Curl command into Tesla post function

I have this command that works in terminal

curl " -d "user[email][cellphone]=112334558864&user[country_code]=49

I tried a few different ways with Tesla using the post function to replicate the request. Nothing I’m trying works but this is the latest attempt

post(client, “/new”, “user[email]=[cellphone]=112334558864&user[country_code]=49”)

Does anyone know of the translation into Tesla for essentially posting arrays with the post function?

You just need to add the Tesla.Middleware.FormUrlencoded plug to your pipeline, then specify a map for the body of the request:

request_body = %{
  "user[email]" => "",
  "user[cellphone]" => 12345,
  "user[country_code]" => 49

So, something like this:

defmodule MyClient do

  use Tesla

  plug Tesla.Middleware.BaseUrl, "" 
  plug Tesla.Middleware.FormUrlencoded

  def go do

    request_body = %{
      "user[email]" => "",
      "user[cellphone]" => 12345,
      "user[country_code]" => 49
    path = "/protected/json/new"

    {:ok, response} = post(path, request_body)



On the server side, I see the post body:


That is different than the post body that your curl command produces:


However, the post body produced by curl does not conform to the spec for the Content-Type application/x-www-form-urlencoded, which is what the -d flag automatically sets as the Content-Type header in the curl post request:

 -d, --data <data>
        (HTTP) Sends the specified data in a POST request  to  the
         HTTP  server,  in  the same way that a browser does when a
         user has filled in an HTML form  and  presses  the  submit
         button.  This  will  cause  curl  to  pass the data to the
         server  using  the content-type application/x-www-form-urlencoded. 

The spec (see 17.13.4 Form content types) requires that all non letter/number characters, i.e. all non alphanumeric characters, be escaped with % character codes:

…Forms submitted with this content type must be encoded as follows:

  1. …names and values are escaped. Space characters are replaced by +, and then reserved characters are escaped as described in RFC1738, section 2.2: Non-alphanumeric characters are replaced by %HH, a percent sign and two hexadecimal digits representing the ASCII code of the character. Line breaks are represented as “CR LF” pairs (i.e., %0D%0A).
  2. The control names/values are listed in the order they appear in the document. The name is separated from the value by = and name/value pairs are separated from each other by &.

curl does allow you to specify that you want the post data to be percent encoded using the --data-urlencode flag instead of -d, but that still doesn’t produce the same post body as tesla. This is what I get:


For some reason, curl does not escape the brackets everywhere as can be seen in user[email]. Confounding. Edit: Ah. To get curl to percent encode the leading name in the data, you have to prepend the data with an equals sign:

--data-urlencode '=user[email][cellphone]=12345&user[country_code]=49'

and the server receives the post body:

Unfortunately, that still does not conform to the spec: curl replaces the equal signs and the ampersands with percent escapes, which confuses the server and the server can’t extract the key/value pairs. Compare to tesla:


Tesla get’s it right and curl doesn’t.


I haven’t checked its behaviour with this data, but in case you wish to try a CLI HTTP client other than curl, I’ve had success with . My issue with curl was body wrapping, and, if I remember correctly, HTTPie just did it right by default.

1 Like

Thanks for the super concise answer @7stud my Tesla function gets a 200 response now. Also @BrightEyesDavid I was having issues with curl in the zsh shell but all of the commands I was testing worked fine in bash so I’ll likely be using the link you provided me ^.^