Merge pull request #2741 from styx/master

Fixes #2737

Author: José Valim

lib/mix/lib/mix/tasks/deps.unlock.ex

@@ -31,8 +31,14 @@ defmodule Mix.Tasks.Deps.Unlock do
 
       apps != [] ->
         lock =
-          Enum.reduce apps, Mix.Dep.Lock.read, fn(app, lock) ->
-            Map.delete(lock, String.to_atom(app))
+          Enum.reduce apps, Mix.Dep.Lock.read, fn(app_str, lock) ->
+            app = String.to_atom(app_str)
+            if Map.has_key?(lock, app) do
+              Map.delete(lock, app)
+            else
+              Mix.shell.error "warning: #{app} dependency is not locked"
+              lock
+            end
           end
         Mix.Dep.Lock.write(lock)
 

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

@@ -199,6 +199,8 @@ defmodule Mix.Tasks.DepsTest do
       Mix.Dep.Lock.write %{git_repo: "abcdef", another: "hash"}
       Mix.Tasks.Deps.Unlock.run ["git_repo", "unknown"]
       assert Mix.Dep.Lock.read == %{another: "hash"}
+      error = "warning: unknown dependency is not locked"
+      assert_received {:mix_shell, :error, [^error]}
     end
   end