Add errcheck linter (#238)

* Add errcheck linter

* Add config for 'fast' linters

* Fix errcheck lint stuff

* Fix errcheck lint

linter-fast.json

+{
+    "Vendor": true,
+    "Cyclo": 12,
+    "Deadline": "5m",
+    "Enable": [
+        "vetshadow",
+        "gotype",
+        "deadcode",
+        "gocyclo",
+        "ineffassign",
+        "gas",
+        "misspell",
+        "errcheck"
+    ]
+}

linter.json

@@ -14,6 +14,7 @@
         "ineffassign",
         "gas",
         "misspell",
-        "unparam"
+        "unparam",
+        "errcheck"
     ]
 }

src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/membership_table.go

@@ -108,7 +108,7 @@ func (s *membershipStatements) selectMembershipsByLocalpart(
 
 	memberships = []authtypes.Membership{}
 
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	for rows.Next() {
 		var m authtypes.Membership
 		m.Localpart = localpart

src/github.com/matrix-org/dendrite/clientapi/events/events.go

@@ -69,7 +69,10 @@ func BuildEvent(
 	authEvents := gomatrixserverlib.NewAuthEvents(nil)
 
 	for i := range queryRes.StateEvents {
-		authEvents.AddEvent(&queryRes.StateEvents[i])
+		err = authEvents.AddEvent(&queryRes.StateEvents[i])
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	refs, err := eventsNeeded.AuthEventReferences(&authEvents)

src/github.com/matrix-org/dendrite/clientapi/httputil/httputil.go

@@ -25,7 +25,7 @@ import (
 // UnmarshalJSONRequest into the given interface pointer. Returns an error JSON response if
 // there was a problem unmarshalling. Calling this function consumes the request body.
 func UnmarshalJSONRequest(req *http.Request, iface interface{}) *util.JSONResponse {
-	defer req.Body.Close()
+	defer req.Body.Close() // nolint: errcheck
 	if err := json.NewDecoder(req.Body).Decode(iface); err != nil {
 		// TODO: We may want to suppress the Error() return in production? It's useful when
 		// debugging because an error will be produced for both invalid/malformed JSON AND

src/github.com/matrix-org/dendrite/clientapi/readers/account_data.go

@@ -52,7 +52,7 @@ func SaveAccountData(
 		return httputil.LogThenError(req, err)
 	}
 
-	defer req.Body.Close()
+	defer req.Body.Close() // nolint: errcheck
 
 	body, err := ioutil.ReadAll(req.Body)
 	if err != nil {

src/github.com/matrix-org/dendrite/clientapi/writers/createroom.go

@@ -185,7 +185,10 @@ func createRoom(req *http.Request, device *authtypes.Device,
 			StateKey: &e.StateKey,
 			Depth:    int64(depth),
 		}
-		builder.SetContent(e.Content)
+		err = builder.SetContent(e.Content)
+		if err != nil {
+			return httputil.LogThenError(req, err)
+		}
 		if i > 0 {
 			builder.PrevEvents = []gomatrixserverlib.EventReference{builtEvents[i-1].EventReference()}
 		}
@@ -194,13 +197,16 @@ func createRoom(req *http.Request, device *authtypes.Device,
 			return httputil.LogThenError(req, err)
 		}
 
-		if err := gomatrixserverlib.Allowed(*ev, &authEvents); err != nil {
+		if err = gomatrixserverlib.Allowed(*ev, &authEvents); err != nil {
 			return httputil.LogThenError(req, err)
 		}
 
 		// Add the event to the list of auth events
 		builtEvents = append(builtEvents, *ev)
-		authEvents.AddEvent(ev)
+		err = authEvents.AddEvent(ev)
+		if err != nil {
+			return httputil.LogThenError(req, err)
+		}
 	}
 
 	// send events to the room server

src/github.com/matrix-org/dendrite/clientapi/writers/joinroom.go

@@ -153,21 +153,35 @@ func (r joinRoomReq) joinRoomByRemoteAlias(
 	return r.joinRoomUsingServers(resp.RoomID, resp.Servers)
 }
 
