Provide ability to ignore custom Jason.Encoder implementations

README.md

@@ -27,7 +27,7 @@ Logger.info(event: %{name: :stuff, safe: false}, user: %User{id: 123})
 
 Outputs nested JSON like this:
 
-```
+```json
 {
   "level":"info",
   "message":{
@@ -92,7 +92,7 @@ If you're using Ecto, you should disable the default logger:
 config :my_app, MyApp.Repo, log: false
 ```
 
-Now replace it with a simple `:telemetry`-based handler that logs structured
+Now replace it with a simple [telemetry](https://hexdocs.pm/telemetry/readme.html)-based handler that logs structured
 queries with metadata:
 
 ```elixir
@@ -108,6 +108,7 @@ end
 ```
 
 And attach:
+
 ```elixir
 :telemetry.attach(
   "ecto-logger",
@@ -117,6 +118,14 @@ And attach:
 )
 ```
 
+Structs that implement [Jason.Encoder](https://hexdocs.pm/jason/Jason.Encoder.html) will use that protocol.
+If any implementation is undesirable, as is the case with `Ecto.Association.NotLoaded`
+and `Ecto.Schema.Metadata` which both raise errors as of `3.12.3`, it can be disabled at runtime.
+
+```elixir
+config, :medea, except: [Ecto.Association.NotLoaded, Ecto.Schema.Metadata]
+```
+
 Additional documentation can be found at [https://hexdocs.pm/medea](https://hexdocs.pm/medea).
 
 [form]: https://hexdocs.pm/logger/Logger.Formatter.html

lib/medea/utils.ex

@@ -9,12 +9,12 @@ defmodule Medea.Utils do
   def clean(%Time{} = time), do: time
 
   # Structs should implement Jason.Encoder
-  def clean(%_{} = struct) do
-    if Encoder.Any != Encoder.impl_for(struct) do
-      map = clean_struct(struct)
-      struct!(struct, map)
-    else
+  def clean(%module{} = struct) do
+    if Encoder.Any == Encoder.impl_for(struct) or
+         module in Application.get_env(:medea, :except, []) do
       clean_struct(struct)
+    else
+      struct!(struct, clean_struct(struct))
     end
   end
 

test/medea/translator_test.exs

@@ -8,13 +8,19 @@ defmodule Medea.TranslatorTest do
   require Protocol
 
   defmodule Struct do
-    @moduledoc false
-
     defstruct id: 1,
               private: %{data: :hidden},
               public: %{data: :visible}
   end
 
+  defmodule RaiseStruct do
+    defimpl Jason.Encoder do
+      def encode(_, _), do: raise("error")
+    end
+
+    defstruct key: :value
+  end
+
   describe "translate/4" do
     property "all terms are safely encoded to iodata" do
       check all message <- message() do
@@ -38,6 +44,15 @@ defmodule Medea.TranslatorTest do
       assert ~s({"id":1,"public":{"data":"visible"}}) == IO.chardata_to_string(iodata)
     end
 
+    test "custom implementations can be ignored" do
+      Application.put_env(:medea, :except, [RaiseStruct])
+
+      assert {:ok, iodata} =
+               Translator.translate(:info, :info, :report, {:logger, %RaiseStruct{}})
+
+      assert ~s({"key":"value"}) == IO.chardata_to_string(iodata)
+    end
+
     test "all non-logger formats or reports are ignored" do
       assert :none = Translator.translate(:info, :info, :report, {:not, :from, :logger})
     end