Add support for optional dependencies

Author: José Valim

lib/mix/lib/mix/deps.ex

@@ -49,6 +49,7 @@ defmodule Mix.Deps do
   * `:env` - The environment to run the dependency on, defaults to :prod
   * `:compile` - A command to compile the dependency, defaults to a mix,
                  rebar or make command
+  * `:optional` - The dependency is optional and used only to specify requirements
 
   ## Git options (`:git`)
 
@@ -230,7 +231,7 @@ defmodule Mix.Deps do
   end
 
   def format_status(Mix.Dep[app: app, status: { :diverged, other }] = dep) do
-    "different specs were given for the #{inspect app} app:\n" <>
+    "different specs were given for the #{app} app:\n" <>
     "#{dep_status(dep)}#{dep_status(other)}" <>
     "\n  Ensure they match or specify one of the above in your #{inspect Mix.Project.get} deps and set `override: true`"
   end
@@ -251,7 +252,7 @@ defmodule Mix.Deps do
     do: "the dependency requires Elixir #{req} but you are running on v#{System.version}"
 
   defp dep_status(Mix.Dep[app: app, requirement: req, opts: opts, from: from]) do
-    info = { app, req, Dict.drop(opts, [:dest, :lock, :env]) }
+    info = { app, req, Dict.drop(opts, [:dest, :lock, :env, :drop]) }
     "\n  > In #{Path.relative_to_cwd(from)}:\n    #{inspect info}\n"
   end
 

lib/mix/lib/mix/deps/converger.ex

@@ -50,7 +50,8 @@ defmodule Mix.Deps.Converger do
     config = [ deps_path: Path.expand(Mix.project[:deps_path]),
                root_lockfile: Path.expand(Mix.project[:lockfile]) ]
     main = Mix.Deps.Retriever.children
-    all(main, [], [], main, config, callback, rest)
+    apps = Enum.map(main, &(&1.app))
+    all(main, [], [], apps, config, callback, rest)
   end
 
   # We traverse the tree of dependencies in a breadth-
@@ -105,8 +106,11 @@ defmodule Mix.Deps.Converger do
         # dependency), we fetch the dependency including its latest info
         # and children information.
         { dep, children } = Mix.Deps.Retriever.fetch(dep, config)
+        children = reject_non_fullfilled_optional(children, current_breadths)
+        dep      = dep.deps(Enum.map(children, &(&1.app)))
+
         { acc, rest } = all(t, [dep|acc], upper_breadths, current_breadths, config, callback, rest)
-        all(children, acc, current_breadths, children ++ current_breadths, config, callback, rest)
+        all(children, acc, current_breadths, dep.deps ++ current_breadths, config, callback, rest)
     end
   end
 
@@ -120,11 +124,7 @@ defmodule Mix.Deps.Converger do
   # overrider is moved to the front of the accumulator to
   # preserve the position of the removed dep.
   defp overriden_deps(acc, upper_breadths, dep) do
-    overriden = Enum.any?(upper_breadths, fn(other) ->
-      other.app == dep.app
-    end)
-
-    if overriden do
+    if dep.app in upper_breadths do
       Mix.Dep[app: app] = dep
 
       { overrider, acc } =
@@ -169,13 +169,23 @@ defmodule Mix.Deps.Converger do
     if match, do: acc
   end
 
+  defp converge?(_, Mix.Dep[scm: Mix.SCM.Optional]) do
+    true
+  end
+
   defp converge?(Mix.Dep[scm: scm, opts: opts1], Mix.Dep[scm: scm, opts: opts2]) do
     scm.equal?(opts1, opts2)
   end
 
   defp converge?(_, _), do: false
 
-  def with_matching_req(Mix.Dep[] = other, Mix.Dep[] = dep) do
+  defp reject_non_fullfilled_optional(children, upper_breadths) do
+    Enum.reject children, fn Mix.Dep[app: app, opts: opts] ->
+      opts[:optional] && not(app in upper_breadths)
+    end
+  end
+
+  defp with_matching_req(Mix.Dep[] = other, Mix.Dep[] = dep) do
     case other.status do
       { :ok, vsn } when not nil?(vsn) ->
         if Mix.Deps.Retriever.vsn_match?(dep.requirement, vsn) do

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

@@ -8,12 +8,12 @@ defmodule Mix.Deps.Retriever do
   Gets all direct children of the current `Mix.Project`
   as a `Mix.Dep` record. Umbrella project dependencies
   are included as children.
+
+  Optional dependencies are filtered out as they only
+  matter as a dependency children.
   """
   def children do
-    scms = Mix.SCM.available
-    from = Path.absname("mix.exs")
-    Enum.map(Mix.project[:deps] || [], &to_dep(&1, scms, from)) ++
-             Mix.Deps.Umbrella.unfetched
+    mix_children |> Enum.reject(fn Mix.Dep[opts: opts] -> opts[:optional] end)
   end
 
