Propagate download errors instead of falling back to a misleading file-not-found

lib/mix/tasks/compile.elixir_make.ex

@@ -231,16 +231,20 @@ defmodule Mix.Tasks.Compile.ElixirMake do
       {:ok, target, nif_version_to_use, url} ->
         archived_fullpath = Artefact.archive_path(config, target, nif_version_to_use)
 
-        unless File.exists?(archived_fullpath) do
-          Mix.shell().info("Downloading precompiled NIF to #{archived_fullpath}")
+        download =
+          unless File.exists?(archived_fullpath) do
+            Mix.shell().info("Downloading precompiled NIF to #{archived_fullpath}")
 
-          with {:ok, archived_data} <- Artefact.download(config, url) do
-            File.mkdir_p(Path.dirname(archived_fullpath))
-            File.write(archived_fullpath, archived_data)
+            with {:ok, archived_data} <- Artefact.download(config, url) do
+              File.mkdir_p(Path.dirname(archived_fullpath))
+              File.write(archived_fullpath, archived_data)
+            end
           end
-        end
 
-        Artefact.verify_and_decompress(archived_fullpath, app_priv)
+        case download do
+          {:error, _} = error -> error
+          _ -> Artefact.verify_and_decompress(archived_fullpath, app_priv)
+        end
 
       {:error, msg} ->
         {:error, msg}

test/mix/tasks/compile.make_test.exs

@@ -32,7 +32,7 @@
     :ok
   end
 
   test "running with a specific executable" do
     in_fixture(fn ->
       with_project_config([make_executable: "nonexistentmake"], fn ->
         assert_raise Mix.Error, ~r/not found in the path/, fn ->
@@ -42,7 +42,7 @@
     end)
   end
 
   test "running without a makefile" do
     msg = ~r/\ACould not compile with/
 
     in_fixture(fn ->
@@ -100,7 +100,7 @@
     end)
   end
 
   test "warns if the cwd contains a space" do
     in_fixture(fn ->
       File.mkdir_p!("subdir with spaces")
 
@@ -185,7 +185,7 @@
     end)
   end
 
   test "overwrite default env" do
     in_fixture(fn ->
       File.write!("Makefile", """
       all:
@@ -198,7 +198,7 @@
     end)
   end
 
   test "specifying a makefile" do
     in_fixture(fn ->
       File.write("MyMakefile", """
       all:
@@ -238,7 +238,7 @@
     end)
   end
 
   test "user-defined executable through environment variable" do
     in_fixture(fn ->
       System.put_env("MAKE", "nonexistentmake")
 
@@ -250,7 +250,7 @@
     end)
   end
 
   test "user-defined executable with no arguments allowed" do
     in_fixture(fn ->
       System.put_env("MAKE", "make -f makefile")
 
@@ -278,7 +278,7 @@
     end)
   end
 
   test "additional args to make" do
     in_fixture(fn ->
       File.write("Makefile", """
       all:
@@ -292,7 +292,7 @@
     end)
   end
 
   test "doesn't clobber existing build artifacts" do
     in_fixture(fn ->
       build_file_path = "./_build/test/lib/my_app/priv/build_file"
 
@@ -381,7 +381,7 @@
     end)
   end
 
   test "custom downloader" do
     in_fixture(fn ->
       File.mkdir!("priv")
 
@@ -421,6 +421,29 @@
     end)
   end
 
+  test "surfaces the download error instead of a misleading file-not-found" do
+    in_fixture(fn ->
+      File.mkdir!("priv")
+
+      File.write("Makefile", """
+      all:
+      \t@touch priv/my_app
+      """)
+
+      with_project_config(
+        [
+          make_precompiler: {:nif, MyApp.Precompiler},
+          make_precompiler_url: "https://example.com/@{artefact_filename}",
+          make_precompiler_downloader: MyApp.FailingDownloader
+        ],
+        fn ->
+          System.put_env("ELIXIR_MAKE_CACHE_DIR", "./cache")
+          assert capture_io(:stderr, fn -> run([]) end) =~ "download boom"
+        end
+      )
+    end)
+  end
+
   defp in_fixture(fun) do
     File.cd!(@fixture_project, fun)
   end
@@ -440,3 +463,10 @@
     File.read(path)
   end
 end
+
+defmodule MyApp.FailingDownloader do
+  @behaviour ElixirMake.Downloader
+
+  @impl true
+  def download(_url), do: {:error, "download boom"}
+end