Use errors.Is everywhere.

This should cover every single case where we were using == or != on an
err.

There may be other cases to address, but this covers a big one.

client.go

@@ -275,7 +275,7 @@ func (c *Client) nextID() uint32 {
 func (c *Client) recvVersion() error {
 	typ, data, err := c.recvPacket(0)
 	if err != nil {
-		if err == io.EOF {
+		if errors.Is(err, io.EOF) {
 			return fmt.Errorf("server unexpectedly closed connection: %w", io.ErrUnexpectedEOF)
 		}
 
@@ -368,7 +368,7 @@ func (c *Client) ReadDir(p string) ([]os.FileInfo, error) {
 			return nil, unimplementedPacketErr(typ)
 		}
 	}
-	if err == io.EOF {
+	if errors.Is(err, io.EOF) {
 		err = nil
 	}
 	return attrs, err
@@ -1238,7 +1238,7 @@ func (f *File) writeToSequential(w io.Writer) (written int64, err error) {
 		}
 
 		if err != nil {
-			if err == io.EOF {
+			if errors.Is(err, io.EOF) {
 				return written, nil // return nil explicitly.
 			}
 
@@ -1435,7 +1435,7 @@ func (f *File) WriteTo(w io.Writer) (written int64, err error) {
 		}
 
 		if packet.err != nil {
-			if packet.err == io.EOF {
+			if errors.Is(packet.err, io.EOF) {
 				return written, nil
 			}
 
@@ -1726,7 +1726,7 @@ func (f *File) ReadFromWithConcurrency(r io.Reader, concurrency int) (read int64
 			}
 
 			if err != nil {
-				if err != io.EOF {
+				if !errors.Is(err, io.EOF) {
 					errCh <- rwErr{off, err}
 				}
 				return
@@ -1878,7 +1878,7 @@ func (f *File) ReadFrom(r io.Reader) (int64, error) {
 		}
 
 		if err != nil {
-			if err == io.EOF {
+			if errors.Is(err, io.EOF) {
 				return read, nil // return nil explicitly.
 			}
 

client_integration_test.go

@@ -1240,7 +1240,7 @@ func TestClientReadSimple(t *testing.T) {
 	defer f2.Close()
 	stuff := make([]byte, 32)
 	n, err := f2.Read(stuff)
-	if err != nil && err != io.EOF {
+	if err != nil && !errors.Is(err, io.EOF) {
 		t.Fatalf("err: %v", err)
 	}
 	if n != 5 {
@@ -2152,7 +2152,7 @@ func TestMatch(t *testing.T) {
 		pattern := tt.pattern
 		s := tt.s
 		ok, err := Match(pattern, s)
-		if ok != tt.match || err != tt.err {
+		if ok != tt.match || !errors.Is(err, tt.err) {
 			t.Errorf("Match(%#q, %#q) = %v, %q want %v, %q", pattern, s, ok, errp(err), tt.match, errp(tt.err))
 		}
 	}
@@ -2411,7 +2411,7 @@ func benchmarkRead(b *testing.B, bufsize int, delay time.Duration) {
 		for offset < size {
 			n, err := io.ReadFull(f2, buf)
 			offset += n
-			if err == io.ErrUnexpectedEOF && offset != size {
+			if errors.Is(err, io.ErrUnexpectedEOF) && offset != size {
 				b.Fatalf("read too few bytes! want: %d, got: %d", size, n)
 			}
 

examples/go-sftp-server/main.go

@@ -4,6 +4,7 @@
 package main
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -136,7 +137,7 @@ func main() {
 		if err != nil {
 			log.Fatal(err)
 		}
-		if err := server.Serve(); err == io.EOF {
+		if err := server.Serve(); errors.Is(err, io.EOF) {
 			server.Close()
 			log.Print("sftp client exited session.")
 		} else if err != nil {

examples/request-server/main.go

@@ -4,6 +4,7 @@
 package main
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -120,7 +121,7 @@ func main() {
 
 		root := sftp.InMemHandler()
 		server := sftp.NewRequestServer(channel, root)
-		if err := server.Serve(); err == io.EOF {
+		if err := server.Serve(); errors.Is(err, io.EOF) {
 			server.Close()
 			log.Print("sftp client exited session.")
 		} else if err != nil {

