cherry pick fix for mix task (#677)

lib/mix/tasks/absinthe.schema.json.ex

@@ -6,7 +6,6 @@ defmodule Mix.Tasks.Absinthe.Schema.Json do
   @shortdoc "Generate a schema.json file for an Absinthe schema"
 
   @default_filename "./schema.json"
-  @default_codec_name "Poison"
 
   @moduledoc """
   Generate a schema.json file
@@ -15,79 +14,117 @@ defmodule Mix.Tasks.Absinthe.Schema.Json do
 
       absinthe.schema.json [FILENAME] [OPTIONS]
 
+    The JSON codec to be used needs to be included in your `mix.exs` dependencies. If using the default codec,
+    see the Jason [installation instructions](https://hexdocs.pm/jason).
+
   ## Options
 
-      --schema The schema. Default: As configured for `:absinthe` `:schema`
-      --json-codec Sets JSON Codec. Default: #{@default_codec_name}
-      --pretty Whether to pretty-print. Default: false
+  * `--schema` - The name of the `Absinthe.Schema` module defining the schema to be generated.
+     Default: As [configured](https://hexdocs.pm/mix/Mix.Config.html) for `:absinthe` `:schema`
+  * `--json-codec` - Codec to use to generate the JSON file (see [Custom Codecs](#module-custom-codecs)).
+     Default: [`Jason`](https://hexdocs.pm/jason/)
+  * `--pretty` - Whether to pretty-print.
+     Default: `false`
+
 
   ## Examples
 
-  Write to default path `#{@default_filename}` using the `:schema` configured for
-  the `:absinthe` application and the default `#{@default_codec_name}` JSON codec:
+  Write to default path `#{@default_filename}` using the `:schema` configured for the `:absinthe` application:
 
       $ mix absinthe.schema.json
 
-  Write to default path `#{@default_filename}` using the `MySchema` schema and
-  the default `#{@default_codec_name}` JSON codec.
+  Write to default path `#{@default_filename}` using the `MySchema` schema:
 
       $ mix absinthe.schema.json --schema MySchema
 
-  Write to path `/path/to/schema.json` using the `MySchema` schema, using the
-  default `#{@default_codec_name}` JSON codec, and pretty-printing:
+  Write to path `/path/to/schema.json` using the `MySchema` schema, with pretty-printing:
 
       $ mix absinthe.schema.json --schema MySchema --pretty /path/to/schema.json
 
-  Write to default path `#{@default_filename}` using the `MySchema` schema and
-  a custom JSON codec, `MyCodec`:
+  Write to default path `#{@default_filename}` using the `MySchema` schema and a custom JSON codec, `MyCodec`:
 
       $ mix absinthe.schema.json --schema MySchema --json-codec MyCodec
 
+
+  ## Custom Codecs
+
+  Any module that provides `encode!/2` can be used as a custom codec:
+
+      encode!(value, options)
+
+  * `value` will be provided as a Map containing the generated schema.
+  * `options` will be a keyword list with a `:pretty` boolean, indicating whether the user requested pretty-printing.
+
+  The function should return a string to be written to the output file.
+
   """
 
-  @introspection_graphql Path.join([:code.priv_dir(:absinthe), "graphql", "introspection.graphql"])
+  defmodule Options do
+    @moduledoc false
+
+    defstruct filename: nil, schema: nil, json_codec: nil, pretty: false
 
+    @type t() :: %__MODULE__{
+            filename: String.t(),
+            schema: module(),
+            json_codec: module(),
+            pretty: boolean()
+          }
+  end
+
+  @doc "Callback implementation for `Mix.Task.run/1`, which receives a list of command-line args."
+  @spec run(argv :: [binary()]) :: any()
   def run(argv) do
     Application.ensure_all_started(:absinthe)
 
     Mix.Task.run("loadpaths", argv)
     Mix.Project.compile(argv)
 
-    {opts, args, _} = OptionParser.parse(argv)
-
-    schema = find_schema(opts)
-    json_codec = find_json(opts)
-    filename = args |> List.first() || @default_filename
-
-    {:ok, query} = File.read(@introspection_graphql)
-
-    case Absinthe.run(query, schema) do
-      {:ok, result} ->
-        create_directory(Path.dirname(filename))
-        content = json_codec.module.encode!(result, json_codec.opts)
-        create_file(filename, content, force: true)
+    opts = parse_options(argv)
 
-      {:error, error} ->
-        raise error
+    case generate_schema(opts) do
+      {:ok, content} -> write_schema(content, opts.filename)
+      {:error, error} -> raise error
     end
   end
 
