Code coverage is not 100%

[winksaville]

• taperable_helix version: 0.8.9
• Python version: 3.7
• Operating System: Linux

Code coverage is not 100%

The reason is that there is an extraenous "if" statement that
can't be tested. This is necessary so make mypy works and
if mypy worked the "if" statement wouldn't be necessary and
we'd then have 100% coverage.

What I Did

The reason make coverage is not 100%:

(py-helix) wink@3900x:~/prgs/CadQuery/projects/taperable-helix (master)
$ make coverage
coverage run --source taperable_helix -m pytest
====================================================== test session starts =======================================================
platform linux -- Python 3.7.8, pytest-6.1.1, py-1.9.0, pluggy-0.13.1
rootdir: /home/wink/prgs/CadQuery/projects/taperable-helix
collected 19 items                                                                                                               

tests/test_taperable_helix.py ...................                                                                          [100%]

======================================================= 19 passed in 0.37s =======================================================
coverage report -m
Name                          Stmts   Miss  Cover   Missing
-----------------------------------------------------------
taperable_helix/__init__.py       4      0   100%
taperable_helix/helix.py         53      1    98%   176
-----------------------------------------------------------
TOTAL                            57      1    98%
# coverage html
# python -c "$BROWSER_PYSCRIPT" htmlcov/index.html

Because to allow make mypy to pass:

(py-helix) wink@3900x:~/prgs/CadQuery/projects/taperable-helix (master)
$ make mypy 
mypy setup.py taperable_helix/ tests/ examples/ docs/
Success: no issues found in 8 source files

The following code is added to helix.py:

            # This if statement is needed to satisfy mypy this is already
            # guaranteed in helix() above so the if statement is always
            # False. Furthermore this means the raise line is untestable.
            # Hopefully this can be fixed in the future.
            if (hl is None) or (hl.radius is None):
                raise ValueError("hl or hl.radius is None, should never happen")

If you comment the code the following are the results of make mypy:

(py-helix) wink@3900x:~/prgs/CadQuery/projects/taperable-helix (master)
$ make mypy 
mypy setup.py taperable_helix/ tests/ examples/ docs/
taperable_helix/helix.py:206: error: Item "None" of "Optional[HelixLocation]" has no attribute "radius"
taperable_helix/helix.py:206: error: Unsupported operand types for + ("None" and "float")
taperable_helix/helix.py:206: note: Both left and right operands are unions
taperable_helix/helix.py:206: error: Item "None" of "Optional[HelixLocation]" has no attribute "horz_offset"
taperable_helix/helix.py:213: error: Item "None" of "Optional[HelixLocation]" has no attribute "vert_offset"
Found 4 errors in 1 file (checked 8 source files)
make: *** [Makefile:93: mypy] Error 1

[winksaville]

I tested this with python 3.7 and 3.8, the same results.
I'm hoping that soon I can test with python 3.9 and maybe
things will work. Right now trying to install 3.9 in conda,
conda create -n py39-helix python=3.9 fails because conda-forge
hasn't been able to compile all dependencies I need for developement
using 3.9, hopefully that will be resolved soon.

[winksaville]

TODO: File a bug on mypy?

[winksaville]

A solution would be don't be "tricky" with using Optionals, but I think its "useful". We'll see :)

[winksaville]

Another solution would be to add a test field in Helix so that path could be tested, but I don't like that ether, LoL.