packet.go

@@ -292,7 +292,7 @@ func recvPacket(r io.Reader, alloc *allocator, orderID uint32) (uint8, []byte, e
 	if _, err := io.ReadFull(r, b[:length]); err != nil {
 		// ReadFull only returns EOF if it has read no bytes.
 		// In this case, that means a partial packet, and thus unexpected.
-		if err == io.EOF {
+		if errors.Is(err, io.EOF) {
 			err = io.ErrUnexpectedEOF
 		}
 		debug("recv packet %d bytes: err %v", length, err)

request-example.go

@@ -86,7 +86,7 @@ func (fs *root) openfile(pathname string, flags uint32) (*memFile, error) {
 	pflags := newFileOpenFlags(flags)
 
 	file, err := fs.fetch(pathname)
-	if err == os.ErrNotExist {
+	if errors.Is(err, os.ErrNotExist) {
 		if !pflags.Creat {
 			return nil, os.ErrNotExist
 		}

request-server.go

@@ -189,7 +189,7 @@ func (rs *RequestServer) Serve() error {
 	// make sure all open requests are properly closed
 	// (eg. possible on dropped connections, client crashes, etc.)
 	for handle, req := range rs.openRequests {
-		if err == io.EOF {
+		if errors.Is(err, io.EOF) {
 			err = io.ErrUnexpectedEOF
 		}
 		req.transferError(err)

request-server_test.go

@@ -2,6 +2,7 @@ package sftp
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -240,7 +241,7 @@ func TestRequestJustRead(t *testing.T) {
 	defer rf.Close()
 	contents := make([]byte, 5)
 	n, err := rf.Read(contents)
-	if err != nil && err != io.EOF {
+	if err != nil && !errors.Is(err, io.EOF) {
 		t.Fatalf("err: %v", err)
 	}
 	assert.Equal(t, 5, n)

request.go

@@ -385,7 +385,7 @@ func fileget(h FileReader, r *Request, pkt requestPacket, alloc *allocator, orde
 
 	n, err := rd.ReadAt(data, offset)
 	// only return EOF error if no data left to read
-	if err != nil && (err != io.EOF || n == 0) {
+	if err != nil && (!errors.Is(err, io.EOF) || n == 0) {
 		return statusFromError(pkt.id(), err)
 	}
 
@@ -422,7 +422,7 @@ func fileputget(h FileWriter, r *Request, pkt requestPacket, alloc *allocator, o
 
 		n, err := rw.ReadAt(data, offset)
 		// only return EOF error if no data left to read
-		if err != nil && (err != io.EOF || n == 0) {
+		if err != nil && (!errors.Is(err, io.EOF) || n == 0) {
 			return statusFromError(pkt.id(), err)
 		}
 
@@ -507,7 +507,7 @@ func filelist(h FileLister, r *Request, pkt requestPacket) responsePacket {
 
 	switch r.Method {
 	case "List":
-		if err != nil && (err != io.EOF || n == 0) {
+		if err != nil && (!errors.Is(err, io.EOF) || n == 0) {
 			return statusFromError(pkt.id(), err)
 		}
 
@@ -560,7 +560,7 @@ func filestat(h FileLister, r *Request, pkt requestPacket) responsePacket {
 
 	switch r.Method {
 	case "Stat", "Lstat":
-		if err != nil && err != io.EOF {
+		if err != nil && !errors.Is(err, io.EOF) {
 			return statusFromError(pkt.id(), err)
 		}
 		if n == 0 {
@@ -576,7 +576,7 @@ func filestat(h FileLister, r *Request, pkt requestPacket) responsePacket {
 			info: finfo[0],
 		}
 	case "Readlink":
-		if err != nil && err != io.EOF {
+		if err != nil && !errors.Is(err, io.EOF) {
 			return statusFromError(pkt.id(), err)
 		}
 		if n == 0 {

server.go

@@ -289,7 +289,7 @@ func handlePacket(s *Server, p orderedRequest) error {
 			err = nil
 			data := p.getDataSlice(s.pktMgr.alloc, orderID)
 			n, _err := f.ReadAt(data, int64(p.Offset))
-			if _err != nil && (_err != io.EOF || n == 0) {
+			if _err != nil && (!errors.Is(_err, io.EOF) || n == 0) {
 				err = _err
 			}
 			rpkt = &sshFxpDataPacket{
@@ -354,7 +354,7 @@ func (svr *Server) Serve() error {
 		pktType, pktBytes, err = svr.serverConn.recvPacket(svr.pktMgr.getNextOrderID())
 		if err != nil {
 			// Check whether the connection terminated cleanly in-between packets.
-			if err == io.EOF {
+			if errors.Is(err, io.EOF) {
 				err = nil
 			}
 			// we don't care about releasing allocated pages here, the server will quit and the allocator freed