Support mix xref graph at umbrella roots, closes #12629

Author: josevalim

lib/mix/lib/mix/tasks/xref.ex

@@ -38,8 +38,9 @@ defmodule Mix.Tasks.Xref do
       $ mix xref trace lib/my_app/router.ex --label compile
 
   If you have an umbrella application, we also recommend using the
-  `--include-siblings` flag to see the dependencies on other
-  umbrella applications.
+  `--include-siblings` flag to see the dependencies from sibling
+  applications. The `trace` command is not currently supported at the
+  umbrella root.
 
   ### Example
 
@@ -222,6 +223,12 @@ defmodule Mix.Tasks.Xref do
       lib/a.ex
       └── lib/b.ex (compile)
 
+  If you have an umbrella application, we also recommend using the
+  `--include-siblings` flag to see the dependencies from sibling
+  applications. When invoked at the umbrella root, the `graph`
+  command will list all files from all umbrella children, without
+  any namespacing.
+
   ### Dependency types
 
   Elixir tracks three types of dependencies between modules: compile,
@@ -289,22 +296,18 @@ defmodule Mix.Tasks.Xref do
 
   @impl true
   def run(args) do
-    if Mix.Project.umbrella?() do
-      Mix.raise(
-        "mix xref is not supported in the umbrella root. Please run it inside the umbrella applications instead"
-      )
-    end
-
     Mix.Task.run("compile", args)
     Mix.Task.reenable("xref")
 
     {opts, args} = OptionParser.parse!(args, strict: @switches)
 
     case args do
       ["callers", module] ->
+        no_umbrella!("callers")
         handle_callers(module, opts)
 
       ["trace", file] ->
+        no_umbrella!("trace")
         handle_trace(file, opts)
 
       ["graph"] ->
@@ -327,6 +330,14 @@ defmodule Mix.Tasks.Xref do
     end
   end
 
+  defp no_umbrella!(task) do
+    if Mix.Project.umbrella?() do
+      Mix.raise(
+        "mix xref #{task} is not supported in the umbrella root. Please run it inside the umbrella applications instead"
+      )
+    end
+  end
+
   @doc """
   Returns a list of information of all the runtime function calls in the project.
 
@@ -1058,12 +1069,18 @@ defmodule Mix.Tasks.Xref do
 
   defp manifests(opts) do
     siblings =
-      if opts[:include_siblings] do
-        for %{scm: Mix.SCM.Path, opts: opts} <- Mix.Dep.cached(),
-            opts[:in_umbrella],
-            do: Path.join([opts[:build], ".mix", @manifest])
-      else
-        []
+      cond do
+        Mix.Project.umbrella?() ->
+          for %{opts: opts} <- Mix.Dep.Umbrella.cached(),
+              do: Path.join([opts[:build], ".mix", @manifest])
+
+        opts[:include_siblings] ->
+          for %{scm: Mix.SCM.Path, opts: opts} <- Mix.Dep.cached(),
+              opts[:in_umbrella],
+              do: Path.join([opts[:build], ".mix", @manifest])
+
+        true ->
+          []
       end
 
     [Path.join(Mix.Project.manifest_path(), @manifest) | siblings]

lib/mix/test/mix/tasks/xref_test.exs

@@ -915,6 +915,43 @@ defmodule Mix.Tasks.XrefTest do
       end)
     end
 
+    test "generates reports from the umbrella root" do
+      Mix.Project.pop()
+
+      in_fixture("umbrella_dep/deps/umbrella", fn ->
+        Mix.Project.in_project(:umbrella, ".", fn _ ->
+          File.write!("apps/bar/lib/bar.ex", """
+          defmodule Bar do
+            def bar do
+              Foo.foo()
+            end
+          end
+          """)
+
+          Mix.Task.run("compile")
+          Mix.shell().flush()
+
+          Mix.Tasks.Xref.run(["graph", "--format", "stats", "--include-siblings"])
+
+          assert receive_until_no_messages([]) == """
+                 Tracked files: 2 (nodes)
+                 Compile dependencies: 0 (edges)
+                 Exports dependencies: 0 (edges)
+                 Runtime dependencies: 1 (edges)
+                 Cycles: 0
+
+                 Top 2 files with most outgoing dependencies:
+                   * lib/bar.ex (1)
+                   * lib/foo.ex (0)
+
+                 Top 2 files with most incoming dependencies:
+                   * lib/foo.ex (1)
+                   * lib/bar.ex (0)
+                 """
+        end)
+      end)
+    end
+
     test "generates reports considering siblings inside umbrellas" do
       Mix.Project.pop()