Python runtime in devappserver2; sys.stdin and sys.stdout are 
pipes connecting the runtime to the devappserver2 parent process.

We should have a better debugging story but it might take us a while to get 
there.

Original comment by bquin...@google.com on 29 Jan 2013 at 2:28

[GoogleCodeExporter]

Original comment by bquin...@google.com on 29 Jan 2013 at 2:29

• Added labels: Type-Enhancement
• Removed labels: Type-Defect

[GoogleCodeExporter]

Thanks for accepting.

As a matter of interest, I have a the highest regards for the Werkzeug debugger 
http://werkzeug.pocoo.org/docs/debug/ - and operates in an environment fairly 
analogous to the development appserver. While not strictly on point, it would 
fall under the rubric of a "better debugging story" :)

Original comment by brianmh...@gmail.com on 29 Jan 2013 at 12:57

[GoogleCodeExporter]

Issue 40 has been merged into this issue.

Original comment by bquin...@google.com on 19 Feb 2013 at 6:24

[GoogleCodeExporter]

I can't stress enough the importance of having a working debugger. I'm afraid 
the average developer won't use this devserver until they can debug their code, 
regardless of any other feature it could have.
Could you provide any insight of how long it will take to fix this? In the 
meantime I'm forced to return to the original devserver and I'd prefer not to.
Thanks, and good work

Original comment by xar...@gmail.com on 19 Feb 2013 at 11:32

[GoogleCodeExporter]

I've started working on this and have written up a description of how I expect 
it to work: 
https://docs.google.com/document/d/1CCSaRiIWCLgbD3OwmuKsRoHHDfBffbROWyVWWL0ZXN4/
edit?usp=sharing

While pdb doesn't work, I have a prototype that works with Komodo IDE, PyDev, 
PyCharm. I would expect that Winpdb would work as well but I haven't tested it.

Feedback welcome!

Original comment by bquin...@google.com on 5 Mar 2013 at 12:36

• Changed state: Started

[GoogleCodeExporter]

I should add that the document that I linked in my last message is meant for 
tool providers, not end users. Hopefully tool provides will provide integration 
using these hooks without any the user have to know how they work.

Original comment by bquin...@google.com on 5 Mar 2013 at 12:39

[GoogleCodeExporter]

We have hooks in place to make it possible to add debugger support. It is up to 
tool vendors now to make use of them.

Original comment by bquin...@google.com on 11 Mar 2013 at 6:13

• Changed state: Fixed

[GoogleCodeExporter]

So your proposal is to make people re-write the core python debugger to work 
with App Engine?

Original comment by adamal...@gmail.com on 3 Apr 2013 at 12:41

[GoogleCodeExporter]

Thanks Brian. Sorry for the delay in giving feedback. The proposed debugger is 
a very cool concept.

This issue as posted relates to console/pdb debugging, and it isn't clear to me 
how one would take advantage of the proposed concept from the command line.

I think a lot of developers (including myself) who use Vim and Emacs also tend 
to be command-line oriented, and we still seem to be without a viable debugging 
option.

The tool command line users would take to is almost certainly pdb. We won't see 
a pdb patch for GAE, but I am hopeful someone can graft something together on 
top of this concept.

All that said, the concept is great and I hope it can be manipulated so that it 
can be taken advantage of from the command line.

Since this issue relates specifically to the command line, and that remains an 
outstanding issue, we may see duplicate issues posted - it may be useful to 
leave the issue open until there is a command line tool someone can point to.

Cheers

Original comment by brianmh...@gmail.com on 3 Apr 2013 at 12:57

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I tried to implement Brian's document recommendations.
Managed to get logging in a remote debugger console, but still no breakpoints.
Exact account of what  I did in here:
http://goo.gl/XRU01

Original comment by michael.kariv on 23 Apr 2013 at 9:03

[GoogleCodeExporter]

I'd like to second @Michael.Kariv on his recent post. I'm having an almost 
identical experience. Find my exact steps on (text after the 'EDIT:'). 
http://stackoverflow.com/questions/16149813/unable-to-debug-dev-appserver-in-goo
gle-app-engine

I think this issue should be reopened - especially since the sample code in 
Brian's document is specific to PyDev - which don't work!!!
PyDev seems to be the canonical debugger/IDE for Python (most traffic in SO, 
and #1 recommendation in many questions).

Is I said in my description in SO, I'm able to verify that the 
--python_startup_script is called, I am breaking to the remote debugger within 
the runtime process, I am able to step out from my script to runtime.py (main 
function), and breakpoints to work within the main function. However, putting a 
breakpoint in my handler will not work. I cannot imagine how do you imagine us 
working without a debugger.

Original comment by u...@london.org.il on 23 Apr 2013 at 11:06

[GoogleCodeExporter]

Another approach could be to monkey patch pdb/ipdb so that they stash the App 
Engine stdin/out streams before displaying the prompt and restore them when the 
user hits enter. I'd be totally cool with app.pdb.set_trace() instead of import 
pdb; pdb.set_trace().

Even better would be to bundle Werkzeug, but let's not get distracted by more 
difficult endeavors - whatever is quicker.

Original comment by rban...@gmail.com on 23 May 2013 at 2:05

[GoogleCodeExporter]

Just for information: Pycharm 2.7.2 allow debugging on new SDK.

Original comment by renzon@gmail.com on 23 May 2013 at 4:27