bug#62536: 30.0.50; Can we add """ ... """ electric pair in elixir, just like python

[Wilhelm Kirschbaum]

> Mou Tong <mou.tong@outlook.com> writes:
>
> > > Will it make sense to also add a newline when closing a 
> > > multiline
> > > comment/heredoc? It feels smoother to me rather than having to
> > > press
> > > enter and then C-o ( open-line ) to position the cursor 
> > > correctly?
> >
> > I agree with you, but I think it might be better to imitate 
> > what
> > `c-mode` did:
> >
> > ```c
> > int main () {|}
> > ```
> >
> > When `electric-pair-mode` is on, input the left `{`, Emacs 
> > helps you
> > complete the right `}`. After press enter, your cursor will 
> > move to
> > the
> > next line and auto-indented according to your offset config:
> >
> > ```c
> > int main () {
> >   |
> > }
> > ```
> >
> > So how about making it work like this?
> >
> > ```elixir-ts
> > @doc """|"""
> >
> > # after press enter
> > @doc """
> >   |
> > """
> > ```
>
> Yes, I think that is better, let me have a go at it.  I was 
> concerned
> of doing unsolicited movement with my suggestion of inserting
> newlines.

Playing around with it I think we should add a newline, I changed 
my mind.

Unlike the c example above, the following syntax is not valid 
elixir: `""""""` and it requires a
newline to make it valid.  Part of the appeal of making the 
heredoc electric is to keep
the syntax valid.  There should never be a reason for the heredoc 
to be
on a single line and also makes the tree-sitter grammar invalid, 
which
causes the blinking issue.

This will mean:

```
@doc ""|
```

when typing `"` it will insert `\n"""` and thus have the minimal 
valid elixir
syntax without doing extra movement.

```
@doc """|
"""
```

This will be the change ( looking at the electric.el code ).