diff --git a/.credo.exs b/.credo.exs
index 74864ac4..f7a2bbb3 100644
--- a/.credo.exs
+++ b/.credo.exs
@@ -61,7 +61,9 @@
 
         {Credo.Check.Readability.FunctionNames},
         {Credo.Check.Readability.LargeNumbers},
-        {Credo.Check.Readability.MaxLineLength, priority: :low, max_length: 80},
+        {Credo.Check.Readability.MaxLineLength,
+         priority: :low, max_length: 80, ignore_specs: true
+        },
         {Credo.Check.Readability.ModuleAttributeNames},
         {Credo.Check.Readability.ModuleDoc},
         {Credo.Check.Readability.ModuleNames},
@@ -70,7 +72,7 @@
         {Credo.Check.Readability.PredicateFunctionNames},
         {Credo.Check.Readability.PreferImplicitTry},
         {Credo.Check.Readability.RedundantBlankLines},
-        {Credo.Check.Readability.Specs},
+        {Credo.Check.Readability.Specs, false},
         {Credo.Check.Readability.StringSigils},
         {Credo.Check.Readability.TrailingBlankLine},
         {Credo.Check.Readability.TrailingWhiteSpace},
diff --git a/.gitignore b/.gitignore
index 77a9c54a..1a813296 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,3 +24,4 @@ cover
 /priv/build
 /tmp
 .esm-cache
+.elixir_ls
diff --git a/lib/elixir_script/beam.ex b/lib/elixir_script/beam.ex
index 254cb803..4473f221 100644
--- a/lib/elixir_script/beam.ex
+++ b/lib/elixir_script/beam.ex
@@ -7,7 +7,7 @@ defmodule ElixirScript.Beam do
   For protocols, this will return a list of
   all the protocol implementations
   """
-  @spec debug_info(atom | bitstring) :: {:ok | :error, map | binary}
+  @spec debug_info(atom | bitstring) :: {:ok, map} | {:ok, atom, map, list} | {:error, binary}
   def debug_info(module)
 
   # We get debug info from String and then replace
@@ -59,7 +59,7 @@ defmodule ElixirScript.Beam do
           {:ok, {^module, attribute_info}} = :beam_lib.chunks(beam, [:attributes]) do
 
           if Keyword.get(attribute_info[:attributes], :protocol) do
-            get_protocol_implementations(module)
+            get_protocol_implementations(module, beam_path)
           else
             backend.debug_info(:elixir_v1, module, data, [])
             |> process_debug_info(beam_path)
@@ -89,6 +89,8 @@ defmodule ElixirScript.Beam do
         Map.put(info, :last_modified, nil)
     end
 
+    info = Map.put(info, :beam_path, beam_path)
+
     {:ok, info}
   end
 
@@ -96,7 +98,9 @@ defmodule ElixirScript.Beam do
     error
   end
 
-  defp get_protocol_implementations(module) do
+  defp get_protocol_implementations(module, beam_path) do
+    {:ok, protocol_module_info} = process_debug_info({:ok, %{}}, beam_path)
+
     implementations = module
     |> Protocol.extract_impls(:code.get_path())
     |> Enum.map(fn(x) -> Module.concat([module, x]) end)
@@ -109,7 +113,7 @@ defmodule ElixirScript.Beam do
       end
     end)
 
-    {:ok, module, implementations}
+    {:ok, module, protocol_module_info, implementations}
   end
 
   defp replace_definitions(original_definitions, replacement_definitions) do
diff --git a/lib/elixir_script/compiler.ex b/lib/elixir_script/compiler.ex
index ba0f869b..0621238e 100644
--- a/lib/elixir_script/compiler.ex
+++ b/lib/elixir_script/compiler.ex
@@ -31,12 +31,12 @@ defmodule ElixirScript.Compiler do
     Translate,
     FindUsedModules,
     FindUsedFunctions,
-    Output
+    Output,
   }
   alias ElixirScript.ModuleSystems.ES
   alias Kernel.ParallelCompiler
 
-  @spec compile(atom | [atom] | binary, []) :: nil
+  @spec compile(atom | [atom] | binary, []) :: map
   def compile(path, opts \\ [])
 
   def compile(path, opts) when is_binary(path) do
@@ -86,7 +86,7 @@ defmodule ElixirScript.Compiler do
 
     State.stop(pid)
 