-func (r joinRoomReq) writeToBuilder(eb *gomatrixserverlib.EventBuilder, roomID string) {
+func (r joinRoomReq) writeToBuilder(eb *gomatrixserverlib.EventBuilder, roomID string) error {
 	eb.Type = "m.room.member"
-	eb.SetContent(r.content)
-	eb.SetUnsigned(struct{}{})
+
+	err := eb.SetContent(r.content)
+	if err != nil {
+		return err
+	}
+
+	err = eb.SetUnsigned(struct{}{})
+	if err != nil {
+		return err
+	}
+
 	eb.Sender = r.userID
 	eb.StateKey = &r.userID
 	eb.RoomID = roomID
 	eb.Redacts = ""
+
+	return nil
 }
 
 func (r joinRoomReq) joinRoomUsingServers(
 	roomID string, servers []gomatrixserverlib.ServerName,
 ) util.JSONResponse {
 	var eb gomatrixserverlib.EventBuilder
-	r.writeToBuilder(&eb, roomID)
+	err := r.writeToBuilder(&eb, roomID)
+	if err != nil {
+		return httputil.LogThenError(r.req, err)
+	}
 
 	var queryRes api.QueryLatestEventsAndStateResponse
 	event, err := events.BuildEvent(r.req.Context(), &eb, r.cfg, r.queryAPI, &queryRes)
@@ -235,7 +249,10 @@ func (r joinRoomReq) joinRoomUsingServer(roomID string, server gomatrixserverlib
 
 	// Set all the fields to be what they should be, this should be a no-op
 	// but it's possible that the remote server returned us something "odd"
-	r.writeToBuilder(&respMakeJoin.JoinEvent, roomID)
+	err = r.writeToBuilder(&respMakeJoin.JoinEvent, roomID)
+	if err != nil {
+		return nil, err
+	}
 
 	now := time.Now()
 	eventID := fmt.Sprintf("$%s:%s", util.RandomString(16), r.cfg.Matrix.ServerName)

src/github.com/matrix-org/dendrite/clientapi/writers/sendevent.go

@@ -60,7 +60,10 @@ func SendEvent(
 		Type:     eventType,
 		StateKey: stateKey,
 	}
-	builder.SetContent(r)
+	err := builder.SetContent(r)
+	if err != nil {
+		return httputil.LogThenError(req, err)
+	}
 
 	var queryRes api.QueryLatestEventsAndStateResponse
 	e, err := events.BuildEvent(req.Context(), &builder, cfg, queryAPI, &queryRes)

src/github.com/matrix-org/dendrite/cmd/create-room-events/main.go

@@ -80,20 +80,20 @@ func main() {
 	b.RoomID = *roomID
 	b.Type = "m.room.create"
 	b.StateKey = &emptyString
-	b.SetContent(map[string]string{"creator": *userID})
+	b.SetContent(map[string]string{"creator": *userID}) // nolint: errcheck
 	create := buildAndOutput()
 
 	// Build a m.room.member event.
 	b.Type = "m.room.member"
 	b.StateKey = userID
-	b.SetContent(map[string]string{"membership": "join"})
+	b.SetContent(map[string]string{"membership": "join"}) // nolint: errcheck
 	b.AuthEvents = []gomatrixserverlib.EventReference{create}
 	member := buildAndOutput()
 
 	// Build a number of m.room.message events.
 	b.Type = "m.room.message"
 	b.StateKey = nil
-	b.SetContent(map[string]string{"body": "Test Message"})
+	b.SetContent(map[string]string{"body": "Test Message"}) // nolint: errcheck
 	b.AuthEvents = []gomatrixserverlib.EventReference{create, member}
 	for i := 0; i < *messageCount; i++ {
 		buildAndOutput()

src/github.com/matrix-org/dendrite/cmd/mediaapi-integration-tests/main.go

@@ -125,7 +125,8 @@ func startMediaAPI(suffix string, dynamicThumbnails bool) (*exec.Cmd, chan error
 }
 
 func cleanUpServer(cmd *exec.Cmd, dir string) {
-	cmd.Process.Kill() // ensure server is dead, only cleaning up so don't care about errors this returns.
+	// ensure server is dead, only cleaning up so don't care about errors this returns
+	cmd.Process.Kill() // nolint: errcheck
 	if err := os.RemoveAll(dir); err != nil {
 		fmt.Printf("WARNING: Failed to remove temporary directory %v: %q\n", dir, err)
 	}
@@ -146,7 +147,7 @@ func main() {
 	// create server1 with only pre-generated thumbnails allowed
 	server1Cmd, server1CmdChan, _, server1ProxyCmd, _, server1ProxyAddr, server1Dir := startMediaAPI("1", false)
 	defer cleanUpServer(server1Cmd, server1Dir)
-	defer server1ProxyCmd.Process.Kill()
+	defer server1ProxyCmd.Process.Kill() // nolint: errcheck
 	testDownload(server1ProxyAddr, server1ProxyAddr, "doesnotexist", 404, server1CmdChan)
 
