uninitialized constant ApplicationRecord error

Question

I am following the RailsTutorial and have been creating a Users model with appropriate attrs and validations. I've run into this error and cannot see where the problem is. The project is configured using Rails5, thus models inheriting from ApplicationRecord should be correct:

User.rb:

class User < ApplicationRecord

before_save { self.email = email.downcase }
validates   :name, presence: true, length: { maximum: 50 }

VALID_EMAIL_REGEX = /\A([\w+\-].?)+@[a-z\d\-]+(\.[a-z]+)*\.[a-z]+\z/i

validates   :email, presence: true, length: { maximum: 255 },
            format: { with: VALID_EMAIL_REGEX },
            uniqueness: { case_sensitive: false }

has_secure_password
validates :password, length: { minimum: 6 }

end

Gemfile:

 source 'https://rubygems.org'
ruby '2.3.0'

gem 'rails',                   '5.0.0.1'
gem 'bcrypt',                  '3.1.11'
gem 'faker',                   '1.6.3'
gem 'carrierwave',             '0.11.2'
gem 'mini_magick',             '4.5.1'
gem 'fog',                     '1.38.0'
gem 'will_paginate',           '3.1.0'
gem 'bootstrap-will_paginate', '0.0.10'
gem 'bootstrap-sass',          '3.3.6'
gem 'puma',                    '3.4.0'
gem 'sass-rails',              '5.0.6'
gem 'uglifier',                '3.0.0'
gem 'coffee-rails',            '4.2.1'
gem 'jquery-rails',            '4.1.1'
gem 'turbolinks',              '5.0.1'
gem 'jbuilder',                '2.4.1'

group :development, :test do
  gem 'sqlite3', '1.3.11'
  gem 'byebug',  '9.0.0', platform: :mri
end

group :development do
  gem 'web-console',           '3.1.1'
  gem 'listen',                '3.0.8'
  gem 'spring',                '1.7.2'
  gem 'spring-watcher-listen', '2.0.0'
end

group :test do
  gem 'rails-controller-testing', '0.1.1'
  gem 'minitest-reporters',       '1.1.9'
  gem 'guard',                    '2.13.0'
  gem 'guard-minitest',           '2.4.4'
end

group :production do
  gem 'pg',   '0.18.4'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

Gemfile.lock:

