Dealing with yaml in Emacs

Sometime ago or at least when I started doing programming in the late 90s XML was all the rage, it promised to be the panacea for everything from data to storage to data presentation and processing. People realised that it was just complexity as Joel Spolski points out an attempt to make the complex seem accessible to ordinary people.. Really people were annoyed to write all those tags as those ‘<‘ and ‘>’ are hard to reach on a qwerty keyboard.

Beginning the new millennia in 2000 the web started to get very popular and things like “web services” popped up everywhere, people realised that actually XML is not that great so started to get a format called Json to get computers talking to each others in a sane manner.

But people realise that json was actually not that great to chat between web services as it was actually designed to serialize objects between programming languages. And really down the line it’s more about the programmers being annoyed by all those { } [ ] brackets

So here came yaml the latest “fashion format” based on the popularity of tab based programming languages.

Most new software lately have been using it, all the containers software ecosystem configure things in yaml so you have to deal with it when you work with them.

I don’t know if I like yaml or not, the only thing i know is that when I have a big ass large yaml file it become quickly unreadable. You have no idea which blocks belong to which one and not sure how many indents you need to add to that block to align to that other one that started 800 lines ago.

This has been driving me crazy as I need to write some large kubernetes/OpenShift yaml files and sometime end up for hours trying to detect where I have my tab alignment.

Some may argue, but you do python and python is tab based. Yeah i have been doing python for the last 10 years and this has never been issue cause first I don’t write kick ass 5000 lines python functions and second the python mode of my editor Emacs is properly configured.

Ah there I say it, the editor needs to be configured properly to have a good workflow so here is Emacs to the rescue to make it bearable (and make that post more productive that another rant from the interweb)

So without further ado and with much fanfare, here is the emacs extension i found to make writing yaml bearable :

Highlight Indentation for Emacs


This mode would give you a visual representation of the current indentation with a bar showing the indentation.

Smart Shift

Make Shift

This mode doesn’t give you a visual but allow you to indent blocks of texts easily. Usually in emacs you would use the Control-C Tab command to indent and prefix it with a number for the number of indent. For example C-u 4 Control-C Tab would indent the text for 4 spaces. Smart shift make things much easier to move around.


Flycheck mode

This is a generics mode you should really configure for all your programming needs, it supports yaml files and will try to validate (with ruby-yaml library) your yaml file and see where you have an error.



This is a function I found in a post on stackoverflow (by the author of Highlight-Indentation-for-Emacs) it allow you to folds all code on an indentation level greater than the current line. A great way to show you the current outline of the file.


Announcing the (Paris (Emacs) Meetup) Group

I am lucky to sit in front of Julien Danjou at work and as the sole Emacs users on the side of our office it was come to our attention that we needed as emacsian to unite ourselves to preach the good parole of the church of Emacs and sexy mens.

It was quite obvious that the only way to convince those in the unkown was to find an excuse for drinks good food between good people and set-up a meetup.

And since eNovance have now a very new fancy office with a large room to organise geeky (or not) oriented meetups, it was just a perfect time.

Within three clicks, three steps of dancing and after 10 minutes trying to do that straight from Emacs before coming back to a modern web browser (Emacs users are pragmatic) the Parisian OpenStack User Group

This is with great success, In less than 5 days we had already 50 members and an informal drink-up organised for thursday.

So if you are based in Paris and you have a love for Emacs or just want to discover what’s that all about come join the group.

How do I manage my copyright headers in Emacs

My day to day being work or personal is to create OpenSource code. As an habit I have taken lately I am adding licenses to all new files I am creating.

I have historically used the `auto-insert-mode with a default template. For example for my newly created python files I would have this for configration :

(auto-insert-mode 't)
(setq auto-insert-alist '((python-mode . "")))

and in my `auto-insert-directory directory there would be a template with my license files.

But that’s not so smart, since I wanted to find a mechanism to switch between work email and personal emails for my copyright I needed those templates to be more dynamic.

Things with auto-insert templates taken from a directory they are not so dynamics and reading through the always excellent emacswiki page it seems that you need to `define-auto-insert the templates to get dynamic variables.

I didn’t want to go to the define-auto-insert because I am always using the yasnippet package for my snippets which has a great expansion support and a nice templating language.

As it’s mostly always the case if you have a problem you can be sure it’s already resolved by others, so a quick search on the internet leaded me to a gist file written by a guy three years ago that does exactly what I wanted :

So now that I had my header loaded from yasnippet I could add some smartness into it. I have first written this function :

(defun yas--magit-email-or-default ()
  "Get email from GIT or use default"
  (if (magit-get-top-dir ".")
      (magit-get "")

this function would check if we are in a git directory and get the git configuration, if we are not it would just reply by the standard emacs variable `user-mail-address.

I have just to plug that in my template like this :

# -*- mode: snippet -*-
# name: header
# --
# -*- coding: utf-8 -*-
# Author: Chmouel Boudjnah < `(yas--magit-email-or-default)`>

and depending of my local configuration of my git repo it will add my license email according to that.

If I really needed to override the user-mail-address without using git I could always just drop a .dir-locals.el with something like this :

((nil . ((user-mail-address . ""))))

which would override the default user-mail-address to whatever I want.

emacs anything with magit

I have been using quite a bit the anything-mode for Emacs, it’s basically a Quicksilver/Alfred or Gnome-do for Emacs and allow to configure a lot of different sources to complete some chosen ‘source’with different actions.

With my work on OpenStack I have found myself jumping a lot between git directories and due configured the variable ‘magit-repo-dirs for easy access to most of them easily.

