Re: Questioning the new behavior of `open-line'.

["Andreas Röhler" <andreas.roehler@online.de>]

  On 11.11.2015 19:08, Karl Fogel wrote:
> Recently, `open-line' has started behaving in a new way due to Arthur Malabarba's recent commits [1].  Here is how `open-line' behaves before and after the changes.
>
> Suppose you have this text in a buffer, in just about any mode (i.e., not necessarily a programming language mode), and it is indented by two spaces as below:
>
>    A lovely haiku
>    An example for this bug
>    For Emacs Devel
>
> Now place point where the imaginary "X" is below and do C-o (`open-line'):
>
> X A lovely haiku
>    An example for this bug
>    For Emacs Devel
>
> Formerly, that would literally insert a newline, but not remove the the two spaces of indendation that come *after* the new newline (the two spaces right before "A lovely haiku").  So this would be the result:
>
> [...this is the new line; imagine it's blank...]
>    A lovely haiku
>    An example for this bug
>    For Emacs Devel
>
> But after the recent commits, those two spaces are removed:
>
> [...this is the new line; imagine it's blank...]
> A lovely haiku
>    An example for this bug
>    For Emacs Devel
>
> So now one can no longer just put point in column 0 and type C-o to open a line right before a block of indented text while preserving the block's indentation.
>
> This is just a result of `electric-indent-mode' being on by default and `open-line' now being sensitive to `electric-indent-mode', I think.  But one of the things I always thought was good about `open-line' was that it *wasn't* sensitive that way -- that you could just put point in a column of your choice and insert a newline, and everything to the right of that column would be preserved after the newline.
>
> Arthur was well aware of this change, and even asked about it in his first post in the thread "A few questions about open-line" [2]:
>
>> 3. I think, when electric-indent-mode is on, open-line should indent
>> the line that was created below if it isn't empty. May I go ahead?
> Had I seen that question at the time, I would have answered "Oh, please don't" :-).  But maybe mine is a minority opinion?  I encounter the new behavior several times a day, and don't like it; turning off `electric-indent-mode' seems like a drastic solution.  But if people generally like this new behavior, I'll certainly live with being in the minority and figure out the appropritae local customization.
>
> So do we think this new behavior is the right one?
>
> (If it stays, then I'll add an item to NEWS about it.)
>
> Best regards,
> -Karl
>
> [1] These two commits (note you have to take them together, as the earlier one accidentally leaves open-line in a syntactically invalid state, and the later one corrects that):
>
>    commit bd4f04f86cea893e3369decdda074a4898491518
>    Author: Artur Malabarba<bruce.connor.am@gmail.com>
>    Date:   Sat Oct 24 22:26:27 2015 +0100
>
>        * lisp/simple.el (open-line): Integrate with electric-indent-mode
>
>        Also run `post-self-insert-hook' when called interactively.
>
>    M	lisp/simple.el
>
>    commit 6939896e2ffe2e742954c14bba6129af456f0857
>    Author: Artur Malabarba<bruce.connor.am@gmail.com>
>    Date:   Sat Oct 24 22:24:09 2015 +0100
>
>        * lisp/simple.el (open-line): Fix docstring
>
>        Also explain apparently redundant line.
>
>    M	lisp/simple.el
>
> [2] https://lists.gnu.org/archive/html/emacs-devel/2015-10/threads.html#02107
>

When registering with joy Emacs now takes course towards a test-backed 
development, may we have a change here too?

I.e, establishing a policy saying core-functions shouldn't be changed 
without prior notice/discussion?