TeslaCurl

TeslaCurl is a middleware for Tesla. It will log a curl command for each request.

The package can be installed by adding tesla_curl to your list of dependencies in mix.exs:

def deps do
  [
    {:tesla, "~> 1.15"},
    {:tesla_curl, "~> 1.4", only: [:dev, :test]}
  ]
end

Usage

As a middleware:

You can use TeslaCurl as a middleware to automatically log cURL commands for each request:

defmodule HelloWorld do
  def middleware do
    [
      Tesla.Middleware.Headers,
      Tesla.Middleware.JSON,
      {Tesla.Middleware.Curl, logger_level: :debug, redact_fields: ["authorization"]}
    ]
  end

  def client do
    Tesla.client(middleware())
  end

  def get_data(path) do
    Tesla.get(client(), path)
  end
end

Tesla executes middlewares in list order for requests (top-to-bottom), meaning Tesla.Middleware.Curl should come after other middlewares that modify the request. For example, if you are using Tesla.Middleware.Headers and Tesla.Middleware.JSON:

# Correct order - Curl logs the final request with headers and JSON encoding
def middleware do
  [
    Tesla.Middleware.Headers,
    Tesla.Middleware.JSON,
    Tesla.Middleware.Curl
  ]
end

# Incorrect order - Curl won't see JSON encoding or headers
def middleware do
  [
    Tesla.Middleware.Curl,
    Tesla.Middleware.Headers,
    Tesla.Middleware.JSON
  ]
end

Standalone usage:

You can also use the TeslaCurl module directly with log/2 without configuring it as middleware:

defmodule HelloWorld do
  def foo(%Tesla.Env{} = env, opts \\ []) do
    Tesla.Middleware.Curl.log(env, opts)
  end
end

Configuration Options

Field Redaction

To prevent sensitive information from being logged, use redact_fields to specify headers or body fields that should be redacted:

{Tesla.Middleware.Curl, redact_fields: ["api_token", "authorization", "password"]}

Sensitive values will be replaced with REDACTED in the generated cURL command.

Using Regex Captures for Redaction

If the request body is a string (e.g., XML or JSON), you can redact values using regular expressions with capture groups, for example, supplying redact_fields: [~r{<password>(.*?)</password>}] will result in "<username>John Doe</username><password>REDACTED</password>"

Follow Redirects

If you would like to enable the flag to follow redirects by default, supply follow_redirects: true in the options list.

Compressed

For compressed responses, you can supply the compressed: true option. This will add the --compressed flag to the curl command.

Logger Level

You can supply the logger_level option to set the level of the logger. The default is :info. Must be one of :debug, :info, :warn, :error, :fatal, :none.

Best Practices

Avoid Logging Sensitive Data: Always use redact_fields in production to prevent exposing secrets.
Use in Development & Debugging: Consider enabling TeslaCurl only in non-production environments.
Define Middleware Order Correctly: Place Tesla.Middleware.Curl after other middlewares that modify the request (like Tesla.Middleware.Headers and Tesla.Middleware.JSON) to ensure it logs the final request state.