Fix Attach/EmbedReader and implement Attach/EmbedReadSeeker

msg.go

@@ -714,11 +714,22 @@ func (m *Msg) AttachFile(n string, o ...FileOption) {
 }
 
 // AttachReader adds an attachment File via io.Reader to the Msg
+//
+// CAVEAT: For AttachReader to work it has to read all data of the io.Reader
+// into memory first, so it can seek through it. Using larger amounts of
+// data on the io.Reader should be avoided. For such, it is recommeded to
+// either use AttachFile or AttachReadSeeker instead
 func (m *Msg) AttachReader(n string, r io.Reader, o ...FileOption) {
 	f := fileFromReader(n, r)
 	m.attachments = m.appendFile(m.attachments, f, o...)
 }
 
+// AttachReadSeeker adds an attachment File via io.ReadSeeker to the Msg
+func (m *Msg) AttachReadSeeker(n string, r io.ReadSeeker, o ...FileOption) {
+	f := fileFromReadSeeker(n, r)
+	m.attachments = m.appendFile(m.attachments, f, o...)
+}
+
 // AttachHTMLTemplate adds the output of a html/template.Template pointer as File attachment to the Msg
 func (m *Msg) AttachHTMLTemplate(n string, t *ht.Template, d interface{}, o ...FileOption) error {
 	f, err := fileFromHTMLTemplate(n, t, d)
@@ -762,11 +773,22 @@ func (m *Msg) EmbedFile(n string, o ...FileOption) {
 }
 
 // EmbedReader adds an embedded File from an io.Reader to the Msg
+//
+// CAVEAT: For AttachReader to work it has to read all data of the io.Reader
+// into memory first, so it can seek through it. Using larger amounts of
+// data on the io.Reader should be avoided. For such, it is recommeded to
+// either use AttachFile or AttachReadSeeker instead
 func (m *Msg) EmbedReader(n string, r io.Reader, o ...FileOption) {
 	f := fileFromReader(n, r)
 	m.embeds = m.appendFile(m.embeds, f, o...)
 }
 
+// EmbedReadSeeker adds an embedded File from an io.ReadSeeker to the Msg
+func (m *Msg) EmbedReadSeeker(n string, r io.ReadSeeker, o ...FileOption) {
+	f := fileFromReadSeeker(n, r)
+	m.embeds = m.appendFile(m.embeds, f, o...)
+}
+
 // EmbedHTMLTemplate adds the output of a html/template.Template pointer as embedded File to the Msg
 func (m *Msg) EmbedHTMLTemplate(n string, t *ht.Template, d interface{}, o ...FileOption) error {
 	f, err := fileFromHTMLTemplate(n, t, d)
@@ -1114,15 +1136,37 @@ func fileFromFS(n string) *File {
 
 // fileFromReader returns a File pointer from a given io.Reader
 func fileFromReader(n string, r io.Reader) *File {
+	d, err := io.ReadAll(r)
+	if err != nil {
+		return &File{}
+	}
+	br := bytes.NewReader(d)
 	return &File{
-		Name:   filepath.Base(n),
+		Name:   n,
+		Header: make(map[string][]string),
+		Writer: func(w io.Writer) (int64, error) {
+			rb, cerr := io.Copy(w, br)
+			if cerr != nil {
+				return rb, cerr
+			}
+			_, cerr = br.Seek(0, io.SeekStart)
+			return rb, cerr
+		},
+	}
+}
+
+// fileFromReadSeeker returns a File pointer from a given io.ReadSeeker
+func fileFromReadSeeker(n string, r io.ReadSeeker) *File {
+	return &File{
+		Name:   n,
 		Header: make(map[string][]string),
 		Writer: func(w io.Writer) (int64, error) {
-			nb, err := io.Copy(w, r)
+			rb, err := io.Copy(w, r)
 			if err != nil {
-				return nb, err
+				return rb, err
 			}
-			return nb, nil
+			_, err = r.Seek(0, io.SeekStart)
+			return rb, err
 		},
 	}
 }

