Advent 2019 part 20, Life Hacks aka Emacs Ginger Tea
This post is part of Advent of Parens 2019, my attempt to publish one blog post a day during the 24 days of the advent.
Here’s a great life hack, to peal ginger don’t use a knife, use a spoon. I’m not kidding. Just scrape off the peal with the tip of the spoon, it’s almost too easy.
Here’s a Clojure + Emacs life hack:
(defun plexus-clojure-extras/cider-pprint-register (register)
(interactive (list (register-read-with-preview "Eval register: ")))
(cider--pprint-eval-form (get-register register)))
So what does this do? It takes the value of a specific register and evaluates it as Clojure code with CIDER, showing the pretty-printed result in a separate buffer.
Registers are these places in Emacs where you can store a snippet of text (among other things) for later use. They have one letter names, so for instance you select some text, then press C-x r s a to put that text into register a.
| Command | Keybinding | Description |
|---|---|---|
| copy-to-register | C-x r s | Copy to region to a register. |
| view-register | See what’s in a register. | |
| insert-register | C-x r i | Insert a given register into the buffer. |
| set-register | Set a register to a given value. |
Try (info "(Emacs)Registers") for more info on registers.
I have a number of these registers prepopulated when my Emacs starts, for instance:
(set-register ?k "(do (require 'kaocha.repl) (kaocha.repl/run))")
(set-register ?K "(do (require 'kaocha.repl) (kaocha.repl/run-all))")
(set-register ?r "(user/refresh)")
But often I’ll also bind them on the fly. Say I’m working on a complicated function, and below the function in the buffer I have some code that calls said function. I can jump back and forth between the two, each time updating the function, then moving to the invocation and checking the result. Or I can copy the invocation to a register, and invoke it from anywhere.
The last piece of the puzzle is binding this to some handy key combination. I’m a Spacemacs user, and I’ve bound this to leader-key + ,. My leader key is also ,, so I can now run the tests for a namespace with ,,k. Pretty handy.
(dolist (m '(clojure-mode
clojurec-mode
clojurescript-mode
clojurex-mode
cider-repl-mode
cider-clojure-interaction-mode))
(spacemacs/set-leader-keys-for-major-mode m
"," 'plexus-clojure-extras/cider-pprint-register))
Hi, my name is Arne (aka @plexus) and I consult companies and teams about application architecture, development process, tooling and testing. I collaborate with other talented people under the banner Gaiwan. If you like to have a chat about how we could help you with your project then please get in touch!
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