Add support for Poison 4

clients/gax/lib/google_api/gax/data_wrapper.ex

@@ -45,7 +45,7 @@ defmodule GoogleApi.Gax.DataWrapper do
   @spec decode(GoogleApi.Gax.DataWrapper.t(), keyword()) :: any()
   def decode(data_wrapper, options) do
     struct = options[:struct]
-    Poison.Decode.decode(data_wrapper.data, as: struct)
+    GoogleApi.Gax.ModelBase.poison_transform(data_wrapper.data, %{as: struct})
   end
 end
 

clients/gax/lib/google_api/gax/model_base.ex

@@ -13,6 +13,8 @@
 # limitations under the License.
 
 defmodule GoogleApi.Gax.ModelBase do
+  require Poison.Decode
+
   @moduledoc """
   This module helps you quickly and concisely define API models.
 
@@ -97,17 +99,38 @@ defmodule GoogleApi.Gax.ModelBase do
   def decode(value, :map, module) when not is_nil(value) do
     value
     |> Enum.map(fn {k, v} ->
-      {k, Poison.Decode.decode(v, as: struct(module))}
+      {k, poison_transform(v, %{as: struct(module)})}
     end)
     |> Enum.into(%{})
   end
 
   def decode(value, :list, module) do
-    Poison.Decode.decode(value, as: [struct(module)])
+    poison_transform(value, %{as: [struct(module)]})
   end
 
   def decode(value, _, module) do
-    Poison.Decode.decode(value, as: struct(module))
+    poison_transform(value, %{as: struct(module)})
+  end
+
+  if function_exported?(Poison.Decode, :decode, 2) do
+    def poison_transform(value, options) do
+      Poison.Decode.decode(value, options)
+    end
+  else
+    # Short-circuit if the value has already been transformed.
+    # This works around a bug in poison 4 where Poison.decode does an extra
+    # transformation pass on sub-structs.
+    def poison_transform(%{__struct__: _} = value, %{as: _}) do
+      value
+    end
+
+    def poison_transform([%{__struct__: _} | _] = value, %{as: [_]}) do
+      value
+    end
+
+    def poison_transform(value, options) do
+      Poison.Decode.transform(value, options)
+    end
   end
 
   @doc """

clients/gax/mix.exs

@@ -1,7 +1,7 @@
 defmodule GoogleApi.Gax.MixProject do
   use Mix.Project
 
-  @version "0.2.0"
+  @version "0.3.0"
 
   def project do
     [
@@ -27,7 +27,7 @@ defmodule GoogleApi.Gax.MixProject do
   defp deps() do
     [
       {:tesla, "~> 1.2"},
-      {:poison, ">= 1.0.0 and < 4.0.0"},
+      {:poison, ">= 3.0.0 and < 5.0.0"},
       {:ex_doc, "~> 0.16", only: :dev},
       {:dialyxir, "~> 0.5", only: [:dev], runtime: false}
     ]