[chore]: enable usestdlibvars linter (part 2) (open-telemetry#36101)

#### Description

[usestdlibvars](https://golangci-lint.run/usage/linters/#usestdlibvars)
is a linter that detect the possibility to use variables/constants from
the Go standard library.

Signed-off-by: Matthieu MOREL <matthieu.morel35@gmail.com>

.golangci.yml

@@ -164,6 +164,7 @@ linters:
     - unconvert
     - unparam
     - unused
+    - usestdlibvars
     - wastedassign
 
 issues:

exporter/datadogexporter/internal/clientutil/api.go

@@ -6,6 +6,7 @@ package clientutil // import "github.com/open-telemetry/opentelemetry-collector-
 import (
 	"context"
 	"errors"
+	"net/http"
 
 	"github.com/DataDog/datadog-api-client-go/v2/api/datadog"
 	"github.com/DataDog/datadog-api-client-go/v2/api/datadogV1"
@@ -45,7 +46,7 @@ func ValidateAPIKey(ctx context.Context, apiKey string, logger *zap.Logger, apiC
 		return nil
 	}
 	if err != nil {
-		if httpresp != nil && httpresp.StatusCode == 403 {
+		if httpresp != nil && httpresp.StatusCode == http.StatusForbidden {
 			return WrapError(ErrInvalidAPI, httpresp)
 		}
 		logger.Warn("Error while validating API key", zap.Error(err))

exporter/datadogexporter/internal/clientutil/error_converter.go

@@ -18,5 +18,5 @@ func WrapError(err error, resp *http.Response) error {
 }
 
 func isNonRetriable(resp *http.Response) bool {
-	return resp.StatusCode == 400 || resp.StatusCode == 404 || resp.StatusCode == 413 || resp.StatusCode == 403
+	return resp.StatusCode == http.StatusBadRequest || resp.StatusCode == http.StatusNotFound || resp.StatusCode == http.StatusRequestEntityTooLarge || resp.StatusCode == http.StatusForbidden
 }

exporter/datadogexporter/internal/clientutil/error_converter_test.go

@@ -13,9 +13,9 @@ import (
 )
 
 func TestWrapError(t *testing.T) {
-	respOK := http.Response{StatusCode: 200}
-	respRetriable := http.Response{StatusCode: 402}
-	respNonRetriable := http.Response{StatusCode: 404}
+	respOK := http.Response{StatusCode: http.StatusOK}
+	respRetriable := http.Response{StatusCode: http.StatusPaymentRequired}
+	respNonRetriable := http.Response{StatusCode: http.StatusNotFound}
 	err := fmt.Errorf("Test error")
 	assert.False(t, consumererror.IsPermanent(WrapError(err, &respOK)))
 	assert.False(t, consumererror.IsPermanent(WrapError(err, &respRetriable)))

exporter/datadogexporter/internal/clientutil/retrier_test.go

@@ -46,7 +46,7 @@ func TestNoRetriesOnPermanentError(t *testing.T) {
 	scrubber := scrub.NewScrubber()
 	retrier := NewRetrier(zap.NewNop(), configretry.NewDefaultBackOffConfig(), scrubber)
 	ctx := context.Background()
-	respNonRetriable := http.Response{StatusCode: 404}
+	respNonRetriable := http.Response{StatusCode: http.StatusNotFound}
 
 	retryNum, err := retrier.DoWithRetries(ctx, func(context.Context) error {
 		return WrapError(fmt.Errorf("test"), &respNonRetriable)