    GEM
  remote: https://rubygems.org/
  specs:
    CFPropertyList (2.3.2)
    actioncable (5.0.0.1)
      actionpack (= 5.0.0.1)
      nio4r (~> 1.2)
      websocket-driver (~> 0.6.1)
    actionmailer (5.0.0.1)
      actionpack (= 5.0.0.1)
      actionview (= 5.0.0.1)
      activejob (= 5.0.0.1)
      mail (~> 2.5, >= 2.5.4)
      rails-dom-testing (~> 2.0)
    actionpack (5.0.0.1)
      actionview (= 5.0.0.1)
      activesupport (= 5.0.0.1)
      rack (~> 2.0)
      rack-test (~> 0.6.3)
      rails-dom-testing (~> 2.0)
      rails-html-sanitizer (~> 1.0, >= 1.0.2)
    actionview (5.0.0.1)
      activesupport (= 5.0.0.1)
      builder (~> 3.1)
      erubis (~> 2.7.0)
      rails-dom-testing (~> 2.0)
      rails-html-sanitizer (~> 1.0, >= 1.0.2)
    activejob (5.0.0.1)
      activesupport (= 5.0.0.1)
      globalid (>= 0.3.6)
    activemodel (5.0.0.1)
      activesupport (= 5.0.0.1)
    activerecord (5.0.0.1)
      activemodel (= 5.0.0.1)
      activesupport (= 5.0.0.1)
      arel (~> 7.0)
    activesupport (5.0.0.1)
      concurrent-ruby (~> 1.0, >= 1.0.2)
      i18n (~> 0.7)
      minitest (~> 5.1)
      tzinfo (~> 1.1)
    ansi (1.5.0)
    arel (7.1.1)
    autoprefixer-rails (6.4.1)
      execjs
    bcrypt (3.1.11)
    bootstrap-sass (3.3.6)
      autoprefixer-rails (>= 5.2.1)
      sass (>= 3.3.4)
    bootstrap-will_paginate (0.0.10)
      will_paginate
    builder (3.2.2)
    byebug (9.0.0)
    carrierwave (0.11.2)
      activemodel (>= 3.2.0)
      activesupport (>= 3.2.0)
      json (>= 1.7)
      mime-types (>= 1.16)
      mimemagic (>= 0.3.0)
    coderay (1.1.1)
    coffee-rails (4.2.1)
      coffee-script (>= 2.2.0)
      railties (>= 4.0.0, < 5.2.x)
    coffee-script (2.4.1)
      coffee-script-source
      execjs
    coffee-script-source (1.10.0)
    concurrent-ruby (1.0.2)
    debug_inspector (0.0.2)
    erubis (2.7.0)
    excon (0.52.0)
    execjs (2.7.0)
    faker (1.6.3)
      i18n (~> 0.5)
    ffi (1.9.14)
    fission (0.5.0)
      CFPropertyList (~> 2.2)
    fog (1.38.0)
      fog-aliyun (>= 0.1.0)
      fog-atmos
      fog-aws (>= 0.6.0)
      fog-brightbox (~> 0.4)
      fog-cloudatcost (~> 0.1.0)
      fog-core (~> 1.32)
      fog-dynect (~> 0.0.2)
      fog-ecloud (~> 0.1)
      fog-google (<= 0.1.0)
      fog-json
      fog-local
      fog-openstack
      fog-powerdns (>= 0.1.1)
      fog-profitbricks
      fog-rackspace
      fog-radosgw (>= 0.0.2)
      fog-riakcs
      fog-sakuracloud (>= 0.0.4)
      fog-serverlove
      fog-softlayer
      fog-storm_on_demand
      fog-terremark
      fog-vmfusion
      fog-voxel
      fog-vsphere (>= 0.4.0)
      fog-xenserver
      fog-xml (~> 0.1.1)
      ipaddress (~> 0.5)
    fog-aliyun (0.1.0)
      fog-core (~> 1.27)
      fog-json (~> 1.0)
      ipaddress (~> 0.8)
      xml-simple (~> 1.1)
    fog-atmos (0.1.0)
      fog-core
      fog-xml
    fog-aws (0.11.0)
      fog-core (~> 1.38)
      fog-json (~> 1.0)
      fog-xml (~> 0.1)
      ipaddress (~> 0.8)
    fog-brightbox (0.11.0)
      fog-core (~> 1.22)
      fog-json
      inflecto (~> 0.0.2)
    fog-cloudatcost (0.1.2)
      fog-core (~> 1.36)
      fog-json (~> 1.0)
      fog-xml (~> 0.1)
      ipaddress (~> 0.8)
    fog-core (1.42.0)
      builder
      excon (~> 0.49)
      formatador (~> 0.2)
    fog-dynect (0.0.3)
      fog-core
      fog-json
      fog-xml
    fog-ecloud (0.3.0)
      fog-core
      fog-xml
    fog-google (0.1.0)
      fog-core
      fog-json
      fog-xml
    fog-json (1.0.2)
      fog-core (~> 1.0)
      multi_json (~> 1.10)
    fog-local (0.3.0)
      fog-core (~> 1.27)
    fog-openstack (0.1.12)
      fog-core (>= 1.40)
      fog-json (>= 1.0)
      ipaddress (>= 0.8)
    fog-powerdns (0.1.1)
      fog-core (~> 1.27)
      fog-json (~> 1.0)
      fog-xml (~> 0.1)
    fog-profitbricks (0.0.5)
      fog-core
      fog-xml
      nokogiri
    fog-rackspace (0.1.1)
      fog-core (>= 1.35)
      fog-json (>= 1.0)
      fog-xml (>= 0.1)
      ipaddress (>= 0.8)
    fog-radosgw (0.0.5)
      fog-core (>= 1.21.0)
      fog-json
      fog-xml (>= 0.0.1)
    fog-riakcs (0.1.0)
      fog-core
      fog-json
      fog-xml
    fog-sakuracloud (1.7.5)