   @doc """
@@ -46,7 +46,6 @@ defmodule Mix.Deps.Retriever do
           mix_dep(dep.manager(:mix), config)
       end
 
-    dep = dep.deps(Enum.map(children, &(&1.app)))
     { validate_app(dep), children }
   end
 
@@ -97,7 +96,7 @@ defmodule Mix.Deps.Retriever do
       ]
     else
       raise Mix.Error, message: "#{inspect Mix.Project.get} did not specify a supported scm " <>
-                                "for app #{inspect app}, expected one of :git, :path or :in_umbrella"
+                                "for app #{inspect app}, expected one of :git, :path, :in_umbrella or :optional"
     end
   end
 
@@ -154,10 +153,17 @@ defmodule Mix.Deps.Retriever do
         true -> status
       end
 
-      { dep.manager(:mix).opts(opts).status(stat), children }
+      { dep.manager(:mix).opts(opts).status(stat), mix_children }
     end)
   end
 
+  defp mix_children do
+    scms = Mix.SCM.available
+    from = Path.absname("mix.exs")
+    Enum.map(Mix.project[:deps] || [], &to_dep(&1, scms, from)) ++
+             Mix.Deps.Umbrella.unfetched
+  end
+
   defp rebar_dep(Mix.Dep[opts: opts] = dep, _config) do
     File.cd!(opts[:dest], fn ->
       config = Mix.Rebar.load_config(".")

lib/mix/lib/mix/scm.ex

@@ -125,5 +125,6 @@ defmodule Mix.SCM do
   def register_builtin do
     register Mix.SCM.Git
     register Mix.SCM.Path
+    register Mix.SCM.Optional
   end
 end

lib/mix/lib/mix/scm/optional.ex

@@ -0,0 +1,40 @@
+defmodule Mix.SCM.Optional do
+  @behavior Mix.SCM
+  @moduledoc false
+
+  def format(_opts) do
+    "[optional]"
+  end
+
+  def format_lock(_lock) do
+    nil
+  end
+
+  def accepts_options(_app, opts) do
+    if opts[:optional], do: opts
+  end
+
+  def checked_out?(_opts) do
+    true
+  end
+
+  def lock_status(_opts) do
+    :ok
+  end
+
+  def equal?(_opts1, _opts2) do
+    true
+  end
+
+  def checkout(_opts) do
+    raise Mix.Error, message: "Cannot checkout optional dependency"
+  end
+
+  def update(_opts) do
+    raise Mix.Error, message: "Cannot update optional dependency"
+  end
+
+  def clean(_opts) do
+    raise Mix.Error, message: "Cannot clean optional dependency"
+  end
+end

lib/mix/test/mix/deps_test.exs

@@ -11,7 +11,9 @@ defmodule Mix.DepsTest do
           { :invalidvsn, "0.2.0", path: "deps/invalidvsn" },
           { :invalidapp, "0.1.0", path: "deps/invalidapp" },
           { :noappfile,  "0.1.0", path: "deps/noappfile" },
-          { :uncloned,            git: "https://github.com/elixir-lang/uncloned.git" }
+          { :uncloned,            git: "https://github.com/elixir-lang/uncloned.git" },
+          { :optional,            optional: true },
+          { :optional_git,        optional: true, git: "https://github.com/elixir-lang/optinal.git" }
         ]
       ]
     end
@@ -34,6 +36,7 @@ defmodule Mix.DepsTest do
 
     in_fixture "deps_status", fn ->
       deps = Mix.Deps.fetched
+      assert length(deps) == 5
       assert Enum.find deps, &match?(Mix.Dep[app: :ok, status: { :ok, _ }], &1)
       assert Enum.find deps, &match?(Mix.Dep[app: :invalidvsn, status: { :invalidvsn, :ok }], &1)
       assert Enum.find deps, &match?(Mix.Dep[app: :invalidapp, status: { :invalidapp, _ }], &1)
@@ -60,7 +63,7 @@ defmodule Mix.DepsTest do
 
     in_fixture "deps_status", fn ->
       msg = "Mix.DepsTest.NoSCMApp did not specify a supported scm for app :ok, " <>
-            "expected one of :git, :path or :in_umbrella"
+            "expected one of :git, :path, :in_umbrella or :optional"
       assert_raise Mix.Error, msg, fn -> Mix.Deps.fetched end
     end
   after
@@ -104,6 +107,32 @@ defmodule Mix.DepsTest do
     Mix.Project.pop
   end
 