exporter/elasticsearchexporter/bulkindexer_test.go

@@ -171,7 +171,7 @@ func TestAsyncBulkIndexer_flush_error(t *testing.T) {
 			name: "500",
 			roundTripFunc: func(*http.Request) (*http.Response, error) {
 				return &http.Response{
-					StatusCode: 500,
+					StatusCode: http.StatusInternalServerError,
 					Header:     http.Header{"X-Elastic-Product": []string{"Elasticsearch"}},
 					Body:       io.NopCloser(strings.NewReader("error")),
 				}, nil
@@ -182,7 +182,7 @@ func TestAsyncBulkIndexer_flush_error(t *testing.T) {
 			name: "429",
 			roundTripFunc: func(*http.Request) (*http.Response, error) {
 				return &http.Response{
-					StatusCode: 429,
+					StatusCode: http.StatusTooManyRequests,
 					Header:     http.Header{"X-Elastic-Product": []string{"Elasticsearch"}},
 					Body:       io.NopCloser(strings.NewReader("error")),
 				}, nil
@@ -200,7 +200,7 @@ func TestAsyncBulkIndexer_flush_error(t *testing.T) {
 			name: "known version conflict error",
 			roundTripFunc: func(*http.Request) (*http.Response, error) {
 				return &http.Response{
-					StatusCode: 200,
+					StatusCode: http.StatusOK,
 					Header:     http.Header{"X-Elastic-Product": []string{"Elasticsearch"}},
 					Body: io.NopCloser(strings.NewReader(
 						`{"items":[{"create":{"_index":".ds-metrics-generic.otel-default","status":400,"error":{"type":"version_conflict_engine_exception","reason":""}}}]}`)),

exporter/influxdbexporter/writer.go

@@ -205,10 +205,10 @@ func (b *influxHTTPWriterBatch) WriteBatch(ctx context.Context) error {
 	if err = res.Body.Close(); err != nil {
 		return err
 	}
-	switch res.StatusCode / 100 {
-	case 2: // Success
+	switch {
+	case res.StatusCode >= 200 && res.StatusCode < 300: // Success
 		break
-	case 5: // Retryable error
+	case res.StatusCode >= 500 && res.StatusCode < 600: // Retryable error
 		return fmt.Errorf("line protocol write returned %q %q", res.Status, string(body))
 	default: // Terminal error
 		return consumererror.NewPermanent(fmt.Errorf("line protocol write returned %q %q", res.Status, string(body)))

exporter/lokiexporter/exporter.go

@@ -90,7 +90,7 @@ func (l *lokiExporter) sendPushRequest(ctx context.Context, tenant string, reque
 		return consumererror.NewPermanent(err)
 	}
 
-	req, err := http.NewRequestWithContext(ctx, "POST", l.config.ClientConfig.Endpoint, bytes.NewReader(buf))
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, l.config.ClientConfig.Endpoint, bytes.NewReader(buf))
 	if err != nil {
 		return consumererror.NewPermanent(err)
 	}

exporter/prometheusremotewriteexporter/exporter.go

@@ -292,7 +292,7 @@ func (prwe *prwExporter) execute(ctx context.Context, writeReq *prompb.WriteRequ
 		}
 
 		// Create the HTTP POST request to send to the endpoint
-		req, err := http.NewRequestWithContext(ctx, "POST", prwe.endpointURL.String(), bytes.NewReader(compressedData))
+		req, err := http.NewRequestWithContext(ctx, http.MethodPost, prwe.endpointURL.String(), bytes.NewReader(compressedData))
 		if err != nil {
 			return backoff.Permanent(consumererror.NewPermanent(err))
 		}

exporter/signalfxexporter/dpclient.go

@@ -119,7 +119,7 @@ func (s *sfxDPClient) postData(ctx context.Context, body io.Reader, headers map[
 	if !strings.HasSuffix(datapointURL.Path, "v2/datapoint") {
 		datapointURL.Path = path.Join(datapointURL.Path, "v2/datapoint")
 	}
-	req, err := http.NewRequestWithContext(ctx, "POST", datapointURL.String(), body)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, datapointURL.String(), body)
 	if err != nil {
 		return consumererror.NewPermanent(err)
 	}

