From 59a3275ee75fc60bf9aa481608d08d554d6eaf59 Mon Sep 17 00:00:00 2001
From: Alexandre Hamez <alexandre.hamez@gmail.com>
Date: Sat, 4 Jul 2020 17:07:25 +0200
Subject: [PATCH] Add mix task to generate files

---
 .travis.yml                      |  2 --
 README.md                        | 16 +++++++++++++++-
 coveralls.json                   |  3 ++-
 lib/mix/tasks/protox/generate.ex | 25 +++++++++++++++++++++++++
 lib/protox.ex                    | 21 +++++++++++++++++++++
 test/protox_test.exs             | 11 +++++++++++
 6 files changed, 74 insertions(+), 4 deletions(-)
 create mode 100644 lib/mix/tasks/protox/generate.ex

diff --git a/.travis.yml b/.travis.yml
index 020037f8..0aa07b8c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,6 @@
 language: elixir
 matrix:
   include:
-    - elixir: 1.6
-      otp_release: 21.0
     - elixir: 1.7
       otp_release: 22.0
     - elixir: 1.8
diff --git a/README.md b/README.md
index a687eeee..6ca8c46b 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,9 @@ Protox is an Elixir library to work with [Google's Protocol Buffers](https://dev
 
 Generally speaking, a lot of efforts have been put into making sure that the library is reliable (for instance using [property based testing](https://github.com/alfert/propcheck) and by having a [100% code coverage](https://coveralls.io/github/ahamez/protox?branch=master)). Therefore, this library passes all the tests of the conformance checker provided by Google. See [Conformance](#conformance) section for more information.
 
-This library is easy to use: you just point to the `*.proto` files or give the schema to the `Protox` macro, no need to generate any file! Furthermore, it provides a full-blown Elixir experience with protobuf messages. For instance, given the following protobuf `msg.proto` file:
+This library is easy to use: you just point to the `*.proto` files or give the schema to the `Protox` macro, no need to generate any file! However, should you need to generate files, a mix task is available (see [Files generation](#files-generation)).
+
+This library also provides a full-blown Elixir experience with protobuf messages. For instance, given the following protobuf `msg.proto` file:
 ```proto
 syntax = "proto3";
 
@@ -292,6 +294,18 @@ When you encode a message that contains unknown fields, they will be reencoded i
 
 The detailed reference of the generated code is available [here](documentation/reference.md).
 
+## Files generation
+
+It's also possible to generate a file that will contain all code corresponding to the protobuf messages:
+
+```shell
+MIX_ENV=prod mix protox.generate --output-path=/path/to/message.ex --include-path=. test/messages.proto test/samples/proto2.proto
+```
+
+The `--include-path` option is the same as the option described in section [Specify import path](#specify-import-path).
+
+The generated file will be usable in any project as long as protox is declared in the dependancies (the generated file is not a standalone, it still needs function from the protox runtime).
+
 ## Types mapping
 
 The following table shows how Protobuf types are mapped to Elixir's ones.
diff --git a/coveralls.json b/coveralls.json
index 4228d57a..22622d2d 100644
--- a/coveralls.json
+++ b/coveralls.json
@@ -1,6 +1,7 @@
 {
   "skip_files": [
     "conformance",
-    "benchmarks"
+    "benchmarks",
+    "generate.ex"
   ]
 }
diff --git a/lib/mix/tasks/protox/generate.ex b/lib/mix/tasks/protox/generate.ex
new file mode 100644
index 00000000..50ee6ce4
--- /dev/null
+++ b/lib/mix/tasks/protox/generate.ex
@@ -0,0 +1,25 @@
+defmodule Mix.Tasks.Protox.Generate do
+  @moduledoc false
+
+  use Mix.Task
+
+  @impl Mix.Task
+  @spec run(any) :: any
+  def run(args) do
+    with {options, files, []} <-
+           OptionParser.parse(args, strict: [output_path: :string, include_path: :string]),
+         {:ok, output_path} <- Keyword.fetch(options, :output_path),
+         include_path <- Keyword.get(options, :include_path) do
+      generate_code(files, output_path, include_path)
+    else
+      err ->
+        IO.puts("Failed to generate code: #{inspect(err)}")
+        :error
+    end
+  end
+
+  defp generate_code(files, output_path, include_path) do
+    code = Protox.generate_code(files, include_path)
+    File.write!(output_path, code)
+  end
+end
diff --git a/lib/protox.ex b/lib/protox.ex
index 4af00e96..0f41305f 100644
--- a/lib/protox.ex
+++ b/lib/protox.ex
@@ -68,6 +68,27 @@ defmodule Protox do
     end
   end
 
+  def generate_code(files, include_path \\ nil) do
+    path =
+      case include_path do
+        nil -> nil
+        _ -> Path.expand(include_path)
+      end
+
+    {:ok, file_descriptor_set} =
+      files
+      |> Enum.map(&Path.expand/1)
+      |> Protox.Protoc.run(path)
+
+    {enums, messages} = Protox.Parse.parse(file_descriptor_set, nil)
+
+    code = quote do: unquote(Protox.Define.define(enums, messages))
+
+    code_str = Macro.to_string(code)
+
+    ["#", " credo:disable-for-this-file\n", code_str]
+  end
+
   defp make_external_resources(files) do
     Enum.map(files, fn file -> quote(do: @external_resource(unquote(file))) end)
   end
diff --git a/test/protox_test.exs b/test/protox_test.exs
index 8508722d..9f20878c 100644
--- a/test/protox_test.exs
+++ b/test/protox_test.exs
@@ -256,6 +256,17 @@ defmodule ProtoxTest do
     assert msg == msg |> Camel.encode!() |> :binary.list_to_bin() |> Camel.decode!()
   end
 
+  test "Generate code" do
+    file = Path.join(__DIR__, "./samples/prefix/bar/bar.proto")
+    str = Protox.generate_code([file], "./test/samples")
+
+    tmp_dir = System.tmp_dir!()
+    tmp_file = Path.join(tmp_dir, "generated_code.ex")
+    File.write!(tmp_file, str)
+
+    assert Code.compile_file(tmp_file) != []
+  end
+
   @tag conformance: true
   test "Launch conformance" do
     {:ok, _} = File.rm_rf("./failing_tests.txt")