      fog-core
      fog-json
    fog-serverlove (0.1.2)
      fog-core
      fog-json
    fog-softlayer (1.1.4)
      fog-core
      fog-json
    fog-storm_on_demand (0.1.1)
      fog-core
      fog-json
    fog-terremark (0.1.0)
      fog-core
      fog-xml
    fog-vmfusion (0.1.0)
      fission
      fog-core
    fog-voxel (0.1.0)
      fog-core
      fog-xml
    fog-vsphere (1.0.1)
      fog-core
      rbvmomi (~> 1.8.0)
    fog-xenserver (0.2.3)
      fog-core
      fog-xml
    fog-xml (0.1.2)
      fog-core
      nokogiri (~> 1.5, >= 1.5.11)
    formatador (0.2.5)
    globalid (0.3.7)
      activesupport (>= 4.1.0)
    guard (2.13.0)
      formatador (>= 0.2.4)
      listen (>= 2.7, <= 4.0)
      lumberjack (~> 1.0)
      nenv (~> 0.1)
      notiffany (~> 0.0)
      pry (>= 0.9.12)
      shellany (~> 0.0)
      thor (>= 0.18.1)
    guard-compat (1.2.1)
    guard-minitest (2.4.4)
      guard-compat (~> 1.2)
      minitest (>= 3.0)
    i18n (0.7.0)
    inflecto (0.0.2)
    ipaddress (0.8.3)
    jbuilder (2.4.1)
      activesupport (>= 3.0.0, < 5.1)
      multi_json (~> 1.2)
    jquery-rails (4.1.1)
      rails-dom-testing (>= 1, < 3)
      railties (>= 4.2.0)
      thor (>= 0.14, < 2.0)
    json (2.0.2)
    listen (3.0.8)
      rb-fsevent (~> 0.9, >= 0.9.4)
      rb-inotify (~> 0.9, >= 0.9.7)
    loofah (2.0.3)
      nokogiri (>= 1.5.9)
    lumberjack (1.0.10)
    mail (2.6.4)
      mime-types (>= 1.16, < 4)
    method_source (0.8.2)
    mime-types (3.1)
      mime-types-data (~> 3.2015)
    mime-types-data (3.2016.0521)
    mimemagic (0.3.2)
    mini_magick (4.5.1)
    mini_portile2 (2.1.0)
    minitest (5.9.0)
    minitest-reporters (1.1.9)
      ansi
      builder
      minitest (>= 5.0)
      ruby-progressbar
    multi_json (1.12.1)
    nenv (0.3.0)
    nio4r (1.2.1)
    nokogiri (1.6.8)
      mini_portile2 (~> 2.1.0)
      pkg-config (~> 1.1.7)
    notiffany (0.1.1)
      nenv (~> 0.1)
      shellany (~> 0.0)
    pg (0.18.4)
    pkg-config (1.1.7)
    pry (0.10.4)
      coderay (~> 1.1.0)
      method_source (~> 0.8.1)
      slop (~> 3.4)
    puma (3.4.0)
    rack (2.0.1)
    rack-test (0.6.3)
      rack (>= 1.0)
    rails (5.0.0.1)
      actioncable (= 5.0.0.1)
      actionmailer (= 5.0.0.1)
      actionpack (= 5.0.0.1)
      actionview (= 5.0.0.1)
      activejob (= 5.0.0.1)
      activemodel (= 5.0.0.1)
      activerecord (= 5.0.0.1)
      activesupport (= 5.0.0.1)
      bundler (>= 1.3.0, < 2.0)
      railties (= 5.0.0.1)
      sprockets-rails (>= 2.0.0)
    rails-controller-testing (0.1.1)
      actionpack (~> 5.x)
      actionview (~> 5.x)
      activesupport (~> 5.x)
    rails-dom-testing (2.0.1)
      activesupport (>= 4.2.0, < 6.0)
      nokogiri (~> 1.6.0)
    rails-html-sanitizer (1.0.3)
      loofah (~> 2.0)
    railties (5.0.0.1)
      actionpack (= 5.0.0.1)
      activesupport (= 5.0.0.1)
      method_source
      rake (>= 0.8.7)
      thor (>= 0.18.1, < 2.0)
    rake (11.2.2)
    rb-fsevent (0.9.7)
    rb-inotify (0.9.7)
      ffi (>= 0.5.0)
    rbvmomi (1.8.2)
      builder
      nokogiri (>= 1.4.1)
      trollop
    ruby-progressbar (1.8.1)
    sass (3.4.22)
    sass-rails (5.0.6)
      railties (>= 4.0.0, < 6)
      sass (~> 3.1)
      sprockets (>= 2.8, < 4.0)
      sprockets-rails (>= 2.0, < 4.0)
      tilt (>= 1.1, < 3)
    shellany (0.0.1)
    slop (3.6.0)
    spring (1.7.2)
    spring-watcher-listen (2.0.0)
      listen (>= 2.7, < 4.0)
      spring (~> 1.2)
    sprockets (3.7.0)
      concurrent-ruby (~> 1.0)
      rack (> 1, < 3)
    sprockets-rails (3.2.0)
      actionpack (>= 4.0)
      activesupport (>= 4.0)
      sprockets (>= 3.0.0)
    sqlite3 (1.3.11)
    thor (0.19.1)
    thread_safe (0.3.5)
    tilt (2.0.5)
    trollop (2.1.2)
    turbolinks (5.0.1)
      turbolinks-source (~> 5)
    turbolinks-source (5.0.0)
    tzinfo (1.2.2)
      thread_safe (~> 0.1)
    uglifier (3.0.0)
      execjs (>= 0.3.0, < 3)
    web-console (3.1.1)
      activemodel (>= 4.2)
      debug_inspector
      railties (>= 4.2)
    websocket-driver (0.6.4)
      websocket-extensions (>= 0.1.0)
    websocket-extensions (0.1.2)
    will_paginate (3.1.0)
    xml-simple (1.1.5)