 	// upload a JPEG file
@@ -163,7 +164,7 @@ func main() {
 	// create server2 with dynamic thumbnail generation
 	server2Cmd, server2CmdChan, _, server2ProxyCmd, _, server2ProxyAddr, server2Dir := startMediaAPI("2", true)
 	defer cleanUpServer(server2Cmd, server2Dir)
-	defer server2ProxyCmd.Process.Kill()
+	defer server2ProxyCmd.Process.Kill() // nolint: errcheck
 	testDownload(server2ProxyAddr, server2ProxyAddr, "doesnotexist", 404, server2CmdChan)
 
 	// pre-generated thumbnail that JPEG file via server2
@@ -189,7 +190,7 @@ func getMediaURI(host, endpoint, query string, components []string) string {
 func testUpload(host, filePath string) {
 	fmt.Printf("==TESTING== upload %v to %v\n", filePath, host)
 	file, err := os.Open(filePath)
-	defer file.Close()
+	defer file.Close() // nolint: errcheck
 	if err != nil {
 		panic(err)
 	}

src/github.com/matrix-org/dendrite/cmd/roomserver-integration-tests/main.go

@@ -114,8 +114,8 @@ func runAndReadFromTopic(runCmd *exec.Cmd, readyURL string, doInput func(), topi
 	readCmd.Stderr = os.Stderr
 
 	// Kill both processes before we exit.
-	defer func() { runCmd.Process.Kill() }()
-	defer func() { readCmd.Process.Kill() }()
+	defer func() { runCmd.Process.Kill() }()  // nolint: errcheck
+	defer func() { readCmd.Process.Kill() }() // nolint: errcheck
 
 	// Run the command, read the messages and wait for a timeout in parallel.
 	go func() {
@@ -228,7 +228,11 @@ func testRoomserver(input []string, wantOutput []string, checkQueries func(api.R
 
 	outputTopic := string(cfg.Kafka.Topics.OutputRoomEvent)
 
-	exe.DeleteTopic(outputTopic)
+	err = exe.DeleteTopic(outputTopic)
+	if err != nil {
+		panic(err)
+	}
+
 	if err = exe.CreateTopic(outputTopic); err != nil {
 		panic(err)
 	}

src/github.com/matrix-org/dendrite/cmd/syncserver-integration-tests/main.go

@@ -175,12 +175,21 @@ func startSyncServer() (*exec.Cmd, chan error) {
 
 // prepareKafka creates the topics which will be written to by the tests.
 func prepareKafka() {
-	exe.DeleteTopic(inputTopic)
-	if err := exe.CreateTopic(inputTopic); err != nil {
+	err := exe.DeleteTopic(inputTopic)
+	if err != nil {
 		panic(err)
 	}
-	exe.DeleteTopic(clientTopic)
-	if err := exe.CreateTopic(clientTopic); err != nil {
+
+	if err = exe.CreateTopic(inputTopic); err != nil {
+		panic(err)
+	}
+
+	err = exe.DeleteTopic(clientTopic)
+	if err != nil {
+		panic(err)
+	}
+
+	if err = exe.CreateTopic(clientTopic); err != nil {
 		panic(err)
 	}
 }
@@ -225,7 +234,8 @@ func main() {
 	fmt.Println("==TESTING==", os.Args[0])
 	prepareKafka()
 	cmd, syncServerCmdChan := startSyncServer()
-	defer cmd.Process.Kill() // ensure server is dead, only cleaning up so don't care about errors this returns.
+	// ensure server is dead, only cleaning up so don't care about errors this returns.
+	defer cmd.Process.Kill() // nolint: errcheck
 
 	// $ curl -XPOST -d '{}' "http://localhost:8009/_matrix/client/r0/createRoom?access_token=@alice:localhost"
 	// $ curl -XPUT -d '{"msgtype":"m.text","body":"hello world"}' "http://localhost:8009/_matrix/client/r0/rooms/%21PjrbIMW2cIiaYF4t:localhost/send/m.room.message/1?access_token=@alice:localhost"

src/github.com/matrix-org/dendrite/common/consumers.go

@@ -91,7 +91,7 @@ func (c *ContinualConsumer) Start() error {
 		pc, err := c.Consumer.ConsumePartition(c.Topic, partition, offset)
 		if err != nil {
 			for _, p := range partitionConsumers {
-				p.Close()
+				p.Close() // nolint: errcheck
 			}
 			return err
 		}
@@ -106,7 +106,7 @@ func (c *ContinualConsumer) Start() error {
 
