Syntax-check go with a standalone script

lib/language/go.rb

@@ -24,18 +24,11 @@ def solution_dump(attributes)
   end
 
   def parsing?(code)
-    return true if code.empty?
     TempDir.for('code.go' => code) do |dir|
-      code_path = dir.join('code.go')
-      build_result = nil
-      gofmt_result = nil
+      script_path = Rails.root.join('lib/language/go/syntax_check.rb')
+      code_path   = dir.join('code.go')
 
-      FileUtils.cd(dir) do
-        build_result = `go build #{code_path} 2>&1`
-        gofmt_result = `gofmt -d #{code_path} 2>&1`
-      end
-
-      build_result.strip.empty? and gofmt_result.strip.empty?
+      system script_path.to_s, code_path.to_s
     end
   end
 

lib/language/go/syntax_check.rb

@@ -0,0 +1,31 @@
+#! /usr/bin/env ruby
+
+require 'tmpdir'
+
+code = ARGF.read
+
+exit 0 if code.empty?
+
+if code !~ /^\s*func\s+main\(\s*\)/
+  code += "\nfunc main() {\n}\n"
+end
+
+build_result = nil
+gofmt_result = nil
+
+Dir.mktmpdir do |dir|
+  FileUtils.cd(dir) do
+    File.open('code.go', 'w') do |f|
+      f.write(code)
+    end
+
+    build_result = `go build code.go 2>&1`
+    gofmt_result = `gofmt -d code.go 2>&1`
+  end
+end
+
+if build_result.strip.empty? and gofmt_result.strip.empty?
+  exit 0
+else
+  exit 1
+end

spec/lib/language/parsing_go_code_spec.rb

@@ -41,6 +41,12 @@
 CODE
   end
 
+  it "returns true for valid code without a main function" do
+    Language::Go.should be_parsing <<CODE
+package main
+CODE
+  end
+
   it "returns true for no code" do
     Language::Go.should be_parsing ""
   end