Move compiler configuration into configuration class (#374)

* Add test for config.asset_host
* Add test for config.relative_url_root
* Isolate env variables for the tests
* Refactor and ease the usage of temporary env variables in test

lib/shakapacker/compiler.rb

@@ -106,9 +106,11 @@ def webpack_env
 
       Shakapacker.set_shakapacker_env_variables_for_backward_compatibility
 
-      env.merge("SHAKAPACKER_ASSET_HOST"        => ENV.fetch("SHAKAPACKER_ASSET_HOST", ActionController::Base.helpers.compute_asset_host),
-                "SHAKAPACKER_RELATIVE_URL_ROOT" => ENV.fetch("SHAKAPACKER_RELATIVE_URL_ROOT", ActionController::Base.relative_url_root),
-                "SHAKAPACKER_CONFIG" => instance.config_path.to_s)
+      env.merge(
+        "SHAKAPACKER_ASSET_HOST"        => instance.config.asset_host,
+        "SHAKAPACKER_RELATIVE_URL_ROOT" => instance.config.relative_url_root,
+        "SHAKAPACKER_CONFIG"            => instance.config_path.to_s
+      )
     end
 
     def bin_shakapacker_path

lib/shakapacker/configuration.rb

@@ -116,6 +116,14 @@ def fetch(key)
     data.fetch(key, defaults[:shakapacker_precompile])
   end
 
+  def asset_host
+    ENV.fetch("SHAKAPACKER_ASSET_HOST", ActionController::Base.helpers.compute_asset_host)
+  end
+
+  def relative_url_root
+    ENV.fetch("SHAKAPACKER_RELATIVE_URL_ROOT", ActionController::Base.relative_url_root)
+  end
+
   private
     def data
       @data ||= load

spec/shakapacker/compiler_spec.rb

@@ -50,10 +50,14 @@
     expect(Shakapacker.compiler.send(:webpack_env)["SHAKAPACKER_ASSET_HOST"]).to be nil
     expect(Shakapacker.compiler.send(:webpack_env)["SHAKAPACKER_RELATIVE_URL_ROOT"]).to be nil
 
-    ENV["SHAKAPACKER_ASSET_HOST"] = "foo.bar"
-    ENV["SHAKAPACKER_RELATIVE_URL_ROOT"] = "/baz"
-
-    expect(Shakapacker.compiler.send(:webpack_env)["SHAKAPACKER_ASSET_HOST"]).to eq "foo.bar"
-    expect(Shakapacker.compiler.send(:webpack_env)["SHAKAPACKER_RELATIVE_URL_ROOT"]).to eq "/baz"
+    custom_env_variables = {
+      "SHAKAPACKER_ASSET_HOST" => "foo.bar",
+      "SHAKAPACKER_RELATIVE_URL_ROOT" => "/baz"
+    }
+
+    with_env_variable(custom_env_variables) do
+      expect(Shakapacker.compiler.send(:webpack_env)["SHAKAPACKER_ASSET_HOST"]).to eq "foo.bar"
+      expect(Shakapacker.compiler.send(:webpack_env)["SHAKAPACKER_RELATIVE_URL_ROOT"]).to eq "/baz"
+    end
   end
 end

spec/shakapacker/configuration_spec.rb

@@ -330,4 +330,52 @@
       expect(actual).to eq(expected)
     end
   end
+
+  describe "#asset_host" do
+    let(:config) do
+      Shakapacker::Configuration.new(
+        root_path: ROOT_PATH,
+        config_path: Pathname.new(File.expand_path("./test_app/config/shakapacker.yml", __dir__)),
+        env: "production"
+      )
+    end
+
+    it "returns the value of SHAKAPACKER_ASSET_HOST if set" do
+      with_env_variable("SHAKAPACKER_ASSET_HOST" => "custom_host.abc") do
+        expect(config.asset_host).to eq "custom_host.abc"
+      end
+    end
+
+    it "returns ActionController::Base.helpers.compute_asset_host if SHAKAPACKER_ASSET_HOST is not set" do
+      allow(ActionController::Base.helpers).to receive(:compute_asset_host).and_return("domain.abc")
+
+      with_env_variable("SHAKAPACKER_ASSET_HOST" => nil) do
+        expect(config.asset_host).to eq "domain.abc"
+      end
+    end
+  end
+
+  describe "#relative_url_root" do
+    let(:config) do
+      Shakapacker::Configuration.new(
+        root_path: ROOT_PATH,
+        config_path: Pathname.new(File.expand_path("./test_app/config/shakapacker.yml", __dir__)),
+        env: "production"
+      )
+    end
+
+    it "returns the value of SHAKAPACKER_RELATIVE_URL_ROOT if set" do
+      with_env_variable("SHAKAPACKER_RELATIVE_URL_ROOT" => "custom_value") do
+        expect(config.relative_url_root).to eq "custom_value"
+      end
+    end
+
+    it "returns ActionController::Base.helpers.compute_asset_host if SHAKAPACKER_RELATIVE_URL_ROOT is not set" do
+      allow(ActionController::Base).to receive(:relative_url_root).and_return("abcd")
+
+      with_env_variable("SHAKAPACKER_RELATIVE_URL_ROOT" => nil) do
+        expect(config.relative_url_root).to eq "abcd"
+      end
+    end
+  end
 end

spec/shakapacker/spec_helper_initializer.rb

@@ -22,3 +22,21 @@ def with_rails_env(env)
   Rails.env = ActiveSupport::StringInquirer.new(original)
   reloaded_config
 end
+
+# Temportarily set env variables to a custom value
+# arg: a hash with key:value for each custom env
+#      Keys could be string or symbol
+def with_env_variable(custom_env_hash)
+  original_env = {}
+  custom_env_hash.each do |key, new_value|
+    upcased_key = key.to_s.upcase
+    original_env[upcased_key] = new_value
+    ENV[upcased_key] = new_value
+  end
+
+  yield
+ensure
+  original_env.each do |key, original_value|
+    ENV[key] = original_value
+  end
+end