Validation before processing

What

I get CarrierWave::ProcessingError error in the controller when creating or updating a model that uses CarrierWave uploader.

How

Just rename a text file from "test.txt" to "test.png" and upload it. The uploader class CookingIngredientPictureUploader < CarrierWave::Uploader::Base is expecting an image.

Why

CarrierWave is running this code first which resizes the images

version :small do
  process resize_to_fit: [128, 128]
end

Solution

The code must run check on extension_allowlist and content_type_allowlist first before processing anything.

I have specified these both in my uploader but they are not checked before the "version" is executed.

def content_type_allowlist
  %w[
    image/jpeg
    image/jpg
    image/png
    image/gif
  ]
end

def extension_allowlist
  %w[jpg jpeg gif png]
end

Temporary Workaround

In my controller I have to use rescue which I am not found of.

def update
  if @cooking_stage_ingredient.update(cooking_stage_ingredient_params)
    redirect_to @cooking_recipe, notice: 'Cooking stage ingredient was successfully updated.', status: :see_other
  else
    render :edit, status: :unprocessable_content
  end
rescue CarrierWave::ProcessingError
  @cooking_stage_ingredient.errors.add(:picture, 'Only JPG, PNG, and GIF are allowed.')
  render :edit, status: :unprocessable_content
end