Move Elixir version mismatch to a warning, closes #1951

Author: José Valim

CHANGELOG.md

@@ -5,6 +5,7 @@
 * Bug fixes
   * [Atom] Inspect `:...` and `:foo@bar` without quoting
   * [Kernel] Guarantee nullary funs/macros are allowed in guards
+  * [Mix] Do not fail if a Mix dependency relies on an outdated Elixir version
 
 * Deprecations
   * [Kernel] `binary_to_term/1`, `binary_to_term/2`, `term_to_binary/1` and `term_to_binary/2` are deprecated in favor of their counterparts in the `:erlang` module

lib/mix/lib/mix/deps.ex

@@ -259,9 +259,6 @@ defmodule Mix.Deps do
   def format_status(Mix.Dep[status: { :elixirlock, _ }]),
     do: "the dependency is built with an out-of-date elixir version, run `mix deps.get`"
 
-  def format_status(Mix.Dep[status: { :elixirreq, req }]),
-    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, :build]) }
     "\n  > In #{Path.relative_to_cwd(from)}:\n    #{inspect info}\n"
@@ -307,7 +304,6 @@ defmodule Mix.Deps do
   def available?(Mix.Dep[status: { :overridden, _ }]),   do: false
   def available?(Mix.Dep[status: { :diverged, _ }]),     do: false
   def available?(Mix.Dep[status: { :divergedreq, _ }]),  do: false
-  def available?(Mix.Dep[status: { :elixirreq, _ }]),    do: false
   def available?(Mix.Dep[status: { :unavailable, _ }]),  do: false
   def available?(Mix.Dep[]), do: true
 
@@ -321,12 +317,6 @@ defmodule Mix.Deps do
     available?(dep) and (manager != :mix or !extra[:umbrella?])
   end
 
-  @doc """
-  Checks if a dependency can be updated.
-  """
-  def updatable?(Mix.Dep[status: { :elixirreq, _ }]), do: true
-  def updatable?(dep), do: available?(dep)
-
   @doc """
   Checks if a dependency is out of date, also considering its
   lock status. Therefore, be sure to call `check_lock` before

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

@@ -149,7 +149,8 @@ defmodule Mix.Deps.Retriever do
       end
 
       if req = old_elixir_req(config) do
-        dep = dep.status({ :elixirreq, req })
+        Mix.shell.error "warning: the dependency #{dep.app} requires Elixir #{inspect req} but you " <>
+                        "are running on v#{System.version}, please run mix deps.update #{dep.app} to update it"
       end
 
       { dep.manager(:mix).opts(opts).extra(umbrella: umbrella?), children }

lib/mix/lib/mix/tasks/deps.update.ex

@@ -20,7 +20,7 @@ defmodule Mix.Tasks.Deps.Update do
 
   """
 
-  import Mix.Deps, only: [unloaded: 2, unloaded_by_name: 3, updatable?: 1, format_dep: 1]
+  import Mix.Deps, only: [unloaded: 2, unloaded_by_name: 3, available?: 1, format_dep: 1]
 
   def run(args) do
     Mix.Project.get! # Require the project to be available
@@ -48,7 +48,7 @@ defmodule Mix.Tasks.Deps.Update do
   end
 
   defp deps_updater(dep, { acc, lock }) do
-    if updatable?(dep) do
+    if available?(dep) do
       Mix.Dep[app: app, scm: scm, opts: opts] = dep
       Mix.shell.info "* Updating #{format_dep(dep)}"
 

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

@@ -83,7 +83,7 @@ defmodule Mix.Tasks.DepsTest do
     end
   end
 
-  test "prints list of dependencies including elixir req mismatches" do
+  test "prints elixir req mismatches" do
     Mix.Project.push ReqDepsApp
 
     in_fixture "deps_status", fn ->
@@ -98,9 +98,10 @@ defmodule Mix.Tasks.DepsTest do
       """
 
       Mix.Tasks.Deps.run []
-      assert_received { :mix_shell, :info, ["* ok (deps/ok)"] }
-      message = "  the dependency requires Elixir ~> 0.1.0 but you are running on v#{System.version}"
-      assert_received { :mix_shell, :info, [^message] }
+
+      msg = "warning: the dependency ok requires Elixir \"~> 0.1.0\" but you are " <>
+            "running on v0.12.3-dev, please run mix deps.update ok to update it"
+      assert_received { :mix_shell, :error, [^msg] }
     end
   end