Path dependencies can only be used with mix projects, closes #1967

Author: José Valim

lib/mix/lib/mix/deps.ex

@@ -248,8 +248,13 @@ defmodule Mix.Deps do
     "\n  Ensure they match or specify one of the above in your #{inspect Mix.Project.get} deps and set `override: true`"
   end
 
-  def format_status(Mix.Dep[status: { :unavailable, _ }]),
-    do: "the dependency is not available, run `mix deps.get`"
+  def format_status(Mix.Dep[status: { :unavailable, _ }, scm: scm]) do
+    if scm.fetchable? do
+      "the dependency is not available, run `mix deps.get`"
+    else
+      "the dependency is not available"
+    end
+  end
 
   def format_status(Mix.Dep[status: { :elixirlock, _ }]),
     do: "the dependency is built with an out-of-date elixir version, run `mix deps.get`"

lib/mix/lib/mix/deps/retriever.ex

@@ -46,7 +46,7 @@ defmodule Mix.Deps.Retriever do
           { dep, [] }
       end
 
-    { validate_app(dep), children }
+    { validate_path(validate_app(dep)), children }
   end
 
   @doc """
@@ -172,6 +172,15 @@ defmodule Mix.Deps.Retriever do
     end) |> Enum.concat
   end
 
+  defp validate_path(Mix.Dep[scm: scm, manager: manager] = dep) do
+    if scm == Mix.SCM.Path and not manager in [:mix, nil] do
+      raise Mix.Error, message: ":path option can only be used with mix projects, " <>
+                                "invalid path dependency for #{inspect dep.app}"
+    else
+      dep
+    end
+  end
+
   defp validate_app(Mix.Dep[opts: opts, requirement: req, app: app, status: status] = dep) do
     opts_app = opts[:app]
 

lib/mix/lib/mix/scm.ex

@@ -8,6 +8,12 @@ defmodule Mix.SCM do
   behavior required by any SCM used by mix.
   """
 
+  @doc """
+  Returns a boolean if the dependency can be fetched
+  or it is meant to be previously available in the filesystem.
+  """
+  defcallback fetchable? :: boolean
+
   @doc """
   Returns a string representing the SCM. This is used
   when printing the dependency and not for inspection,

lib/mix/lib/mix/scm/git.ex

@@ -2,6 +2,10 @@ defmodule Mix.SCM.Git do
   @behavior Mix.SCM
   @moduledoc false
 
+  def fetchable? do
+    true
+  end
+
   def format(opts) do
     opts[:git]
   end

lib/mix/lib/mix/scm/path.ex

@@ -2,6 +2,10 @@ defmodule Mix.SCM.Path do
   @behavior Mix.SCM
   @moduledoc false
 
+  def fetchable? do
+    false
+  end
+
   def format(opts) do
     opts[:path]
   end

lib/mix/lib/mix/tasks/deps.get.ex

@@ -49,9 +49,8 @@ defmodule Mix.Tasks.Deps.Get do
     Mix.Dep[app: app, scm: scm, opts: opts] = dep = check_lock(dep, lock)
 
     cond do
-      # Path dependencies are specially handled because they cannot
-      # be fetched although they are always compiled afterwards
-      scm == Mix.SCM.Path ->
+      # Dependencies that cannot be fetched are always compiled afterwards
+      not scm.fetchable? ->
         { dep, { [app|acc], lock } }
 
       # If the dependency is not available or we have a lock mismatch

lib/mix/test/mix/rebar_test.exs

@@ -3,6 +3,30 @@ Code.require_file "../test_helper.exs", __DIR__
 defmodule Mix.RebarTest do
   use MixTest.Case
 
+  # Have our own path implementation that bypasses some
+  # Path validation checks. We use this just for testing.
+  defmodule MyPath do
+    @behaviour Mix.SCM
+
+    lc { name, arity } inlist Mix.SCM.Path.__info__(:functions) do
+      args = tl Enum.map 0..arity, &{ :"x#{&1}", [], nil }
+      def unquote(name)(unquote_splicing(args)) do
+        Mix.SCM.Path.unquote(name)(unquote_splicing(args))
+      end
+    end
+  end
+
+  setup do
+    available = Mix.SCM.available
+    :application.set_env(:mix, :scm, [Mix.SCM.Git, MyPath])
+    { :ok, [scm: available] }
+  end
+
+  teardown context do
+    :application.set_env(:mix, :scm, context[:scm])
+    :ok
+  end
+
   defmodule RebarAsDep do
     def project do
       [ app: :rebar_as_dep,

lib/mix/test/mix/tasks/deps.path_test.exs

@@ -41,4 +41,21 @@ defmodule Mix.Tasks.DepsPathTest do
   after
     Mix.Project.pop
   end
-end
+
+  defmodule InvalidPathDepsApp do
+    def project do
+      [
+        app: :rebar_as_dep,
+        version: "0.1.0",
+        deps: [{ :rebar_dep, path: MixTest.Case.tmp_path("rebar_dep") }]
+      ]
+    end
+  end
+
+  test "raises on non-mix path deps" do
+    Mix.Project.push InvalidPathDepsApp
+    assert_raise Mix.Error, %r/:path option can only be used with mix projects/, fn ->
+      Mix.Tasks.Deps.Get.run []
+    end
+  end
+end