Debugger does not work when another trace function is set

[DonJayamanne]

From @Sathisz on November 9, 2017 10:6

Environment data

VS Code version: 1.18
Python Extension version: latest
Python Version: 3.4.3
OS and version: Linux Mint 18.1

Actual behavior

No action performed

Expected behavior

Stops at the break point when it hits

Steps to reproduce:

Logs

Output from Python output panel

Output from Console window (Help->Developer Tools menu)

Copied from original issue: DonJayamanne/pythonVSCode#1377

[naeco2008]

Sometimes i encounter this issue as well. When i set the breakpoint on the first line, it would not stop.

[sathiz1993]

I am using flask, flask have inbuild debugger so while running the flask app with debug mode in vscode , vscode debugger not working. But when I disabled flask debugger, the vscode debugger works as excepted. So the problem is when inbuild debugger is present, vscode debugger not working until we disable inbuild debugger.
I have some suggestions , If vscode debugger is on , all other debuggers present already should be disabled by vscode.

[brettcannon]

@Sathisz ah, so you already have already called sys.settrace() indirectly via Flask. Whether we stomp on a previously set trace function is a feature enhancement that we will have to discuss as it gets complicated trying to make more than one of those work appropriately at once.

[zubialevich]

I have a similar issue, debuger runs the code, but doesn't stops on breakpoint. I see the output in the output window, but no stops in code.
In the output window for extensions I see next message on every debug session:

attempt to send more than one response for command launch(node:6204) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): TypeError: Cannot read property 'SendExceptionInfo' of null
(node:6204) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

[zubialevich]

Maybe this can also be helpful. The output from developer tools:

index.js:44 Error: TypeError: Cannot read property 'Threads' of undefined
    at PythonDebugger.threadsRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\out\client\debugger\Main.js:365:27)
    at PythonDebugger.DebugSession.dispatchRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\debugSession.js:439:22)
    at PythonDebugger.ProtocolServer._handleData (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:104:38)
    at Socket.<anonymous> (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:24:60)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20)
    at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2490899
    at Object.v [as _notify] (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:63281)
    at Object.enter (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:66555)
    at n.Class.derive._oncancel._run (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:67876)
    at n.Class.derive._oncancel._error (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:67393)
    at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2128430
    at _.e.dispatch (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2129781)
    at _.e.handleData (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2129289)
    at Socket.<anonymous> (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2128290)
    at emitOne (events.js:96:13)
onError @ index.js:44
(anonymous) @ index.js:110
emitOne @ events.js:96
emit @ events.js:191
window.onerror @ C:\Program Files\Microsoft VS Code\resources\electron.asar\renderer\init.js:135
i.globals.onerror @ errorTelemetry.ts:64
rawDebugSession.ts:193 Uncaught Error: TypeError: Cannot read property 'Threads' of undefined
    at PythonDebugger.threadsRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\out\client\debugger\Main.js:365:27)
    at PythonDebugger.DebugSession.dispatchRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\debugSession.js:439:22)
    at PythonDebugger.ProtocolServer._handleData (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:104:38)
    at Socket.<anonymous> (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:24:60)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20)
    at PythonDebugger.threadsRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\out\client\debugger\Main.js:365:27)
    at PythonDebugger.DebugSession.dispatchRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\debugSession.js:439:22)
    at PythonDebugger.ProtocolServer._handleData (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:104:38)
    at Socket.<anonymous> (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:24:60)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20)
    at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2490899
    at Object.v [as _notify] (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:63281)
    at Object.enter (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:66555)
    at n.Class.derive._oncancel._run (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:67876)
    at n.Class.derive._oncancel._error (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:67393)
    at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2128430
    at _.e.dispatch (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2129781)
    at _.e.handleData (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2129289)
    at Socket.<anonymous> (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2128290)
    at emitOne (events.js:96:13)
(anonymous) @ rawDebugSession.ts:193
v @ winjs.base.raw.js:1209
enter @ winjs.base.raw.js:901
_run @ winjs.base.raw.js:1068
_error @ winjs.base.raw.js:1041
(anonymous) @ v8Protocol.ts:53
e.dispatch @ v8Protocol.ts:136
e.handleData @ v8Protocol.ts:104
(anonymous) @ v8Protocol.ts:41
emitOne @ events.js:96
emit @ events.js:191
readableAddChunk @ _stream_readable.js:178
Readable.push @ _stream_readable.js:136
onread @ net.js:560
shell.ts:459 disposed: Error: disposed
    at e.request (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:737792)
    at Object.call (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:737675)
    at e.log (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1440690)
    at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1442488
    at n.Class.define.cancel.then (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:69309)
    at e.publicLog (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1442362)
    at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2490512
    at Object.v [as _notify] (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:63281)
    at Object.enter (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:66555)
    at n.Class.derive._oncancel._run (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:67876)
e.onUnexpectedError @ shell.ts:459
(anonymous) @ shell.ts:419
e.onUnexpectedError @ errors.ts:119
o @ errors.ts:138
(anonymous) @ errors.ts:49
(anonymous) @ errors.ts:44
shell.ts:459 TypeError: Cannot read property 'Threads' of undefined
    at PythonDebugger.threadsRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\out\client\debugger\Main.js:365:27)
    at PythonDebugger.DebugSession.dispatchRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\debugSession.js:439:22)
    at PythonDebugger.ProtocolServer._handleData (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:104:38)
    at Socket.<anonymous> (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:24:60)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20): Error: TypeError: Cannot read property 'Threads' of undefined
    at PythonDebugger.threadsRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\out\client\debugger\Main.js:365:27)
    at PythonDebugger.DebugSession.dispatchRequest (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\debugSession.js:439:22)
    at PythonDebugger.ProtocolServer._handleData (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:104:38)
    at Socket.<anonymous> (C:\Users\Дмитрий\.vscode\extensions\ms-python.python-0.8.0\node_modules\vscode-debugadapter\lib\protocol.js:24:60)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20)
    at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2490899
    at Object.v [as _notify] (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:63281)
    at Object.enter (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:66555)
    at n.Class.derive._oncancel._run (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:67876)
    at n.Class.derive._oncancel._error (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:67393)
    at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2128430
    at _.e.dispatch (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2129781)
    at _.e.handleData (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2129289)
    at Socket.<anonymous> (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2128290)
    at emitOne (events.js:96:13)

[brettcannon]

Closing this as it requires https://github.com/microsoft/ptvsd to support it; please request there if you still want this feature.