Faraday Response is never JSON

I can never get a JSON response from Faraday, within Ruby 3.1.3 and Faraday 2.7.5:

    def connection
      @connection ||= Faraday.new(
        url: url,
        headers: headers
      ) do |faraday|
        faraday.response :json
        faraday.request :json
      end
    end

    def headers
      { content_type: 'application/json',
        accept: 'application/json' }
    end

    def send_request
      connection.send(method) do |req|
        req.body = body
      end
    end

When running though, I check response.body, and it is never JSON (even though I have faraday.response :json:

[1] pry(#<App>)> response.body
=> "{\"data\":{\"date\":\"some_data\"}}"

I have to:

[2] pry(#<>)> JSON.parse response.body
=> {"data"=>{"date"=>"some_data"}}

The test I am checking this with is:

 let(:response_body) { { data: { date: 'some_data' } }.to_json }
 
 ...

stub_request(:post, url)
  .with(
     body: body.to_json,
     headers: custom_headers
   ).to_return(status: status, body: response_body, headers: {})
end

it 'POSTS to a url' do
  subject
  expect(a_request(:post, url)).to have_been_made
 end
end

Is my test wrong, or is the client code wrong to have json always returned?

Solution

My guess is that the API you are requesting is not setting the right content-type response header.

I haven't dug very deep in the Faraday code, but it seems that if the response is not in format 'application/json' the response.body is delivered as plain string.

conn = Faraday.new do |f|
   f.request :json 
   f.response :json
end

res = conn.get("https://dummyjson.com/products/1")
res.body["id"]
# => 1

res.body.class
# => Hash

res.headers["content-type"]
# => "application/json; charset=utf-8"

res = conn.get("https://example.com")
res.headers["content-type"]
# => "text/html; charset=UTF-8"

res.body[0, 80]
# => "<!doctype html>\n<html>\n<head>\n    <title>Example Domain</title>\n\n    <meta chars"

res.body.class
# => String