json_file is undefined. Use USER_CONFIG

scripts/config/lib/ngx_mruby/headers.rb

@@ -4,7 +4,7 @@ eval(File.read('/app/bin/config/lib/nginx_config_util.rb'))
 USER_CONFIG = "/app/static.json"
 
 config = {}
-config = JSON.parse(File.read(USER_CONFIG)) if File.exist?(json_file)
+config = JSON.parse(File.read(USER_CONFIG)) if File.exist?(USER_CONFIG)
 req    = Nginx::Request.new
 uri    = req.var.uri
 

spec/fixtures/no_config/public_html/index.html

+Hello World

spec/simple_spec.rb

@@ -24,6 +24,16 @@ RSpec.describe "Simple" do
     expect(response.body.chomp).to eq("Hello World")
   end
 
+  describe "no config" do
+    let(:name) { "no_config" }
+
+    it "should serve out of public_html by default" do
+      response = app.get("/")
+      expect(response.code).to eq("200")
+      expect(response.body.chomp).to eq("Hello World")
+    end
+  end
+
   describe "root" do
     let(:name) { "different_root" }