*: avoid direct error comparisons

This adds a linter that checks that `error` object
are not compared directly with non-`nil` values using
`==` or `!=`.

Release note: None

pkg/acceptance/cluster/docker.go

@@ -388,7 +388,7 @@ func (cli resilientDockerClient) ContainerStart(
 
 		// Keep going if ContainerStart timed out, but client's context is not
 		// expired.
-		if errors.Cause(err) == context.DeadlineExceeded && clientCtx.Err() == nil {
+		if errors.Is(err, context.DeadlineExceeded) && clientCtx.Err() == nil {
 			log.Warningf(clientCtx, "ContainerStart timed out, retrying")
 			continue
 		}

pkg/ccl/importccl/load.go

@@ -74,7 +74,7 @@ func getDescriptorFromDB(
 			keys.RootNamespaceID,
 			dbName,
 		).Scan(&dbDescBytes); err != nil {
-			if err == gosql.ErrNoRows {
+			if errors.Is(err, gosql.ErrNoRows) {
 				continue
 			}
 			return nil, errors.Wrap(err, "fetch database descriptor")

pkg/ccl/importccl/read_import_mysql.go

@@ -110,7 +110,7 @@ func (m *mysqldumpReader) readFile(
 		if err == io.EOF {
 			break
 		}
-		if err == mysql.ErrEmpty {
+		if errors.Is(err, mysql.ErrEmpty) {
 			continue
 		}
 		if err != nil {
@@ -300,7 +300,7 @@ func readMysqlCreateTable(
 		if err == io.EOF {
 			break
 		}
-		if err == mysql.ErrEmpty {
+		if errors.Is(err, mysql.ErrEmpty) {
 			continue
 		}
 		if err != nil {

pkg/ccl/importccl/read_import_pgcopy.go

@@ -166,7 +166,7 @@ func (p *postgreStreamCopy) Next() (copyData, error) {
 	// Attempt to read an entire line.
 	scanned := p.s.Scan()
 	if err := p.s.Err(); err != nil {
-		if err == bufio.ErrTooLong {
+		if errors.Is(err, bufio.ErrTooLong) {
 			err = errors.New("line too long")
 		}
 		return nil, err

pkg/ccl/importccl/read_import_pgdump.go

@@ -78,7 +78,7 @@ func splitSQLSemicolon(data []byte, atEOF bool) (advance int, token []byte, err
 func (p *postgreStream) Next() (interface{}, error) {
 	if p.copy != nil {
 		row, err := p.copy.Next()
-		if err == errCopyDone {
+		if errors.Is(err, errCopyDone) {
 			p.copy = nil
 			return errCopyDone, nil
 		}
@@ -125,8 +125,8 @@ func (p *postgreStream) Next() (interface{}, error) {
 		}
 	}
 	if err := p.s.Err(); err != nil {
-		if err == bufio.ErrTooLong {
-			err = errors.New("line too long")
+		if errors.Is(err, bufio.ErrTooLong) {
+			err = errors.HandledWithMessage(err, "line too long")
 		}
 		return nil, err
 	}

pkg/ccl/workloadccl/fixture.go

@@ -142,7 +142,7 @@ func GetFixture(
 
 			fixtureFolder := generatorToGCSFolder(config, gen)
 			_, err := b.Objects(ctx, &storage.Query{Prefix: fixtureFolder, Delimiter: `/`}).Next()
-			if err == iterator.Done {
+			if errors.Is(err, iterator.Done) {
 				notFound = true
 				return errors.Errorf(`fixture not found: %s`, fixtureFolder)
 			} else if err != nil {
@@ -153,7 +153,7 @@ func GetFixture(
 			for _, table := range gen.Tables() {
 				tableFolder := filepath.Join(fixtureFolder, table.Name)
 				_, err := b.Objects(ctx, &storage.Query{Prefix: tableFolder, Delimiter: `/`}).Next()
-				if err == iterator.Done {
+				if errors.Is(err, iterator.Done) {
 					return errors.Errorf(`fixture table not found: %s`, tableFolder)
 				} else if err != nil {
 					return err
@@ -619,14 +619,14 @@ func ListFixtures(
 	gensPrefix := config.GCSPrefix + `/`
 	for genIter := b.Objects(ctx, &storage.Query{Prefix: gensPrefix, Delimiter: `/`}); ; {
 		gen, err := genIter.Next()
-		if err == iterator.Done {
+		if errors.Is(err, iterator.Done) {
 			break
 		} else if err != nil {
 			return nil, err
 		}
 		for genConfigIter := b.Objects(ctx, &storage.Query{Prefix: gen.Prefix, Delimiter: `/`}); ; {
 			genConfig, err := genConfigIter.Next()
-			if err == iterator.Done {
+			if errors.Is(err, iterator.Done) {
 				break
 			} else if err != nil {
 				return nil, err

