Add Mix.Rebar.available?/1 for explicit availability checks

Author: josevalim

lib/mix/lib/mix/dep/loader.ex

@@ -332,7 +332,7 @@ defmodule Mix.Dep.Loader do
   defp rebar_dep(dep, children, manager, locked?) do
     %Mix.Dep{app: app, opts: opts, extra: overrides} = dep
 
-    if locked? and is_nil(Mix.Rebar.rebar_path(manager)) do
+    if locked? and not Mix.Rebar.available?(manager) do
       Mix.Tasks.Local.Rebar.run(["--force"])
     end
 

lib/mix/lib/mix/rebar.ex

@@ -2,25 +2,36 @@ defmodule Mix.Rebar do
   @moduledoc false
 
   # TODO: Remove on Elixir v1.20 because phx_new and other installers rely on it.
-  @deprecated "Use global_rebar_path/1 instead"
+  @deprecated "Use env_rebar_path/1 instead"
   def global_rebar_cmd(manager) do
-    global_rebar_path(manager)
+    env_rebar_path(manager)
   end
 
   @deprecated "Use local_rebar_path/1 instead"
   def local_rebar_cmd(manager) do
     local_rebar_path(manager)
   end
 
-  @deprecated "Use rebar_path/1 instead"
+  @deprecated "Use rebar_args/2 or available?/1 instead"
   def rebar_cmd(manager) do
     global_rebar_cmd(manager) || local_rebar_cmd(manager)
   end
 
+  @doc """
+  Returns if Rebar is available or not.
+  """
+  def available?(manager) do
+    env_rebar_path(manager) != nil or File.regular?(local_rebar_path(manager))
+  end
+
   @doc """
   Receives a Rebar executable and returns how it must be invoked.
+
+  It returns a result even if Rebar is not available.
   """
-  def rebar_args(rebar, args) do
+  def rebar_args(:rebar3, args) do
+    rebar = env_rebar_path(:rebar3) || local_rebar_path(:rebar3)
+
     if match?({:win32, _}, :os.type()) and not String.ends_with?(rebar, ".cmd") do
       {"escript.exe", [rebar | args]}
     else
@@ -29,16 +40,9 @@ defmodule Mix.Rebar do
   end
 
   @doc """
-  Returns either the global or local rebar path.
-  """
-  def rebar_path(:rebar3) do
-    global_rebar_path(:rebar3) || local_rebar_path(:rebar3)
-  end
-
-  @doc """
-  Finds the global rebar path.
+  Returns the global rebar path.
   """
-  def global_rebar_path(:rebar3) do
+  def env_rebar_path(:rebar3) do
     System.get_env("MIX_REBAR3")
   end
 

lib/mix/lib/mix/tasks/deps.compile.ex

@@ -180,6 +180,10 @@ defmodule Mix.Tasks.Deps.Compile do
   end
 
   defp do_rebar3(%Mix.Dep{opts: opts} = dep, config) do
+    unless Mix.Rebar.available?(:rebar3) do
+      handle_rebar_not_found(dep)
+    end
+
     dep_path = opts[:dest]
     build_path = opts[:build]
     File.mkdir_p!(build_path)
@@ -207,8 +211,7 @@ defmodule Mix.Tasks.Deps.Compile do
       {"TERM", "dumb"}
     ]
 
-    rebar = Mix.Rebar.local_rebar_path(:rebar3) || handle_rebar_not_found(dep)
-    {exec, args} = Mix.Rebar.rebar_args(rebar, ["bare", "compile", "--paths", lib_path])
+    {exec, args} = Mix.Rebar.rebar_args(:rebar3, ["bare", "compile", "--paths", lib_path])
 
     if Mix.shell().cmd({exec, args}, opts_for_cmd(dep, config, env)) != 0 do
       Mix.raise(
@@ -253,7 +256,10 @@ defmodule Mix.Tasks.Deps.Compile do
     end
 
     Mix.Tasks.Local.Rebar.run(["--force"])
-    Mix.Rebar.local_rebar_path(manager) || Mix.raise("\"#{manager}\" installation failed")
+
+    unless Mix.Rebar.available?(manager) do
+      Mix.raise("\"#{manager}\" installation failed")
+    end
   end
 
   defp do_make(dep, config) do

lib/mix/test/mix/rebar_test.exs

@@ -240,7 +240,7 @@ defmodule Mix.RebarTest do
       in_tmp("rebar3 env with spaces", fn ->
         File.cp!(Mix.Rebar.local_rebar_path(:rebar3), "rebar3")
         System.put_env("MIX_REBAR3", Path.absname("rebar3"))
-        assert Mix.Rebar.rebar_path(:rebar3) =~ " "
+        assert Mix.Rebar.rebar_args(:rebar3, []) |> elem(0) =~ " "
 
         Mix.Project.push(RebarAsDep)
         Mix.Tasks.Deps.Get.run([])