-    result
+    transform_output(modules, result, opts)
   end
 
   defp build_compiler_options(opts) do
@@ -103,4 +103,25 @@ defmodule ElixirScript.Compiler do
   defp on_module_compile(pid, _file, module, beam) do
     State.put_in_memory_module(pid, module, beam)
   end
+
+  defp transform_output(modules, compiled_js, opts) do
+    output_path = if opts.output == nil or opts.output == :stdout do
+     ""
+    else
+      Path.dirname(opts.output)
+    end
+
+    Enum.reduce(modules, %{}, fn {module, info}, current_data ->
+      info = %{
+        references: info.used_modules,
+        last_modified: info.last_modified,
+        beam_path: Map.get(info, :beam_path),
+        source: Map.get(info, :file),
+        js_path: Path.join(output_path, "#{module}.js"),
+        js_code: Keyword.get(compiled_js, module)
+      }
+
+      Map.put(current_data, module, info)
+    end)
+  end
 end
diff --git a/lib/elixir_script/manifest.ex b/lib/elixir_script/manifest.ex
new file mode 100644
index 00000000..5ed1915f
--- /dev/null
+++ b/lib/elixir_script/manifest.ex
@@ -0,0 +1,21 @@
+defmodule ElixirScript.Manifest do
+  @moduledoc false
+
+  @spec read_manifest(binary) :: nil
+  def read_manifest(_manifest) do
+
+  end
+
+  @spec write_manifest(binary, map) :: :ok
+  def write_manifest(manifest_path, modules) do
+    data = Enum.reduce(modules, %{}, fn {module, info}, current_data ->
+      Map.put(current_data, module, Map.drop(info, [:js_code]))
+    end)
+
+    data = :erlang.term_to_binary(data, [:compressed])
+    File.mkdir_p!(Path.dirname(manifest_path))
+    File.write!(manifest_path, data)
+
+    :ok
+  end
+end
diff --git a/lib/elixir_script/passes/find_used_modules.ex b/lib/elixir_script/passes/find_used_modules.ex
index ae75d9e6..d738a006 100644
--- a/lib/elixir_script/passes/find_used_modules.ex
+++ b/lib/elixir_script/passes/find_used_modules.ex
@@ -6,7 +6,7 @@ defmodule ElixirScript.FindUsedModules do
   @doc """
   Takes a list of entry modules and finds modules they use.
   """
-  @spec execute([atom], pid) :: nil
+  @spec execute([atom], pid) :: :ok
   def execute(modules, pid) do
     modules
     |> List.wrap
@@ -26,8 +26,8 @@ defmodule ElixirScript.FindUsedModules do
     case result do
       {:ok, info} ->
         walk_module(module, info, pid)
-      {:ok, module, implementations} ->
-        walk_protocol(module, implementations, pid)
+      {:ok, module, module_info, implementations} ->
+        walk_protocol(module, module_info, implementations, pid)
       {:error, "Unknown module"} ->
         Logger.warn fn() ->
           "ElixirScript: #{inspect module} is missing or unavailable"
@@ -83,7 +83,7 @@ defmodule ElixirScript.FindUsedModules do
     end)
   end
 
-  defp walk_protocol(module, implementations, pid) do
+  defp walk_protocol(module, module_info, implementations, pid) do
     impls = Enum.map(implementations, fn {impl, %{attributes: attrs}} ->
       protocol_impl = Keyword.fetch!(attrs, :protocol_impl)
       impl_for = Keyword.fetch!(protocol_impl, :for)
@@ -94,7 +94,12 @@ defmodule ElixirScript.FindUsedModules do
 
     functions = Enum.map(first_implementation_functions, fn { name, _, _, _} -> name end)
 
-    ModuleState.put_module(pid, module, %{protocol: true, impls: impls, functions: functions})
+    module_info = Map.merge(
+      module_info,
+      %{protocol: true, impls: impls, functions: functions}
+    )
+
+    ModuleState.put_module(pid, module, module_info)
 
     Enum.each(implementations, fn {impl, info} ->
       ModuleState.add_used_module(pid, module, impl)
@@ -303,15 +308,14 @@ defmodule ElixirScript.FindUsedModules do
   end
 
   defp walk({:., _, [module, function]}, state) do
-    cond do
-      ElixirScript.Translate.Module.is_elixir_module(module) ->
-        ModuleState.add_used_module(state.pid, state.module, module)
-        if ModuleState.get_module(state.pid, module) == nil do
-          do_execute(module, state.pid)
-        end
-      true ->
-        walk(module, state)
-        walk(function, state)
+    if ElixirScript.Translate.Module.is_elixir_module(module) do
+      ModuleState.add_used_module(state.pid, state.module, module)
+      if ModuleState.get_module(state.pid, module) == nil do
+        do_execute(module, state.pid)
+      end
+    else
+      walk(module, state)
+      walk(function, state)
     end
   end
 
diff --git a/lib/elixir_script/passes/output.ex b/lib/elixir_script/passes/output.ex
index baaf05ba..26ccc96b 100644
--- a/lib/elixir_script/passes/output.ex
+++ b/lib/elixir_script/passes/output.ex
@@ -7,9 +7,9 @@ defmodule ElixirScript.Output do
   @doc """
   Takes outputs the JavaScript code in the specified output
   """
-  @spec execute([atom], pid, map) :: nil
+  @spec execute([atom], pid, map) :: [{atom, binary}]
   def execute(modules, pid, opts) do
-    modules = modules
+    prepared_modules = modules
     |> Enum.filter(fn {_, info} -> Map.has_key?(info, :js_ast) end)
     |> Enum.map(fn {module, info} ->
         {module, info.js_ast, info.used_modules}
@@ -27,8 +27,7 @@ defmodule ElixirScript.Output do
         {module, name, path, import_path}
     end)
 
