enable errorlint linter and fix issues

.golangci.yml

@@ -1,6 +1,7 @@
 linters:
   enable:
     - bodyclose
+    - errorlint
     - goconst
     - godot
     - gofmt
@@ -10,5 +11,4 @@ linters:
   disable:
     # Temporarily disabling so it can be addressed in a dedicated PR.
     - errcheck
-    - errorlint
     - goerr113

client_test.go

@@ -3,6 +3,7 @@ package kafka
 import (
 	"bytes"
 	"context"
+	"errors"
 	"io"
 	"math/rand"
 	"net"
@@ -262,7 +263,7 @@ func TestClientProduceAndConsume(t *testing.T) {
 		for {
 			r, err := res.Records.ReadRecord()
 			if err != nil {
-				if err != io.EOF {
+				if !errors.Is(err, io.EOF) {
 					t.Fatal(err)
 				}
 				break

compress/snappy/go-xerial-snappy/snappy_test.go

@@ -2,6 +2,7 @@ package snappy
 
 import (
 	"bytes"
+	"errors"
 	"testing"
 )
 
@@ -92,7 +93,7 @@ func TestSnappyDecodeMalformedTruncatedHeader(t *testing.T) {
 	for i := 0; i < len(xerialHeader); i++ {
 		buf := make([]byte, i)
 		copy(buf, xerialHeader[:i])
-		if _, err := Decode(buf); err != ErrMalformed {
+		if _, err := Decode(buf); !errors.Is(err, ErrMalformed) {
 			t.Errorf("expected ErrMalformed got %v", err)
 		}
 	}
@@ -104,7 +105,7 @@ func TestSnappyDecodeMalformedTruncatedSize(t *testing.T) {
 	for _, size := range sizes {
 		buf := make([]byte, size)
 		copy(buf, xerialHeader)
-		if _, err := Decode(buf); err != ErrMalformed {
+		if _, err := Decode(buf); !errors.Is(err, ErrMalformed) {
 			t.Errorf("expected ErrMalformed got %v", err)
 		}
 	}
@@ -116,7 +117,7 @@ func TestSnappyDecodeMalformedBNoData(t *testing.T) {
 	copy(buf, xerialHeader)
 	// indicate that there's one byte of data to be read
 	buf[len(buf)-1] = 1
-	if _, err := Decode(buf); err != ErrMalformed {
+	if _, err := Decode(buf); !errors.Is(err, ErrMalformed) {
 		t.Errorf("expected ErrMalformed got %v", err)
 	}
 }
@@ -128,7 +129,7 @@ func TestSnappyMasterDecodeFailed(t *testing.T) {
 	buf[len(buf)-2] = 1
 	// A payload which will not decode
 	buf[len(buf)-1] = 1
-	if _, err := Decode(buf); err == ErrMalformed || err == nil {
+	if _, err := Decode(buf); errors.Is(err, ErrMalformed) || err == nil {
 		t.Errorf("unexpected err: %v", err)
 	}
 }

conn.go

@@ -1231,11 +1231,10 @@ func (c *Conn) writeRequest(apiKey apiKey, apiVersion apiVersion, correlationID
 
 func (c *Conn) readResponse(size int, res interface{}) error {
 	size, err := read(&c.rbuf, size, res)
-	switch err.(type) {
-	case Error:
-		var e error
-		if size, e = discardN(&c.rbuf, size, size); e != nil {
-			err = e
+	if err != nil {
+		var kafkaError Error
+		if errors.As(err, &kafkaError) {
+			size, err = discardN(&c.rbuf, size, size)
 		}
 	}
 	return expectZeroSize(size, err)
@@ -1294,9 +1293,8 @@ func (c *Conn) do(d *connDeadline, write func(time.Time, int32) error, read func
 	}
 
 	if err = read(deadline, size); err != nil {
-		switch err.(type) {
-		case Error:
-		default:
+		var kafkaError Error
+		if !errors.As(err, &kafkaError) {
 			c.conn.Close()
 		}
 	}

conn_test.go

@@ -389,9 +389,11 @@ func testConnWrite(t *testing.T, conn *Conn) {
 func testConnCloseAndWrite(t *testing.T, conn *Conn) {
 	conn.Close()
 
-	switch _, err := conn.Write([]byte("Hello World!")); err.(type) {
-	case *net.OpError:
-	default:
+	_, err := conn.Write([]byte("Hello World!"))
+
+	// expect a network error
+	var netOpError *net.OpError
+	if !errors.As(err, &netOpError) {
 		t.Error(err)
 	}
 }
@@ -489,7 +491,7 @@ func testConnSeekDontCheck(t *testing.T, conn *Conn) {
 		t.Error("bad offset:", offset)
 	}
 
