Category: Uncategorized

Contributing to Open Source – Getting Started

A sign in LegoLand saying "Adventure Land"

Recently, I started to contribute more to open source projects I use and like. When I started to contribute at all, I did so, with the most obvious thing for me: Bug reports. 🙂 This can be particularly useful, since the bug reports that I write for my projects, stay behind closed doors. – Like it or not, companies producing commercial software very often don’t fancy public bug reports. That’s a long story for another time…

Here are some tips:

  • Start small. Probably smaller than that.
    You can start on documentation. ➙ It can be unclear or contain typos.
    My smallest contribution so far, was fixing a typo in the Cucumber documentation.
    The steps to deliver it were large, compared to the fix itself:
    • Fork a repository
    • Create a branch on the fork
    • Fix the typo
    • Create a pull request
    • Get it accepted
      This seems like a lot, just to fix a typo.
      However, I think the learning experience was worth it.
  • Learn about the two most used models used in open source projects, the “Fork and Pull Model” and the “Shared Repository Model”.
    Both are explained in the GitHub docs about “collaborative development models“.
  • Check out Marko Denic on Twitter. He wrote “Make Your First Open Source Contribution” which explains to to get started on GitHub.
    You can contribute to his site https://tech-blogs.dev by adding you own blog, if you have one. The project is hosted on GitHub.
  • Start in a friendly & helpful community
    I find this really important: When you have a safe place to ask all the question you may have, and can expect a friendly answer, that will help actually asking those questions. It certainly helped me, asking about which development model is used, how big or small a pull request should be, etc.
  • Create your own project and make it open source
    Again: You can start really small. My smallest GitHub repository is probably https://github.com/s2k/seasidetestings-iterm-colours. It’s just only file that can be used as a colour preset in iTerm2 and some documentation how to load the file in iTerm.
  • If you find that something can be improved or isn’t working as expected, provide a bug report. These are important contributions to any software project: If the people writing the software don’t know that something’s wrong with it, they can’t fix it.
    For example I wrote https://github.com/fakefs/fakefs/issues/224, when I noticed that this Rubygem didn’t worked the way I expected.
    Since I knew how to write the RSpec to check this, I did – and it probably helped to get it fixed.

If you’re looking for much more information about how contributing to open source this book may be for you: “Forge Your Future with Open Source” by VM (Vicky) Brasseur.

Conveniently start a JavaScript shell (jsc) on macOS

For one of my projects I wanted an easy way to try JavaScript on a command line (similar to pry or irb in Ruby). Here’s how I found out where the program is located and how to set up my Mac to conveniently start it.

1. Find out where jsc is located on the machine:

$ find / -name jsc -type f 2>/dev/null
/System/iOSSupport/…/JavaScriptCore.framework/Versions/A/Helpers/jsc
/System/…/JavaScriptCore.framework/Versions/A/Helpers/jsc
/System/Volumes/Data/…/JavaScriptCore.framework/Versions/A/Helpers/jsc
/System/Volumes/Data/…/JavaScriptCore.framework/Versions/A/Helpers/jsc    

Searching from the root folder may be a bit excessive, though. You may consider a more limited search.

2. Look into the ‘system frameworks’ for versions

The path /System/Library/Frameworks/… was where I went to look what else is inside:

$ ll /System/Library/Frameworks/JavaScriptCore.framework/Versions
total 0
drwxr-xr-x  4 root  wheel  128 Jan  1  2020 .
drwxr-xr-x  4 root  wheel  128 Jan  1  2020 ..
drwxr-xr-x  5 root  wheel  160 Jan  1  2020 A
lrwxr-xr-x  1 root  wheel    1 Jan  1  2020 Current -> A

Aha, there’s a link named Current that (currently) points to A. I used this link in the next step. This way I can still use the same link, even if (when!) an OS update causes the file that’s linked to changes.

3. Link to the current version

I set a link somewhere in within $PATH. I have a bin folder in my home directory, so it put the link there:

ln -s /System/Library/Frameworks/JavaScriptCore.framework/Versions/Current/Helpers/jsc ~/bin/jsc

3. Set a variable ‘console’ for output

To output things, use this to define a variable console in a running JavaScript shell.

var console = {log : debug};

While jsc provides a print function, I find it convenient to stick to the more idiomatic console.log.

4. Use ‘jsc’

$ jsc
>>> var console = {log : debug};
undefined
>>> console.log(function(){})
--> function (){}
undefined
>>> 1 + 1
2 

Moving Left and Right in zsh (in macOS)

I use the command line a lot on my Macs, in particular, I use iTerm2.

When moving left and right in a command the shortcuts I knew about so far were:

Key (combination)Moves Cursor…
Right Arrow ‘→’One character right
Left Arrow ‘←’One character left
CTRL + aBeginning of the line
CTRL+ eEnd of the line

After adding the following lines to ~/.zshrc, I now can also move left and right per word using ALT-← and ALT-→ respectively:

bindkey "[D" backward-word # ALT-left-arrow  ⌥ + ←
bindkey "[C" forward-word  # ALT-right-arrow ⌥ + →

Especially when moving around in long command lines, this is really convenient & saves a lot of time.

