The middleware specification.

Middleware is an extension of basic Tesla functionality. It is a module that must implement Tesla.Middleware.call/3.

Middleware options

Options can be passed to middleware in second param of Tesla.Builder.plug/2 macro:

plug Tesla.Middleware.BaseUrl, "https://example.com"

or inside tuple in case of dynamic middleware (Tesla.client/1):

Tesla.client([{Tesla.Middleware.BaseUrl, "https://example.com"}])

Writing custom middleware

Writing custom middleware is as simple as creating a module implementing Tesla.Middleware.call/3.

See Tesla.Middleware.call/3 for details.

Examples

defmodule MyProject.InspectHeadersMiddleware do
  @behaviour Tesla.Middleware

  @impl true
  def call(env, next, _options) do
    IO.inspect(env.headers)

    with {:ok, env} <- Tesla.run(env, next) do
      IO.inspect(env.headers)
      {:ok, env}
    end
  end
end