pkg/cli/sql.go

@@ -1349,7 +1349,7 @@ func (c *cliState) configurePreShellDefaults() (cleanupFn func(), err error) {
 		c.ins, c.exitErr = readline.InitFiles("cockroach",
 			true, /* wideChars */
 			stdin, os.Stdout, stderr)
-		if c.exitErr == readline.ErrWidecharNotSupported {
+		if errors.Is(c.exitErr, readline.ErrWidecharNotSupported) {
 			log.Warning(context.TODO(), "wide character support disabled")
 			c.ins, c.exitErr = readline.InitFiles("cockroach",
 				false, stdin, os.Stdout, stderr)

pkg/cli/sql_util.go

@@ -173,7 +173,7 @@ func (c *sqlConn) getServerMetadata() (
 ) {
 	// Retrieve the node ID and server build info.
 	rows, err := c.Query("SELECT * FROM crdb_internal.node_build_info", nil)
-	if err == driver.ErrBadConn {
+	if errors.Is(err, driver.ErrBadConn) {
 		return 0, "", "", err
 	}
 	if err != nil {
@@ -241,7 +241,7 @@ func (c *sqlConn) checkServerMetadata() error {
 	}
 
 	_, newServerVersion, newClusterID, err := c.getServerMetadata()
-	if err == driver.ErrBadConn {
+	if errors.Is(err, driver.ErrBadConn) {
 		return err
 	}
 	if err != nil {
@@ -394,7 +394,7 @@ func (c *sqlConn) Exec(query string, args []driver.Value) error {
 	}
 	_, err := c.conn.Exec(query, args)
 	c.flushNotices()
-	if err == driver.ErrBadConn {
+	if errors.Is(err, driver.ErrBadConn) {
 		c.reconnecting = true
 		c.Close()
 	}
@@ -409,7 +409,7 @@ func (c *sqlConn) Query(query string, args []driver.Value) (*sqlRows, error) {
 		fmt.Fprintln(stderr, ">", query)
 	}
 	rows, err := c.conn.Query(query, args)
-	if err == driver.ErrBadConn {
+	if errors.Is(err, driver.ErrBadConn) {
 		c.reconnecting = true
 		c.Close()
 	}
@@ -447,7 +447,7 @@ func (c *sqlConn) Close() {
 	c.flushNotices()
 	if c.conn != nil {
 		err := c.conn.Close()
-		if err != nil && err != driver.ErrBadConn {
+		if err != nil && !errors.Is(err, driver.ErrBadConn) {
 			log.Infof(context.TODO(), "%v", err)
 		}
 		c.conn = nil
@@ -485,7 +485,7 @@ func (r *sqlRows) Tag() string {
 func (r *sqlRows) Close() error {
 	r.conn.flushNotices()
 	err := r.rows.Close()
-	if err == driver.ErrBadConn {
+	if errors.Is(err, driver.ErrBadConn) {
 		r.conn.reconnecting = true
 		r.conn.Close()
 	}
@@ -498,7 +498,7 @@ func (r *sqlRows) Close() error {
 // (since this is unobvious and unexpected behavior) outweigh.
 func (r *sqlRows) Next(values []driver.Value) error {
 	err := r.rows.Next(values)
-	if err == driver.ErrBadConn {
+	if errors.Is(err, driver.ErrBadConn) {
 		r.conn.reconnecting = true
 		r.conn.Close()
 	}

