Lint free

.golangci.yml

@@ -15,6 +15,7 @@ linters:
   enable:
     - depguard
     - dupl
+    - errcheck
     - goconst
     - gocritic
     - gofmt
@@ -30,8 +31,6 @@ linters:
     - stylecheck
     - unconvert
     - unparam
-  disable:
-    - errcheck # TODO
 
 linters-settings:
   dupl:

doc.go

@@ -2,5 +2,4 @@
 // efficiently.
 //
 // More info on Github: https://github.com/go-mail/mail
-//
 package gomail

message_test.go

@@ -351,9 +351,9 @@ func TestRename(t *testing.T) {
 	m.SetHeader("From", "from@example.com")
 	m.SetHeader("To", "to@example.com")
 	m.SetBody("text/plain", "Test")
-	name, copy := mockCopyFile("/tmp/test.pdf")
+	name, copyFile := mockCopyFile("/tmp/test.pdf")
 	rename := Rename("another.pdf")
-	m.Attach(name, copy, rename)
+	m.Attach(name, copyFile, rename)
 
 	want := &message{
 		from: "from@example.com",

smtp.go

@@ -4,6 +4,7 @@ import (
 	"crypto/tls"
 	"fmt"
 	"io"
+	"log/slog"
 	"net"
 	"net/smtp"
 	"strings"
@@ -94,7 +95,9 @@ func (d *Dialer) Dial() (SendCloser, error) {
 	}
 
 	if d.Timeout > 0 {
-		conn.SetDeadline(time.Now().Add(d.Timeout))
+		if tErr := conn.SetDeadline(time.Now().Add(d.Timeout)); tErr != nil {
+			slog.Error("unable to set connection deadline", "error", tErr.Error())
+		}
 	}
 
 	if d.LocalName != "" {
@@ -113,7 +116,9 @@ func (d *Dialer) Dial() (SendCloser, error) {
 
 		if ok {
 			if err := c.StartTLS(d.tlsConfig()); err != nil {
-				c.Close()
+				if cErr := c.Close(); cErr != nil {
+					slog.Error("unable to close smtpClient after attempting to startTLS", "error", cErr.Error())
+				}
 				return nil, err
 			}
 		}
@@ -138,7 +143,9 @@ func (d *Dialer) Dial() (SendCloser, error) {
 
 	if d.Auth != nil {
 		if err = c.Auth(d.Auth); err != nil {
-			c.Close()
+			if cErr := c.Close(); cErr != nil {
+				slog.Error("unable to close smtpClient after attempting to set Auth", "error", cErr.Error())
+			}
 			return nil, err
 		}
 	}
@@ -205,7 +212,12 @@ func (d *Dialer) DialAndSend(m ...*Message) error {
 	if err != nil {
 		return err
 	}
-	defer s.Close()
+
+	defer func() {
+		if sErr := s.Close(); sErr != nil {
+			slog.Error("unable to close sendCloser after attempting to Close", "error", sErr.Error())
+		}
+	}()
 
 	return Send(s, m...)
 }
@@ -230,7 +242,9 @@ func (c *smtpSender) retryError(err error) bool {
 
 func (c *smtpSender) Send(from string, to []string, msg io.WriterTo) error {
 	if c.d.Timeout > 0 {
-		c.conn.SetDeadline(time.Now().Add(c.d.Timeout))
+		if err := c.conn.SetDeadline(time.Now().Add(c.d.Timeout)); err != nil {
+			slog.Error("unable to set context deadline in send", "error", err.Error())
+		}
 	}
 
 	if err := c.Mail(from); err != nil {
@@ -260,7 +274,9 @@ func (c *smtpSender) Send(from string, to []string, msg io.WriterTo) error {
 	}
 
 	if _, err = msg.WriteTo(w); err != nil {
-		w.Close()
+		if wErr := w.Close(); wErr != nil {
+			slog.Error("unable to close writeCloser after attempting to write message", "error", wErr.Error())
+		}
 		return err
 	}
 

writeto.go

@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"errors"
 	"io"
+	"log/slog"
 	"mime"
 	"mime/multipart"
 	"path/filepath"
@@ -80,7 +81,9 @@ type messageWriter struct {
 func (w *messageWriter) openMultipart(mimeType, boundary string) {
 	mw := multipart.NewWriter(w)
 	if boundary != "" {
-		mw.SetBoundary(boundary)
+		if err := mw.SetBoundary(boundary); err != nil {
+			slog.Error("unable to set boundary in openMultipart", "error", err.Error())
+		}
 	}
 	contentType := "multipart/" + mimeType + ";\r\n boundary=" + mw.Boundary()
 	w.writers[w.depth] = mw
@@ -102,7 +105,9 @@ func (w *messageWriter) createPart(h map[string][]string) {
 
 func (w *messageWriter) closeMultipart() {
 	if w.depth > 0 {
-		w.writers[w.depth-1].Close()
+		if err := w.writers[w.depth-1].Close(); err != nil {
+			slog.Error("unable to close writers in closeMultipart", "error", err.Error())
+		}
 		w.depth--
 	}
 }
@@ -270,13 +275,17 @@ func (w *messageWriter) writeBody(f func(io.Writer) error, enc Encoding) {
 	case Base64:
 		wc := base64.NewEncoder(base64.StdEncoding, newBase64LineWriter(subWriter))
 		w.err = f(wc)
-		wc.Close()
+		if err := wc.Close(); err != nil {
+			slog.Error("unable to close writer for base64 write body", "error", err.Error())
+		}
 	case Unencoded:
 		w.err = f(subWriter)
 	default:
 		wc := newQPWriter(subWriter)
 		w.err = f(wc)
-		wc.Close()
+		if err := wc.Close(); err != nil {
+			slog.Error("unable to close newQPWriter", "error", err.Error())
+		}
 	}
 }
 
@@ -297,14 +306,21 @@ func newBase64LineWriter(w io.Writer) *base64LineWriter {
 func (w *base64LineWriter) Write(p []byte) (int, error) {
 	n := 0
 	for len(p)+w.lineLen > maxLineLen {
-		w.w.Write(p[:maxLineLen-w.lineLen])
-		w.w.Write([]byte("\r\n"))
+		if _, err := w.w.Write(p[:maxLineLen-w.lineLen]); err != nil {
+			slog.Error("unable to write line", "error", err.Error())
+		}
+
+		if _, err := w.w.Write([]byte("\r\n")); err != nil {
+			slog.Error("unable to write newline characters", "error", err.Error())
+		}
 		p = p[maxLineLen-w.lineLen:]
 		n += maxLineLen - w.lineLen
 		w.lineLen = 0
 	}
 
-	w.w.Write(p)
+	if _, err := w.w.Write(p); err != nil {
+		slog.Error("unable to write final line", "error", err.Error())
+	}
 	w.lineLen += len(p)
 
 	return n + len(p), nil