Prevent Orbit creation with non scalar quantities

[dragonlost]

Hello.
I recently use poliastro but i have a bug.
when i use propagate fonction :

    xyz_c.append(ss.r)
  File "/home/sdurand/miniconda3/lib/python3.7/site-packages/poliastro/twobody/orbit.py", line 99, in r
    return self._state.to_vectors().r
  File "/home/sdurand/miniconda3/lib/python3.7/site-packages/poliastro/twobody/_states.py", line 113, in to_vectors
    self.nu.to(u.rad).value,
  File "/home/sdurand/miniconda3/lib/python3.7/site-packages/numba/dispatcher.py", line 350, in _compile_for_args
    error_rewrite(e, 'typing')
  File "/home/sdurand/miniconda3/lib/python3.7/site-packages/numba/dispatcher.py", line 317, in error_rewrite
    reraise(type(e), e, None)
  File "/home/sdurand/miniconda3/lib/python3.7/site-packages/numba/six.py", line 658, in reraise
    raise value.with_traceback(tb)
numba.errors.TypingError: Failed in nopython mode pipeline (step: nopython frontend)
Failed in nopython mode pipeline (step: nopython frontend)
Type of variable 'v_pqw' cannot be determined, operation: $0.45, location: /home/sdurand/miniconda3/lib/python3.7/site-packages/poliastro/core/elements.py (76)

File "../../../../../miniconda3/lib/python3.7/site-packages/poliastro/core/elements.py", line 76:
def rv_pqw(k, p, ecc, nu):
    <source elided>
    r_pqw = (np.array([cos(nu), sin(nu), 0 * nu]) * p / (1 + ecc * cos(nu))).T
    v_pqw = (np.array([-sin(nu), (ecc + cos(nu)), 0]) * sqrt(k / p)).T
    ^

[1] During: resolving callee type: type(CPUDispatcher(<function rv_pqw at 0x7f1c6406b0d0>))
[2] During: typing of call at /home/sdurand/miniconda3/lib/python3.7/site-packages/poliastro/core/elements.py (102)


File "../../../../../miniconda3/lib/python3.7/site-packages/poliastro/core/elements.py", line 102:
def coe2rv(k, p, ecc, inc, raan, argp, nu):
    <source elided>
    """
    r_pqw, v_pqw = rv_pqw(k, p, ecc, nu)
    ^

This is not usually a problem with Numba itself but instead often caused by
the use of unsupported features or an issue in resolving types.

To see Python/NumPy features supported by the latest release of Numba visit:
http://numba.pydata.org/numba-doc/dev/reference/pysupported.html
and
http://numba.pydata.org/numba-doc/dev/reference/numpysupported.html

For more information about typing errors and how to debug them visit:
http://numba.pydata.org/numba-doc/latest/user/troubleshoot.html#my-code-doesn-t-compile

If you think your code should work with Numba, please report the error message
and traceback, along with a minimal reproducer at:
https://github.com/numba/numba/issues/new

[astrojuanlu]

Hi @dragonlost! Can you display ss.classical()?

[astrojuanlu]

This is probably a bug, I'm sure we can prevent the user from doing this.

[astrojuanlu]

Also, we will need your poliastro version, Python version, and operative system.

[dragonlost]

for ss.classical() : (<Quantity [6878.14] km>, <Quantity [0.]>, <Quantity 20. deg>, <Quantity 0. deg>, <Quantity 0. deg>, <Quantity 0. deg>)

My operative system : Ubuntu Mate 18.04.2
My python version : Python 3.7.2 with Anaconda 3 (gcc 7.3.0)
My poliastro version : 0.12.0 (build : py_0, conda-forge)

and conda 4.7.5 and numba 0.43.1
`

[astrojuanlu]

I see that the first two are arrays with one element, did you notice the brackets?

[dragonlost]

ok is my fault. I had a bad upstream conversion that would create me "a" and "e" as a list

[dragonlost]

Thank for very very fast support !!

[astrojuanlu]

😄 You're welcome! We'll try to find a way to prevent this in the future, that numba error is impossible to understand :)

[astrojuanlu]

I just got bitten by a slightly different version of this