[ClojureScript] Run all tests in multiple namespaces in REPL

From ClojureScript wiki, it says

If you have many test namespaces it's idiomatic to create a test runner namespace which imports all of your test namespaces and then invokes run-tests

I personally couldn't get it to work. Though I have managed to make run-all-tests works. This is an example

(ns myns.test.runner
  (:require [cljs.test :refer-macros [run-all-tests]]
            [myns.test.ns1]
            [myns.test.ns2]))

(run-all-tests #"myns.test.*")

[DataScript][Solved] Error: Expected number or lookup ref for entity id, got

When you are trying to use Map specification of Datomic's pull api and you got this error

Error: Expected number or lookup ref for entity id, got ....

This happens because you didn't specify schema for that data attribute. Schema is optional on DataScript but it is required in this case. Add this line to your database, the issue should be fixed

{:your-attribute1 {:db/valueType :db.type/ref}
 :your-attribute2 {:db/valueType :db.type/ref}}

Terminal.app doesn't save history in El Capitan and you are using RVM

The cause is described here https://github.com/rvm/rvm/issues/3540#issue-113491283
The fix is here https://github.com/rvm/rvm/issues/3540#issuecomment-152824133

I copied the fix here just in case it's removed in the future

Another option is to create .bash_logout with a single line:

shell_session_update

Setup Debian/Ubuntu apt package cache server with Ansible

Install elnappoo.apt-cacher-ng with Ansible Galaxy and then follow the instruction in the README tab or README in the github repository. Refer to the test.yml file as an example. If you cache server doesn't have ufw running, don't forget to set apt_cacher_ng_setup_ufw: False

How to get caller function in Clojure

I posted this question on Clojurians slack channel.

What's clojure equivalent of ruby's `caller` method? http://ruby-doc.org/core-2.2.3/Kernel.html#method-i-caller

To put it another way, if a function is call from multiple places, at runtime, is there a way to print out caller for debugging purpose?

Thanks to Alex Miller. He answered

the Thread class has methods to inspect the stack

(Thread/dumpStack) will just dump that thread's stack to stderr

or (Thread/getStackTrace) gives you an array of StackTraceElement's that you can traverse and do whatever

Basically, we can just use Java's Thread class. To be more precise, getStackTrace is an instance method so we have to call it this way.

(.getStackTrace (Thread/currentThread))

We'll get back Java's array of StackTraceElement class.

You can copy and just use a function I wrote here https://gist.github.com/visibletrap/bdf16dd5596c9a72ec73

Convert FLV to MP4 with FFmpeg

Only for no AV recording

$ ffmpeg -i input.flv -c copy -copyts output.mp4

Tested on: OS X 10.11
Credit: http://superuser.com/a/860127

How to clear terminal screen in Clojure

Print some ANSI characters

(print (str (char 27) "[2J")) ; clear screen
(print (str (char 27) "[;H")) ; move cursor to the top left corner of the screen

Credit: http://codereview.stackexchange.com/questions/17603/critique-my-clojure-game-of-life-code