Rob Lacey

Brighton, UK -

Software Engineer working since 2008 with Ruby / Ruby on Rails, love a bit of Elixir / Phoenix. I also poke through other people's code and make PRs for OpenSource Ruby projects that sometimes make it. Currently working at Juniper Education making code for UK schools.

Porting Ruby to JS.

module Rack
  module Utils
    def append_to_query_string(url, params = {})
      base, query = url.split('?')
      params = parse_query(query).merge(params.stringify_keys)
      params = params.sort_by { |k, _v| k.to_s }.to_h
      query = build_query(params)
      [base, query].reject(&:blank?).join('?')
    module_function :append_to_query_string

window.BLAHUtils = {
  isPresent: function(object) {
    return object != undefined &&  object.toString().trim() !== ''
  presense: function(object) {
    return this.isPresent(object) ? object : null
  appendToQueryString: function(url, params = {}) {
    [base, query] = url.split('?')
    params = {
    query = this.buildQuery(params)
    return [base, query].filter(v => this.isPresent(v)).join('?')
  parseQuery: function(query) {
    if (!this.isPresent(query)) {
      return {}
    return query.split('&').reduce((h, pair) => {
      [k, v] = pair.split('=')
      h[k] = decodeURIComponent(v)
      return h
    }, {})
  buildQuery: function(params) {
    return Object.entries(params).map(([k, v]) => {
      return [k, encodeURIComponent(v)].join('=')

USB debugging on Redmi Android phones

USB debugging on a Redmi.

JS Mystery #667

This doesn’t appear anywhere in our codebase. Does iPhone Safari inject this under some circumstances?

undefined is not an object (evaluating 'document.getElementsByTagName('video')[0].webkitExitFullScreen')

When in doubt write that shit down

I do know how to write, but today the only thing I can make out is Nagios and rubocop -A

Somewhere in there there is something about JSONAPI-Resources attributes, maybe.

Rails 6.0.4 mangled SQL

Looks like Rails 6.0.4 upgrade has mangled the SQL JSONAPI-Resources is constructing.

        Expected response code '500' to match '200'
        Response body: {
          "errors": [
              "title": "Internal Server Error",
              "detail": "Internal Server Error",
              "code": "INTERNAL_SERVER_ERROR",
              "status": "500",
              "meta": {
                "exception": "Mysql2::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '.\"id\" AS \"users_id\", users.last_name, users.first_name FROM `users` INNER JOIN `' at line 1",

The backtrace has lead me here.

From: /Users/rl/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/activerecord-6.0.4/lib/active_record/relation/calculations.rb:186 ActiveRecord::Calculations#pluck:

    181: def pluck(*column_names)
    182:   if loaded? && ( - @klass.attribute_names - @klass.attribute_aliases.keys).empty?
    183:     return records.pluck(*column_names)
    184:   end
 => 186:   binding.pry
    188:   if has_include?(column_names.first)
    189:     relation = apply_join_dependency
    190:     relation.pluck(*column_names)
    191:   else
    192:     klass.disallow_raw_sql!(column_names)
    193:     relation = spawn
    194:     relation.select_values = column_names
    195:     result = skip_query_cache_if_necessary { klass.connection.select_all(relation.arel, nil) }
    196:     result.cast_values(klass.attribute_types)
    197:   end
    198: end

[1] pry(#<User::ActiveRecord_Relation>)> column_names
=> ["\"users\".\"id\" AS \"users_id\"", "users.last_name", "users.first_name"]      
What’s up with that? Looking.

The scariest day of my life. Tainted master branch

You wake in a dark room and someone has only gone and tainted your master branch by merging in multiple commits spanning weeks of work. We can’t possibly unpick 100+ commits, what the hell even were they? But we need master back as it was.

We can however, reset our master to a particular commit in the past that we trust.

git checkout master
git reset --hard <somehash>
git push --force origin <somehash>:master

Total 0 (delta 0), reused 0 (delta 0), pack-reused 0
 + <someotherhash>...<somehash> <somehash> -> master (forced update)

There were tears of joy and shaky hands, but it was fine.

ImageMagic not installing on MacOSX

Building RMagick with native extensions is playing up again… I use homebrew so I was looking for the right solution.

