CMCDragonkai

// you often want to check if a value is truthy
function booleanise(v) {
  return !!v;
}

booleanise(0) // false
booleanise('') // false (empty strings is falsey)
booleanise(false) // false
booleanise(null) // false
booleanise(undefined) // false

CMCDragonkai

Journey into Nix Package Repository

There are 2 commits that I need in my build:

• 8d0e3ad603dda85462161bba1351893b84339462
• 83e01aa5e48a9107f3b988c9d4c1c21d610626fb

Clone nixpkgs and add the nixpkgs-channels as a remote.

CMCDragonkai

Nix Overrides

• overrideDerivation is used to override the call to derivation
• overrideAttrs is used to override the call to stdenv.mkDerivation
• override is used to override the last function call. Often this will be the callPackage call.
• overridePythonAttrs is used to override the call to buildPython*.

This PR https://github.com/NixOS/nixpkgs/pull/46842 discusses the idea to have a generic overrideArgs that works like overridePythonAttrs for all language infrastructures.

CMCDragonkai

Understanding Nix Inputs

Every Nix derivation produces a Nix store output that has 3 things:

• Executables
• Libraries
• Data

Executables are always exported using the PATH environment variable. This is pretty much automatic.

CMCDragonkai

import functools

def prepost(func=None, *, prefix=''):
    def prepost_(func):
        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            print(f'{prefix} start')
            result = func(*args, **kwargs)
            print(f'{prefix} end')
            return result

CMCDragonkai

#!/usr/bin/env sh

# basically we go into a directory
# we list all immediate files/directories
# then we filter it by a numeric (timestamp) range
# and then we perform a deletion on them

unixtime-gc () {
  find "$1" \
    -maxdepth 1 \

CMCDragonkai

Asynchronous exceptions for Python threads

• https://www.geeksforgeeks.org/python-different-ways-to-kill-a-thread/
• https://github.com/glenfant/stopit

CMCDragonkai

import io
import subprocess
import threading
import logging


def subprocess_with_logger(logger, check=False, *args, **kwargs):
    def log_stream(pipe, logger):
        # by default stderr will be a binary stream
        # we wrap it into a text stream

CMCDragonkai

#!/usr/bin/env sh

# show the output paths of a derivation
nix-store --query --outputs $(nix-instantiate)
# show the immediate dependencies of a derivation
nix-store --query --references $(nix-instantiate)
# show the transitive dependencies of a derivation
nix-store --query --requisites $(nix-instantiate)
# show the dependers of a store-path
nix-store --query --referrers $(nix-instantiate)

CMCDragonkai

-- safe-exceptions Control.Exception.Safe > exceptions Control.Monad.Catch > base Control.Exception
import Control.Exception.Safe
import Control.Monad.IO.Class (MonadIO, liftIO)

data WhatException = ThisError
                   | ThatError
                   deriving (Show)

instance Exception WhatException