Demonstration of Extension Approach 1

apps/extensions_manager/.gitignore

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+/_build
+/cover
+/deps
+erl_crash.dump
+*.ez
+
+
+# Vim Swap Files
+*.swp
+/**/*.swp
+/**/**/*.swp
+/**/**/**/*.swp
+/**/**/**/**/*.swp

apps/extensions_manager/README.md

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+# Extensions Manager

apps/extensions_manager/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 for your application as:
+#
+#     config :extensions_manager, key: :value
+#
+# And access this configuration in your application as:
+#
+#     Application.get_env(:extensions_manager, :key)
+#
+# Or 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"

apps/extensions_manager/lib/extensions_manager.ex

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+defmodule ExtensionsManager do
+end

apps/extensions_manager/lib/extensions_manager/install_extensions.ex

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+defmodule ExtensionsManager.ExtendProduct do
+  use ExtensionsManager.ModelExtension
+  use FavoriteProducts.NectarExtension, install: "products"
+end
+
+defmodule ExtensionsManager.ExtendUser do
+  use ExtensionsManager.ModelExtension
+  use FavoriteProducts.NectarExtension, install: "users"
+end
+
+defmodule ExtensionsManager.Router do
+  use ExtensionsManager.RouterExtension
+  use FavoriteProducts.NectarExtension, install: "router"
+end

apps/extensions_manager/lib/extensions_manager/model_extension.ex

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+defmodule ExtensionsManager.ModelExtension do
+  defmacro __using__(_opts) do
+    quote do
+      Module.register_attribute(__MODULE__, :schema_changes, accumulate: true)
+      Module.register_attribute(__MODULE__, :method_block, accumulate: true)
+
+      import ExtensionsManager.ModelExtension, only: [add_to_schema: 4, add_to_schema: 3, include_method: 1]
+      @before_compile ExtensionsManager.ModelExtension
+
+      defmacro __using__(_opts) do
+        quote do
+          import unquote(__MODULE__), only: [extensions: 0, schema_changes: 0, include_methods: 0, method_blocks: 0]
+          @before_compile unquote(__MODULE__)
+        end
+      end
+
+      defmacro __before_compile__(_env) do
+        quote do
+          include_methods
+        end
+      end
+    end
+  end
+
+  defmacro add_to_schema(method, name, through) do
+    quote bind_quoted: [name: name, through: through, method: method], location: :keep do
+      Module.put_attribute(__MODULE__, :schema_changes, {method, name, through})
+    end
+  end
+  defmacro add_to_schema(method, name, type, options) do
+    quote bind_quoted: [name: name, type: type, options: options, method: method], location: :keep do
+      Module.put_attribute(__MODULE__, :schema_changes, {method, name, type, options})
+    end
+  end
+
+  defmacro include_method(methd) do
+    block = Macro.escape(methd)
+    quote bind_quoted: [block: block] do
+      Module.put_attribute(__MODULE__, :method_block, block)
+    end
+  end
+
+  defmacro __before_compile__(_env) do
+    quote do
+      defmacro extensions do
+        quote do
+          Enum.map(schema_changes, fn
+            ({:field, name, type, options}) -> field name, type, options
+            ({:has_one, name, type, options}) -> has_one name, type, options
+            ({:has_many, name, type, options}) -> has_many name, type, options
+            ({:has_many, name, through}) -> has_many name, through
+          end)
+        end
+      end
+
+      def schema_changes do
+        @schema_changes
+      end
+
+      defmacro include_methods do
+        quote do
+          unquote(Enum.map(method_blocks, fn (method_block) -> method_block end))
+        end
+      end
+
+      def method_blocks do
+        @method_block
+      end
+    end
+  end
+end
+
+defmodule ExtensionsManager.DefaultExtend do
+  use ExtensionsManager.ModelExtension
+end

apps/extensions_manager/lib/extensions_manager/nectar_extender.ex

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+defmodule ExtensionsManager.NectarExtender do
+  defmacro __using__(_opts) do
+    # determine from env which model we want to extend
+    # load all impls for extend#Module here
+    # use SayHelloWorldInProduct
+    useable_module = infer_module_from_caller(__CALLER__)
+    quote do
+      use unquote(useable_module)
+    end
+  end
+
+  def infer_module_from_caller(caller) do
+    module_to_extend = caller.module |> Module.split |> List.last
+    module_name = String.to_atom("Elixir.ExtensionsManager.Extend" <> module_to_extend)
+    if Code.ensure_loaded?(module_name) do
+      apply(module_name, :__info__, [:module])
+    else
+      apply(ExtensionsManager.DefaultExtend, :__info__, [:module])
+    end
+  end
+end

