Active Storage Validations

If you are using active_storage gem and you want to add simple validations for it, like presence or content_type you need to write a custom validation method.

This gems doing it for you. Just use attached: true or content_type: 'image/png' validation.

What it can do

validates if file(s) attached
validates content type
validates size of files
validates total size of files
validates dimension of images/videos
validates number of uploaded files (min/max required)
validates aspect ratio (if square, portrait, landscape, is_16_9, ...)
validates if file can be processed by MiniMagick or Vips
custom error messages
allow procs for dynamic determination of values

Usage

For example you have a model like this and you want to add validation.

class User < ApplicationRecord
  has_one_attached :avatar
  has_many_attached :photos
  has_one_attached :image

  validates :name, presence: true

  validates :avatar, attached: true, content_type: 'image/png',
                                     dimension: { width: 200, height: 200 }
  validates :photos, attached: true, content_type: ['image/png', 'image/jpeg'],
                                     dimension: { width: { min: 800, max: 2400 },
                                                  height: { min: 600, max: 1800 }, message: 'is not given between dimension' }
  validates :image, attached: true,
                    processable_image: true,
                    content_type: ['image/png', 'image/jpeg'],
                    aspect_ratio: :landscape
end

class Project < ApplicationRecord
  has_one_attached :logo
  has_one_attached :preview
  has_one_attached :attachment
  has_many_attached :documents

  validates :title, presence: true

  validates :logo, attached: true, size: { less_than: 100.megabytes , message: 'is too large' }
  validates :preview, attached: true, size: { between: 1.kilobyte..100.megabytes , message: 'is not given between size' }
  validates :attachment, attached: true, content_type: { in: 'application/pdf', message: 'is not a PDF' }
  validates :documents, limit: { min: 1, max: 3 }, total_size: { less_than: 5.megabytes }
end

More examples

Content type validation using symbols or regex.

class User < ApplicationRecord
  has_one_attached :avatar
  has_many_attached :photos

  validates :avatar, attached: true, content_type: :png
  # or
  validates :photos, attached: true, content_type: [:png, :jpg, :jpeg]
  # or
  validates :avatar, content_type: /\Aimage\/.*\z/
end

Please note that the symbol types must be registered by Marcel::EXTENSIONS that's used by this gem to infer the full content type. Example code for adding a new content type to Marcel:

# config/initializers/mime_types.rb
Marcel::MimeType.extend "application/ino", extensions: %w(ino), parents: "text/plain" # Registering arduino INO files

Content type spoofing protection

File content type spoofing happens when an ill-intentioned user uploads a file which hides its true content type by faking its extension and its declared content type value. For example, a user may try to upload a .exe file (application/x-msdownload content type) dissimulated as a .jpg file (image/jpeg content type).

By default, the gem does not prevent content type spoofing (prevent it by default is a breaking change that will be implemented in v2). The spoofing protection relies on both the linux file command and Marcel gem. Be careful, since it needs to load the whole file io to perform the analysis, it will use a lot of RAM for very large files. Therefore it could be a wise decision not to enable it in this case.

Take note that the file analyzer will not find the exactly same content type as the ActiveStorage blob (its content type detection relies on a different logic using content+filename+extension). To handle this issue, we consider a close parent content type to be a match. For example, for an ActiveStorage blob which content type is video/x-ms-wmv, the file analyzer will probably detect a video/x-ms-asf content type, this will be considered as a valid match because these 2 content types are closely related. The correlation mapping is based on Marcel::TYPE_PARENTS.

The difficulty to accurately predict a mime type may generate false positives, if so there are two solutions available:

If the ActiveStorage blob content type is closely related to the detected content type using the file analyzer, you can enhance Marcel::TYPE_PARENTS mapping using Marcel::MimeType.extend "application/x-rar-compressed", parents: %(application/x-rar) in the config/initializers/mime_types.rb file. (Please drop an issue so we can add it to the gem for everyone!)
If the ActiveStorage blob content type is not closely related, you still can disable the content type spoofing protection in the validator, if so, please drop us an issue so we can fix it for everyone!

