Update Error Handling to Produce Clearer Invalid Regex Errors

[JackEAllen]

Invalid Regex does not currently produce a clear, meaningful error message.

This pull request aims to fix this by returning which function the invalid regex is present within and the invalid regex command as part of a runtime error.

Testing Performed Before Making this Pull Request

• Install this version of lewis (%PYDIR%\python.exe -m pip install --force-reinstall git+git://github.com/ISISComputingGroup/lewis@ba2773bc3f0e0deebd2fdcf66588836b6f3a134d)
• Write an emulator with a bad regex in the stream interface
• Confirm that the error message produced points you at which command is wrong

[mattclarke]

This looks good - would it be possible to add a test for this?

[DominicOram]

@JackEAllen, I know you were struggling to write the tests due to the dependencies of StreamHandler. I had to deal with this in https://github.com/ess-dmsc/lewis/pull/295/files, maybe you can use some of that?

[mattclarke]

Would something like this work?

def test_func_throws_on_construction_if_regex_invalid():
    f = lambda : 0

    with pytest.raises(RuntimeError):
        func = Func(f, "NOT A REGEX")

If this is possible then it can go into a new test file called test_stream_func.py. If you want extra brownie points you could add tests for the other throwing parts of the constructor if not callable(func):, inspect.getcallargs(func, *[None] * self.matcher.arg_count), etc. ;)

[JackEAllen]

Would something like this work?

def test_func_throws_on_construction_if_regex_invalid():
    f = lambda : 0

    with pytest.raises(RuntimeError):
        func = Func(f, "NOT A REGEX")

If this is possible then it can go into a new test file called test_stream_func.py. If you want extra brownie points you could add tests for the other throwing parts of the constructor if not callable(func):, inspect.getcallargs(func, *[None] * self.matcher.arg_count), etc. ;)

Thank you! I always forget that lambda's are a thing as I'm usually so against using them. But they do have their use cases! Works perfectly for me. Will add a few more unit tests to justify placing in a new file.

[DominicOram]

I think lambdas are awesome, why don't you like them?

[mattclarke]

I've pulled the changes into https://github.com/ess-dmsc/lewis/pull/305 so I could tweak the formatting etc.