fix path_string crash when path includes list

and add documentation for path_string/1

this fix is absinthe-graphql#1337
absinthe-graphql#1337

lib/absinthe/resolution.ex

@@ -235,8 +235,29 @@ defmodule Absinthe.Resolution do
 
   def call(res, _), do: res
 
+  @doc """
+  Get a list of strings representing the path to this field resolution.
+  The index of list items is dropped and the schema type is included.
+
+  ## Examples
+  Given some query:
+  ```graphql
+  query {users { email }}
+  ```
+
+  If you called this function inside a resolver on the users email field it
+  returns a value like:
+
+  ```elixir
+  resolve fn _, _, resolution ->
+    Absinthe.Resolution.path(resolution) #=> ["email", "users", "query"]
+  end
+  ```
+  """
   def path_string(%__MODULE__{path: path}) do
-    Enum.map(path, fn
+    path
+    |> Enum.reject(fn x -> is_integer(x) end)
+    |> Enum.map(fn
       %{name: name, alias: alias} ->
         alias || name
 

test/absinthe/resolution/middleware_test.exs

@@ -74,6 +74,10 @@ defmodule Absinthe.MiddlewareTest do
       field :path, :path do
         resolve fn _, _ -> {:ok, %{}} end
       end
+
+      field :list_of_paths, list_of(:path) do
+        resolve fn _, _ -> {:ok, [%{}]} end
+      end
     end
 
     object :path do
@@ -188,13 +192,13 @@ defmodule Absinthe.MiddlewareTest do
 
   test "it gets the path of the current field" do
     doc = """
-    {foo: path { bar: path { result }}}
+    {foo: listOfPaths { bar: path { result }}}
     """
 
     assert {:ok, %{data: data}} =
              Absinthe.run(doc, __MODULE__.Schema, context: %{current_user: %{}})
 
-    assert %{"foo" => %{"bar" => %{"result" => ["result", "bar", "foo", "RootQueryType"]}}} ==
+    assert %{"foo" => [%{"bar" => %{"result" => ["result", "bar", "foo", "RootQueryType"]}}]} ==
              data
   end
 end