-    modules
-    |> create_modules(opts, js_modules)
+    create_modules(prepared_modules, opts, js_modules)
   end
 
   defp concat(code) do
@@ -39,17 +38,6 @@ defmodule ElixirScript.Output do
     """
   end
 
-  defp prepare_js_ast(js_ast) do
-    case js_ast do
-      modules when is_list(modules) ->
-        modules
-        |> Enum.reduce([], &(&2 ++ &1.body))
-        |> Builder.program
-      _ ->
-        js_ast
-    end
-  end
-
   defp create_modules(modules, opts, js_modules) do
     modules
     |> Task.async_stream(fn({module, [body, exports], used_modules}) ->
@@ -62,7 +50,6 @@ defmodule ElixirScript.Output do
 
       js_parts
       |> Builder.program
-      |> prepare_js_ast
       |> Generator.generate
       |> concat
       |> output(module, Map.get(opts, :output), js_modules)
@@ -84,12 +71,10 @@ defmodule ElixirScript.Output do
     |> String.replace(".", "$")
   end
 
-  defp output(code, _, nil, _) do
-     code
-  end
-
-  defp output(code, _, :stdout, _) do
+  defp output(code, module, nil, _), do: {module, code}
+  defp output(code, module, :stdout, _) do
     IO.puts(code)
+    {module, code}
   end
 
   defp output(code, module, path, js_modules) do
@@ -112,6 +97,8 @@ defmodule ElixirScript.Output do
 
     copy_bootstrap_js(output_dir)
     File.write!(file_name, code)
+
+    {module, code}
   end
 
   defp copy_bootstrap_js(directory) do
diff --git a/lib/mix/tasks/compile.elixir_script.ex b/lib/mix/tasks/compile.elixir_script.ex
index 617a92e4..cdb05da9 100644
--- a/lib/mix/tasks/compile.elixir_script.ex
+++ b/lib/mix/tasks/compile.elixir_script.ex
@@ -1,7 +1,10 @@
 defmodule Mix.Tasks.Compile.ElixirScript do
   use Mix.Task
+  alias ElixirScript.Manifest
 
   @recursive true
+  @manifest ".compile.elixir_script"
+  @manifest_vsn 1
 
   @moduledoc """
   Mix compiler to allow mix to compile Elixirscript source files into JavaScript
@@ -41,13 +44,18 @@ defmodule Mix.Tasks.Compile.ElixirScript do
 
   defp do_compile() do
     {input, opts} = get_compiler_params()
-    ElixirScript.Compiler.compile(input, opts)
+    result = ElixirScript.Compiler.compile(input, opts)
+
+    Manifest.write_manifest(manifest(), result)
   end
 
   def clean do
     :ok
   end
 
+  def manifests, do: [manifest()]
+  defp manifest, do: Path.join(Mix.Project.manifest_path(), @manifest)
+
   @doc false
   def get_compiler_params() do
     elixirscript_config = get_elixirscript_config()
diff --git a/test/beam_test.exs b/test/beam_test.exs
index bc6671a3..66369a94 100644
--- a/test/beam_test.exs
+++ b/test/beam_test.exs
@@ -10,6 +10,6 @@ defmodule ElixirScript.Beam.Test do
   end
 
   test "can get ast from beam that is protocol" do
-    assert {:ok, Enumerable, _} = ElixirScript.Beam.debug_info(Enumerable)
+    assert {:ok, Enumerable, _, _} = ElixirScript.Beam.debug_info(Enumerable)
   end
 end
diff --git a/test/compiler_test.exs b/test/compiler_test.exs
index b4d82ec5..439975f5 100644
--- a/test/compiler_test.exs
+++ b/test/compiler_test.exs
@@ -3,17 +3,17 @@ defmodule ElixirScript.Compiler.Test do
 
   test "Can compile one entry module" do
     result = ElixirScript.Compiler.compile(Version)
-    assert is_binary(hd(result))
+    assert result |> Map.to_list |> hd |> elem(1) |> Map.get(:js_code) |> is_binary
   end
 
   test "Can compile multiple entry modules" do
     result = ElixirScript.Compiler.compile([Atom, String, Agent])
-    assert is_binary(hd(result))
+    assert result |> Map.to_list |> hd |> elem(1) |> Map.get(:js_code) |> is_binary
   end
 
   test "Output" do
     result = ElixirScript.Compiler.compile(Atom, [])
-    assert hd(result) =~ "export default"
+    assert result |> Map.to_list |> hd |> elem(1) |> Map.get(:js_code) =~ "export default"
   end
 
   test "compile file" do
diff --git a/test/manifest_test.exs b/test/manifest_test.exs
new file mode 100644
index 00000000..52efd044
--- /dev/null
+++ b/test/manifest_test.exs
@@ -0,0 +1,12 @@
+defmodule ElixirScript.Manifest.Test do
+  use ExUnit.Case
+  alias ElixirScript.Manifest
+
+  test "write manifest" do
+    result = ElixirScript.Compiler.compile(Atom)
+    path = Path.join([System.tmp_dir(), "write_manifest_test", ".compile.elixir_script"])
+    Manifest.write_manifest(path, result)
+    assert File.exists?(path)
+  end
+
+end