Only load JSON logic if JSON module is loaded

lib/tesla/middleware/json/json_adapter.ex

@@ -1,16 +1,18 @@
-defmodule Tesla.Middleware.JSON.JSONAdapter do
-  @moduledoc false
-  # An adapter for Elixir's built-in JSON module introduced in Elixir 1.18
-  # that adjusts for Tesla's assumptions about a JSON engine, which are not satisfied by
-  # Elixir's JSON module. The assumptions are:
-  # - the module provides encode/2 and decode/2 functions
-  # - the 2nd argument to the functions is opts
-  # - the functions return {:ok, json} or {:error, reason} - not the case for JSON.encode!/2
-  #
-  # We do not support custom encoders and decoders.
-  # The purpose of this adapter is to allow `engine: JSON` to be set easily. If more advanced
-  # customization is required, the `:encode` and `:decode` functions can be supplied to the
-  # middleware instead of the `:engine` option.
-  def encode(data, _opts), do: {:ok, JSON.encode!(data)}
-  def decode(binary, _opts), do: JSON.decode(binary)
+if Code.ensure_loaded?(JSON) do
+  defmodule Tesla.Middleware.JSON.JSONAdapter do
+    @moduledoc false
+    # An adapter for Elixir's built-in JSON module introduced in Elixir 1.18
+    # that adjusts for Tesla's assumptions about a JSON engine, which are not satisfied by
+    # Elixir's JSON module. The assumptions are:
+    # - the module provides encode/2 and decode/2 functions
+    # - the 2nd argument to the functions is opts
+    # - the functions return {:ok, json} or {:error, reason} - not the case for JSON.encode!/2
+    #
+    # We do not support custom encoders and decoders.
+    # The purpose of this adapter is to allow `engine: JSON` to be set easily. If more advanced
+    # customization is required, the `:encode` and `:decode` functions can be supplied to the
+    # middleware instead of the `:engine` option.
+    def encode(data, _opts), do: {:ok, JSON.encode!(data)}
+    def decode(binary, _opts), do: JSON.decode(binary)
+  end
 end

test/tesla/middleware/json/json_adapter_test.exs

@@ -1,21 +1,23 @@
-defmodule Tesla.Middleware.JSON.JSONAdapterTest do
-  use ExUnit.Case, async: true
+if Code.ensure_loaded?(JSON) do
+  defmodule Tesla.Middleware.JSON.JSONAdapterTest do
+    use ExUnit.Case, async: true
 
-  alias Tesla.Middleware.JSON.JSONAdapter
+    alias Tesla.Middleware.JSON.JSONAdapter
 
-  describe "encode/2" do
-    test "encodes as expected with default encoder" do
-      assert {:ok, ~S({"hello":"world"})} == JSONAdapter.encode(%{hello: "world"}, [])
+    describe "encode/2" do
+      test "encodes as expected with default encoder" do
+        assert {:ok, ~S({"hello":"world"})} == JSONAdapter.encode(%{hello: "world"}, [])
+      end
     end
-  end
 
-  describe "decode/2" do
-    test "returns {:ok, term} on success" do
-      assert {:ok, %{"hello" => "world"}} = JSONAdapter.decode(~S({"hello":"world"}), [])
-    end
+    describe "decode/2" do
+      test "returns {:ok, term} on success" do
+        assert {:ok, %{"hello" => "world"}} = JSONAdapter.decode(~S({"hello":"world"}), [])
+      end
 
-    test "returns {:error, reason} on failure" do
-      assert {:error, {:invalid_byte, _, _}} = JSONAdapter.decode("invalid_json", [])
+      test "returns {:error, reason} on failure" do
+        assert {:error, {:invalid_byte, _, _}} = JSONAdapter.decode("invalid_json", [])
+      end
     end
   end
 end