jmitchell · May 10, 2019 20:15 · May 10, 2019
diff --git a/protobuf_regenerate.sh b/protobuf_regenerate.sh
@@ -0,0 +1,25 @@
+#! /usr/bin/env nix-shell
+#! nix-shell -i bash -p elixir_1_8 erlang protobuf curl
+#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-19.03.tar.gz
+
+## Adapted from directions at https://github.com/tony612/protobuf-elixir
+
+# lives at ./script/protobuf_regenerate.sh
+
+set -ex
+
+TARGET_DIR="$(dirname "$0")/../lib"
+SCHEMA_URL="$1"
+SCHEMA_FILE="${TARGET_DIR}/schema.proto"
+
+# install protoc-gen-elixir plugin to ~/.mix/escripts/
+mix escript.install --force hex protobuf
+
+# download protobuf schema
+curl "$SCHEMA_URL" > "$SCHEMA_FILE"
+
+# generate elixir modules
+protoc --proto_path="$TARGET_DIR" \
+       --elixir_out="$TARGET_DIR" \
+       --plugin="protoc-gen-elixir=$HOME/.mix/escripts/protoc-gen-elixir" \
+       "$SCHEMA_FILE"
diff --git a/regenerate.ex b/regenerate.ex
@@ -0,0 +1,29 @@
+# lives at ./lib/mix/tasks/protobuf/regenerate.ex
+
+defmodule Mix.Tasks.Protobuf.Regenerate do
+  use Mix.Task
+
+  @default_schema_url "FIXME"
+
+  @moduledoc """
+  Fetches a protobuf schema and regenerates modules.
+
+      mix protobuf.regenerate [URL]
+
+  The protobuf schema URL is downloaded to ./lib/schema.proto. Then Elixir
+  modules are generated to ./lib/schema.pb.ex.
+
+  When URL is omitted it defaults to #{@default_schema_url}.
+
+  *Notice*: This task assumes the [nix package
+  manager](https://nixos.org/nix/) is installed.
+  """
+
+  @shortdoc "Fetches protobuf schema and regenerates modules."
+  def run([url]) do
+    script_path = Path.join([File.cwd!(), "script", "protobuf_regenerate.sh"])
+    System.cmd(script_path, [url], into: IO.stream(:stdio, :line), stderr_to_stdout: true)
+  end
+
+  def run([]), do: run([@default_schema_url])
+end