Correctif sur la disponibilité de la seule ressource hébergée sur Goo…

…gle Drive (#4127)

* Add a note about #3464

* Implement hot-fix for Google Drive hosted content (#4122)

* Fix credo warning

* Mix format

* Tests pour redirection http de GDrive

---------

Co-authored-by: Frédéric Menou <[email protected]>

apps/transport/lib/transport/availability_checker.ex

@@ -41,6 +41,7 @@ defmodule Transport.AvailabilityChecker do
       # https://github.com/edgurgel/httpoison/issues/171#issuecomment-244029927
       # https://github.com/etalab/transport-site/issues/3463
       {:error, %HTTPoison.Error{reason: {:invalid_redirection, _}}} ->
+        # NOTE: this does not actually verifies that the target is available at the moment!
         true
 
       _ ->
@@ -49,7 +50,22 @@ defmodule Transport.AvailabilityChecker do
   end
 
   def available?(format, url, false) when is_binary(url) do
-    case http_client().head(url, [], follow_redirect: true) do
+    options = [follow_redirect: true]
+    # Hot-fix for https://github.com/etalab/transport-site/issues/4122
+    # Least intrusive fix, only pass `force_redirection` to `HTTPoison` if the param value is true, else
+    # do not specify it, to avoid side-effect.
+    # See: https://github.com/benoitc/hackney/blob/eca5fbb1ff2d84facefb2a633e00f6ca16e7ddfd/src/hackney_stream.erl#L173
+    # Google Drive content (1 instance at time of writing) returns a 303, and by default `hackney` only allows
+    # POST method for this, but here HEAD/GET are supported and required. By using `force_redirection` in `hackney`
+    # options, this indicated `hackney` that the redirect should still occur.
+    options =
+      if URI.parse(url).host == "drive.google.com" do
+        options |> Keyword.merge(hackney: [force_redirect: true])
+      else
+        options
+      end
+
+    case http_client().head(url, [], options) do
       # See https://developer.mozilla.org/en-US/docs/Web/HTTP/Status#successful_responses
       # Other 2xx status codes don't seem appropriate here
       {:ok, %Response{status_code: 200}} ->

apps/transport/test/transport/availability_checker_test.exs

@@ -67,6 +67,14 @@ defmodule Transport.AvailabilityCheckerTest do
     test_fallback_to_stream(403)
   end
 
+  test "redirection for Google Drive" do
+    expect(Transport.HTTPoison.Mock, :head, fn _url, [], [follow_redirect: true, hackney: [force_redirect: true]] ->
+      {:ok, %HTTPoison.Response{status_code: 200}}
+    end)
+
+    assert AvailabilityChecker.available?("GTFS", "https://drive.google.com/test_url")
+  end
+
   defp mock_head_with_status(status_code) do
     expect(Transport.HTTPoison.Mock, :head, fn _url, [], [follow_redirect: true] ->
       {:ok, %HTTPoison.Response{status_code: status_code}}