Always use Jason to encode/decode JSON

Instead of using `Appsignal.Json` to conditionally pick between
Poison and Jason, adding the complexity of having to install one
of the two alongside AppSignal itself, add Jason as a direct
dependency.

.changesets/always-use-jason-to-encode-json.md

@@ -0,0 +1,6 @@
+---
+bump: "minor"
+type: "change"
+---
+
+Always use Jason to encode JSON. This removes the need to install either Jason or Poison alongside AppSignal, simplifying our installation instructions.

lib/appsignal.ex

@@ -191,7 +191,7 @@ defmodule Appsignal do
   defp fetch_installed_architecture_target do
     case File.read(Path.join([:code.priv_dir(:appsignal), "install.report"])) do
       {:ok, raw_report} ->
-        case Appsignal.Json.decode(raw_report) do
+        case Jason.decode(raw_report) do
           {:ok, report} ->
             %{"build" => %{"architecture" => arch, "target" => target}} = report
             {parse_architecture(arch), target}

lib/appsignal/diagnose/agent.ex

@@ -9,7 +9,7 @@ defmodule Appsignal.Diagnose.Agent do
     if @nif.loaded?() do
       report_string = to_string(@nif.diagnose)
 
-      case Appsignal.Json.decode(report_string) do
+      case Jason.decode(report_string) do
         {:ok, report} -> {:ok, report}
         {:error, _} -> {:error, report_string}
       end

lib/appsignal/diagnose/report.ex

@@ -19,14 +19,14 @@ defmodule Appsignal.Diagnose.Report do
       })
 
     url = "#{config[:diagnose_endpoint]}?#{params}"
-    body = Appsignal.Json.encode!(%{diagnose: report})
+    body = Jason.encode!(%{diagnose: report})
     headers = [{"Content-Type", "application/json; charset=UTF-8"}]
 
     case Transmitter.request(:post, url, headers, body) do
       {:ok, 200, _, reference} ->
         {:ok, body} = :hackney.body(reference)
 
-        case Appsignal.Json.decode(body) do
+        case Jason.decode(body) do
           {:ok, response} -> {:ok, response["token"]}
           {:error, _} -> {:error, %{status_code: 200, body: body}}
         end

lib/appsignal/span.ex

@@ -343,6 +343,6 @@ defmodule Appsignal.Span do
   @doc false
   def to_map(%Span{reference: reference}) do
     {:ok, json} = Nif.span_to_json(reference)
-    Appsignal.Json.decode!(json)
+    Jason.decode!(json)
   end
 end

lib/mix/tasks/appsignal.diagnose.ex

@@ -126,7 +126,7 @@ defmodule Mix.Tasks.Appsignal.Diagnose do
   defp do_fetch_installation_report(file) do
     case File.read(Path.join([:code.priv_dir(:appsignal), "#{file}.report"])) do
       {:ok, raw_report} ->
-        case Appsignal.Json.decode(raw_report) do
+        case Jason.decode(raw_report) do
           {:ok, report} ->
             {:ok, report}
 

mix.exs

@@ -108,12 +108,6 @@ defmodule Appsignal.Mixfile do
         false -> "1.18.1"
       end
 
-    poison_version =
-      case Version.compare(system_version, "1.6.0") do
-        :lt -> ">= 1.3.0 and < 4.0.0"
-        _ -> ">= 1.3.0"
-      end
-
     decorator_version =
       case Version.compare(system_version, "1.5.0") do
         :lt -> "~> 1.2.3"
@@ -142,8 +136,7 @@ defmodule Appsignal.Mixfile do
       {:decimal, "~> 2.0"},
       {:benchee, "~> 1.0", only: :bench},
       {:hackney, hackney_version},
-      {:jason, "~> 1.0", optional: true},
-      {:poison, poison_version, optional: true},
+      {:jason, "~> 1.0"},
       {:decorator, decorator_version},
       {:plug, plug_version, only: [:test, :test_no_nif]},
       {:plug_cowboy, "~> 1.0", only: [:test, :test_no_nif]},

mix_helpers.exs

@@ -612,38 +612,8 @@ defmodule Mix.Appsignal.Helper do
     # Write nothing if no download details are recorded in the report
   end
 
-  cond do
-    Code.ensure_loaded?(Jason) ->
-      defp json_encoder, do: {:ok, Jason}
-
-    Code.ensure_loaded?(Poison) ->
-      defp json_encoder, do: {:ok, Poison}
-
-    true ->
-      defp json_encoder do
-        {:error,
-         """
-         No JSON encoder found. Please add jason to your list of dependencies in mix.exs:
-
-             def deps do
-               [
-                 {:appsignal, "~> 1.0"},
-                 {:jason, "~> 1.1"}
-               ]
-             end
-         """}
-      end
-  end
-
-  defp encode_report_file(report) do
-    case json_encoder() do
-      {:ok, encoder} -> encoder.encode(report)
-      {:error, reason} -> {:error, reason}
-    end
-  end
-
   defp write_report_file(file, report) do
-    case encode_report_file(report) do
+    case Jason.encode(report) do
       {:ok, body} ->
         File.mkdir_p!(priv_dir())