Docs state advantage of protocol consolidation as below:
Consolidation directly links protocols to their implementations in a way that invoking a function from a consolidated protocol is equivalent to invoking two remote functions.
For solving the problem in original post - you have to create the module and encoder in a file say test.ex in lib folder and it will work.
I have the same issue. If I get it right from the Consolidation docs, adding this to the mix.exs file would have fixed the warning:
def project do
...
elixirc_paths: elixirc_paths(Mix.env())
...
end
defp elixirc_paths(:test), do: ["lib", "test/support"]
defp elixirc_paths(_), do: ["lib"]
But I still have it.
Here is how I defined my module and marked the fields to encode:
defmodule Draft.Json.User do
@derive {Jason.Encoder, only: [:name, :email, :age]}
defstruct [:name, :email, :age]
end
And here is a custom encoder module:
defmodule Draft.Json.JsonReader do
alias Draft.Json.User
def to_json(%User{} = user) do
Jason.encode!(user)
end
def to_model(json) do
Jason.decode!(json)
end
end
When starting an IEx session, the warning pooped up as before:
Erlang/OTP 27 [erts-15.0] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit]
warning: the Jason.Encoder protocol has already been consolidated, an implementation for Draft.Json.User has no effect. If you want to implement protocols after compilation or during tests, check the "Consolidation" section in the Protocol module documentation
│
4 │ defstruct [:name, :email, :age]
│ ~~~~~~~~~~~~~~~~~~~~~~~~
│
└─ lib/json/user.ex:4: Draft.Json.User (module)
What am I missing?
Pff, my bad, I named my module in a wrong way, sorry for confusing. It had to be:
defmodule ElixirDraft.Json.JsonReader do
alias ElixirDraft.Json.User
def to_json(%User{} = user) do
Jason.encode!(user)
end
def to_model(json) do
Jason.decode!(json)
end
end
No warnings, it worked as expected :).