Do you have keyboard shortcuts that you use regularly on the command line (or elsewhere)? I’d love to hear about them!

Collecting Lists In a Ruby Hash and the ‘<<=' operator

The other day, I needed to quickly analyse a data set that came in form of a large CSV file. I wanted to collect a particular column of that table and collect all entries categorised by a key in another column.

A simplified version of the table could look like this:

Key Value1 Interesting_Value Other_Value
foo1723.5X
bar211.75Q
foo4212.6B
baz2717.8F
bar4947.2K

I strived for something like this:

result = { 
  foo: [23.5, 12.6],
  bar: [1.75, 47.2],
  baz: [17.8],
 }

Iterating over the rows is easy, and getting to the columns is no problem either: The CSV gem is well documented and supports this easily.

A nice way to accumulate data is Enumerable#each_with_object. Since I wanted the result to be grouped by a key value, I’d pass a Hash as the initial argument.

Step 1: each_with_object({})

However, since I’ve planned to append values for changing keys, the default value needed to be an Array, not the default of nil.

Step 2: each_with_object(Hash.new([])

This, however, returns the same empty Array, when a key isn’t found, but I wanted a new empty Array:

Step 3: each_with_object(Hash.new { [] })

This executs the block every time a default values is needed (i.e. the given key isn’t yet in the Hash).

The next step is to append the value found in a row to the (potentially new and empty) Array for the given key.

I thought it would work this way:

data_table.each_with_object( Hash.new { [] }) do |row, acc|
  acc[row['Key']] << row['Interesting_Value'] 
end

But, no, the result of this code is an empty Hash! It needs to be the <<= operator to work, as shown in the snippet of a pry session:

[2] pry(main)> data_table = CSV.read 'table.csv', headers: true
=> #<CSV::Table mode:col_or_row row_count:6>
[3] pry(main)> data_table.each_with_object( Hash.new { [] }) do |row, acc|
[3] pry(main)*   acc[row['Key']] <<= row['Interesting_Value']
[3] pry(main)* end
=> {"foo"=>["23.5", "12.6"], "bar"=>["1.75", "47.2"], "baz"=>["17.8"]}

It seems to me, that the Hash lookup with the given default value [] returns an Array, and the append operator << does in fact append the passed object to that Array, but then the result of that does not end up as a (new) value fo the given Hash key. In contrast, the <<= operator does assign the result of the append operation.

Generating a Preview on LeanPub Using Rake

While working on the e-books I published on LeanPub, I have developed a number of useful approaches to get fast(er) feedback on how the book looks. Two earlier blog posts describe some of this:

While this provides a nice feedback cycle, sometimes I like to generate a new preview without pushing to the GitHub repository I am using to share the book content with LeanPub. This happens, when I change settings on the Leanpub site that affect the generation of the book (the title image, font faces and sizes are set via the book’s pages on LeanPub, not a configuration file in the repository).

While I could click thought the UI and navigate to the page where I can generate a new preview, I prefer using a command line tool from my local machine: Rake

The Setup

A warning: The LeanPub API documentation says: “Using the Leanpub API requires a Pro plan.

To use the LeanPub API, an API key is needed. The link to the API documentation above has information where to get that key. To easily use this API key, I store it in an environment variable LEANPUB_API_KEY.

The Rake Task Definition

In the repository of my book I have a Rakefile containing the task definitions. Here’s the one to trigger the generation of a preview on Leanpub:

require 'rest-client'

namespace :leanpub do
  LEANPUB_BASE_URL = "https://leanpub.com/<book_id_on_leanpub>"
  namespace :preview do
    desc "Generate new Preview on LeanPub"
    task :generate do |t|
      what_to_generate = t.name.split(':')[1]
      url = "#{LEANPUB_BASE_URL}/#{what_to_generate}.json"
      begin
        RestClient.post url, api_key: ENV['LEANPUB_API_KEY']
      rescue RestClient::Exception => e
        puts "Got error #{e.message} in", caller.first
        exit 1
      end
      puts "Generation of preview was triggered"
    end
  end
end

I can now easily generate a preview, without having to leave the IDE I’m using to write the book (or the command line) using this:

$ rake leanpub:preview:generate
Generation of preview was triggered

The Rakefile will likely change, for example to also support publishing a new version of the current ebook, or to make it more flexible in order to handle different ebooks.

Update (8. Jan 2021): It turns out that this is really useful: LeanPub provides a web hook to generate a _sub set_ of the book that also generates the PDF (but not the ebook and mobi file). This saves some time from pushing to GitHub to being able to review the generated file. I now use this web hook most of the time.

I now only generate for full book in all formats when I want to check that the book looks good enough to be published. Since this happens less regularly than pushing to the repository, I use the Rake task.

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