 // consumePartition consumes the room events for a single partition of the kafkaesque stream.
 func (c *ContinualConsumer) consumePartition(pc sarama.PartitionConsumer) {
-	defer pc.Close()
+	defer pc.Close() // nolint: errcheck
 	for message := range pc.Messages() {
 		msgErr := c.ProcessMessage(message)
 		// Advance our position in the stream so that we will start at the right position after a restart.

src/github.com/matrix-org/dendrite/common/keydb/keydb.go

@@ -37,7 +37,10 @@ func NewDatabase(dataSourceName string) (*Database, error) {
 		return nil, err
 	}
 	d := &Database{}
-	d.statements.prepare(db)
+	err = d.statements.prepare(db)
+	if err != nil {
+		return nil, err
+	}
 	return d, nil
 }
 

src/github.com/matrix-org/dendrite/common/keydb/server_key_table.go

@@ -83,7 +83,7 @@ func (s *serverKeyStatements) bulkSelectServerKeys(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	results := map[gomatrixserverlib.PublicKeyRequest]gomatrixserverlib.ServerKeys{}
 	for rows.Next() {
 		var serverName string

src/github.com/matrix-org/dendrite/common/partition_offset_table.go

@@ -71,7 +71,7 @@ func (s *PartitionOffsetStatements) SelectPartitionOffsets(topic string) ([]Part
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	var results []PartitionOffset
 	for rows.Next() {
 		var offset PartitionOffset

src/github.com/matrix-org/dendrite/common/sql.go

@@ -30,9 +30,9 @@ type Transaction interface {
 // If the transaction succeeded then it is committed, otherwise it is rolledback.
 func EndTransaction(txn Transaction, succeeded *bool) {
 	if *succeeded {
-		txn.Commit()
+		txn.Commit() // nolint: errcheck
 	} else {
-		txn.Rollback()
+		txn.Rollback() // nolint: errcheck
 	}
 }
 

src/github.com/matrix-org/dendrite/common/test/client.go

@@ -69,7 +69,7 @@ func CanonicalJSONInput(jsonData []string) []string {
 }
 
 // Do issues a request and checks the status code and body of the response
-func (r *Request) Do() error {
+func (r *Request) Do() (err error) {
 	client := &http.Client{
 		Timeout: 5 * time.Second,
 		Transport: &http.Transport{
@@ -82,7 +82,7 @@ func (r *Request) Do() error {
 	if err != nil {
 		return err
 	}
-	defer res.Body.Close()
+	defer (func() { err = res.Body.Close() })()
 
 	if res.StatusCode != r.WantedStatusCode {
 		return fmt.Errorf("incorrect status code. Expected: %d  Got: %d", r.WantedStatusCode, res.StatusCode)

src/github.com/matrix-org/dendrite/common/test/config.go

@@ -120,16 +120,21 @@ func WriteConfig(cfg *config.Dendrite, configDir string) error {
 }
 
 // NewMatrixKey generates a new ed25519 matrix server key and writes it to a file.
-func NewMatrixKey(matrixKeyPath string) error {
+func NewMatrixKey(matrixKeyPath string) (err error) {
 	var data [35]byte
-	if _, err := rand.Read(data[:]); err != nil {
+	_, err = rand.Read(data[:])
+	if err != nil {
 		return err
 	}
 	keyOut, err := os.OpenFile(matrixKeyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
 	if err != nil {
 		return err
 	}
-	defer keyOut.Close()
+
+	defer (func() {
+		err = keyOut.Close()
+	})()
+
 	if err = pem.Encode(keyOut, &pem.Block{
 		Type: "MATRIX PRIVATE KEY",
 		Headers: map[string]string{
@@ -176,7 +181,7 @@ func NewTLSKey(tlsKeyPath, tlsCertPath string) error {
 	if err != nil {
 		return err
 	}
-	defer certOut.Close()
+	defer certOut.Close() // nolint: errcheck
 	if err = pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
 		return err
 	}
@@ -185,7 +190,7 @@ func NewTLSKey(tlsKeyPath, tlsCertPath string) error {
 	if err != nil {
 		return err
 	}
-	defer keyOut.Close()
+	defer keyOut.Close() // nolint: errcheck
 	if err = pem.Encode(keyOut, &pem.Block{
 		Type:  "RSA PRIVATE KEY",
 		Bytes: x509.MarshalPKCS1PrivateKey(priv),