pkg/cli/sql_util_test.go

@@ -22,6 +22,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/testutils"
 	"github.com/cockroachdb/cockroach/pkg/testutils/sqlutils"
 	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
+	"github.com/cockroachdb/errors"
 )
 
 func TestConnRecover(t *testing.T) {
@@ -54,7 +55,7 @@ func TestConnRecover(t *testing.T) {
 	// and starts delivering ErrBadConn. We don't know the timing of
 	// this however.
 	testutils.SucceedsSoon(t, func() error {
-		if sqlRows, err := conn.Query(`SELECT 1`, nil); err != driver.ErrBadConn {
+		if sqlRows, err := conn.Query(`SELECT 1`, nil); !errors.Is(err, driver.ErrBadConn) {
 			return fmt.Errorf("expected ErrBadConn, got %v", err)
 		} else if err == nil {
 			if closeErr := sqlRows.Close(); closeErr != nil {
@@ -78,7 +79,7 @@ func TestConnRecover(t *testing.T) {
 
 	// Ditto from Query().
 	testutils.SucceedsSoon(t, func() error {
-		if err := conn.Exec(`SELECT 1`, nil); err != driver.ErrBadConn {
+		if err := conn.Exec(`SELECT 1`, nil); !errors.Is(err, driver.ErrBadConn) {
 			return fmt.Errorf("expected ErrBadConn, got %v", err)
 		}
 		return nil

pkg/cmd/cr2pg/sqlstream/stream.go

@@ -74,8 +74,8 @@ func (s *Stream) Next() (tree.Statement, error) {
 		}
 	}
 	if err := s.scan.Err(); err != nil {
-		if err == bufio.ErrTooLong {
-			err = errors.New("line too long")
+		if errors.Is(err, bufio.ErrTooLong) {
+			err = errors.HandledWithMessage(err, "line too long")
 		}
 		return nil, err
 	}

pkg/cmd/reduce/main.go

@@ -29,6 +29,7 @@ import (
 
 	"github.com/cockroachdb/cockroach/pkg/testutils/reduce"
 	"github.com/cockroachdb/cockroach/pkg/testutils/reduce/reducesql"
+	"github.com/cockroachdb/errors"
 )
 
 var (
@@ -124,7 +125,7 @@ func reduceSQL(path, contains string, workers int, verbose bool) (string, error)
 		out, err := cmd.CombinedOutput()
 		switch err := err.(type) {
 		case *exec.Error:
-			if err.Err == exec.ErrNotFound {
+			if errors.Is(err.Err, exec.ErrNotFound) {
 				log.Fatal(err)
 			}
 		case *os.PathError:

pkg/cmd/roachprod/cloud/gc.go

@@ -26,6 +26,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachprod/config"
 	"github.com/cockroachdb/cockroach/pkg/cmd/roachprod/vm"
 	"github.com/cockroachdb/cockroach/pkg/util/timeutil"
+	"github.com/cockroachdb/errors"
 	"github.com/nlopes/slack"
 )
 
@@ -314,7 +315,7 @@ func GCClusters(cloud *Cloud, dryrun bool) error {
 			userChannel, err := findUserChannel(client, user+config.EmailDomain)
 			if err == nil {
 				postStatus(client, userChannel, dryrun, status, nil)
-			} else if err != errNoSlackClient {
+			} else if !errors.Is(err, errNoSlackClient) {
 				log.Printf("could not deliver Slack DM to %s: %v", user+config.EmailDomain, err)
 			}
 		}

pkg/cmd/roachprod/vm/azure/azure.go

@@ -412,7 +412,7 @@ func (p *Provider) List() (vm.List, error) {
 		if err != nil {
 			return nil, err
 		}
-		if err := p.fillNetworkDetails(ctx, &m, nicID); err == vm.ErrBadNetwork {
+		if err := p.fillNetworkDetails(ctx, &m, nicID); errors.Is(err, vm.ErrBadNetwork) {
 			m.Errors = append(m.Errors, err)
 		} else if err != nil {
 			return nil, err

