fix(cloud/local): propagate destination listing errors

internal/cloud/provider_local.go

@@ -41,7 +41,7 @@ func (p localFolder) list() ([]CloudFile, error) {
 	}
 	entries, err := os.ReadDir(p.cfg.URL)
 	if err != nil {
-		return []CloudFile{}, nil
+		return nil, fmt.Errorf("read local folder destination %q: %w", p.cfg.URL, err)
 	}
 	var files []CloudFile
 	for _, e := range entries {

internal/cloud/provider_local_integrity_test.go

@@ -0,0 +1,45 @@
+package cloud
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/opensave/opensave/internal/store"
+)
+
+func TestLocalFolderListPropagatesDirectoryErrors(t *testing.T) {
+	t.Run("absent directory", func(t *testing.T) {
+		missing := filepath.Join(t.TempDir(), "missing-share")
+		files, err := (localFolder{cfg: store.CloudConfig{URL: missing}}).list()
+		if err == nil {
+			t.Fatalf("list = %+v, nil error; want missing-directory error", files)
+		}
+	})
+
+	t.Run("configured path is not a directory", func(t *testing.T) {
+		path := filepath.Join(t.TempDir(), "not-a-directory")
+		if err := os.WriteFile(path, []byte("x"), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		files, err := (localFolder{cfg: store.CloudConfig{URL: path}}).list()
+		if err == nil {
+			t.Fatalf("list = %+v, nil error; want directory-read error", files)
+		}
+	})
+}
+
+func TestLocalFolderListStillSupportsOrdinaryFolders(t *testing.T) {
+	dir := t.TempDir()
+	want := []byte("synthetic zip")
+	if err := os.WriteFile(filepath.Join(dir, "game__main__snap_1.zip"), want, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	files, err := (localFolder{cfg: store.CloudConfig{URL: dir}}).list()
+	if err != nil {
+		t.Fatalf("list: %v", err)
+	}
+	if len(files) != 1 || files[0].Name != "game__main__snap_1.zip" || files[0].SizeBytes != int64(len(want)) {
+		t.Fatalf("list = %+v", files)
+	}
+}