src/github.com/matrix-org/dendrite/federationapi/writers/send.go

@@ -180,7 +180,10 @@ func (t *txnReq) processEvent(e gomatrixserverlib.Event) error {
 func checkAllowedByState(e gomatrixserverlib.Event, stateEvents []gomatrixserverlib.Event) error {
 	authUsingState := gomatrixserverlib.NewAuthEvents(nil)
 	for i := range stateEvents {
-		authUsingState.AddEvent(&stateEvents[i])
+		err := authUsingState.AddEvent(&stateEvents[i])
+		if err != nil {
+			return err
+		}
 	}
 	return gomatrixserverlib.Allowed(e, &authUsingState)
 }

src/github.com/matrix-org/dendrite/federationapi/writers/threepid.go

@@ -257,7 +257,10 @@ func buildMembershipEvent(
 	authEvents := gomatrixserverlib.NewAuthEvents(nil)
 
 	for i := range queryRes.StateEvents {
-		authEvents.AddEvent(&queryRes.StateEvents[i])
+		err = authEvents.AddEvent(&queryRes.StateEvents[i])
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	if err = fillDisplayName(builder, authEvents); err != nil {

src/github.com/matrix-org/dendrite/federationsender/storage/joined_hosts_table.go

@@ -105,7 +105,7 @@ func (s *joinedHostsStatements) selectJoinedHosts(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	var result []types.JoinedHost
 	for rows.Next() {

src/github.com/matrix-org/dendrite/mediaapi/fileutils/fileutils.go

@@ -105,12 +105,14 @@ func RemoveDir(dir types.Path, logger *log.Entry) {
 }
 
 // WriteTempFile writes to a new temporary file
-func WriteTempFile(reqReader io.Reader, maxFileSizeBytes config.FileSizeBytes, absBasePath config.Path) (types.Base64Hash, types.FileSizeBytes, types.Path, error) {
+func WriteTempFile(reqReader io.Reader, maxFileSizeBytes config.FileSizeBytes, absBasePath config.Path) (hash types.Base64Hash, size types.FileSizeBytes, path types.Path, err error) {
+	size = -1
+
 	tmpFileWriter, tmpFile, tmpDir, err := createTempFileWriter(absBasePath)
 	if err != nil {
-		return "", -1, "", err
+		return
 	}
-	defer tmpFile.Close()
+	defer (func() { err = tmpFile.Close() })()
 
 	// The amount of data read is limited to maxFileSizeBytes. At this point, if there is more data it will be truncated.
 	limitedReader := io.LimitReader(reqReader, int64(maxFileSizeBytes))
@@ -121,13 +123,18 @@ func WriteTempFile(reqReader io.Reader, maxFileSizeBytes config.FileSizeBytes, a
 	teeReader := io.TeeReader(limitedReader, hasher)
 	bytesWritten, err := io.Copy(tmpFileWriter, teeReader)
 	if err != nil && err != io.EOF {
-		return "", -1, "", err
+		return
 	}
 
-	tmpFileWriter.Flush()
+	err = tmpFileWriter.Flush()
+	if err != nil {
+		return
+	}
 
-	hash := hasher.Sum(nil)
-	return types.Base64Hash(base64.RawURLEncoding.EncodeToString(hash[:])), types.FileSizeBytes(bytesWritten), tmpDir, nil
+	hash = types.Base64Hash(base64.RawURLEncoding.EncodeToString(hasher.Sum(nil)[:]))
+	size = types.FileSizeBytes(bytesWritten)
+	path = tmpDir
+	return
 }
 
 // moveFile attempts to move the file src to dst

src/github.com/matrix-org/dendrite/mediaapi/thumbnailer/thumbnailer_nfnt.go

@@ -83,7 +83,7 @@ func readFile(src string) (image.Image, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer file.Close()
+	defer file.Close() // nolint: errcheck
 
 	img, _, err := image.Decode(file)
 	if err != nil {
@@ -93,12 +93,12 @@ func readFile(src string) (image.Image, error) {
 	return img, nil
 }
 
