Surface the real download error instead of a misleading file-not-found

gmile · gmile · commit c403d6704f56 · 2026-06-10T11:47:54.000+02:00
When a precompiled NIF download failed, the error from Artefact.download/2 was
discarded and verify_and_decompress/2 then ran on the missing file, reporting a
misleading :enoent. Capture the download result and only verify on success.
diff --git a/lib/mix/tasks/compile.elixir_make.ex b/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}
diff --git a/test/mix/tasks/compile.make_test.exs b/test/mix/tasks/compile.make_test.exs
@@ -421,6 +421,29 @@ defmodule Mix.Tasks.Compile.ElixirMakeTest do
     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 @@ defmodule MyApp.Downloader do
     File.read(path)
   end
 end
+
+defmodule MyApp.FailingDownloader do
+  @behaviour ElixirMake.Downloader
+
+  @impl true
+  def download(_url), do: {:error, "download boom"}
+end