PLATFORMS
  ruby

DEPENDENCIES
  bcrypt (= 3.1.11)
  bootstrap-sass (= 3.3.6)
  bootstrap-will_paginate (= 0.0.10)
  byebug (= 9.0.0)
  carrierwave (= 0.11.2)
  coffee-rails (= 4.2.1)
  faker (= 1.6.3)
  fog (= 1.38.0)
  guard (= 2.13.0)
  guard-minitest (= 2.4.4)
  jbuilder (= 2.4.1)
  jquery-rails (= 4.1.1)
  listen (= 3.0.8)
  mini_magick (= 4.5.1)
  minitest-reporters (= 1.1.9)
  pg (= 0.18.4)
  puma (= 3.4.0)
  rails (= 5.0.0.1)
  rails-controller-testing (= 0.1.1)
  sass-rails (= 5.0.6)
  spring (= 1.7.2)
  spring-watcher-listen (= 2.0.0)
  sqlite3 (= 1.3.11)
  turbolinks (= 5.0.1)
  tzinfo-data
  uglifier (= 3.0.0)
  web-console (= 3.1.1)
  will_paginate (= 3.1.0)

RUBY VERSION
   ruby 2.3.0p0

BUNDLED WITH
   1.12.5

Backtrace from running heroku run console:

    ... up, run.9075 (Free)
/app/app/models/user.rb:1:in `<top (required)>': uninitialized constant ApplicationRecord (NameError)
    from /app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.0.0.1/lib/active_support/dependencies/interlock.rb:12:in `block in loading'
    from /app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.0.0.1/lib/active_support/concurrency/share_lock.rb:117:in `exclusive'
    from /app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.0.0.1/lib/active_support/dependencies/interlock.rb:11:in `loading'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/engine.rb:476:in `block (2 levels) in eager_load!'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/engine.rb:475:in `each'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/engine.rb:475:in `block in eager_load!'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/engine.rb:473:in `each'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/engine.rb:473:in `eager_load!'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/engine.rb:354:in `eager_load!'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/application/finisher.rb:59:in `each'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/application/finisher.rb:59:in `block in <module:Finisher>'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/initializable.rb:30:in `instance_exec'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/initializable.rb:30:in `run'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/initializable.rb:55:in `block in run_initializers'
    from /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:228:in `block in tsort_each'
    from /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
    from /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:431:in `each_strongly_connected_component_from'
    from /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:349:in `block in each_strongly_connected_component'
    from /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:347:in `each'
    from /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:347:in `call'
    from /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:347:in `each_strongly_connected_component'
    from /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:226:in `tsort_each'
    from /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:205:in `tsort_each'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/initializable.rb:54:in `run_initializers'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/application.rb:352:in `initialize!'
    from /app/config/environment.rb:5:in `<top (required)>'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/application.rb:328:in `require'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/application.rb:328:in `require_environment!'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/commands/commands_tasks.rb:157:in `require_application_and_environment!'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/commands/commands_tasks.rb:77:in `console'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/commands/commands_tasks.rb:49:in `run_command!'
    from /app/vendor/bundle/ruby/2.3.0/gems/railties-5.0.0.1/lib/rails/commands.rb:18:in `<top (required)>'
    from bin/rails:9:in `require'
    from bin/rails:9:in `<main>'

boot.rb:

    ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)

require 'bundler/setup' # Set up gems listed in the Gemfile.

console histroy, for what it's worth:

      387  cd RailsTutorial/
  388  cd sample_app/
  389  subl .
  390  git st
  391  rails g migration add_password_digest_to_users password_digest:string
  392  bundle exec rake db:migrate
  393  rails console
  394  git st
  395  git add ,
  396  git add .
  397  git commit -am 'Make basic user model (inc secure passwords)"
  398  '
  399  git br
  400  git co master
  401  git push origin master
  402  git push heroku
  403  heroku run rake db:migrate
  404  heroku run console
  405  heroku run console --sandbox
  406  heroku run rake db:migrate
  407  heroku run console --sandbox
  408  git st
  409  git commit -am "Updating has_secure_password in User model"
  410  '
  411  git commit -am "Updating has_secure_password in User model"
  412  '
  413  git commit -am "Updating has_secure_password in User model"
  414  git add .
  415  git commit -am "Updating has_secure_password in User model"
  416  git push origin master
  417  git push heroku master
  418  heroku run rake db:migrate
  419  heroku console --sandbox
  420  heroku console --sandbox
  421  heroku run console --sandbox
  422  git push heroku master
  423  git st
  424  heroku run console --sandbox
  425  heroku run console
  426  git st
  427  git br
  428  git commit -am 'bugging < ApplicationRecord error'
  429  git push origin master
  430  git push heroku master
  431  heroku run rake db:migrate
  432  herokue run console --sandbox
  433  heroku run console --sandbox
  434  rails s
  435  git diff
  436  git st
  437  git br
  438  git co modelling-users
  439  git st
  440  git co master
  441  bundle exec guard
  442  ruby /test/integration/site_layout_test.rb --name layout links
  443  ruby /test/integration/site_layout_test.rb
  444  ruby test/integration/site_layout_test.rb
  445  rake test
  446  rake test/integration/site_layout_test.rb
  447  rake test/integration/site_layout_test.rb
  448  ruby /test/integration/site_layout_test.rb --name layout links
  449  ruby test/integration/site_layout_test.rb --name layout links
  450  rake test TEST=test/integration/site_layout_test.rb
  451  rake test TEST=test/integration/site_layout_test.rb name- layout links
  452  ruby test/integration/site_layout_test.rb name- layout links
  453  ruby test/integration/site_layout_test.rb --name layout links
  454  rake test TEST=test/integration/site_layout_test.rb --name layout links
  455  rake test TEST=test/integration/site_layout_test.rb --name layout links
  456  ruby -Itest test/integration/site_layout_test.rb --name layout links
  457  ruby -Itest test/integration/site_layout_test.rb --name layout_links
  458  ruby -Itest test/integration/site_layout_test.rb --name layout_links
  459  rake test TEST=test/integration/site_layout_test.rb
  460  bundle exec guard
  461  bundle exec guard
  462  bundle exec guard
  463  git st
  464  git add .
  465  git st
  466  git st
  467  git commit -am 'adding, migrating and testing user model with name and email attrs'
  468  git st
  469  git push origina master
  470  git push heroku
  471  git push heroku
  472  bundle exec guard
  473  bundle exec guard
  474  bundle exec guard
  475  rails s
  476  rails s
  477  rails s
  478  pswl
  479  psql
  480  pwd
  481  cd Code/
  482  ls
  483  cd RailsTutorial/sample_app/
  484  rails test
  485  rails test:models
  486  bundle exec rake db:migrate
  487  rails test:models
  488  ls
  489  git st
  490  git diff
  491  rails test:models
  492  git st
  493  git add .
  494  git commit -am 'debugging ApplicationRecord'
  495  git br
  496  rails test
  497  git push heroku master
  498  heroku run rake db:migrate
  499  heroku run console
  500  pwd
  501  cd Code/RailsTutorial/sample_app/
  502  rails test
  503  subl .
  504  psql
  505  rails test
  506  rails test
  507  git history
  508  git hist
  509  history