-func writeFile(img image.Image, dst string) error {
+func writeFile(img image.Image, dst string) (err error) {
 	out, err := os.Create(dst)
 	if err != nil {
 		return err
 	}
-	defer out.Close()
+	defer (func() { err = out.Close() })()
 
 	return jpeg.Encode(out, img, &jpeg.Options{
 		Quality: 85,

src/github.com/matrix-org/dendrite/mediaapi/writers/download.go

@@ -148,7 +148,9 @@ func (r *downloadRequest) jsonErrorResponse(w http.ResponseWriter, res util.JSON
 	// Set status code and write the body
 	w.WriteHeader(res.Code)
 	r.Logger.WithField("code", res.Code).Infof("Responding (%d bytes)", len(resBytes))
-	w.Write(resBytes)
+
+	// we don't really care that much if we fail to write the error response
+	w.Write(resBytes) // nolint: errcheck
 }
 
 // Validate validates the downloadRequest fields
@@ -234,7 +236,7 @@ func (r *downloadRequest) respondFromLocalFile(
 		return nil, errors.Wrap(err, "failed to get file path from metadata")
 	}
 	file, err := os.Open(filePath)
-	defer file.Close()
+	defer file.Close() // nolint: errcheck
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to open file")
 	}
@@ -256,7 +258,7 @@ func (r *downloadRequest) respondFromLocalFile(
 	if r.IsThumbnailRequest {
 		thumbFile, thumbMetadata, resErr := r.getThumbnailFile(types.Path(filePath), activeThumbnailGeneration, maxThumbnailGenerators, db, dynamicThumbnails, thumbnailSizes)
 		if thumbFile != nil {
-			defer thumbFile.Close()
+			defer thumbFile.Close() // nolint: errcheck
 		}
 		if resErr != nil {
 			return nil, resErr
@@ -360,16 +362,16 @@ func (r *downloadRequest) getThumbnailFile(
 	thumbPath := string(thumbnailer.GetThumbnailPath(types.Path(filePath), thumbnail.ThumbnailSize))
 	thumbFile, err := os.Open(string(thumbPath))
 	if err != nil {
-		thumbFile.Close()
+		thumbFile.Close() // nolint: errcheck
 		return nil, nil, errors.Wrap(err, "failed to open file")
 	}
 	thumbStat, err := thumbFile.Stat()
 	if err != nil {
-		thumbFile.Close()
+		thumbFile.Close() // nolint: errcheck
 		return nil, nil, errors.Wrap(err, "failed to stat file")
 	}
 	if types.FileSizeBytes(thumbStat.Size()) != thumbnail.MediaMetadata.FileSizeBytes {
-		thumbFile.Close()
+		thumbFile.Close() // nolint: errcheck
 		return nil, nil, errors.New("thumbnail file sizes on disk and in database differ")
 	}
 	return thumbFile, thumbnail, nil
@@ -564,7 +566,7 @@ func (r *downloadRequest) fetchRemoteFile(absBasePath config.Path, maxFileSizeBy
 		// Remote file not found
 		return "", false, nil
 	}
-	defer resp.Body.Close()
+	defer resp.Body.Close() // nolint: errcheck
 
 	// get metadata from request and set metadata on response
 	contentLength, err := strconv.ParseInt(resp.Header.Get("Content-Length"), 10, 64)

src/github.com/matrix-org/dendrite/roomserver/alias/alias.go

@@ -183,7 +183,10 @@ func (r *RoomserverAliasAPI) sendUpdatedAliasesEvent(
 	// Add auth events
 	authEvents := gomatrixserverlib.NewAuthEvents(nil)
 	for i := range res.StateEvents {
-		authEvents.AddEvent(&res.StateEvents[i])
+		err = authEvents.AddEvent(&res.StateEvents[i])
+		if err != nil {
+			return err
+		}
 	}
 	refs, err := eventsNeeded.AuthEventReferences(&authEvents)
 	if err != nil {

src/github.com/matrix-org/dendrite/roomserver/api/query.go

@@ -283,7 +283,7 @@ func (h *httpRoomserverQueryAPI) QueryServerAllowedToSeeEvent(
 	ctx context.Context,
 	request *QueryServerAllowedToSeeEventRequest,
 	response *QueryServerAllowedToSeeEventResponse,
-) error {
+) (err error) {
 	apiURL := h.roomserverURL + RoomserverQueryServerAllowedToSeeEventPath
 	return postJSON(ctx, h.httpClient, apiURL, request, response)
 }
@@ -306,7 +306,7 @@ func postJSON(
 
