[PATCH 1 of 4] mail: let headencode() return a native string

[Yuya Nishihara]

On Sat, 09 Nov 2019 17:06:40 +0100, Denis Laxalde wrote:
> # HG changeset patch
> # User Denis Laxalde <denis at laxalde.org>
> # Date 1573299914 -3600
> #      Sat Nov 09 12:45:14 2019 +0100
> # Node ID 1c7a66bf3315f69036420e2b07b584abacfef881
> # Parent  a78a65c33b5aa84cc9c3ae5f7dad636d371f149c
> mail: let headencode() return a native string

Queued the first two, thanks.

> diff --git a/mercurial/mail.py b/mercurial/mail.py
> --- a/mercurial/mail.py
> +++ b/mercurial/mail.py
> @@ -365,13 +365,13 @@ def headencode(ui, s, charsets=None, dis
>      if not display:
>          # split into words?
>          s, cs = _encode(ui, s, charsets)
> -        return encoding.strtolocal(email.header.Header(s, cs).encode())
> -    return s
> +        return email.header.Header(s, cs).encode()
> +    return encoding.strfromlocal(s)

I think we should add some type comments to help readers to see which string
type is returned/accepted/used. Mixing bytes and unicode is a nightmare.

I'm not an expert, but maybe we can annotate both functions and variables
with "# type: <type expr>" comment?

https://google.github.io/pytype/user_guide.html#variable-annotations

Augie, do you have any idea?