apps/extensions_manager/lib/extensions_manager/router_extension.ex

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+defmodule ExtensionsManager.RouterExtension do
+  defmacro __using__(_opts) do
+    quote do
+      Module.register_attribute(__MODULE__, :defined_routes, accumulate: true)
+
+      import ExtensionsManager.RouterExtension, only: [define_route: 1]
+      @before_compile ExtensionsManager.RouterExtension
+    end
+  end
+
+  defmacro define_route([do: rt]) do
+    block = Macro.escape(rt)
+    quote bind_quoted: [block: block] do
+      Module.put_attribute(__MODULE__, :defined_routes, block)
+    end
+  end
+
+  defmacro __before_compile__(_env) do
+    quote do
+      defmacro mount do
+        @defined_routes
+      end
+    end
+  end
+end

apps/extensions_manager/lib/extensions_manager/sample_macro.ex

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+defmodule ExtensionsManager.SampleMacro do
+  defmacro __using__(_opts) do
+    quote do
+      Module.register_attribute(__MODULE__, :module_blocks, accumulate: true)
+      import ExtensionsManager.SampleMacro, only: [define_model: 1]
+      @before_compile ExtensionsManager.SampleMacro
+
+      defmacro __using__(_opts) do
+        quote do
+          import unquote(__MODULE__), only: [include_models: 0]
+          @before_compile unquote(__MODULE__)
+        end
+      end
+
+      defmacro __before_compile__(_env) do
+        quote do
+          include_models
+        end
+      end
+    end
+  end
+
+  defmacro __before_compile__(_env) do
+    quote do
+      defmacro include_models do
+        quote do
+          unquote(Enum.map(module_blocks, fn (module_block) -> module_block end))
+        end
+      end
+      def module_blocks do
+        @module_blocks
+      end
+    end
+  end
+
+  defmacro define_model([do: block]) do
+    quote bind_quoted: [block: block] do
+      Module.put_attribute(__MODULE__, :module_blocks, block)
+    end
+  end
+end

apps/extensions_manager/mix.exs

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+defmodule ExtensionsManager.Mixfile do
+  use Mix.Project
+
+  def project do
+    [app: :extensions_manager,
+     version: "0.0.1",
+     build_path: "../../_build",
+     config_path: "../../config/config.exs",
+     deps_path: "../../deps",
+     lockfile: "../../mix.lock",
+     elixir: "~> 1.2",
+     build_embedded: Mix.env == :prod,
+     start_permanent: Mix.env == :prod,
+     deps: deps]
+  end
+
+  # Configuration for the OTP application
+  #
+  # Type "mix help compile.app" for more information
+  def application do
+    [applications: [:logger]]
+  end
+
+  # Dependencies can be Hex packages:
+  #
+  #   {:mydep, "~> 0.3.0"}
+  #
+  # Or git/path repositories:
+  #
+  #   {:mydep, git: "https://github.com/elixir-lang/mydep.git", tag: "0.1.0"}
+  #
+  # To depend on another app inside the umbrella:
+  #
+  #   {:myapp, in_umbrella: true}
+  #
+  # Type "mix help deps" for more examples and options
+  defp deps do
+    [{:favorite_products, in_umbrella: true}]
+  end
+end

apps/extensions_manager/test/extensions_manager_test.exs

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+defmodule ExtensionsManagerTest do
+  use ExUnit.Case
+
+  test "the truth" do
+    assert 1 + 1 == 2
+  end
+end

apps/extensions_manager/test/test_helper.exs

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+ExUnit.start()

apps/favorite_products/.gitignore

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+# App artifacts
+/_build
+/db
+/deps
+/*.ez
+
+# Generate on crash by the VM
+erl_crash.dump
+
+# Static artifacts
+/node_modules
+
+# Since we are building assets from web/static,
+# we ignore priv/static. You may want to comment
+# this depending on your deployment strategy.
+/priv/static/
+
+# The config/prod.secret.exs file by default contains sensitive
+# data and you should not commit it into version control.
+#
+# Alternatively, you may comment the line below and commit the
+# secrets file as long as you replace its contents by environment
+# variables.
+/config/prod.secret.exs
+/config/dev.secret.exs
+/config/test.secret.exs
+
+# Vim Swap Files
+*.swp
+/**/*.swp
+/**/**/*.swp
+/**/**/**/*.swp
+/**/**/**/**/*.swp
+
+# Misc
+.DS_Store
+**/.DS_Store

apps/favorite_products/README.md

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+# FavoriteProducts
+
+To start your Phoenix app:
+
+  * Install dependencies with `mix deps.get`
+  * Create and migrate your database with `mix ecto.create && mix ecto.migrate`
+  * Install Node.js dependencies with `npm install`
+  * Start Phoenix endpoint with `mix phoenix.server`
+
+Now you can visit [`localhost:4000`](http://localhost:4000) from your browser.
+
+Ready to run in production? Please [check our deployment guides](http://www.phoenixframework.org/docs/deployment).
+
+## Learn more
+
+  * Official website: http://www.phoenixframework.org/
+  * Guides: http://phoenixframework.org/docs/overview
+  * Docs: http://hexdocs.pm/phoenix
+  * Mailing list: http://groups.google.com/group/phoenix-talk
+  * Source: https://github.com/phoenixframework/phoenix