Using rexml 3.2.4
Fetching rmagick 2.13.4
Installing rmagick 2.13.4 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /Users/rl/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rmagick-2.13.4/ext/RMagick
/Users/rl/.rbenv/versions/2.6.6/bin/ruby -I /Users/rl/.rbenv/versions/2.6.6/lib/ruby/2.6.0 -r ./siteconf20210707-24851-uczhdh.rb extconf.rb
checking for Ruby version >= 1.8.5... yes
checking for clang... yes
checking for Magick-config... no
checking for pkg-config... yes
checking for ImageMagick version >= 6.4.9... yes
checking for stdint.h... yes
checking for sys/types.h... yes
checking for wand/MagickWand.h... no

Can't install RMagick 2.13.4. Can't find MagickWand.h.
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:

To see why this extension failed to compile, please check the mkmf.log which can be found here:


extconf failed, exit code 1

Gem files will remain installed in /Users/rl/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rmagick-2.13.4 for inspection.
Results logged to /Users/rl/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/extensions/x86_64-darwin-20/2.6.0/rmagick-2.13.4/gem_make.out

An error occurred while installing rmagick (2.13.4), and Bundler cannot continue.
Make sure that `gem install rmagick -v '2.13.4' --source ''` succeeds before bundling.

Seems need to reset pkg-config.

brew remove imagemagick
brew uninstall pkg-config
brew install pkg-config
brew unlink pkg-config && brew link pkg-config
brew install imagemagick
gem install rmagick

Thanks to

Mongoid OR queries are seriously dangerous

Upgrading to Mongoid 7.x and found a pretty frightening change in behaviour for OR queries. Any unclear OR declarations could have devastating side-effects.


irb(main):001:0> Train.where(id: 1).or(:expiry.gte =>
=> #<Mongoid::Criteria
  selector: {"_id"=>1, "$or"=>[{"expiry"=>{"$gte"=>2021-07-07 00:00:00 UTC}}]}
  options:  {:sort=>{"number"=>1}}
  class:    Train
  embedded: false>

irb(main):002:0> Train.or(:expiry.gte => 1)
=> #<Mongoid::Criteria
  selector: {"$or"=>[{"expiry"=>{"$gte"=>2021-07-07 00:00:00 UTC}}], "_id"=>1}
  options:  {:sort=>{"number"=>1}}
  class:    Tenant
  embedded: false>

Previously, or queries would append the selector so where(id: 1) and some OR statement


irb(main):006:0> Train.where(id: 1).or(:expiry.gte =>
=> #<Mongoid::Criteria
  selector: {"$or"=>[{"_id"=>1}, {"expiry"=>{"$gte"=>2021-07-07 00:00:00 UTC}}]}
  options:  {:sort=>{"number"=>1}}
  class:    Train
  embedded: false>

irb(main):007:0> Train.or(:expiry.gte => 1)
=> #<Mongoid::Criteria
  selector: {"$or"=>[{"expiry"=>{"$gte"=>2021-07-07 00:00:00 UTC}}], "_id"=>1}
  options:  {:sort=>{"number"=>1}}
  class:    Train
  embedded: false>

Now it combines them depending on the order they are declared. I am not entirely sure I like either way of declaring this. Having come from ActiveRecord land I would nearly always assume that you’re AND-ing everything you chain onto a scope.

So in this case we could look for our Tenant by ID, but actually find the first unexpired one instead. That’s one hell of a security hole.

I think the lesson here is to be extra cautious when using ‘OR’ in either ActiveRecord or Mongoid since the outcome is not always as obvious as you might think.

Finally got CSS comments with source location back

An upgrade or two back our Rails 6 app lost line comments. I can’t remember if it was trying to improve speed or the upgrade to sassc. Well it’s fixed now.

# Debug mode disables concatenation and preprocessing of assets.
  # This option may cause significant delays in view rendering with a large
  # number of complex assets.
  # config.assets.debug = true
  # config.sass.line_comments = false
  config.sass.inline_source_maps = true


So... I'm writing a book

No really I am. Well two. Over the past year I’ve spent too much time trying to solve the Staff Scheduling Problem and learned a bit about using OR-Tools as a constraint solver. I thought this would be perfect to put my findings into wordsings and publish it. It might just help someone else, how selfless am I? Right?

I could jump in on that but then realistically I’m still learning, but I have spent the last 13 years working with Ruby / Rails and having to fix bugs, and make horrid hacks, and get all of the stuffs working. I realised I could cut my teeth on something I have more experience of and all the sorts of things I post on here, if I remember, and in more detail.

So this year we will have Ruby Expletives (things I learned whilst swearing at Ruby).