[HOWTO] Not add trailing whitespaces on newlines in js2-mode?

[sooqua]

What I want to achieve
elisp mode (good):

js2-mode (bad):

How can I achieve the same behavior in js2-mode as in elisp? I want enter key to add newlines at the same indentation level but don't keep the trailing whitespace on the previous.

System information

- OS: gnu/linux (x86_64-pc-linux-gnu)
- Shell: /usr/bin/zsh
- Emacs: 26.2 (Apr 12, 2019)
- Doom: 2.0.9 (HEAD -> develop, _upgrade/develop f754d4ff 2019-07-23 18:23:17 +0200)
- Graphic display: t (daemon: nil)
- System features: XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS GLIB NOTIFY ACL GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS LIBSYSTEMD LCMS2
- Details:
  ```elisp
  env bootstrapper: envvar-file
  elc count: 0
  uname -a:  Linux 5.2.8-arch1-1-ARCH #1 SMP PREEMPT Fri Aug 9 21:36:07 UTC 2019 x86_64
  modules:   (:completion company ivy :ui doom hl-todo modeline nav-flash ophints (popup +all +defaults) treemacs vc-gutter vi-tilde-fringe window-select workspaces :editor evil file-templates fold multiple-cursors rotate-text snippets :emacs dired electric vc :tools eval flycheck (lookup +docsets) magit :lang cc data emacs-lisp javascript lua markdown (org +dragndrop +ipython +pandoc +present) sh web :config default)
  packages:  n/a
  exec-path: (/usr/local/bin /usr/bin /bin /usr/local/sbin /usr/bin/site_perl /usr/bin/vendor_perl /usr/bin/core_perl /usr/lib/emacs/26.2/x86_64-pc-linux-gnu/)
  ```

[sooqua]

And why is this not working?

(defun +javascript/newline-and-indent ()
  "TODO"
  (interactive)
  (doom/backward-kill-to-bol-and-indent)
  (newline-and-indent)
  )
(map! :map js2-mode-map [remap newline] #'+javascript/newline-and-indent)

C-h k <enter> still shows (newline-and-indent). Why is map! not working here? This is taken from here.

[sooqua]

This is the only thing that works:

(defun +javascript/newline-and-indent ()
  "TODO"
  (doom/backward-kill-to-bol-and-indent))
(advice-add #'newline-and-indent :before #'+javascript/newline-and-indent)

But it overrides newline-and-indent for every mode. Is there a better way?

EDIT: Oh and it kills the line if the cursor is not at the first character =\
And there is no python-indent-context alternative for js so I don't know how to differentiate between empty and non-empty lines.

[hlissner]

Try this instead:

(map! :map js2-mode-map [remap newline-and-indent] #'+javascript/newline-and-indent)

[hlissner]

That said, Doom enables ws-butler-global-mode by default. It will clean up trailing whitespace (on lines you've touched) when you save, so is manually cleaning it up necessary?

[sooqua]

Well it leaves that trailing red block behind, as if it's telling "something is wrong", until I save, or manually go there and 0D it. This is a bit distracting. I changed the value of indent-line-function in js2-mode from rjsx-indent-line to indent-relative as in elisp-mode, but it just inserts 2 spaces where it needs to be 4 and then continues on column 0 (doesn't keep indentation).
What can I write in +javascript/newline-and-indent? Sorry I'm new to elisp. I just need a way to check if a line is empty and to reset the indentation, but I can probably use evil-shift-left for that...

[sooqua]

This worked for me:
(advice-add 'newline-and-indent :override #'reindent-then-newline-and-indent)

[hlissner]

You can detect if the current line is empty with:

(save-excursion
  (beginning-of-line)
  (looking-at-p "[ \t]*$")) ; returns non-nil if the line is just whitespace

Or use the (sp-point-in-blank-line) function (essentially does the above).

[sooqua]

Wait! It's this override that's causing the issue! It doesn't call (delete-horizontal-space t) before (newline nil t) like original newline-and-indent does.

[hlissner]

I could've sworn there was a good reason for that, but the advise was written so many years ago I don't remember anymore. I've added the delete-horizontal-space call back to +default*newline-indent-and-continue-comments, which I hope resolves your issue. If that isn't the case, let me know and I will reopen this issue. Thanks for bringing it to my attention!