Add User-Agent header.

lib/line_bot/api_client.ex

@@ -57,9 +57,16 @@ defmodule LineBot.APIClient do
   @doc """
   Adds the OAuth Bearer token to the `Authorization` header.
   The token is retrieved by calling `LineBot.TokenServer.get_token/0`.
+
+  Also adds the `User-Agent` header with a value of `line-botsdk-elixir/vX.X.X`.
+  This follows the pattern of Line Bot libraries in other languages.
   """
   def process_request_headers(headers) do
-    [{"Authorization", "Bearer #{@token_server.get_token()}"} | super(headers)]
+    [
+      {"Authorization", "Bearer #{@token_server.get_token()}"},
+      {"User-Agent", "line-botsdk-elixir/v#{Application.spec(:line_bot, :vsn)}"}
+      | super(headers)
+    ]
   end
 
   @impl HTTPoison.Base

lib/line_bot/token_server.ex

@@ -68,7 +68,12 @@ defmodule LineBot.TokenServer do
     %{state | token: token, expires_on: expires_on}
   end
 
-  @headers [{"Content-Type", "application/x-www-form-urlencoded"}]
+  defp headers do
+    [
+      {"Content-Type", "application/x-www-form-urlencoded"},
+      {"User-Agent", "line-botsdk-elixir/v#{Application.spec(:line_bot, :vsn)}"}
+    ]
+  end
 
   defp post_request_token(client_id, client_secret) do
     data = [
@@ -79,7 +84,7 @@ defmodule LineBot.TokenServer do
 
     %{"access_token" => access_token, "expires_in" => expires_in} =
       "https://api.line.me/v2/oauth/accessToken"
-      |> @http.post!({:form, data}, @headers)
+      |> @http.post!({:form, data}, headers())
       |> Map.get(:body)
       |> Jason.decode!()
 
@@ -90,7 +95,7 @@ defmodule LineBot.TokenServer do
     @http.post!(
       "https://api.line.me/v2/oauth/revoke",
       {:form, [access_token: access_token]},
-      @headers
+      headers()
     )
   end
 

test/line_bot/api_client_test.exs

@@ -33,14 +33,20 @@ defmodule LineBot.APIClientTest do
       assert %{"foo" => "bar"} == APIClient.process_response(response).body
     end
 
-    test "process_request_headers adds auth header from token server" do
+    test "process_request_headers adds auth and user-agent headers" do
       expect(MockTokenServer, :get_token, fn -> "dummy_token" end)
       expect(MockTokenServer, :get_token, fn -> "changed_token" end)
 
-      assert [{"Authorization", "Bearer dummy_token"}] == APIClient.process_request_headers([])
+      assert [
+               {"Authorization", "Bearer dummy_token"},
+               {"User-Agent", "line-botsdk-elixir/v" <> _}
+             ] = APIClient.process_request_headers([])
 
-      assert [{"Authorization", "Bearer changed_token"}, {"other", "header"}] ==
-               APIClient.process_request_headers([{"other", "header"}])
+      assert [
+               {"Authorization", "Bearer changed_token"},
+               {"User-Agent", "line-botsdk-elixir/v" <> _},
+               {"other", "header"}
+             ] = APIClient.process_request_headers([{"other", "header"}])
     end
 
     # TODO these call super. Not sure how to test them without calling HTTPoison.