internal/download: only report stale existing downloads

internal/download/download.go

@@ -22,6 +22,7 @@ import (
 	"bytes"
 	"crypto/sha256"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"io"
 	"iter"
@@ -180,12 +181,13 @@ func (db *ChecksumDB) DownloadFile(url, dstPath string) error {
 		return fmt.Errorf("no known hash for file %q", basename)
 	}
 	// Shortcut if already downloaded.
-	if verifyHash(dstPath, hash) == nil {
+	if err := verifyHash(dstPath, hash); err == nil {
 		fmt.Printf("%s is up-to-date\n", dstPath)
 		return nil
+	} else if !errors.Is(err, os.ErrNotExist) {
+		fmt.Printf("%s is stale\n", dstPath)
 	}
 
-	fmt.Printf("%s is stale\n", dstPath)
 	fmt.Printf("downloading from %s\n", url)
 	resp, err := http.Get(url)
 	if err != nil {

internal/download/download_test.go

@@ -0,0 +1,109 @@
+// Copyright 2026 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package download
+
+import (
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestDownloadFileMissingDoesNotReportStale(t *testing.T) {
+	db, server := newTestChecksumDB(t, "payload")
+	defer server.Close()
+
+	dst := filepath.Join(t.TempDir(), "payload.dat")
+	var downloadErr error
+	output := captureStdout(t, func() {
+		downloadErr = db.DownloadFile(server.URL+"/payload.dat", dst)
+	})
+	if downloadErr != nil {
+		t.Fatal(downloadErr)
+	}
+	if strings.Contains(output, "is stale") {
+		t.Fatalf("missing file reported as stale:\n%s", output)
+	}
+	if !strings.Contains(output, "downloading from "+server.URL+"/payload.dat") {
+		t.Fatalf("missing download log not found:\n%s", output)
+	}
+}
+
+func TestDownloadFileHashMismatchReportsStale(t *testing.T) {
+	db, server := newTestChecksumDB(t, "payload")
+	defer server.Close()
+
+	dst := filepath.Join(t.TempDir(), "payload.dat")
+	if err := os.WriteFile(dst, []byte("old payload"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	var downloadErr error
+	output := captureStdout(t, func() {
+		downloadErr = db.DownloadFile(server.URL+"/payload.dat", dst)
+	})
+	if downloadErr != nil {
+		t.Fatal(downloadErr)
+	}
+	if !strings.Contains(output, dst+" is stale") {
+		t.Fatalf("stale download log not found:\n%s", output)
+	}
+}
+
+func newTestChecksumDB(t *testing.T, content string) (*ChecksumDB, *httptest.Server) {
+	t.Helper()
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = io.WriteString(w, content)
+	}))
+	sum := sha256.Sum256([]byte(content))
+	db, err := ParseChecksums([]byte(fmt.Sprintf("%x  payload.dat\n", sum)))
+	if err != nil {
+		server.Close()
+		t.Fatal(err)
+	}
+	return db, server
+}
+
+func captureStdout(t *testing.T, fn func()) string {
+	t.Helper()
+
+	previous := os.Stdout
+	reader, writer, err := os.Pipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer reader.Close()
+	os.Stdout = writer
+	defer func() {
+		os.Stdout = previous
+	}()
+
+	fn()
+	if err := writer.Close(); err != nil {
+		t.Fatal(err)
+	}
+	output, err := io.ReadAll(reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(output)
+}