golangci: enable errorlint and fix everything it found

.golangci.yml

@@ -44,6 +44,7 @@ linters:
     # - exhaustive
     - bodyclose
     - contextcheck
+    - errorlint
     - gofmt
     - whitespace
     - goimports

cli/server_test.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"io"
 	"os"
 	"path/filepath"
@@ -110,7 +111,7 @@ func TestServerStart(t *testing.T) {
 			var line string
 			require.Eventually(t, func() bool {
 				line, err = e.Out.ReadString('\n')
-				if err != nil && err != io.EOF {
+				if err != nil && !errors.Is(err, io.EOF) {
 					t.Fatalf("unexpected error while reading CLI output: %s", err)
 				}
 				return err == nil

cli/wallet/wallet.go

@@ -947,7 +947,7 @@ func readWallet(ctx *cli.Context) (*wallet.Wallet, *string, error) {
 	if path == "-" {
 		w := &wallet.Wallet{}
 		if err := json.NewDecoder(os.Stdin).Decode(w); err != nil {
-			return nil, nil, fmt.Errorf("js %s", err)
+			return nil, nil, fmt.Errorf("js %w", err)
 		}
 		return w, nil, nil
 	}

pkg/core/blockchain.go

@@ -1702,7 +1702,7 @@ func (bc *Blockchain) HasTransaction(hash util.Uint256) bool {
 	if bc.memPool.ContainsKey(hash) {
 		return true
 	}
-	return bc.dao.HasTransaction(hash) == dao.ErrAlreadyExists
+	return errors.Is(bc.dao.HasTransaction(hash), dao.ErrAlreadyExists)
 }
 
 // HasBlock returns true if the blockchain contains the given
@@ -1761,7 +1761,7 @@ func (bc *Blockchain) HeaderHeight() uint32 {
 // GetContractState returns contract by its script hash.
 func (bc *Blockchain) GetContractState(hash util.Uint160) *state.Contract {
 	contract, err := bc.contracts.Management.GetContract(bc.dao, hash)
-	if contract == nil && err != storage.ErrKeyNotFound {
+	if contract == nil && !errors.Is(err, storage.ErrKeyNotFound) {
 		bc.log.Warn("failed to get contract state", zap.Error(err))
 	}
 	return contract

pkg/core/dao/dao.go

@@ -176,7 +176,7 @@ func (dao *Simple) GetTokenTransferInfo(acc util.Uint160) (*state.TokenTransferI
 	key := dao.makeTTIKey(acc)
 	bs := state.NewTokenTransferInfo()
 	err := dao.GetAndDecode(bs, key)
-	if err != nil && err != storage.ErrKeyNotFound {
+	if err != nil && !errors.Is(err, storage.ErrKeyNotFound) {
 		return nil, err
 	}
 	return bs, nil
@@ -257,7 +257,7 @@ func (dao *Simple) GetTokenTransferLog(acc util.Uint160, newestTimestamp uint64,
 	key := dao.getTokenTransferLogKey(acc, newestTimestamp, index, isNEP11)
 	value, err := dao.Store.Get(key)
 	if err != nil {
-		if err == storage.ErrKeyNotFound {
+		if errors.Is(err, storage.ErrKeyNotFound) {
 			return new(state.TokenTransferLog), nil
 		}
 		return nil, err
@@ -306,7 +306,7 @@ func (dao *Simple) GetAppExecResults(hash util.Uint256, trig trigger.Type) ([]st
 			aer := new(state.AppExecResult)
 			aer.DecodeBinary(r)
 			if r.Err != nil {
-				if r.Err == iocore.EOF {
+				if errors.Is(r.Err, iocore.EOF) {
 					break
 				}
 				return nil, r.Err

pkg/core/native/management.go

@@ -173,7 +173,7 @@ func (m *Management) getContract(ic *interop.Context, args []stackitem.Item) sta
 	hash := toHash160(args[0])
 	ctr, err := m.GetContract(ic.DAO, hash)
 	if err != nil {
-		if err == storage.ErrKeyNotFound {
+		if errors.Is(err, storage.ErrKeyNotFound) {
 			return stackitem.Null{}
 		}
 		panic(err)

pkg/core/native/notary.go

@@ -469,7 +469,7 @@ func (n *Notary) GetDepositFor(dao *dao.Simple, acc util.Uint160) *state.Deposit
 	if err == nil {
 		return deposit
 	}
-	if err == storage.ErrKeyNotFound {
+	if errors.Is(err, storage.ErrKeyNotFound) {
 		return nil
 	}
 	panic(fmt.Errorf("failed to get deposit for %s from storage: %w", acc.StringBE(), err))

pkg/core/storage/leveldb_store.go

@@ -1,6 +1,8 @@
 package storage
 
 import (
+	"errors"
+
 	"github.com/nspcc-dev/neo-go/pkg/core/storage/dbconfig"
 	"github.com/syndtr/goleveldb/leveldb"
 	"github.com/syndtr/goleveldb/leveldb/filter"
@@ -35,7 +37,7 @@ func NewLevelDBStore(cfg dbconfig.LevelDBOptions) (*LevelDBStore, error) {
 // Get implements the Store interface.
 func (s *LevelDBStore) Get(key []byte) ([]byte, error) {
 	value, err := s.db.Get(key, nil)
-	if err == leveldb.ErrNotFound {
+	if errors.Is(err, leveldb.ErrNotFound) {
 		err = ErrKeyNotFound
 	}
 	return value, err

pkg/neorpc/errors.go

@@ -1,6 +1,7 @@
 package neorpc
 
 import (
+	"errors"
 	"fmt"
 )
 