class User < ApplicationRecord
  has_one_attached :avatar

  validates :avatar, attached: true, content_type: :png # spoofing_protection not enabled, at your own risks!
  validates :avatar, attached: true, content_type: { with: :png, spoofing_protection: true } # spoofing_protection enabled
end

Dimension validation with width, height and in.

class User < ApplicationRecord
  has_one_attached :avatar
  has_many_attached :photos

  validates :avatar, dimension: { width: { in: 80..100 }, message: 'is not given between dimension' }
  validates :photos, dimension: { height: { in: 600..1800 } }
end

Dimension validation with min and max range for width and height:

class User < ApplicationRecord
  has_one_attached :avatar
  has_many_attached :photos

  validates :avatar, dimension: { min: 200..100 }
  # Equivalent to:
  # validates :avatar, dimension: { width: { min: 200 }, height: { min: 100  } }
  validates :photos, dimension: { min: 200..100, max: 400..200 }
  # Equivalent to:
  # validates :avatar, dimension: { width: { min: 200, max: 400 }, height: { min: 100, max: 200  } }
end

Aspect ratio validation:

class User < ApplicationRecord
  has_one_attached :avatar
  has_one_attached :photo
  has_many_attached :photos

  validates :avatar, aspect_ratio: :square
  validates :photo, aspect_ratio: :landscape

  # you can also pass dynamic aspect ratio, like :is_4_3, :is_16_9, etc
  validates :photos, aspect_ratio: :is_4_3
end

Proc Usage:

Procs can be used instead of values in all the above examples. They will be called on every validation.

class User < ApplicationRecord
  has_many_attached :proc_files

  validates :proc_files, limit: { max: -> (record) { record.admin? ? 100 : 10 } }
end

Internationalization (I18n)

Active Storage Validations uses I18n for error messages. For this, add these keys in your translation file:

en:
  errors:
    messages:
      content_type_invalid: "has an invalid content type"
      file_size_not_less_than: "file size must be less than %{max_size} (current size is %{file_size})"
      file_size_not_less_than_or_equal_to: "file size must be less than or equal to %{max_size} (current size is %{file_size})"
      file_size_not_greater_than: "file size must be greater than %{min_size} (current size is %{file_size})"
      file_size_not_greater_than_or_equal_to: "file size must be greater than or equal to %{min_size} (current size is %{file_size})"
      file_size_not_between: "file size must be between %{min_size} and %{max_size} (current size is %{file_size})"
      total_file_size_not_less_than: "total file size must be less than %{max_size} (current size is %{total_file_size})"
      total_file_size_not_less_than_or_equal_to: "total file size must be less than or equal to %{max_size} (current size is %{total_file_size})"
      total_file_size_not_greater_than: "total file size must be greater than %{min_size} (current size is %{total_file_size})"
      total_file_size_not_greater_than_or_equal_to: "total file size must be greater than or equal to %{min_size} (current size is %{total_file_size})"
      total_file_size_not_between: "total file size must be between %{min_size} and %{max_size} (current size is %{total_file_size})"
      limit_out_of_range: "total number is out of range"
      image_metadata_missing: "is not a valid image"
      dimension_min_inclusion: "must be greater than or equal to %{width} x %{height} pixel"
      dimension_max_inclusion: "must be less than or equal to %{width} x %{height} pixel"
      dimension_width_inclusion: "width is not included between %{min} and %{max} pixel"
      dimension_height_inclusion: "height is not included between %{min} and %{max} pixel"
      dimension_width_greater_than_or_equal_to: "width must be greater than or equal to %{length} pixel"
      dimension_height_greater_than_or_equal_to: "height must be greater than or equal to %{length} pixel"
      dimension_width_less_than_or_equal_to: "width must be less than or equal to %{length} pixel"
      dimension_height_less_than_or_equal_to: "height must be less than or equal to %{length} pixel"
      dimension_width_equal_to: "width must be equal to %{length} pixel"
      dimension_height_equal_to: "height must be equal to %{length} pixel"
      aspect_ratio_not_square: "must be a square image"
      aspect_ratio_not_portrait: "must be a portrait image"
      aspect_ratio_not_landscape: "must be a landscape image"
      aspect_ratio_is_not: "must have an aspect ratio of %{aspect_ratio}"
      image_not_processable: "is not a valid image"