exporter/signalfxexporter/eventclient.go

@@ -58,7 +58,7 @@ func (s *sfxEventClient) pushLogsData(ctx context.Context, ld plog.Logs) (int, e
 	if !strings.HasSuffix(eventURL.Path, "v2/event") {
 		eventURL.Path = path.Join(eventURL.Path, "v2/event")
 	}
-	req, err := http.NewRequestWithContext(ctx, "POST", eventURL.String(), body)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, eventURL.String(), body)
 	if err != nil {
 		return ld.LogRecordCount(), consumererror.NewPermanent(err)
 	}

exporter/signalfxexporter/internal/apm/correlations/client_test.go

@@ -85,7 +85,7 @@ func makeHandler(t *testing.T, corCh chan<- *request, forcedRespCode *atomic.Val
 
 			body, err := io.ReadAll(r.Body)
 			if err != nil {
-				rw.WriteHeader(400)
+				rw.WriteHeader(http.StatusBadRequest)
 				return
 			}
 			cor = &request{

exporter/signalfxexporter/internal/dimensions/dimclient.go

@@ -330,7 +330,7 @@ func (dc *DimensionClient) makePatchRequest(ctx context.Context, dim *DimensionU
 
 	req, err := http.NewRequestWithContext(
 		ctx,
-		"PATCH",
+		http.MethodPatch,
 		strings.TrimRight(url.String(), "/")+"/_/sfxagent",
 		bytes.NewReader(json))
 	if err != nil {

exporter/splunkhecexporter/hec_worker.go

@@ -32,7 +32,7 @@ func (hec *defaultHecWorker) send(ctx context.Context, buf buffer, headers map[s
 	nb := make([]byte, buf.Len())
 	copy(nb, buf.Bytes())
 	bodyBuf := bytes.NewReader(nb)
-	req, err := http.NewRequestWithContext(ctx, "POST", hec.url.String(), bodyBuf)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, hec.url.String(), bodyBuf)
 	if err != nil {
 		return consumererror.NewPermanent(err)
 	}

exporter/sumologicexporter/exporter_test.go

@@ -166,7 +166,7 @@ func TestLogsResourceAttributesSentAsFields(t *testing.T) {
 func TestAllFailed(t *testing.T) {
 	test := prepareExporterTest(t, createTestConfig(), []func(w http.ResponseWriter, req *http.Request){
 		func(w http.ResponseWriter, req *http.Request) {
-			w.WriteHeader(500)
+			w.WriteHeader(http.StatusInternalServerError)
 
 			body := extractBody(t, req)
 			assert.Equal(t, "Example log\nAnother example log", body)
@@ -204,7 +204,7 @@ func TestPartiallyFailed(t *testing.T) {
 			assert.Empty(t, req.Header.Get("X-Sumo-Fields"))
 		},
 		func(w http.ResponseWriter, req *http.Request) {
-			w.WriteHeader(500)
+			w.WriteHeader(http.StatusInternalServerError)
 
 			body := extractBody(t, req)
 			assert.Equal(t, "Another example log", body)
@@ -395,7 +395,7 @@ func TestAllMetricsFailed(t *testing.T) {
 			name: "sent together when metrics under the same resource",
 			callbacks: []func(w http.ResponseWriter, req *http.Request){
 				func(w http.ResponseWriter, req *http.Request) {
-					w.WriteHeader(500)
+					w.WriteHeader(http.StatusInternalServerError)
 
 					body := extractBody(t, req)
 					expected := `test.metric.data{test="test_value",test2="second_value"} 14500 1605534165000
@@ -421,7 +421,7 @@ gauge_metric_name{test="test_value",test2="second_value",remote_name="156955",ur
 			name: "sent together when metrics under different resources",
 			callbacks: []func(w http.ResponseWriter, req *http.Request){
 				func(w http.ResponseWriter, req *http.Request) {
-					w.WriteHeader(500)
+					w.WriteHeader(http.StatusInternalServerError)
 
 					body := extractBody(t, req)
 					expected := `test.metric.data{test="test_value",test2="second_value"} 14500 1605534165000

exporter/sumologicexporter/sender.go

@@ -215,7 +215,7 @@ func (s *sender) handleReceiverResponse(resp *http.Response) error {
 