 	res, err := httpClient.Do(req.WithContext(ctx))
 	if res != nil {
-		defer res.Body.Close()
+		defer (func() { err = res.Body.Close() })()
 	}
 	if err != nil {
 		return err

src/github.com/matrix-org/dendrite/roomserver/input/events.go

@@ -117,7 +117,10 @@ func processRoomEvent(
 				return err
 			}
 		}
-		db.SetState(ctx, stateAtEvent.EventNID, stateAtEvent.BeforeStateSnapshotNID)
+		err = db.SetState(ctx, stateAtEvent.EventNID, stateAtEvent.BeforeStateSnapshotNID)
+		if err != nil {
+			return err
+		}
 	}
 
 	if input.Kind == api.KindBackfill {

src/github.com/matrix-org/dendrite/roomserver/storage/event_json_table.go

@@ -85,7 +85,7 @@ func (s *eventJSONStatements) bulkSelectEventJSON(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	// We know that we will only get as many results as event NIDs
 	// because of the unique constraint on event NIDs.

src/github.com/matrix-org/dendrite/roomserver/storage/event_state_keys_table.go

@@ -119,7 +119,7 @@ func (s *eventStateKeyStatements) bulkSelectEventStateKeyNID(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	result := make(map[string]types.EventStateKeyNID, len(eventStateKeys))
 	for rows.Next() {
@@ -153,7 +153,7 @@ func (s *eventStateKeyStatements) bulkSelectEventStateKey(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	result := make(map[types.EventStateKeyNID]string, len(eventStateKeyNIDs))
 	for rows.Next() {

src/github.com/matrix-org/dendrite/roomserver/storage/event_types_table.go

@@ -131,7 +131,7 @@ func (s *eventTypeStatements) bulkSelectEventTypeNID(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	result := make(map[string]types.EventTypeNID, len(eventTypes))
 	for rows.Next() {

src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go

@@ -191,7 +191,7 @@ func (s *eventStatements) bulkSelectStateEventByID(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	// We know that we will only get as many results as event IDs
 	// because of the unique constraint on event IDs.
 	// So we can allocate an array of the correct size now.
@@ -231,7 +231,7 @@ func (s *eventStatements) bulkSelectStateAtEventByID(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	results := make([]types.StateAtEvent, len(eventIDs))
 	i := 0
 	for ; rows.Next(); i++ {
@@ -269,7 +269,7 @@ func (s *eventStatements) selectEventSentToOutput(
 	ctx context.Context, txn *sql.Tx, eventNID types.EventNID,
 ) (sentToOutput bool, err error) {
 	stmt := common.TxStmt(txn, s.selectEventSentToOutputStmt)
-	stmt.QueryRowContext(ctx, int64(eventNID)).Scan(&sentToOutput)
+	err = stmt.QueryRowContext(ctx, int64(eventNID)).Scan(&sentToOutput)
 	return
 }
 
@@ -295,7 +295,7 @@ func (s *eventStatements) bulkSelectStateAtEventAndReference(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	results := make([]types.StateAtEventAndReference, len(eventNIDs))
 	i := 0
 	for ; rows.Next(); i++ {
@@ -333,7 +333,7 @@ func (s *eventStatements) bulkSelectEventReference(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	results := make([]gomatrixserverlib.EventReference, len(eventNIDs))
 	i := 0
 	for ; rows.Next(); i++ {
@@ -354,7 +354,7 @@ func (s *eventStatements) bulkSelectEventID(ctx context.Context, eventNIDs []typ
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	results := make(map[types.EventNID]string, len(eventNIDs))
 	i := 0
 	for ; rows.Next(); i++ {
@@ -378,7 +378,7 @@ func (s *eventStatements) bulkSelectEventNID(ctx context.Context, eventIDs []str
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	results := make(map[string]types.EventNID, len(eventIDs))
 	for rows.Next() {
 		var eventID string

src/github.com/matrix-org/dendrite/roomserver/storage/invite_table.go

@@ -113,22 +113,21 @@ func (s *inviteStatements) insertInviteEvent(
 func (s *inviteStatements) updateInviteRetired(
 	ctx context.Context,
 	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
-) ([]string, error) {
+) (eventIDs []string, err error) {
 	stmt := common.TxStmt(txn, s.updateInviteRetiredStmt)
 	rows, err := stmt.QueryContext(ctx, roomNID, targetUserNID)
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
-	var result []string
+	defer (func() { err = rows.Close() })()
 	for rows.Next() {
 		var inviteEventID string
 		if err := rows.Scan(&inviteEventID); err != nil {
 			return nil, err
 		}
-		result = append(result, inviteEventID)
+		eventIDs = append(eventIDs, inviteEventID)
 	}
-	return result, nil
+	return
 }
 
