PR here: https://github.com/sympy/sympy/pull/20047

On Fri, Aug 28, 2020 at 6:05 AM Faisal Riyaz <[email protected]>
wrote:

> Hello,
>
> This looks like a bug. Please do submit a PR.
>
> Thanks
> Faisal Riyaz
>
> On Thu, Aug 27, 2020 at 4:10 AM Alexander Lindsay <
> [email protected]> wrote:
>
>> This patch fixes the bad behavior:
>>
>> diff --git a/sympy/vector/operators.py b/sympy/vector/operators.py
>> index 2f303ee690..994894f379 100644
>> --- a/sympy/vector/operators.py
>> +++ b/sympy/vector/operators.py
>> @@ -362,6 +362,4 @@ def _diff_conditional(expr, base_scalar, coeff_1,
>> coeff_2):
>>      """
>>      from sympy.vector.functions import express
>>      new_expr = express(expr, base_scalar.system, variables=True)
>> -    if base_scalar in new_expr.atoms(BaseScalar):
>> -        return Derivative(coeff_1 * coeff_2 * new_expr, base_scalar)
>> -    return S.Zero
>> +    return Derivative(coeff_1 * coeff_2 * new_expr, base_scalar)
>>
>> Should I submit a PR?
>>
>> On Wed, Aug 26, 2020 at 3:30 PM Alexander Lindsay <
>> [email protected]> wrote:
>>
>>> Execution of the below code:
>>>
>>> From sympy.vector import divergence, gradient, Vector, CoordSys3D
>>> R = CoordSys3D('R', transformation='cylindrical')
>>> divergence(R.i)
>>>
>>> generates a zero result. I believe the result should be 1/r, right?
>>>
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>>
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