Removing breakpoints in remote debugging does not work

[DonJayamanne]

@DonJayamanne commented on Mon Jan 28 2019

Launch python code for debugging:

• Mac, Python3.6
• Ptvsd version 4.2.2

import ptvsd
ptvsd.enable_attach(('localhost', 3000))

import time
for i in range(1000):
    time.sleep(1)
    print(i)

• Launch program
• Attach debugger
• Add a breakpoint to the print line
• Breakpoint hits
• Remove breakpoint
• Continue
• Program stops at print line again, even when there are no breakpoints!!!
• Disconnect debugger, program is stuck!!

Two problems:

• Program stops at print line again, even when there are no breakpoints!!!
• Disconnect debugger, program is stuck!!

[DonJayamanne]

This same bug can be reproduced in a simple launch scenario:
I.e. bug is not specific to remote debugging.

• Start debugging following code:

import time
for i in range(1000):
    time.sleep(1)
    print(i)

• Add breakpoint
• Break point is hit,
• Remove breakpoint and continue,
• Code will stop again at line where previous breakpoint was hit!!

[karthiknadig]

/cc @fabioz

[karthiknadig]

Request response logs from VSC for the setBreakpoints command.
Setting break-point:

{"command":"setBreakpoints","arguments":{"source":{"name":"mytest.py","path":"C:\\GIT\\pyscratch2\\mytest.py"},"lines":[14],"breakpoints":[{"line":14}],"sourceModified":false},"type":"request","seq":4}
To Client:
Content-Length: 177

{"type": "response", "seq": 4, "request_seq": 4, "success": true, "command": "setBreakpoints", "message": "", "body": {"breakpoints": [{"id": 0, "verified": true, "line": 14}]}}
From Client:
Content-Length: 99

Removing break-point:

{"command":"setBreakpoints","arguments":{"source":{"path":"C:\\GIT\\pyscratch2\\mytest.py","sourceReference":0},"lines":[],"breakpoints":[],"sourceModified":false},"type":"request","seq":13}
To Client:
Content-Length: 140

{"type": "response", "seq": 22, "request_seq": 13, "success": true, "command": "setBreakpoints", "message": "", "body": {"breakpoints": []}}
From Client:
Content-Length: 75

[fabioz]

I'll take a look at it (although I'll probably only be able to provide a fix tomorrow).

[fabioz]

Actually, the issue was simpler than I thought, so, I've provided a fix for it already (but without tests for today -- see comments on #1127).

[karthiknadig]

Reopening because resuming a run sometimes causes exception:

Repro steps:

import time
for x in range(10):
    time.sleep(1)
    print(x)
print('done')

1. set breakpoint on line 4 and run
2. when breakpoint is hit, remove breakpoint and resume.
   You should see this exception, but this does not happen every time.

FIY: use following configuration with latest VSC to run master version of the debugger.

        {
            "customDebugger": true,
            "name": "File",
            "type": "python",
            "request": "launch",
            "program": "${file}",
            "console": "integratedTerminal",
            "env":{
                "PYTHONPATH":"C:\\ptvsd\\src",
            },
        },

[karthiknadig]

Found the issue, it is in the following function call:
Looks like _pydev_stop_at_break gets called even after removing all breakpoints. In that function, the following line sets breakpoints_for_file to None, breakpoints_for_file = debugger.breakpoints.get(filename) if there are no other breakpoints set in the file. Later this fails with 'NoneType' is not subscriptable.

/cc @fabioz

[fabioz]

Fixed by #1134