+  test "nested optional deps are never added" do
+    Mix.Project.push NestedDepsApp
+
+    in_fixture "deps_status", fn ->
+      File.write!("custom/deps_repo/mix.exs", """)
+      defmodule DepsRepo do
+        use Mix.Project
+
+        def project do
+          [
+            app: :deps_repo,
+            version: "0.1.0",
+            deps: [
+              { :git_repo, "0.2.0", optional: true }
+            ]
+          ]
+        end
+      end
+      """
+
+      assert Enum.map(Mix.Deps.fetched, &(&1.app)) == [:deps_repo]
+    end
+  after
+    Mix.Project.pop
+  end
+
   defmodule ConvergedDepsApp do
     def project do
       [
@@ -126,4 +155,30 @@ defmodule Mix.DepsTest do
   after
     Mix.Project.pop
   end
+
+  test "correctly order converged deps even with optional dependencies" do
+    Mix.Project.push ConvergedDepsApp
+
+    in_fixture "deps_status", fn ->
+      File.write!("custom/deps_repo/mix.exs", """)
+      defmodule DepsRepo do
+        use Mix.Project
+
+        def project do
+          [
+            app: :deps_repo,
+            version: "0.1.0",
+            deps: [
+              { :git_repo, "0.2.0", optional: true }
+            ]
+          ]
+        end
+      end
+      """
+
+      assert Enum.map(Mix.Deps.fetched, &(&1.app)) == [:git_repo, :deps_repo]
+    end
+  after
+    Mix.Project.pop
+  end
 end

lib/mix/test/mix/tasks/deps_test.exs

@@ -27,17 +27,6 @@ defmodule Mix.Tasks.DepsTest do
     end
   end
 
-  defmodule OutOfDateDepsApp do
-    def project do
-      [
-        deps: [
-          { :ok,       "0.1.0", git: "https://github.com/elixir-lang/ok.git" },
-          { :uncloned, "0.1.0", git: "https://github.com/elixir-lang/uncloned.git" }
-        ]
-      ]
-    end
-  end
-
   defmodule ReqDepsApp do
     def project do
       [
@@ -132,7 +121,7 @@ defmodule Mix.Tasks.DepsTest do
     Mix.Project.pop
   end
 
-  test "check list of dependencies and their status with success" do
+  test "checks list of dependencies and their status with success" do
     Mix.Project.push SuccessfulDepsApp
 
     in_fixture "deps_status", fn ->
@@ -142,20 +131,6 @@ defmodule Mix.Tasks.DepsTest do
     Mix.Project.pop
   end
 
-  test "check slist of dependencies and their status with failure" do
-    Mix.Project.push OutOfDateDepsApp
-
-    in_fixture "deps_status", fn ->
-      assert_raise Mix.Error, fn ->
-        Mix.Tasks.Deps.Check.run []
-      end
-
-      assert_received { :mix_shell, :error, ["* uncloned (https://github.com/elixir-lang/uncloned.git)"] }
-    end
-  after
-    Mix.Project.pop
-  end
-
   test "checks list of dependencies and their status on failure" do
     Mix.Project.push DepsApp
 
@@ -359,7 +334,7 @@ defmodule Mix.Tasks.DepsTest do
       end
 
       receive do
-        { :mix_shell, :error, ["  different specs were given for the :git_repo app:" <> _ = msg] } ->
+        { :mix_shell, :error, ["  different specs were given for the git_repo app:" <> _ = msg] } ->
           assert msg =~ "In custom/deps_repo/mix.exs:"
           assert msg =~ "{:git_repo, \"0.1.0\", [git: #{inspect fixture_path("git_repo")}]}"
       after
@@ -406,6 +381,36 @@ defmodule Mix.Tasks.DepsTest do
     Mix.Project.pop
   end
 
+  test "fails on diverged dependencies even when optional" do
+    Mix.Project.push ConvergedDepsApp
+
+    in_fixture "deps_status", fn ->
+      File.write!("custom/deps_repo/mix.exs", """)
+      defmodule DepsRepo do
+        use Mix.Project
+
+        def project do
+          [
+            app: :deps_repo,
+            version: "0.1.0",
+            deps: [
+              { :git_repo, git: MixTest.Case.fixture_path("bad_git_repo"), branch: "omg" }
+            ]
+          ]
+        end
+      end
+      """
+
+      assert_raise Mix.Error, fn ->
+        Mix.Tasks.Deps.Get.run []
+      end
+
+      assert_received { :mix_shell, :error, ["  the dependency git_repo in mix.exs is overriding" <> _] }
+    end
+  after
+    Mix.Project.pop
+  end
+
   test "works with converged dependencies" do
     Mix.Project.push ConvergedDepsApp
 
@@ -454,8 +459,6 @@ defmodule Mix.Tasks.DepsTest do
       assert_received { :mix_shell, :info, [^message] }
       message = "* Updating git_repo (#{fixture_path("git_repo")})"
       assert_received { :mix_shell, :info, [^message] }
-
-      Mix.Tasks.Deps.Check.run []
     end
   after
     purge [GitRepo, GitRepo.Mix]