pkg/cmd/roachtest/cluster.go

@@ -2527,7 +2527,7 @@ func (m *monitor) wait(args ...string) error {
 		cmd.Stdout = io.MultiWriter(pipeW, monL.stdout)
 		cmd.Stderr = monL.stderr
 		if err := cmd.Run(); err != nil {
-			if err != context.Canceled && !strings.Contains(err.Error(), "killed") {
+			if !errors.Is(err, context.Canceled) && !strings.Contains(err.Error(), "killed") {
 				// The expected reason for an error is that the monitor was killed due
 				// to the context being canceled. Any other error is an actual error.
 				setMonitorCmdErr(err)

pkg/cmd/roachtest/rebalance_load.go

@@ -19,6 +19,7 @@ import (
 	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/util/timeutil"
+	"github.com/cockroachdb/errors"
 	"golang.org/x/sync/errgroup"
 )
 
@@ -73,7 +74,7 @@ func registerRebalanceLoad(r *testRegistry) {
 				"./workload run kv --read-percent=95 --tolerate-errors --concurrency=%d "+
 					"--duration=%v {pgurl:1-%d}",
 				concurrency, maxDuration, len(roachNodes)))
-			if ctx.Err() == context.Canceled {
+			if errors.Is(ctx.Err(), context.Canceled) {
 				// We got canceled either because lease balance was achieved or the
 				// other worker hit an error. In either case, it's not this worker's
 				// fault.

pkg/cmd/roachvet/main.go

@@ -15,6 +15,7 @@ package main
 
 import (
 	"github.com/cockroachdb/cockroach/pkg/testutils/lint/passes/descriptormarshal"
+	"github.com/cockroachdb/cockroach/pkg/testutils/lint/passes/errcmp"
 	"github.com/cockroachdb/cockroach/pkg/testutils/lint/passes/fmtsafe"
 	"github.com/cockroachdb/cockroach/pkg/testutils/lint/passes/hash"
 	"github.com/cockroachdb/cockroach/pkg/testutils/lint/passes/nocopy"
@@ -57,6 +58,7 @@ func main() {
 		timer.Analyzer,
 		unconvert.Analyzer,
 		fmtsafe.Analyzer,
+		errcmp.Analyzer,
 
 		// Standard go vet analyzers:
 		asmdecl.Analyzer,

pkg/gossip/infostore.go

@@ -399,7 +399,7 @@ func (is *infoStore) combine(
 		// the data in *is is newer than in *delta.
 		if addErr := is.addInfo(key, &infoCopy); addErr == nil {
 			freshCount++
-		} else if addErr != errNotFresh {
+		} else if !errors.Is(addErr, errNotFresh) {
 			err = addErr
 		}
 	}

pkg/jobs/jobsprotectedts/jobs_protected_ts_test.go

@@ -32,6 +32,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/testutils/testcluster"
 	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
 	"github.com/cockroachdb/cockroach/pkg/util/uuid"
+	"github.com/cockroachdb/errors"
 	"github.com/stretchr/testify/require"
 )
 
@@ -90,7 +91,7 @@ func TestJobsProtectedTimestamp(t *testing.T) {
 	_, recRemains := mkJobAndRecord()
 	ensureNotExists := func(ctx context.Context, txn *kv.Txn, ptsID uuid.UUID) (err error) {
 		_, err = ptp.GetRecord(ctx, txn, ptsID)
-		if err == protectedts.ErrNotExists {
+		if errors.Is(err, protectedts.ErrNotExists) {
 			return nil
 		}
 		return fmt.Errorf("waiting for %v, got %v", protectedts.ErrNotExists, err)

pkg/kv/kvclient/kvcoord/range_cache_test.go

@@ -493,7 +493,7 @@ func TestRangeCacheContextCancellation(t *testing.T) {
 	}
 
 	expectContextCancellation := func(t *testing.T, c <-chan error) {
-		if err := <-c; errors.Cause(err) != context.Canceled {
+		if err := <-c; !errors.Is(err, context.Canceled) {
 			t.Errorf("expected context cancellation error, found %v", err)
 		}
 	}

