fix(http): close prefetch response when temporary-file setup fails

internal/protocol/http/fetcher.go

@@ -512,6 +512,17 @@ func (f *Fetcher) asyncPrefetch() {
 		return
 	}
 
+	defer func() {
+		// Close the response even if temporary-file setup fails or shutdown
+		// rejects a late prefetch. Otherwise the server can remain blocked writing.
+		f.resolveRespLock.Lock()
+		if f.resolveResp != nil {
+			f.resolveResp.Body.Close()
+			f.resolveResp = nil
+		}
+		f.resolveRespLock.Unlock()
+	}()
+
 	// Create temporary file for prefetch data
 	tempDir := ""
 	if f.ctl != nil && f.ctl.TempDir != "" {
@@ -537,16 +548,6 @@ func (f *Fetcher) asyncPrefetch() {
 	f.prefetchFile = tmpFile
 	f.prefetchFilePath = tmpFile.Name()
 
-	defer func() {
-		// Close response body when prefetch stops
-		f.resolveRespLock.Lock()
-		if f.resolveResp != nil {
-			f.resolveResp.Body.Close()
-			f.resolveResp = nil
-		}
-		f.resolveRespLock.Unlock()
-	}()
-
 	buf := make([]byte, 32*1024) // 32KB buffer
 	reader := f.responseReader(resp)
 

internal/protocol/http/prefetch_setup_test.go

@@ -0,0 +1,74 @@
+package http
+
+import (
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/internal/controller"
+	"github.com/GopeedLab/gopeed/internal/tempfiles"
+)
+
+type prefetchSetupBody struct {
+	io.Reader
+	closed bool
+}
+
+func (b *prefetchSetupBody) Close() error {
+	b.closed = true
+	return nil
+}
+
+func TestPrefetchSetupFailureClosesResponse(t *testing.T) {
+	for _, closedScope := range []bool{false, true} {
+		name := "invalid_temp_directory"
+		if closedScope {
+			name = "downloader_already_closed"
+		}
+		t.Run(name, func(t *testing.T) {
+			root := t.TempDir()
+			scope := &tempfiles.Scope{}
+			dir := root
+			if closedScope {
+				if err := scope.Close(); err != nil {
+					t.Fatal(err)
+				}
+			} else {
+				dir = filepath.Join(root, "file")
+				if err := os.WriteFile(dir, nil, 0600); err != nil {
+					t.Fatal(err)
+				}
+			}
+			body := &prefetchSetupBody{Reader: strings.NewReader("unused response")}
+			f := &Fetcher{
+				ctl:         &controller.Controller{TempDir: dir, TempFiles: scope},
+				resolveResp: &http.Response{Body: body},
+			}
+			f.asyncPrefetch()
+			if f.prefetchErr == nil {
+				t.Fatal("expected temporary-file initialization to fail")
+			}
+			if !body.closed {
+				t.Error("prefetch setup failure left the response body open")
+			}
+			if f.resolveResp != nil {
+				t.Error("prefetch retained its failed resolve response")
+			}
+			if !f.prefetchDone.Load() {
+				t.Error("prefetch did not report completion")
+			}
+			if closedScope {
+				entries, err := os.ReadDir(root)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if len(entries) != 0 {
+					t.Errorf("late prefetch left temporary files: %v", entries)
+				}
+			}
+		})
+	}
+}