Add --no-load-deps flag to deps.loadpaths task (#8256)

Author: ericmj

lib/mix/lib/mix/tasks/deps.loadpaths.ex

@@ -16,6 +16,7 @@ defmodule Mix.Tasks.Deps.Loadpaths do
 
     * `--no-deps-check` - does not check or compile deps, only load available ones
     * `--no-compile` - does not compile dependencies
+    * `--no-load-deps` - do not load deps from the code path
 
   """
 
@@ -26,14 +27,16 @@ defmodule Mix.Tasks.Deps.Loadpaths do
       deps_check(all, "--no-compile" in args)
     end
 
-    load_paths =
-      for dep <- all,
-          path <- Mix.Dep.load_paths(dep) do
-        _ = Code.prepend_path(path)
-        path
-      end
+    unless "--no-load-deps" in args do
+      load_paths =
+        for dep <- all,
+            path <- Mix.Dep.load_paths(dep) do
+          _ = Code.prepend_path(path)
+          path
+        end
 
-    prune_deps(load_paths, "--no-deps-check" in args)
+      prune_deps(load_paths, "--no-deps-check" in args)
+    end
   end
 
   # If the build is per environment, we should be able to look

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

@@ -242,6 +242,36 @@ defmodule Mix.Tasks.DepsTest do
     end)
   end
 
+  test "does not load or prune builds with --no-load-deps" do
+    Mix.Project.push(SuccessfulDepsApp)
+
+    in_fixture("deps_status", fn ->
+      # Start from scratch!
+      File.rm_rf("_build")
+
+      Mix.Tasks.Deps.Compile.run([])
+      Mix.Tasks.Deps.Loadpaths.run([])
+      assert File.exists?("_build/dev/lib/ok/ebin/ok.app")
+      assert File.exists?("_build/dev/lib/ok/priv/sample")
+
+      Mix.Tasks.Compile.run([])
+      assert to_charlist(Path.expand("_build/dev/lib/ok/ebin/")) in :code.get_path()
+      assert File.exists?("_build/dev/lib/sample/ebin/sample.app")
+
+      # Remove the deps without build_path
+      Mix.ProjectStack.post_config(deps: [])
+      Mix.ProjectStack.clear_cache()
+      Mix.Project.pop()
+      Mix.Project.push(SuccessfulDepsApp)
+      Code.delete_path("_build/dev/lib/ok/ebin")
+
+      Mix.Tasks.Deps.Loadpaths.run(["--no-load-deps"])
+      refute to_charlist(Path.expand("_build/dev/lib/ok/ebin/")) in :code.get_path()
+      assert File.exists?("_build/dev/lib/ok/ebin/ok.app")
+      assert File.exists?("_build/dev/lib/sample/ebin/sample.app")
+    end)
+  end
+
   ## deps.unlock
 
   test "unlocks all deps", context do