pkg/kv/kvclient/kvcoord/txn_coord_sender_savepoints.go

@@ -122,7 +122,7 @@ func (tc *TxnCoordSender) RollbackToSavepoint(ctx context.Context, s kv.Savepoin
 	sp := s.(*savepoint)
 	err := tc.checkSavepointLocked(sp)
 	if err != nil {
-		if err == errSavepointInvalidAfterTxnRestart {
+		if errors.Is(err, errSavepointInvalidAfterTxnRestart) {
 			err = roachpb.NewTransactionRetryWithProtoRefreshError(
 				"cannot rollback to savepoint after a transaction restart",
 				tc.mu.txn.ID,
@@ -169,7 +169,7 @@ func (tc *TxnCoordSender) ReleaseSavepoint(ctx context.Context, s kv.SavepointTo
 
 	sp := s.(*savepoint)
 	err := tc.checkSavepointLocked(sp)
-	if err == errSavepointInvalidAfterTxnRestart {
+	if errors.Is(err, errSavepointInvalidAfterTxnRestart) {
 		err = roachpb.NewTransactionRetryWithProtoRefreshError(
 			"cannot release savepoint after a transaction restart",
 			tc.mu.txn.ID,

pkg/kv/kvserver/client_raft_test.go

@@ -1066,7 +1066,7 @@ func TestFailedSnapshotFillsReservation(t *testing.T) {
 	// "snapshot accepted" message.
 	expectedErr := errors.Errorf("")
 	stream := fakeSnapshotStream{nil, expectedErr}
-	if err := mtc.stores[1].HandleSnapshot(&header, stream); err != expectedErr {
+	if err := mtc.stores[1].HandleSnapshot(&header, stream); !errors.Is(err, expectedErr) {
 		t.Fatalf("expected error %s, but found %v", expectedErr, err)
 	}
 	if n := mtc.stores[1].ReservationCount(); n != 0 {

pkg/kv/kvserver/client_test.go

@@ -1399,7 +1399,7 @@ func (m *multiTestContext) heartbeatLiveness(ctx context.Context, store int) err
 	}
 
 	for r := retry.StartWithCtx(ctx, retry.Options{MaxRetries: 5}); r.Next(); {
-		if err = nl.Heartbeat(ctx, l); err != kvserver.ErrEpochIncremented {
+		if err = nl.Heartbeat(ctx, l); !errors.Is(err, kvserver.ErrEpochIncremented) {
 			break
 		}
 	}

pkg/kv/kvserver/concurrency/lock_table_waiter.go

@@ -24,6 +24,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 	"github.com/cockroachdb/cockroach/pkg/util/stop"
 	"github.com/cockroachdb/cockroach/pkg/util/timeutil"
+	"github.com/cockroachdb/errors"
 )
 
 // LockTableLivenessPushDelay sets the delay before pushing in order to detect
@@ -278,7 +279,7 @@ func (w *lockTableWaiterImpl) WaitOn(
 				pushCtx, pushCancel := context.WithCancel(ctx)
 				go w.watchForNotifications(pushCtx, pushCancel, newStateC)
 				err = w.pushRequestTxn(pushCtx, req, timerWaitingState)
-				if pushCtx.Err() == context.Canceled {
+				if errors.Is(pushCtx.Err(), context.Canceled) {
 					// Ignore the context canceled error. If this was for the
 					// parent context then we'll notice on the next select.
 					err = nil

pkg/kv/kvserver/gc_queue.go

@@ -472,7 +472,7 @@ func (gcq *gcQueue) process(ctx context.Context, repl *Replica, sysCfg *config.S
 							gcq.store.metrics.GCResolveSuccess.Inc(int64(len(intents)))
 						}
 					})
-			if errors.Cause(err) == stop.ErrThrottled {
+			if errors.Is(err, stop.ErrThrottled) {
 				log.Eventf(ctx, "processing txn %s: %s; skipping for future GC", txn.ID.Short(), err)
 				return nil
 			}

pkg/kv/kvserver/idalloc/id_alloc_test.go

@@ -184,7 +184,7 @@ func TestAllocateErrorAndRecovery(t *testing.T) {
 	defer cancel()
 	for i := 0; i < routines; i++ {
 		id, err := idAlloc.Allocate(ctx)
-		if id != 0 || err != context.DeadlineExceeded {
+		if id != 0 || !errors.Is(err, context.DeadlineExceeded) {
 			t.Fatalf("expected context cancellation, found id=%d, err=%v", id, err)
 		}
 	}