Fix lint errors introduced by textproto import (#285)

* textproto: Add comments to make go vet pass

* textproto: fix errcheck lint errors from imported files

internal/textproto/reader.go

@@ -180,7 +180,7 @@ func (r *Reader) skipSpace() int {
 			break
 		}
 		if c != ' ' && c != '\t' {
-			r.R.UnreadByte()
+			_ = r.R.UnreadByte()
 			break
 		}
 		n++
@@ -373,7 +373,7 @@ func (d *dotReader) Read(b []byte) (n int, err error) {
 			}
 			// Not part of .\r\n.
 			// Consume leading dot and emit saved \r.
-			br.UnreadByte()
+			_ = br.UnreadByte()
 			c = '\r'
 			d.state = stateData
 
@@ -383,7 +383,7 @@ func (d *dotReader) Read(b []byte) (n int, err error) {
 				break
 			}
 			// Not part of \r\n. Emit saved \r
-			br.UnreadByte()
+			_ = br.UnreadByte()
 			c = '\r'
 			d.state = stateData
 
@@ -418,7 +418,7 @@ func (r *Reader) closeDot() {
 	for r.dot != nil {
 		// When Read reaches EOF or an error,
 		// it will set r.dot == nil.
-		r.dot.Read(buf)
+		_, _ = r.dot.Read(buf)
 	}
 }
 
@@ -589,7 +589,7 @@ var nl = []byte("\n")
 // that will be in this header. If it gets confused, it returns 0.
 func (r *Reader) upcomingHeaderNewlines() (n int) {
 	// Try to determine the 'hint' size.
-	r.R.Peek(1) // force a buffer load if empty
+	_, _ = r.R.Peek(1) // force a buffer load if empty
 	s := r.R.Buffered()
 	if s == 0 {
 		return

internal/textproto/reader_email.go

@@ -6,6 +6,10 @@ import (
 	"math"
 )
 
+// ReadEmailMIMEHeader reads a MIME-style header from r.
+//
+// This is a modified version of the stock func that better handles the characters
+// we must support in email, instead of just HTTP.
 func (r *Reader) ReadEmailMIMEHeader() (MIMEHeader, error) {
 	return readEmailMIMEHeader(r, math.MaxInt64)
 }
@@ -91,6 +95,11 @@ func readEmailMIMEHeader(r *Reader, lim int64) (MIMEHeader, error) {
 	}
 }
 
+// CanonicalEmailMIMEHeaderKey returns the canonical format of the
+// MIME header key s.
+//
+// This is a modified version of the stock func that better handles the characters
+// we must support in email, instead of just HTTP.
 func CanonicalEmailMIMEHeaderKey(s string) string {
 	// Quick check for canonical encoding.
 	upper := true

internal/textproto/reader_test.go

@@ -387,9 +387,9 @@ func TestIssue46363(t *testing.T) {
 	r, w := net.Pipe()
 	go func() {
 		// ReadMIMEHeader calls canonicalMIMEHeaderKey, which reads from commonHeader
-		NewConn(r).ReadMIMEHeader()
+		_, _ = NewConn(r).ReadMIMEHeader()
 	}()
-	w.Write([]byte("A: 1\r\nB: 2\r\nC: 3\r\n\r\n"))
+	_, _ = w.Write([]byte("A: 1\r\nB: 2\r\nC: 3\r\n\r\n"))
 
 	// CanonicalMIMEHeaderKey calls commonHeaderOnce.Do(initCommonHeader) which initializes commonHeader
 	CanonicalMIMEHeaderKey("a")

internal/textproto/writer.go

@@ -29,7 +29,7 @@ var dotcrnl = []byte{'.', '\r', '\n'}
 func (w *Writer) PrintfLine(format string, args ...any) error {
 	w.closeDot()
 	fmt.Fprintf(w.W, format, args...)
-	w.W.Write(crnl)
+	_, _ = w.W.Write(crnl)
 	return w.W.Flush()
 }
 
@@ -73,7 +73,7 @@ func (d *dotWriter) Write(b []byte) (n int, err error) {
 			d.state = wstateData
 			if c == '.' {
 				// escape leading dot
-				bw.WriteByte('.')
+				_ = bw.WriteByte('.')
 			}
 			fallthrough
 
@@ -82,7 +82,7 @@ func (d *dotWriter) Write(b []byte) (n int, err error) {
 				d.state = wstateCR
 			}
 			if c == '\n' {
-				bw.WriteByte('\r')
+				_ = bw.WriteByte('\r')
 				d.state = wstateBeginLine
 			}
 
@@ -107,13 +107,13 @@ func (d *dotWriter) Close() error {
 	bw := d.w.W
 	switch d.state {
 	default:
-		bw.WriteByte('\r')
+		_ = bw.WriteByte('\r')
 		fallthrough
 	case wstateCR:
-		bw.WriteByte('\n')
+		_ = bw.WriteByte('\n')
 		fallthrough
 	case wstateBeginLine:
-		bw.Write(dotcrnl)
+		_, _ = bw.Write(dotcrnl)
 	}
 	return bw.Flush()
 }