Updated plug, getting dialyzer errors

Questions / Help
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1

I recently updated plug to 1.12.0 and am getting new Dialyzer errors.

lib/my_app_web/plugs/graphiql_context.ex:8:callback_arg_type_mismatch
The inferred type for the 1st argument is not a
supertype of the expected type for the call/2 callback
in the Plug behaviour.

Success type:
%Plug.Conn{
  :adapter => {atom(), _},
  :assigns => %{atom() => _},
  :body_params => %Plug.Conn.Unfetched{:aspect => atom(), binary() => _},
  :cookies => %Plug.Conn.Unfetched{:aspect => atom(), binary() => _},
  :halted => boolean(),
  :host => binary(),
  :method => binary(),
  :owner => pid(),
  :params => %Plug.Conn.Unfetched{:aspect => atom(), binary() => _},
  :path_info => [binary()],
  :path_params => %{
    binary() =>
      binary() | [binary() | [any()] | map()] | %{binary() => binary() | [any()] | map()}
  },
  :port => char(),
  :private => %{:absinthe => map(), atom() => _},
  :query_params => %Plug.Conn.Unfetched{
    :aspect => atom(),
    binary() =>
      binary() | [binary() | [any()] | map()] | %{binary() => binary() | [any()] | map()}
  },
  :query_string => binary(),
  :remote_ip =>
    {byte(), byte(), byte(), byte()}
    | {char(), char(), char(), char(), char(), char(), char(), char()},
  :req_cookies => %Plug.Conn.Unfetched{:aspect => atom(), binary() => binary()},
  :req_headers => [{binary(), binary()}],
  :request_path => binary(),
  :resp_body =>
    nil
    | binary()
    | maybe_improper_list(
        binary() | maybe_improper_list(any(), binary() | []) | byte(),
        binary() | []
      ),
  :resp_cookies => %{binary() => map()},
  :resp_headers => [{binary(), binary()}],
  :scheme => :http | :https,
  :script_name => [binary()],
  :secret_key_base => nil | binary(),
  :state => :chunked | :file | :sent | :set | :set_chunked | :set_file | :unset,
  :status => nil | non_neg_integer()
}

Behaviour callback type:
%Plug.Conn{
  :adapter => {atom(), _},
  :assigns => %{atom() => _},
  :before_send => [
    (%Plug.Conn{
       :adapter => {_, _},
       :assigns => map(),
       :before_send => [(_ -> any())],
       _ => _
     } ->
       %Plug.Conn{
         :adapter => {_, _},
         :assigns => map(),
         :before_send => [(_ -> any())],
         _ => _
       })
  ],
  :body_params => %Plug.Conn.Unfetched{:aspect => atom(), binary() => _},
  :cookies => %Plug.Conn.Unfetched{:aspect => atom(), binary() => _},
  :halted => boolean(),
  :host => binary(),
  :method => binary(),
  :owner => pid(),
  :params => %Plug.Conn.Unfetched{:aspect => atom(), binary() => _},
  :path_info => [binary()],
  :path_params => %{
    binary() =>
      binary()
      | [binary() | [any()] | %{binary() => _}]
      | %{binary() => binary() | [any()] | %{binary() => _}}
  },
  :port => char(),
  :private => %{atom() => _},
  :query_params => %Plug.Conn.Unfetched{
    :aspect => atom(),
    binary() =>
      binary()
      | [binary() | [any()] | %{binary() => _}]
      | %{binary() => binary() | [any()] | %{binary() => _}}
  },
  :query_string => binary(),
  :remote_ip =>
    {byte(), byte(), byte(), byte()}
    | {char(), char(), char(), char(), char(), char(), char(), char()},
  :req_cookies => %Plug.Conn.Unfetched{:aspect => atom(), binary() => binary()},
  :req_headers => [{binary(), binary()}],
  :request_path => binary(),
  :resp_body =>
    nil
    | binary()
    | maybe_improper_list(
        binary() | maybe_improper_list(any(), binary() | []) | byte(),
        binary() | []
      ),
  :resp_cookies => %{binary() => %{}},
  :resp_headers => [{binary(), binary()}],
  :scheme => :http | :https,
  :script_name => [binary()],
  :secret_key_base => nil | binary(),
  :state => :chunked | :file | :sent | :set | :set_chunked | :set_file | :unset,
  :status => nil | non_neg_integer()
}

The diff appear to be:

image
image2246×458 43.3 KB

and

image
image2340×1130 311 KB

Line 8 is the def call function:

defmodule MyAppWeb.Plugs.GraphiQLContext do
  @behaviour Plug

  import Plug.Conn

  def init(opts), do: opts

  def call(conn, _) do
    context = build_context(conn)
    Absinthe.Plug.put_options(conn, context: context)
  end
  ...

How do I resolve this?

Thank you

1 Like
2

Hi! Wild guess, did you do a clean build (remove the _build directory)?

3 Likes
3

Thank you. That helped!

It raised another dialyzer warning :laughing: but I’ve decided to add it to my .dialyzer_ignore.exs and move on

1 Like
4

I hit this issue too. Fix was to not only do a clean build but also remove any existing .plt files that had been previously generated by dialyzer.

2 Likes