pytest syntax_error.py --pdb should not drop into pdb?

[asottile]

$ pytest --version
This is pytest version 3.6.2, imported from /private/tmp/x/venv/lib/python3.6/site-packages/pytest.py

# t.py
syntax error

$ pytest t.py --pdb
============================ test session starts =============================
platform darwin -- Python 3.6.5, pytest-3.6.2, py-1.5.4, pluggy-0.6.0
rootdir: /private/tmp/x, inifile:
collecting 0 items                                                           
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> traceback >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
venv/lib/python3.6/site-packages/_pytest/python.py:468: in _importtestmodule
    mod = self.fspath.pyimport(ensuresyspath=importmode)
venv/lib/python3.6/site-packages/py/_path/local.py:668: in pyimport
    __import__(modname)
E     File "/private/tmp/x/t.py", line 1
E       syntax error
E                  ^
E   SyntaxError: invalid syntax
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> entering PDB >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> /private/tmp/x/venv/lib/python3.6/site-packages/_pytest/python.py(471)_importtestmodule()
-> _pytest._code.ExceptionInfo().getrepr(style="short")
(Pdb) list
466  	        importmode = self.config.getoption("--import-mode")
467  	        try:
468  	            mod = self.fspath.pyimport(ensuresyspath=importmode)
469  	        except SyntaxError:
470  	            raise self.CollectError(
471  ->	                _pytest._code.ExceptionInfo().getrepr(style="short")
472  	            )
473  	        except self.fspath.ImportMismatchError:
474  	            e = sys.exc_info()[1]
475  	            raise self.CollectError(
476  	                "import file mismatch:\n"
(Pdb) q
collected 0 items / 1 errors                                                 

!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!
========================== 1 error in 8.44 seconds ===========================

as far as I can tell, it has always done this -- is this a desirable behaviour?

[pytestbot]

GitMate.io thinks possibly related issues are #1932 (pytest --pdb is no longer working with Flask_testing), #3245 (py.test on pytest fails when not limiting to the testing folder), #1411 (Pytest stops), #262 (--pdb drops you into pdb if you have an xfail), and #2574 (pytest --fixtures drops indentation from fixture docstring).

[Zac-HD]

The except SyntaxError: line is responsible for the detailed traceback, which probably is desirable.

Entering the debugger is unrelated though, so we'd have to write a lot of new code to check why the debugger was being entered and conditionally skip it. IMO syntax errors with a debugger set are too rare to justify maintaining that extra code.

[asottile]

no no, this is definitely worth fixing

[Tadaboody]

I think that in general, debugger should not be launched in the collection phase