 	// API responds with a 200 or 204 with ConentLength set to 0 when all data
 	// has been successfully ingested.
-	if resp.ContentLength == 0 && (resp.StatusCode == 200 || resp.StatusCode == 204) {
+	if resp.ContentLength == 0 && (resp.StatusCode == http.StatusOK || resp.StatusCode == http.StatusNoContent) {
 		return nil
 	}
 
@@ -229,7 +229,7 @@ func (s *sender) handleReceiverResponse(resp *http.Response) error {
 	// API responds with a 200 or 204 with a JSON body describing what issues
 	// were encountered when processing the sent data.
 	switch resp.StatusCode {
-	case 200, 204:
+	case http.StatusOK, http.StatusNoContent:
 		if resp.ContentLength < 0 {
 			s.logger.Warn("Unknown length of server response")
 			return nil
@@ -259,7 +259,7 @@ func (s *sender) handleReceiverResponse(resp *http.Response) error {
 		l.Warn("There was an issue sending data")
 		return nil
 
-	case 401:
+	case http.StatusUnauthorized:
 		return errUnauthorized
 
 	default:

exporter/sumologicexporter/sender_test.go

@@ -329,7 +329,7 @@ func TestSendLogsSplit(t *testing.T) {
 func TestSendLogsSplitFailedOne(t *testing.T) {
 	test := prepareSenderTest(t, NoCompression, []func(w http.ResponseWriter, req *http.Request){
 		func(w http.ResponseWriter, req *http.Request) {
-			w.WriteHeader(500)
+			w.WriteHeader(http.StatusInternalServerError)
 			_, err := fmt.Fprintf(
 				w,
 				`{"id":"1TIRY-KGIVX-TPQRJ","errors":[{"code":"internal.error","message":"Internal server error."}]}`,
@@ -368,7 +368,7 @@ func TestSendLogsSplitFailedOne(t *testing.T) {
 func TestSendLogsSplitFailedAll(t *testing.T) {
 	test := prepareSenderTest(t, NoCompression, []func(w http.ResponseWriter, req *http.Request){
 		func(w http.ResponseWriter, req *http.Request) {
-			w.WriteHeader(500)
+			w.WriteHeader(http.StatusInternalServerError)
 
 			body := extractBody(t, req)
 			assert.Equal(t, "Example log", body)
@@ -687,7 +687,7 @@ func TestSendLogsJsonSplit(t *testing.T) {
 func TestSendLogsJsonSplitFailedOne(t *testing.T) {
 	test := prepareSenderTest(t, NoCompression, []func(w http.ResponseWriter, req *http.Request){
 		func(w http.ResponseWriter, req *http.Request) {
-			w.WriteHeader(500)
+			w.WriteHeader(http.StatusInternalServerError)
 
 			body := extractBody(t, req)
 
@@ -732,7 +732,7 @@ func TestSendLogsJsonSplitFailedOne(t *testing.T) {
 func TestSendLogsJsonSplitFailedAll(t *testing.T) {
 	test := prepareSenderTest(t, NoCompression, []func(w http.ResponseWriter, req *http.Request){
 		func(w http.ResponseWriter, req *http.Request) {
-			w.WriteHeader(500)
+			w.WriteHeader(http.StatusInternalServerError)
 
 			body := extractBody(t, req)
 
