What is the correct way to typeset a vector when there is subscript or superscript?

Question

Consider this MWE:

\documentclass{article}

\begin{document}

\[\vec{v}_{12345}^{12345678}\]

\[\overrightarrow{P_{12345}P_{12345}^{12345678}}\]

\end{document}

As you can see, \vec is designed to typeset a vector with an arrow above the argument.

However, when we do not have a unary symbol to represent a vector (e.g. the difference between the coordinates of two points) then we can use \overrightarrow. But this notation has two problems:

1. When we are working with long chain of numbers \overrightarrow collides with it, as shown in the example.
2. And I think the most important: it is not consistent with \vec. Why? Because \vec stops the arrow before the subscript/superscript, but \overrightarrow continues the arrow to the end regardless of the existence or not of subscript/superscript.

Remember that we are writing vectors, no matter the length of the text that represents the vector.

What I want

With your huge help, I would like to write the following:

Thanks!!

Answer 1

This seems a really confusing (and ugly) convention, but..

\documentclass{article}

\begin{document}

\sbox0{$P$}
\[\overrightarrow{\strut P_{12345}\kern\wd0}\kern-\wd0P_{12345}^{12345678}\]

\end{document}