In several cases, Active Storage Validations provides variables to help you customize messages:

Aspect ratio

The keys starting with aspect_ratio_ support two variables that you can use:

aspect_ratio containing the expected aspect ratio, especially useful for custom aspect ratio
filename containing the current file name

For example :

aspect_ratio_is_not: "must be a %{aspect_ratio} image"

Content type

The content_type_invalid key has three variables that you can use:

content_type containing the exact content type of the sent file
human_content_type containing a more user-friendly version of the sent file content type (e.g. 'TXT' for 'text/plain')
authorized_types containing the list of authorized content types
filename containing the current file name

For example :

content_type_invalid: "has an invalid content type : %{content_type}, authorized types are %{authorized_types}"

Dimension

The keys starting with dimension_ support six variables that you can use:

min containing the minimum width or height allowed
max containing the maximum width or height allowed
width containing the minimum or maximum width allowed
height containing the minimum or maximum width allowed
length containing the exact width or height allowed
filename containing the current file name

For example :

dimension_min_inclusion: "must be greater than or equal to %{width} x %{height} pixel."

File size

The keys starting with file_size_not_ support four variables that you can use:

file_size containing the current file size
min containing the minimum file size
max containing the maximum file size
filename containing the current file name

For example :

file_size_not_between: "file size must be between %{min_size} and %{max_size} (current size is %{file_size})"

Total file size

The keys starting with total_file_size_not_ support three variables that you can use:

total_file_size containing the current total file size
min containing the minimum file size
max containing the maximum file size

For example :

total_file_size_not_between: "total file size must be between %{min_size} and %{max_size} (current size is %{total_file_size})"

Number of files

The limit_out_of_range key supports two variables that you can use:

min containing the minimum number of files
max containing the maximum number of files

For example :

limit_out_of_range: "total number is out of range. range: [%{min}, %{max}]"

Processable image

The image_not_processable key supports one variable that you can use:

filename containing the current file name

For example :

image_not_processable: "is not a valid image (file: %{filename})"

Installation

Add this line to your application's Gemfile:

gem 'active_storage_validations'

# Optional, to use :dimension validator or :aspect_ratio validator
gem 'mini_magick', '>= 4.9.5'
# Or
gem 'ruby-vips', '>= 2.1.0'

And then execute:

$ bundle

Sample

Very simple example of validation with file attached, content type check and custom error message.

Test matchers

Provides RSpec-compatible and Minitest-compatible matchers for testing the validators.

RSpec

In spec_helper.rb, you'll need to require the matchers:

require 'active_storage_validations/matchers'

And include the module:

RSpec.configure do |config|
  config.include ActiveStorageValidations::Matchers
end

Matcher methods available:

describe User do
  # aspect_ratio:
  # #allowing, #rejecting
  it { is_expected.to validate_aspect_ratio_of(:avatar).allowing(:square) }
  it { is_expected.to validate_aspect_ratio_of(:avatar).rejecting(:portrait) }

  # attached
  it { is_expected.to validate_attached_of(:avatar) }

  # processable_image
  it { is_expected.to validate_processable_image_of(:avatar) }

  # limit
  # #min, #max
  it { is_expected.to validate_limit_of(:avatar).min(1) }
  it { is_expected.to validate_limit_of(:avatar).max(5) }

  # content_type:
  # #allowing, #rejecting
  it { is_expected.to validate_content_type_of(:avatar).allowing('image/png', 'image/gif') }
  it { is_expected.to validate_content_type_of(:avatar).rejecting('text/plain', 'text/xml') }

  # dimension:
  # #width, #height, #width_min, #height_min, #width_max, #height_max, #width_between, #height_between
  it { is_expected.to validate_dimensions_of(:avatar).width(250) }
  it { is_expected.to validate_dimensions_of(:avatar).height(200) }
  it { is_expected.to validate_dimensions_of(:avatar).width_min(200) }
  it { is_expected.to validate_dimensions_of(:avatar).height_min(100) }
  it { is_expected.to validate_dimensions_of(:avatar).width_max(500) }
  it { is_expected.to validate_dimensions_of(:avatar).height_max(300) }
  it { is_expected.to validate_dimensions_of(:avatar).width_between(200..500) }
  it { is_expected.to validate_dimensions_of(:avatar).height_between(100..300) }