msg_test.go

@@ -2667,3 +2667,127 @@ func TestMsg_GetBccString(t *testing.T) {
 			`"Toni Cc" <[email protected]>"`, fh[0])
 	}
 }
+
+// TestMsg_AttachEmbedReader_consecutive tests the Msg.AttachReader and Msg.EmbedReader
+// methods with consecutive calls to Msg.WriteTo to make sure the attachments are not
+// lost (see Github issue #110)
+func TestMsg_AttachEmbedReader_consecutive(t *testing.T) {
+	ts1 := "This is a test string"
+	ts2 := "Another test string"
+	m := NewMsg()
+	m.AttachReader("attachment.txt", bytes.NewBufferString(ts1))
+	m.EmbedReader("embeded.txt", bytes.NewBufferString(ts2))
+	obuf1 := &bytes.Buffer{}
+	obuf2 := &bytes.Buffer{}
+	_, err := m.WriteTo(obuf1)
+	if err != nil {
+		t.Errorf("WriteTo to first output buffer failed: %s", err)
+	}
+	_, err = m.WriteTo(obuf2)
+	if err != nil {
+		t.Errorf("WriteTo to second output buffer failed: %s", err)
+	}
+	if !strings.Contains(obuf1.String(), "VGhpcyBpcyBhIHRlc3Qgc3RyaW5n") {
+		t.Errorf("Expected file attachment string not found in first output buffer")
+	}
+	if !strings.Contains(obuf2.String(), "VGhpcyBpcyBhIHRlc3Qgc3RyaW5n") {
+		t.Errorf("Expected file attachment string not found in second output buffer")
+	}
+	if !strings.Contains(obuf1.String(), "QW5vdGhlciB0ZXN0IHN0cmluZw==") {
+		t.Errorf("Expected embeded file string not found in first output buffer")
+	}
+	if !strings.Contains(obuf2.String(), "QW5vdGhlciB0ZXN0IHN0cmluZw==") {
+		t.Errorf("Expected embded file string not found in second output buffer")
+	}
+}
+
+// TestMsg_AttachEmbedReadSeeker_consecutive tests the Msg.AttachReadSeeker and
+// Msg.EmbedReadSeeker methods with consecutive calls to Msg.WriteTo to make
+// sure the attachments are not lost (see Github issue #110)
+func TestMsg_AttachEmbedReadSeeker_consecutive(t *testing.T) {
+	ts1 := []byte("This is a test string")
+	ts2 := []byte("Another test string")
+	m := NewMsg()
+	m.AttachReadSeeker("attachment.txt", bytes.NewReader(ts1))
+	m.EmbedReadSeeker("embeded.txt", bytes.NewReader(ts2))
+	obuf1 := &bytes.Buffer{}
+	obuf2 := &bytes.Buffer{}
+	_, err := m.WriteTo(obuf1)
+	if err != nil {
+		t.Errorf("WriteTo to first output buffer failed: %s", err)
+	}
+	_, err = m.WriteTo(obuf2)
+	if err != nil {
+		t.Errorf("WriteTo to second output buffer failed: %s", err)
+	}
+	if !strings.Contains(obuf1.String(), "VGhpcyBpcyBhIHRlc3Qgc3RyaW5n") {
+		t.Errorf("Expected file attachment string not found in first output buffer")
+	}
+	if !strings.Contains(obuf2.String(), "VGhpcyBpcyBhIHRlc3Qgc3RyaW5n") {
+		t.Errorf("Expected file attachment string not found in second output buffer")
+	}
+	if !strings.Contains(obuf1.String(), "QW5vdGhlciB0ZXN0IHN0cmluZw==") {
+		t.Errorf("Expected embeded file string not found in first output buffer")
+	}
+	if !strings.Contains(obuf2.String(), "QW5vdGhlciB0ZXN0IHN0cmluZw==") {
+		t.Errorf("Expected embded file string not found in second output buffer")
+	}
+}
+
+// TestMsg_AttachReadSeeker tests the Msg.AttachReadSeeker method
+func TestMsg_AttachReadSeeker(t *testing.T) {
+	m := NewMsg()
+	ts := []byte("This is a test string")
+	r := bytes.NewReader(ts)
+	m.AttachReadSeeker("testfile.txt", r)
+	if len(m.attachments) != 1 {
+		t.Errorf("AttachReadSeeker() failed. Number of attachments expected: %d, got: %d", 1,
+			len(m.attachments))
+		return
+	}
+	file := m.attachments[0]
+	if file == nil {
+		t.Errorf("AttachReadSeeker() failed. Attachment file pointer is nil")
+		return
+	}
+	if file.Name != "testfile.txt" {
+		t.Errorf("AttachReadSeeker() failed. Expected file name: %s, got: %s", "testfile.txt",
+			file.Name)
+	}
+	wbuf := bytes.Buffer{}
+	if _, err := file.Writer(&wbuf); err != nil {
+		t.Errorf("execute WriterFunc failed: %s", err)
+	}
+	if wbuf.String() != string(ts) {
+		t.Errorf("AttachReadSeeker() failed. Expected string: %q, got: %q", ts, wbuf.String())
+	}
+}
+
+// TestMsg_EmbedReadSeeker tests the Msg.EmbedReadSeeker method
+func TestMsg_EmbedReadSeeker(t *testing.T) {
+	m := NewMsg()
+	ts := []byte("This is a test string")
+	r := bytes.NewReader(ts)
+	m.EmbedReadSeeker("testfile.txt", r)
+	if len(m.embeds) != 1 {
+		t.Errorf("EmbedReadSeeker() failed. Number of attachments expected: %d, got: %d", 1,
+			len(m.embeds))
+		return
+	}
+	file := m.embeds[0]
+	if file == nil {
+		t.Errorf("EmbedReadSeeker() failed. Embedded file pointer is nil")
+		return
+	}
+	if file.Name != "testfile.txt" {
+		t.Errorf("EmbedReadSeeker() failed. Expected file name: %s, got: %s", "testfile.txt",
+			file.Name)
+	}
+	wbuf := bytes.Buffer{}
+	if _, err := file.Writer(&wbuf); err != nil {
+		t.Errorf("execute WriterFunc failed: %s", err)
+	}
+	if wbuf.String() != string(ts) {
+		t.Errorf("EmbedReadSeeker() failed. Expected string: %q, got: %q", ts, wbuf.String())
+	}
+}