@@ -125,9 +126,9 @@ func (e *Error) Error() string {
 
 // Is denotes whether the error matches the target one.
 func (e *Error) Is(target error) bool {
-	clTarget, ok := target.(*Error)
-	if !ok {
-		return false
+	var clTarget *Error
+	if errors.As(target, &clTarget) {
+		return e.Code == clTarget.Code
 	}
-	return e.Code == clTarget.Code
+	return false
 }

pkg/network/message.go

@@ -176,7 +176,7 @@ func (m *Message) decodePayload() error {
 	}
 	r := io.NewBinReaderFromBuf(buf)
 	p.DecodeBinary(r)
-	if r.Err == nil || r.Err == payload.ErrTooManyHeaders {
+	if r.Err == nil || errors.Is(r.Err, payload.ErrTooManyHeaders) {
 		m.Payload = p
 	}
 

pkg/network/server.go

@@ -417,9 +417,9 @@ func (s *Server) run() {
 					zap.Error(drop.reason),
 					zap.Int("peerCount", s.PeerCount()))
 				addr := drop.peer.PeerAddr().String()
-				if drop.reason == errIdenticalID {
+				if errors.Is(drop.reason, errIdenticalID) {
 					s.discovery.RegisterBadAddr(addr)
-				} else if drop.reason == errAlreadyConnected {
+				} else if errors.Is(drop.reason, errAlreadyConnected) {
 					// There is a race condition when peer can be disconnected twice for the this reason
 					// which can lead to no connections to peer at all. Here we check for such a possibility.
 					stillConnected := false
@@ -1380,15 +1380,15 @@ func (s *Server) iteratePeersWithSendMsg(msg *Message, send func(Peer, bool, []b
 				continue
 			}
 			err := send(peer, blocking, pkt)
-			switch err {
-			case nil:
+			if err == nil {
 				if msg.Command == CMDGetAddr {
 					peer.AddGetAddrSent()
 				}
 				sentN++
-			case errBusy: // Can be retried.
+			} else if errors.Is(err, errBusy) {
+				// Can be retried.
 				continue
-			default:
+			} else {
 				deadN++
 			}
 			finished[i] = true

pkg/network/tcp_peer.go

@@ -170,7 +170,7 @@ func (p *TCPPeer) handleConn() {
 			msg := &Message{StateRootInHeader: p.server.config.StateRootInHeader}
 			err = msg.Decode(r)
 
-			if err == payload.ErrTooManyHeaders {
+			if errors.Is(err, payload.ErrTooManyHeaders) {
 				p.server.log.Warn("not all headers were processed")
 				r.Err = nil
 			} else if err != nil {

pkg/services/metrics/metrics.go

@@ -2,6 +2,7 @@ package metrics
 
 import (
 	"context"
+	"errors"
 	"net/http"
 
 	"github.com/nspcc-dev/neo-go/pkg/config"
@@ -21,7 +22,7 @@ func (ms *Service) Start() {
 	if ms.config.Enabled {
 		ms.log.Info("service is running", zap.String("endpoint", ms.Addr))
 		err := ms.ListenAndServe()
-		if err != nil && err != http.ErrServerClosed {
+		if err != nil && !errors.Is(err, http.ErrServerClosed) {
 			ms.log.Warn("service couldn't start on configured port")
 		}
 	} else {

pkg/services/oracle/response.go

@@ -69,7 +69,7 @@ var ErrResponseTooLarge = errors.New("too big response")
 func readResponse(rc gio.ReadCloser, limit int) ([]byte, error) {
 	buf := make([]byte, limit+1)
 	n, err := gio.ReadFull(rc, buf)
-	if err == gio.ErrUnexpectedEOF && n <= limit {
+	if errors.Is(err, gio.ErrUnexpectedEOF) && n <= limit {
 		return buf[:n], nil
 	}
 	if err == nil || n > limit {

pkg/services/rpcsrv/server.go

@@ -340,7 +340,7 @@ func (s *Server) Start() {
 			}
 			s.https.Addr = ln.Addr().String()
 			err = s.https.ServeTLS(ln, cfg.CertFile, cfg.KeyFile)
-			if err != http.ErrServerClosed {
+			if !errors.Is(err, http.ErrServerClosed) {
 				s.log.Error("failed to start TLS RPC server", zap.Error(err))
 				s.errChan <- err
 			}
@@ -354,7 +354,7 @@ func (s *Server) Start() {
 	s.Addr = ln.Addr().String() // set Addr to the actual address
 	go func() {
 		err = s.Serve(ln)
-		if err != http.ErrServerClosed {
+		if !errors.Is(err, http.ErrServerClosed) {
 			s.log.Error("failed to start RPC server", zap.Error(err))
 			s.errChan <- err
 		}

pkg/vm/cli/cli.go

@@ -678,7 +678,7 @@ func (c *VMCLI) Run() error {
 	l := getReadlineInstanceFromContext(c.shell)
 	for {
 		line, err := l.Readline()
-		if err == io.EOF || err == readline.ErrInterrupt {
+		if errors.Is(err, io.EOF) || errors.Is(err, readline.ErrInterrupt) {
 			return nil // OK, stop execution.
 		}
 		if err != nil {

pkg/vm/stackitem/json.go

@@ -169,7 +169,7 @@ func FromJSON(data []byte, maxCount int) (Item, error) {
 	d.UseNumber()
 	if item, err := d.decode(); err != nil {
 		return nil, err
-	} else if _, err := d.Token(); err != gio.EOF {
+	} else if _, err := d.Token(); !errors.Is(err, gio.EOF) {
 		return nil, fmt.Errorf("%w: unexpected items", ErrInvalidValue)
 	} else {
 		return item, nil