Set content type in S3 when attaching via Paperclip 4?

Question

I'm trying to attach CSV files to a Rails3 model using paperclip 4.1.1, but I'm having trouble getting the content-type as reported by S3 to be text/csv (instead I am getting text/plain). When I subsequently download the file from S3, the extension is getting changed to match the content-type instead of preserving the original extension (so test.csv is downloaded as test.txt).

From what I can see, when you upload a file, the FileAdapter will cache the content-type on creation with whatever value was determined by the ContentTypeDetector (which calls file -b --mime filename). Unfortunately, CSV files return text/plain which makes sense, as how can you really distinguish this? Attempts to set the content-type with attachment.instance_write(:content_type, 'text/csv') only set the value in the model and do not affect what gets written to S3.

FileAdapter's content_type initialized here: https://github.com/thoughtbot/paperclip/blob/v4.0/lib/paperclip/io_adapters/file_adapter.rb#L14

Call which creates that io_adapter: https://github.com/thoughtbot/paperclip/blob/v4.0/lib/paperclip/attachment.rb#L98

I really have a generic upload here (so I can't hard-code the content type in the S3 headers definition in has_attached_file), and I don't really want the content-type spoofing protection. Any ideas/suggestions? I would prefer not to downgrade to 3.5 because it would mean just delaying the pain, but if that's the only way, I'll entertain it...

Are you using s3 or s3 through fog for your storage provider? You could pass a lambda into the s3_headers to determine if you should overwrite the content_type value, but the fog implementation doesn't have an equivalent :fog_headers option... — stereoscott, May 29 '14 at 01:32
@stereoscott If I use S3 through Fog, do I have any other ways to override the header? — The Lazy Log, Jun 16 '14 at 04:58

score 14 · Answer 1 · answered Jun 19 '14 at 02:21

14

If you are using fog then you can do something like this:

has_attached_file :report,
  fog_file: lambda { |attachment|
    {
      content_type: 'text/csv',
      content_disposition: "attachment; filename=#{attachment.original_filename}",
    }
  }

If you are using Amazon S3 as your storage provider, then something like this should work:

has_attached_file :report
  s3_headers: lambda { |attachment|
    { 
      'Content-Type' => 'text/csv',
      'Content-Disposition' => "attachment; filename=#{attachment.original_filename}",
    }
  }

answered Jun 19 '14 at 02:21

stereoscott

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In your setup, do you mean that we can only upload 'text/csv'? What about other format? – The Lazy Log Jun 19 '14 at 10:03
I think you have an extra comma at the end of the 'Content-Disposition' lines. The s3_headers section works fine if using s3 with fog. – FuzzyJulz Aug 13 '14 at 01:47
1

`attachment` instance here is the model itself, taking the example above - `original_filename` here is a method or could be an attribute in your model. – Marvin Apr 04 '18 at 11:25
1

Almost there... but the `attachment` is empty entity (_before save_) when sending to s3, so `attachment.original_filename` is always nil. How could I access the original filename before it's saved? – Maris May 23 '19 at 06:18
I have the exact same issue. Did you figure out a workaround? – Zain Zafar Aug 14 '20 at 14:33

score 0 · Answer 2 · answered Mar 05 '21 at 05:16

Had this problem just recently and both the post process and the lambda don't work so did a work around. Same with others observation, the values of the attachment is empty when calling the s3 lambda headers.

add this line to the model

attr_accessor :tmp_content_type, :tmp_file_name

override the file assignment method so we could get the file info and store it for later use

 def file=(f)
  set_tmp_values(f.path)
  file.assign(f)
end

def set_tmp_values(file_path)
  self.tmp_file_name = File.basename(file_path)
  self.tmp_content_type = MIME::Types.type_for(file_path).first.content_type
end

Use the temp vars

:s3_headers => lambda { |attachment|
  {
    'Content-Type' => attachment.tmp_content_type,
    "Content-Disposition" => "attachment; filename=\"# {attachment.tmp_file_name}\""
  }
}

Set content type in S3 when attaching via Paperclip 4?

2 Answers2

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