feat: pass through hot: only to webpack-dev-server (#378)

* feat: pass through `hot: only` to `webpack-dev-server`

* chore: changelog

* add test

Author: SimenB

CHANGELOG.md

@@ -11,6 +11,7 @@ _Please add entries here for your pull requests that are not yet released._
 
 ### Added
 - Experimental support for other JS package managers using `package_json` gem [PR 349](https://github.com/shakacode/shakapacker/pull/349) by [G-Rath](https://github.com/g-rath).
+- Support `hmr: only` configuration [PR 378](https://github.com/shakacode/shakapacker/pull/378) by [SimenB](https://github.com/SimenB).
 
 ### Fixed
 - Recommend `server` option instead of deprecated `https` option when `--https` is provided [PR 380](https://github.com/shakacode/shakapacker/pull/380) by [G-Rath](https://github.com/g-rath)

lib/shakapacker/dev_server_runner.rb

@@ -87,6 +87,8 @@ def execute_cmd
         cmd += ["--progress", "--color"] if @pretty
 
         cmd += ["--hot"] if @hot
+        cmd += ["only"] if @hot == "only"
+
         cmd += @argv
 
         Dir.chdir(@app_path) do

spec/shakapacker/dev_server_runner_spec.rb

@@ -173,6 +173,22 @@
       verify_command(cmd)
     end
 
+    it "supports --hot being 'only'" do
+      cmd = ["#{test_app_path}/node_modules/.bin/webpack", "serve", "--config", "#{test_app_path}/config/webpack/webpack.config.js", "--hot", "only"]
+
+      allow(Shakapacker::DevServer).to receive(:new).and_return(
+        double(
+          host: "localhost",
+          port: "3035",
+          pretty?: false,
+          protocol: "http",
+          hmr?: "only"
+        )
+      )
+
+      verify_command(cmd)
+    end
+
     it "accepts environment variables" do
       cmd = ["#{test_app_path}/node_modules/.bin/webpack", "serve", "--config", "#{test_app_path}/config/webpack/webpack.config.js"]
       env = Shakapacker::Compiler.env.dup