First commit, project generated and everything inside the minefield

.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where 3rd-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+interceptor-*.tar
+

README.md

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+# Interceptor
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `interceptor` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:interceptor, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at [https://hexdocs.pm/interceptor](https://hexdocs.pm/interceptor).
+

config/config.exs

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+# This file is responsible for configuring your application
+# and its dependencies with the aid of the Mix.Config module.
+use Mix.Config
+
+# This configuration is loaded before any dependency and is restricted
+# to this project. If another project depends on this project, this
+# file won't be loaded nor affect the parent project. For this reason,
+# if you want to provide default values for your application for
+# 3rd-party users, it should be done in your "mix.exs" file.
+
+# You can configure your application as:
+#
+#     config :interceptor, key: :value
+#
+# and access this configuration in your application as:
+#
+#     Application.get_env(:interceptor, :key)
+#
+# You can also configure a 3rd-party app:
+#
+#     config :logger, level: :info
+#
+
+# It is also possible to import configuration files, relative to this
+# directory. For example, you can emulate configuration per environment
+# by uncommenting the line below and defining dev.exs, test.exs and such.
+# Configuration from the imported file will override the ones defined
+# here (which is why it is important to import them last).
+#
+#     import_config "#{Mix.env()}.exs"

lib/interceptor.ex

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+defmodule Interceptor do
+  @moduledoc """
+  Documentation for Interceptor.
+  """
+
+  @doc """
+  Hello world.
+
+  ## Examples
+
+      iex> Interceptor.hello()
+      :world
+
+  """
+  def hello do
+    :world
+  end
+end

minefield.ex

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+defmodule Outsider do
+  def count(message), do: IO.puts("OUTSIDE!!! #{message}")
+end
+
+defmodule Intercept do
+  defmacro me([do: {_block, _metadata, definitions} = do_block]) do
+    # IO.inspect(definitions)
+
+    updated_do_block = definitions
+                      |> Enum.map(&add_calls/1)
+                      |> update_block_definitions(do_block)
+
+    [do: updated_do_block]
+  end
+
+  def add_calls({:def, _metadata, [function_hdr | [[do: function_body]]]} = function) do
+    quoted_call = quote do
+      Kernel.apply(Outsider, :count, ["Hi there"])
+    end
+
+    new_function_body = prepend_to_function_body(function_body, quoted_call)
+
+    new_function = function
+    |> put_elem(2, [function_hdr | [[do: new_function_body]]])
+
+    IO.puts("NEW DEF function ####################")
+    IO.inspect(new_function)
+  end
+
+  def add_calls({:defp, _metadata, [function_hdr | [[do: function_body]]]} = function) do
+    function
+  end
+
+  def add_calls(something_else) do
+    something_else
+  end
+
+
+  defp prepend_to_function_body({:__block__, _metadata, statements} = body, quoted_call) do
+    body
+    |> put_elem(2, [quoted_call | statements])
+  end
+
+  defp prepend_to_function_body(single_statement, quoted_call) do
+    {:__block__, [], [quoted_call, single_statement]}
+  end
+
+  defp update_block_definitions(new_definitions, {_block, _metadata, _definitions} = do_block) do
+    do_block
+    |> put_elem(2, new_definitions)
+  end
+end
+
+defmodule Foo do
+  require Intercept
+
+  Intercept.me do
+    def abc(x) do
+      IO.puts("Hey abc #{x}")
+      IO.puts("second entry")
+    end
+
+    def yyy(), do: IO.puts("alo from yyy")
+    def zzz(), do: lalalu("From ZZZ")
+
+    defp lalalu(foo), do: "#{foo} Fa #{foo}"
+  end
+
+  def xyz(x) do
+    IO.puts("Hey xyz #{x}")
+  end
+end

mix.exs

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+defmodule Interceptor.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :interceptor,
+      version: "0.1.0",
+      elixir: "~> 1.7",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"},
+    ]
+  end
+end

test/interceptor_test.exs

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+defmodule InterceptorTest do
+  use ExUnit.Case
+  doctest Interceptor
+
+  test "greets the world" do
+    assert Interceptor.hello() == :world
+  end
+end

test/test_helper.exs

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+ExUnit.start()