Plugging those two just seemed natural I had already this in my emacs to quickly open those magit repository directories :

(global-set-key (read-kbd-macro "C-S-o") '(lambda ()(interactive) (dired (magit-read-top-dir nil))))

But going with anything is much nicer and I can add another action for openning the source to  magit so I quickly came up with this magit source :

so now I open my different OpenStack Swift projects quickly with only a few keyboard touch (I bind my custom anything function to C-z) which shows graphically like this :

anything switch to magit dirs.

as always my full emacs config is available here:

Emacs and nosetests

Sometime you just need a long trans atlantic flight and a stupidly long stop-over in a random city to do some of those task that can improve your day to day but you never take some time to do it.

When using emacs I wanted a simple way to launch a nosetests on the current function my cursor is in Emacs. The syntax on nosetests is a bit tricky and I actually always have to look at my shell history to know the proper syntax (nosetests directory/

I created a simple wrapper for emacs for  that which allow to just hit a key to copy the nosetests command to feed to your shell or to use it for the compile buffer.

It’s available from here :

I have binded those keys for my python mode hook :

(local-set-key (kbd "C-S-t") 'nosetests-copy-shell-comand)
(local-set-key (kbd "C-S-r") 'nosetests-compile)

Happy TDD!!!!

UPDATE: There was an another nose mode already that does much more available here :

Customize face at point in Emacs

It’s probably interesting only for the hardcore Emacs users but the last CVS version of emacs (2009-12-17) get a nifty new improvement if you need to customize a face property.

If you point on the text where you want to customize it will detect it automatically which face point you are on and ask you if this is what you want to customize (after launching the command M-x customize-face). No guessing around with list-face-displays anymore.

I am just mentioning that because it does not seems to me mentioned in the CHANGES file.

Emacs transparency with mouse wheel

Emacs is playing fancy on the latest version (since emacs 23) it has now support for transparency at least on Linux when you have a composited Windows Manager.

As explained on the Emacs wiki here everything is controlled by this frame parameter like this :

 (set-frame-parameter (selected-frame) 'alpha '(85 50))

I have automated the thing to allow the transparency to increase or decrease when combined with the alt key just put this code somewhere in your $HOME/.emacs or $HOME/.emacs.d/init.el :

(defun my-increase-opacity()
  (let ((increase (+ 10 (car (frame-parameter nil 'alpha)))))
    (if (> increase 99)(setq increase 99))
    (set-frame-parameter (selected-frame) 'alpha (values increase 75)))

(defun my-decrease-opacity()
  (let ((decrease (- (car (frame-parameter nil 'alpha)) 10)))
    (if (< decrease 20)(setq decrease 20))
    (set-frame-parameter (selected-frame) 'alpha (values decrease 75)))

(global-set-key (kbd "M-") 'my-increase-opacity)
(global-set-key (kbd "M-") 'my-decrease-opacity)

python syntax warning in emacs

One of the best feature to have with Emacs when doing python development is to have a real time syntax error/warning check highlighted in your code to avoid many errors or superfluous code.

This code is taken from the brillant Emacswiki python page.

You need to install pyflakes first which should be available on your linux distro by default in a package or for the other OS you may follow the procedure from the pyflakes webpage.

and add this configuration to your .emacs :

(when (load "flymake" t)
(defun flymake-pyflakes-init ()
  (let* ((temp-file (flymake-init-create-temp-buffer-copy
         (local-file (file-relative-name
                      (file-name-directory buffer-file-name))))
    (list "pyflakes" (list local-file))))
(add-to-list 'flymake-allowed-file-name-masks
             '("\\.py\\'" flymake-pyflakes-init)))

make sure pyflakes is in your path and enable flymake-mode by default if you like for all python mode :

(add-hook 'python-mode-hook 'my-python-mode-hook)

go by M-x customize flymake as well if you like to customise some variables.

emacs daemon and Xdefaults

It does not seems that emacs started with –daemon read the .Xdefauls resource it seems that the only way setting it is by the default-frame-alist variable.

I have my setup like this :

(setq default-frame-alist '((font-backend . "xft")
                            (font . "Inconsolata-14")
                            (left-fringe . -1)
                            (right-fringe . -1)
                            (fullscreen . fullboth)
                            (menu-bar-lines . 0)
                            (tool-bar-lines . 0)

PS: inconsolata font can be installed from the package ttf-inconsolata

Update Emacs/VIM tags with inotify

When you use the tags interface for Emacs or with VIM you have to generate your tag file everytime you have a new class or things get changed.  Would not be cool to have inotify monitoring your project directory and run the etags command to generate it.

With incron you have cron that can watch some portion of the filesystem and generate an action if certain event appears.  So after installed (aptitude/urpmi) it I have configured this incrontab entry :

/home/chmouel/git/myproject IN_CLOSE_WRITE /home/chmouel/ py $@ $@/$#

The script takes 3 argument one is the type of file to update when it’s changed it accept multipe of them if you delimit with a pipe ie: py|inc|php|c and the two others are identifier from incron to give the base directory and the full path which is something you should not have to change.

The update-ctags is simple as follow which could be hacked for your convenience :


ACCEPTED_EXTENSION="$(echo $1|sed 's/|/ /g')"

[[ -z ${FILE_EXT} ]] && exit

for extension in $ACCEPTED_EXTENSION;do
    [[ $extension == $FILE_EXT ]] && processing=true

find ${BASE_DIR} ! -wholename './.git/*'  -a ! -wholename './.svn/*' -a ! -name '*.pyc' -a ! -name '*~' -a ! -name '*#' -print0| xargs -0 etags -o ${BASE_DIR}/TAGS 2>/dev/null >/dev/null
/home/chmouel/git/swift-container IN_CLOSE_WRITE /home/chmouel/ py $@ $@/$#