team-humaki · Sep 17, 2026
diff --git a/data_source.go b/data_source.go
@@ -59,16 +59,33 @@ func (s *sourceReadCloser) ReadCloser() (io.ReadCloser, error) {
 	return s.reader, nil
 }
 
+func snapshotReader(r io.Reader, c io.Closer) (dataSource, error) {
+	data, err := io.ReadAll(r)
+	var cerr error
+	if c != nil {
+		cerr = c.Close()
+	}
+	if err != nil {
+		return nil, err
+	}
+	if cerr != nil {
+		return nil, cerr
+	}
+	return &sourceData{data}, nil
+}
+
 func parseDataSource(source interface{}) (dataSource, error) {
 	switch s := source.(type) {
 	case string:
 		return sourceFile{s}, nil
 	case []byte:
 		return &sourceData{s}, nil
 	case io.ReadCloser:
-		return &sourceReadCloser{s}, nil
+		// Snapshot so Reload/Append can re-read after the original closer is
+		// consumed (io.Reader is not rewindable; Close made a second pass fail).
+		return snapshotReader(s, s)
 	case io.Reader:
-		return &sourceReadCloser{io.NopCloser(s)}, nil
+		return snapshotReader(s, nil)
 	default:
 		return nil, fmt.Errorf("error parsing data source: unknown type %q", s)
 	}

diff --git a/file_test.go b/file_test.go
@@ -16,9 +16,11 @@ package ini
 
 import (
 	"bytes"
+	"io"
 	"os"
 	"runtime"
 	"sort"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -399,6 +401,41 @@ NAME = Unknwon`)))
 	})
 }
 
+type closeOnceReader struct {
+	r      *strings.Reader
+	closed bool
+}
+
+func (c *closeOnceReader) Read(p []byte) (int, error) {
+	if c.closed {
+		return 0, os.ErrClosed
+	}
+	return c.r.Read(p)
+}
+
+func (c *closeOnceReader) Close() error {
+	c.closed = true
+	return nil
+}
+
+func TestFile_AppendReadersTwice(t *testing.T) {
+	f := Empty()
+	require.NotNil(t, f)
+
+	r1 := &closeOnceReader{r: strings.NewReader("[one]\na = 1\n")}
+	require.NoError(t, f.Append(r1))
+	assert.Equal(t, "1", f.Section("one").Key("a").String())
+
+	r2 := io.NopCloser(strings.NewReader("[two]\nb = 2\n"))
+	require.NoError(t, f.Append(r2))
+	assert.Equal(t, "1", f.Section("one").Key("a").String())
+	assert.Equal(t, "2", f.Section("two").Key("b").String())
+
+	require.NoError(t, f.Reload())
+	assert.Equal(t, "1", f.Section("one").Key("a").String())
+	assert.Equal(t, "2", f.Section("two").Key("b").String())
+}
+
 func TestFile_WriteTo(t *testing.T) {
 	if runtime.GOOS == "windows" {
 		t.Skip("Skipping testing on Windows")