Add helper to insert values into context

[jayjun]

Absinthe.Plug.put_options(conn, context: context) overwrites any previously set context.

This pull request adds assign_context which merges values instead. This allows multiple plugs that configure context to be composed.

conn
|> Absinthe.Plug.assign_context(current_user: current_user)
|> Absinthe.Plug.assign_context(foo: "bar")

I considered naming it put_in_context but conventionally put and put_in functions do not merge. Phoenix’s assign appears closest in behaviour.

[benwilson512]

The merge order here is probably counter to what you want. assigns should be merged into the current context not the other way around, so that if you do want to override an existing assign it works as expected.

Suggested change

	context =
	absinthe
	|> Map.get(:context, %{})
	|> Map.merge(Enum.into(assigns, %{}))
	context =
	assigns
	|> Map.new
	|> Map.merge(Map.get(absinthe, :assigns, %{}))

[jayjun]

My understanding is that right wins.

iex> Map.merge(%{foo: "bar"}, %{foo: "baz"})      
%{foo: "baz"}

So the current code un-pipelined

context = Map.get(absinthe, :context, %{})
context = Map.merge(context, Map.new(assigns))

looks correct to me.

[benwilson512]

You are correct! I got Map.merge and Enum.into backwards, my bad!

[benwilson512]

This is a great idea, just a couple of changes and we'll have it merged in, thank you!

[benwilson512]

Suggested change

	put_options(conn, context: Enum.into(assigns, %{}))
	put_options(conn, context: Map.new(assigns))

[jayjun]

Done! put_options itself needs the same change. Let me know if you want those included here.

[benwilson512]

Can you add a test case that tests assigning a value that is already assigned?

[jayjun]

Done.

[jeroenvisser101]

@benwilson512 are you planning to released this in 1.5.1(-rc)? We'd love to use this :)