 // selectInviteActiveForUserInRoom returns a list of sender state key NIDs
@@ -142,7 +141,7 @@ func (s *inviteStatements) selectInviteActiveForUserInRoom(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	var result []types.EventStateKeyNID
 	for rows.Next() {
 		var senderUserNID int64

src/github.com/matrix-org/dendrite/roomserver/storage/state_block_table.go

@@ -137,7 +137,7 @@ func (s *stateBlockStatements) bulkSelectStateBlockEntries(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	results := make([]types.StateEntryList, len(stateBlockNIDs))
 	// current is a pointer to the StateEntryList to append the state entries to.
@@ -193,7 +193,7 @@ func (s *stateBlockStatements) bulkSelectFilteredStateBlockEntries(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	var results []types.StateEntryList
 	var current types.StateEntryList

src/github.com/matrix-org/dendrite/roomserver/storage/state_snapshot_table.go

@@ -97,7 +97,7 @@ func (s *stateSnapshotStatements) bulkSelectStateBlockNIDs(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	results := make([]types.StateBlockNIDList, len(stateNIDs))
 	i := 0
 	for ; rows.Next(); i++ {

src/github.com/matrix-org/dendrite/roomserver/storage/storage.go

@@ -287,19 +287,19 @@ func (d *Database) GetLatestEventsForUpdate(
 	eventNIDs, lastEventNIDSent, currentStateSnapshotNID, err :=
 		d.statements.selectLatestEventsNIDsForUpdate(ctx, txn, roomNID)
 	if err != nil {
-		txn.Rollback()
+		txn.Rollback() // nolint: errcheck
 		return nil, err
 	}
 	stateAndRefs, err := d.statements.bulkSelectStateAtEventAndReference(ctx, txn, eventNIDs)
 	if err != nil {
-		txn.Rollback()
+		txn.Rollback() // nolint: errcheck
 		return nil, err
 	}
 	var lastEventIDSent string
 	if lastEventNIDSent != 0 {
 		lastEventIDSent, err = d.statements.selectEventID(ctx, txn, lastEventNIDSent)
 		if err != nil {
-			txn.Rollback()
+			txn.Rollback() // nolint: errcheck
 			return nil, err
 		}
 	}
@@ -459,7 +459,7 @@ func (d *Database) MembershipUpdater(
 	succeeded := false
 	defer func() {
 		if !succeeded {
-			txn.Rollback()
+			txn.Rollback() // nolint: errcheck
 		}
 	}()
 

src/github.com/matrix-org/dendrite/syncapi/storage/account_data_table.go

@@ -87,7 +87,7 @@ func (s *accountDataStatements) insertAccountData(
 	ctx context.Context,
 	userID, roomID, dataType string,
 ) (pos int64, err error) {
-	s.insertAccountDataStmt.QueryRowContext(ctx, userID, roomID, dataType).Scan(&pos)
+	err = s.insertAccountDataStmt.QueryRowContext(ctx, userID, roomID, dataType).Scan(&pos)
 	return
 }
 

src/github.com/matrix-org/dendrite/syncapi/storage/current_room_state_table.go

@@ -122,7 +122,7 @@ func (s *currentRoomStateStatements) selectJoinedUsers(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	result := make(map[string][]string)
 	for rows.Next() {
@@ -147,7 +147,7 @@ func (s *currentRoomStateStatements) selectRoomIDsWithMembership(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	var result []string
 	for rows.Next() {
@@ -169,7 +169,7 @@ func (s *currentRoomStateStatements) selectCurrentState(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 
 	return rowsToEvents(rows)
 }
@@ -208,7 +208,7 @@ func (s *currentRoomStateStatements) selectEventsWithEventIDs(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	return rowsToStreamEvents(rows)
 }
 

src/github.com/matrix-org/dendrite/syncapi/storage/output_room_events_table.go

@@ -213,7 +213,7 @@ func (s *outputRoomEventsStatements) selectRecentEvents(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	events, err := rowsToStreamEvents(rows)
 	if err != nil {
 		return nil, err
@@ -233,7 +233,7 @@ func (s *outputRoomEventsStatements) selectEvents(
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer rows.Close() // nolint: errcheck
 	return rowsToStreamEvents(rows)
 }