-	if _, err := conn.ReadMessage(1024); err != OffsetOutOfRange {
+	if _, err := conn.ReadMessage(1024); !errors.Is(err, OffsetOutOfRange) {
 		t.Error("unexpected error:", err)
 	}
 }
@@ -659,13 +661,15 @@ func waitForCoordinator(t *testing.T, conn *Conn, groupID string) {
 		_, err := conn.findCoordinator(findCoordinatorRequestV0{
 			CoordinatorKey: groupID,
 		})
-		switch err {
-		case nil:
+		if err != nil {
+			if errors.Is(err, GroupCoordinatorNotAvailable) {
+				time.Sleep(250 * time.Millisecond)
+				continue
+			} else {
+				t.Fatalf("unable to find coordinator for group: %v", err)
+			}
+		} else {
 			return
-		case GroupCoordinatorNotAvailable:
-			time.Sleep(250 * time.Millisecond)
-		default:
-			t.Fatalf("unable to find coordinator for group: %v", err)
 		}
 	}
 
@@ -690,15 +694,18 @@ func createGroup(t *testing.T, conn *Conn, groupID string) (generationID int32,
 					},
 				},
 			})
-			switch err {
-			case nil:
+			if err != nil {
+				if errors.Is(err, NotCoordinatorForGroup) {
+					time.Sleep(250 * time.Millisecond)
+					continue
+				} else {
+					t.Fatalf("bad joinGroup: %s", err)
+				}
+			} else {
 				return
-			case NotCoordinatorForGroup:
-				time.Sleep(250 * time.Millisecond)
-			default:
-				t.Fatalf("bad joinGroup: %s", err)
 			}
 		}
+
 		return
 	}
 
@@ -742,12 +749,11 @@ func testConnFindCoordinator(t *testing.T, conn *Conn) {
 		}
 		response, err := conn.findCoordinator(findCoordinatorRequestV0{CoordinatorKey: groupID})
 		if err != nil {
-			switch err {
-			case GroupCoordinatorNotAvailable:
+			if errors.Is(err, GroupCoordinatorNotAvailable) {
 				continue
-			default:
-				t.Fatalf("bad findCoordinator: %s", err)
 			}
+
+			t.Fatalf("bad findCoordinator: %s", err)
 		}
 
 		if response.Coordinator.NodeID == 0 {

consumergroup.go

@@ -523,19 +523,21 @@ func (g *Generation) partitionWatcher(interval time.Duration, topic string) {
 				return
 			case <-ticker.C:
 				ops, err := g.conn.readPartitions(topic)
-				switch err {
-				case nil, UnknownTopicOrPartition:
+				switch {
+				case err == nil, errors.Is(err, UnknownTopicOrPartition):
 					if len(ops) != oParts {
 						g.log(func(l Logger) {
 							l.Printf("Partition changes found, reblancing group: %v.", g.GroupID)
 						})
 						return
 					}
+
 				default:
 					g.logError(func(l Logger) {
 						l.Printf("Problem getting partitions while checking for changes, %v", err)
 					})
-					if _, ok := err.(Error); ok {
+					var kafkaError Error
+					if errors.As(err, &kafkaError) {
 						continue
 					}
 					// other errors imply that we lost the connection to the coordinator, so we
@@ -724,20 +726,24 @@ func (cg *ConsumerGroup) run() {
 		// to the next generation.  it will be non-nil in the case of an error
 		// joining or syncing the group.
 		var backoff <-chan time.Time
-		switch err {
-		case nil:
+
+		switch {
+		case err == nil:
 			// no error...the previous generation finished normally.
 			continue
-		case ErrGroupClosed:
+
+		case errors.Is(err, ErrGroupClosed):
 			// the CG has been closed...leave the group and exit loop.
 			_ = cg.leaveGroup(memberID)
 			return
-		case RebalanceInProgress:
+
+		case errors.Is(err, RebalanceInProgress):
 			// in case of a RebalanceInProgress, don't leave the group or
 			// change the member ID, but report the error.  the next attempt
 			// to join the group will then be subject to the rebalance
 			// timeout, so the broker will be responsible for throttling
 			// this loop.
+
 		default:
 			// leave the group and report the error if we had gotten far
 			// enough so as to have a member ID.  also clear the member id
@@ -984,7 +990,7 @@ func (cg *ConsumerGroup) makeJoinGroupRequestV1(memberID string) (joinGroupReque
 	for _, balancer := range cg.config.GroupBalancers {
 		userData, err := balancer.UserData()
 		if err != nil {
-			return joinGroupRequestV1{}, fmt.Errorf("unable to construct protocol metadata for member, %v: %v", balancer.ProtocolName(), err)
+			return joinGroupRequestV1{}, fmt.Errorf("unable to construct protocol metadata for member, %v: %w", balancer.ProtocolName(), err)
 		}
 		request.GroupProtocols = append(request.GroupProtocols, joinGroupRequestGroupProtocolV1{
 			ProtocolName: balancer.ProtocolName(),
@@ -1050,7 +1056,7 @@ func (cg *ConsumerGroup) makeMemberProtocolMetadata(in []joinGroupResponseMember
 		metadata := groupMetadata{}
 		reader := bufio.NewReader(bytes.NewReader(item.MemberMetadata))
 		if remain, err := (&metadata).readFrom(reader, len(item.MemberMetadata)); err != nil || remain != 0 {
-			return nil, fmt.Errorf("unable to read metadata for member, %v: %v", item.MemberID, err)
+			return nil, fmt.Errorf("unable to read metadata for member, %v: %w", item.MemberID, err)
 		}
 
