test(gopher): add resume coverage for typeInformation

internal/protocol/gopher/gopher_test.go

@@ -494,3 +494,103 @@ func TestGopherResumeIgnoredWhenWriterSet(t *testing.T) {
 		t.Error("Output file should not be created when Writer is set")
 	}
 }
+
+// TestGopherResumeInformation verifies that resume machinery works for the
+// informational (type i) response path, which is also routed through
+// downloadText. Informational lines are passed through verbatim (no
+// metadata strip), so the resume offset matches the raw line length
+// including trailing CR/LF.
+func TestGopherResumeInformation(t *testing.T) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer listener.Close()
+	port := listener.Addr().(*net.TCPAddr).Port
+
+	cancelReady := make(chan struct{})
+	connReady := make(chan struct{})
+	go func() {
+		for i := 0; i < 2; i++ {
+			conn, lerr := listener.Accept()
+			if lerr != nil {
+				return
+			}
+			r := bufio.NewReader(conn)
+			r.ReadString('\n')
+			if i == 0 {
+				// First half: send two info lines, then wait
+				// for the client to cancel before closing.
+				conn.Write([]byte("iFirst line.\r\n"))
+				conn.Write([]byte("iSecond line.\r\n"))
+				<-cancelReady
+				conn.Close()
+				connReady <- struct{}{}
+			} else {
+				// Second half: full body.
+				conn.Write([]byte("iFirst line.\r\n"))
+				conn.Write([]byte("iSecond line.\r\n"))
+				conn.Write([]byte(".\r\n"))
+				conn.Close()
+			}
+		}
+	}()
+
+	tmp := t.TempDir()
+	outPath := tmp + "/info.txt"
+
+	proto := NewProtocol()
+	u, _ := url.Parse("gopher://127.0.0.1:" + strconv.Itoa(port) + "/info")
+
+	progress := make(chan int64, 1)
+	ctx1, cancel1 := context.WithCancel(context.Background())
+	errCh := make(chan error, 1)
+	go func() {
+		_, dlErr := proto.Download(ctx1, &core.DownloadRequest{
+			URL:    u,
+			Output: outPath,
+			ProgressCallback: func(current, total int64, speed float64) {
+				select {
+				case progress <- current:
+				default:
+				}
+			},
+		})
+		errCh <- dlErr
+	}()
+	<-progress
+	cancel1()
+	cancelReady <- struct{}{}
+	<-connReady
+	if dlErr := <-errCh; dlErr == nil {
+		t.Fatal("expected error from cancelled context")
+	}
+
+	// Resume should append the missing bytes. For informational lines
+	// we do not strip metadata, so the output preserves the server CR/LF.
+	result, resErr := proto.Download(context.Background(), &core.DownloadRequest{
+		URL:    u,
+		Output: outPath,
+		Resume: true,
+	})
+	if resErr != nil {
+		t.Fatalf("resume download failed: %v", resErr)
+	}
+	if !result.Resumed {
+		t.Error("expected Resumed=true")
+	}
+	if result.ContentType != "text/plain" {
+		t.Errorf("ContentType = %q, want text/plain", result.ContentType)
+	}
+
+	data, _ := os.ReadFile(outPath)
+	// Informational lines are passed through verbatim: the 'i' item-type
+	// prefix and CR/LF framing from the server survive into the output.
+	want := "iFirst line.\r\niSecond line.\r\n"
+	if string(data) != want {
+		t.Errorf("content = %q, want %q", string(data), want)
+	}
+	if output.FileExists(outPath + output.ResumeMetaFileSuffix) {
+		t.Error("expected .goget.meta to be deleted after successful resume")
+	}
+}