-  defp find_json(opts) do
-    case Keyword.get(opts, :json_codec, Poison) do
-      module when is_atom(module) ->
-        %{module: module, opts: codec_opts(module, opts)}
-
-      other ->
-        other
+  @doc false
+  @spec generate_schema(Options.t()) :: String.t()
+  def generate_schema(%Options{
+        pretty: pretty,
+        schema: schema,
+        json_codec: json_codec
+      }) do
+    with {:ok, result} <- Absinthe.Schema.introspect(schema),
+         content <- json_codec.encode!(result, pretty: pretty) do
+      {:ok, content}
+    else
+      {:error, reason} -> {:error, reason}
+      error -> {:error, error}
     end
   end
 
-  defp codec_opts(Poison, opts) do
-    [pretty: Keyword.get(opts, :pretty, false)]
+  @doc false
+  @spec parse_options([String.t()]) :: Options.t()
+  def parse_options(argv) do
+    parse_options = [strict: [schema: :string, json_codec: :string, pretty: :boolean]]
+    {opts, args, _} = OptionParser.parse(argv, parse_options)
+
+    %Options{
+      filename: args |> List.first() || @default_filename,
+      schema: find_schema(opts),
+      json_codec: json_codec_as_atom(opts),
+      pretty: Keyword.get(opts, :pretty, false)
+    }
   end
 
-  defp codec_opts(_, _) do
-    []
+  defp json_codec_as_atom(opts) do
+    opts
+    |> Keyword.fetch(:json_codec)
+    |> case do
+      {:ok, codec} -> Module.concat([codec])
+      _ -> Jason
+    end
   end
 
   defp find_schema(opts) do
@@ -99,4 +136,9 @@ defmodule Mix.Tasks.Absinthe.Schema.Json do
         [value] |> Module.safe_concat()
     end
   end
+
+  defp write_schema(content, filename) do
+    create_directory(Path.dirname(filename))
+    create_file(filename, content, force: true)
+  end
 end

test/mix/tasks/absinthe.schema.json_test.exs

@@ -0,0 +1,76 @@
+defmodule Mix.Tasks.Absinthe.Schema.JsonTest do
+  use Absinthe.Case, async: true
+
+  alias Mix.Tasks.Absinthe.Schema.Json, as: Task
+
+  defmodule TestSchema do
+    use Absinthe.Schema
+
+    query do
+      field :item, :item
+    end
+
+    object :item do
+      description "A Basic Type"
+      field :id, :id
+      field :name, :string
+    end
+  end
+
+  defmodule TestEncoder do
+    def encode!(_map, opts) do
+      pretty_flag = Keyword.get(opts, :pretty, false)
+      pretty_string = if pretty_flag, do: "pretty", else: "ugly"
+      "test-encoder-#{pretty_string}"
+    end
+  end
+
+  @test_schema "Mix.Tasks.Absinthe.Schema.JsonTest.TestSchema"
+  @test_encoder "Mix.Tasks.Absinthe.Schema.JsonTest.TestEncoder"
+
+  describe "absinthe.schema.json" do
+    test "parses options" do
+      argv = ["output.json", "--schema", @test_schema, "--json-codec", @test_encoder, "--pretty"]
+
+      opts = Task.parse_options(argv)
+
+      assert opts.filename == "output.json"
+      assert opts.json_codec == TestEncoder
+      assert opts.pretty == true
+      assert opts.schema == TestSchema
+    end
+
+    test "provides default options" do
+      argv = ["--schema", @test_schema]
+
+      opts = Task.parse_options(argv)
+
+      assert opts.filename == "./schema.json"
+      assert opts.json_codec == Jason
+      assert opts.pretty == false
+      assert opts.schema == TestSchema
+    end
+
+    test "fails if no schema arg is provided" do
+      argv = []
+      catch_error(Task.parse_options(argv))
+    end
+
+    test "fails if codec hasn't been loaded" do
+      argv = ["--schema", @test_schema, "--json-codec", "UnloadedCodec"]
+      opts = Task.parse_options(argv)
+      catch_error(Task.generate_schema(opts))
+    end
+
+    test "can use a custom codec" do
+      argv = ["--schema", @test_schema, "--json-codec", @test_encoder, "--pretty"]
+
+      opts = Task.parse_options(argv)
+      {:ok, pretty_content} = Task.generate_schema(opts)
+      {:ok, ugly_content} = Task.generate_schema(%{opts | pretty: false})
+
+      assert pretty_content == "test-encoder-pretty"
+      assert ugly_content == "test-encoder-ugly"
+    end
+  end
+end