 		members = append(members, GroupMember{

createtopics.go

@@ -3,6 +3,7 @@ package kafka
 import (
 	"bufio"
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"time"
@@ -384,12 +385,14 @@ func (c *Conn) CreateTopics(topics ...TopicConfig) error {
 	_, err := c.createTopics(createTopicsRequestV0{
 		Topics: requestV0Topics,
 	})
+	if err != nil {
+		if errors.Is(err, TopicAlreadyExists) {
+			// ok
+			return nil
+		}
 
-	switch err {
-	case TopicAlreadyExists:
-		// ok
-		return nil
-	default:
 		return err
 	}
+
+	return nil
 }

dialer_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/tls"
 	"crypto/x509"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -294,7 +295,7 @@ func TestDialerConnectTLSHonorsContext(t *testing.T) {
 	defer cancel()
 
 	_, err := d.connectTLS(ctx, conn, d.TLS)
-	if context.DeadlineExceeded != err {
+	if !errors.Is(err, context.DeadlineExceeded) {
 		t.Errorf("expected err to be %v; got %v", context.DeadlineExceeded, err)
 		t.FailNow()
 	}

discard_test.go

@@ -3,6 +3,7 @@ package kafka
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"io"
 	"testing"
 )
@@ -52,7 +53,7 @@ func TestDiscardN(t *testing.T) {
 			scenario: "discard more than available",
 			function: func(t *testing.T, r *bufio.Reader, sz int) {
 				remain, err := discardN(r, sz, sz+1)
-				if err != errShortRead {
+				if !errors.Is(err, errShortRead) {
 					t.Errorf("Expected errShortRead, got %v", err)
 				}
 				if remain != 0 {
@@ -64,7 +65,7 @@ func TestDiscardN(t *testing.T) {
 			scenario: "discard returns error",
 			function: func(t *testing.T, r *bufio.Reader, sz int) {
 				remain, err := discardN(r, sz+2, sz+1)
-				if err != io.EOF {
+				if !errors.Is(err, io.EOF) {
 					t.Errorf("Expected EOF, got %v", err)
 				}
 				if remain != 2 {
@@ -76,7 +77,7 @@ func TestDiscardN(t *testing.T) {
 			scenario: "errShortRead doesn't mask error",
 			function: func(t *testing.T, r *bufio.Reader, sz int) {
 				remain, err := discardN(r, sz+1, sz+2)
-				if err != io.EOF {
+				if !errors.Is(err, io.EOF) {
 					t.Errorf("Expected EOF, got %v", err)
 				}
 				if remain != 1 {

example_consumergroup_test.go

@@ -2,6 +2,7 @@ package kafka_test
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 
@@ -42,18 +43,20 @@ func ExampleGeneration_Start_consumerGroupParallelReaders() {
 				reader.SetOffset(offset)
 				for {
 					msg, err := reader.ReadMessage(ctx)
-					switch err {
-					case kafka.ErrGenerationEnded:
-						// generation has ended.  commit offsets.  in a real app,
-						// offsets would be committed periodically.
-						gen.CommitOffsets(map[string]map[int]int64{"my-topic": {partition: offset + 1}})
-						return
-					case nil:
-						fmt.Printf("received message %s/%d/%d : %s\n", msg.Topic, msg.Partition, msg.Offset, string(msg.Value))
-						offset = msg.Offset
-					default:
+					if err != nil {
+						if errors.Is(err, kafka.ErrGenerationEnded) {
+							// generation has ended.  commit offsets.  in a real app,
+							// offsets would be committed periodically.
+							gen.CommitOffsets(map[string]map[int]int64{"my-topic": {partition: offset + 1}})
+							return
+						}
+
 						fmt.Printf("error reading message: %+v\n", err)
+						return
 					}
+
+					fmt.Printf("received message %s/%d/%d : %s\n", msg.Topic, msg.Partition, msg.Offset, string(msg.Value))
+					offset = msg.Offset
 				}
 			})
 		}

message_test.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"io"
 	"math/rand"
@@ -551,7 +552,7 @@ func TestMessageSetReaderEmpty(t *testing.T) {
 	if headers != nil {
 		t.Errorf("expected nil headers, got %v", headers)
 	}
-	if err != RequestTimedOut {
+	if !errors.Is(err, RequestTimedOut) {
 		t.Errorf("expected RequestTimedOut, got %v", err)
 	}