Just gone through whole directory file by file and have seen that my migrations directory and contents has completely dissapeared. V strange. The schema.rb is completely up to date. Command history above shows what's been done since I last saw the migrations directory and its correct migration file contents. Previous git commit was unfortunately before this whole model was generated thus have no previous commit with these migration contents

Any ideas of how to get me out of my amateur muddle? Thanks

Interloper

Possible duplicate of uninitialized constant ApplicationRecord – Astilbe

what is the difference? – Astilbe

how's your Gemfile.lock look like? – Brusa

Difference is this project is already using Rails 5, thus all models should inherit from ApplicationRecord, as correctly detailed in User.rb – Interloper

When you say "configured to use Rails5", what do you mean? Did you edit an existing Gemfile to bump the Rails version to 5? Did you generate the application from scratch using Rails 5? When I generate a Rails5 app from scratch it gives me a standard app/models/application_record.rb file. – Slumgullion

I mean just that the project was started in Rails5, no adaptation from previous Rails version. Only mentionig that the project is in Rails5 because other questions with the same error were due to usage of wrong rails versions and the first poster here flagged that this could be a duplicate of one of these other questions, it is not. Rails5 app from day#1. – Interloper

can you also post your boot.rb file? – Quill

ok I've just gone through whole directory file by file and have seen that my migrations directory and contents has completely dissapeared. V strange. The schema.rb is completely up to date. The only thing that consciously has been done since I last saw the directory and its correct migration file contents was is git merge to master, git commit, git origin push and git heroku push. This may have been done whilst a terminal psql session was running. Previous git commit was unfortunately before this whole model was generated thus have no previous commit with these migration contents. – Interloper

boot.rb copied above – Interloper

do you see the application_record.rb file in your models directory? – Chalone

No application_record.rb file in model directory. (neither this file nor the migrations directory & its contents have been manually removed, only thing that has been done dince tests were passing fine was the pushes to origin and heroku and the attempted heroku run db:migrate, all as per history. FYI postgres developent db tables in tact from previous local db:migrate). – Interloper

Strange, how have these files dissapeared and presumably this is somehow the source of the ApplicationRecord uninitialized constant error? – Interloper

Answer 1

Create a new file called app/models/application_record.rb with the following contents:

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
end

Explanation: When generating a new Rails 5+ project the application_record.rb file will be created automatically, but if using a project that was generated on an earlier version and upgraded to 5+ you need to create this file yourself.

Hepza

This worked for me as well, but I don't really get what's happening. Any clues? – Detribalize

When generating a new Rails 5+ project the application_record.rb file will be created automatically, but if using a project that was generated on an earlier version and upgraded to 5+ you need to create this file yourself. blog.bigbinary.com/2015/12/28/… – Hepza

Answer 2

Turns out I had by mistake checked out from the brand where the migrations and models were created, back into master branch where these migrations and models were not present. Without those models present neither was the application_record.rb file thus the error of uninitialized constant ApplicationRecord.

Interloper