  # size:
  # #less_than, #less_than_or_equal_to, #greater_than, #greater_than_or_equal_to, #between
  it { is_expected.to validate_size_of(:avatar).less_than(50.kilobytes) }
  it { is_expected.to validate_size_of(:avatar).less_than_or_equal_to(50.kilobytes) }
  it { is_expected.to validate_size_of(:avatar).greater_than(1.kilobyte) }
  it { is_expected.to validate_size_of(:avatar).greater_than_or_equal_to(1.kilobyte) }
  it { is_expected.to validate_size_of(:avatar).between(100..500.kilobytes) }

  # total_size:
  # #less_than, #less_than_or_equal_to, #greater_than, #greater_than_or_equal_to, #between
  it { is_expected.to validate_total_size_of(:avatar).less_than(50.kilobytes) }
  it { is_expected.to validate_total_size_of(:avatar).less_than_or_equal_to(50.kilobytes) }
  it { is_expected.to validate_total_size_of(:avatar).greater_than(1.kilobyte) }
  it { is_expected.to validate_total_size_of(:avatar).greater_than_or_equal_to(1.kilobyte) }
  it { is_expected.to validate_total_size_of(:avatar).between(100..500.kilobytes) }
end

(Note that matcher methods are chainable)

All matchers can currently be customized with Rails validation options:

describe User do
  # :allow_blank
  it { is_expected.to validate_attached_of(:avatar).allow_blank }

  # :on
  it { is_expected.to validate_attached_of(:avatar).on(:update) }
  it { is_expected.to validate_attached_of(:avatar).on(%i[update custom]) }

  # :message
  it { is_expected.to validate_dimensions_of(:avatar).width(250).with_message('Invalid dimensions.') }
end

Minitest

To use the matchers, make sure you have the shoulda-context gem up and running.

You need to require the matchers:

require 'active_storage_validations/matchers'

And extend the module:

class ActiveSupport::TestCase
  extend ActiveStorageValidations::Matchers
end

Then you can use the matchers with the syntax specified in the RSpec section, just use should validate_method instead of it { is_expected_to validate_method } as specified in the shoulda-context gem.

Todo

verify with remote storages (s3, etc)
verify how it works with direct upload
add more translations

Tests & Contributing

To run tests in root folder of gem:

BUNDLE_GEMFILE=gemfiles/rails_6_1_4.gemfile bundle exec rake test to run for Rails 7.0
BUNDLE_GEMFILE=gemfiles/rails_7_0.gemfile bundle exec rake test to run for Rails 7.0
BUNDLE_GEMFILE=gemfiles/rails_7_1.gemfile bundle exec rake test to run for Rails 7.1
BUNDLE_GEMFILE=gemfiles/rails_7_2.gemfile bundle exec rake test to run for Rails 7.2
BUNDLE_GEMFILE=gemfiles/rails_8_0.gemfile bundle exec rake test to run for Rails 8.0

Snippet to run in console:

BUNDLE_GEMFILE=gemfiles/rails_6_1_4.gemfile bundle
BUNDLE_GEMFILE=gemfiles/rails_7_0.gemfile bundle
BUNDLE_GEMFILE=gemfiles/rails_7_1.gemfile bundle
BUNDLE_GEMFILE=gemfiles/rails_7_2.gemfile bundle
BUNDLE_GEMFILE=gemfiles/rails_8_0.gemfile bundle
BUNDLE_GEMFILE=gemfiles/rails_6_1_4.gemfile bundle exec rake test
BUNDLE_GEMFILE=gemfiles/rails_7_0.gemfile bundle exec rake test
BUNDLE_GEMFILE=gemfiles/rails_7_1.gemfile bundle exec rake test
BUNDLE_GEMFILE=gemfiles/rails_7_2.gemfile bundle exec rake test
BUNDLE_GEMFILE=gemfiles/rails_8_0.gemfile bundle exec rake test

Tips:

To focus a specific test, use the focus class method provided by minitest-focus
To focus a specific file, use the TEST option provided by minitest, e.g. to only run size_validator_test.rb file you will execute the following command: bundle exec rake test TEST=test/validators/size_validator_test.rb