@@ -1192,7 +1192,7 @@ func TestSendMetricsSplitBySource(t *testing.T) {
 func TestSendMetricsSplitFailedOne(t *testing.T) {
 	test := prepareSenderTest(t, NoCompression, []func(w http.ResponseWriter, req *http.Request){
 		func(w http.ResponseWriter, req *http.Request) {
-			w.WriteHeader(500)
+			w.WriteHeader(http.StatusInternalServerError)
 
 			body := extractBody(t, req)
 			expected := `test.metric.data{test="test_value",test2="second_value"} 14500 1605534165000`
@@ -1233,7 +1233,7 @@ func TestSendMetricsSplitFailedOne(t *testing.T) {
 func TestSendMetricsSplitFailedAll(t *testing.T) {
 	test := prepareSenderTest(t, NoCompression, []func(w http.ResponseWriter, req *http.Request){
 		func(w http.ResponseWriter, req *http.Request) {
-			w.WriteHeader(500)
+			w.WriteHeader(http.StatusInternalServerError)
 
 			body := extractBody(t, req)
 			expected := `test.metric.data{test="test_value",test2="second_value"} 14500 1605534165000`
@@ -1302,7 +1302,7 @@ func TestSendMetricsUnexpectedFormat(t *testing.T) {
 func TestBadRequestCausesPermanentError(t *testing.T) {
 	test := prepareSenderTest(t, NoCompression, []func(w http.ResponseWriter, req *http.Request){
 		func(res http.ResponseWriter, _ *http.Request) {
-			res.WriteHeader(400)
+			res.WriteHeader(http.StatusBadRequest)
 		},
 	})
 	test.s.config.MetricFormat = OTLPMetricFormat

exporter/zipkinexporter/zipkin.go

@@ -74,7 +74,7 @@ func (ze *zipkinExporter) pushTraces(ctx context.Context, td ptrace.Traces) erro
 		return consumererror.NewPermanent(fmt.Errorf("failed to push trace data via Zipkin exporter: %w", err))
 	}
 
-	req, err := http.NewRequestWithContext(ctx, "POST", ze.url, bytes.NewReader(body))
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, ze.url, bytes.NewReader(body))
 	if err != nil {
 		return fmt.Errorf("failed to push trace data via Zipkin exporter: %w", err)
 	}

extension/asapauthextension/extension_test.go

@@ -53,7 +53,7 @@ func TestRoundTripper(t *testing.T) {
 	assert.NoError(t, err)
 	assert.NotNil(t, roundTripper)
 
-	req := &http.Request{Method: "Get", Header: map[string][]string{}}
+	req := &http.Request{Method: http.MethodGet, Header: map[string][]string{}}
 	resp, err := roundTripper.RoundTrip(req)
 	assert.NoError(t, err)
 	authHeaderValue := resp.Header.Get("Authorization")

extension/bearertokenauthextension/bearertokenauth_test.go

@@ -57,7 +57,7 @@ func TestBearerAuthenticatorHttp(t *testing.T) {
 	assert.NoError(t, err)
 	assert.NotNil(t, c)
 
-	request := &http.Request{Method: "Get"}
+	request := &http.Request{Method: http.MethodGet}
 	resp, err := c.RoundTrip(request)
 	assert.NoError(t, err)
 	authHeaderValue := resp.Header.Get("Authorization")
@@ -171,7 +171,7 @@ func TestBearerTokenFileContentUpdate(t *testing.T) {
 	assert.NoError(t, err)
 	assert.NotNil(t, rt)
 
-	request := &http.Request{Method: "Get"}
+	request := &http.Request{Method: http.MethodGet}
 	resp, err := rt.RoundTrip(request)
 	assert.NoError(t, err)
 	authHeaderValue := resp.Header.Get("Authorization")
@@ -185,7 +185,7 @@ func TestBearerTokenFileContentUpdate(t *testing.T) {
 	assert.NoError(t, err)
 
 	// check if request is updated with the new token
-	request = &http.Request{Method: "Get"}
+	request = &http.Request{Method: http.MethodGet}
 	resp, err = rt.RoundTrip(request)
 	assert.NoError(t, err)
 	authHeaderValue = resp.Header.Get("Authorization")
@@ -196,7 +196,7 @@ func TestBearerTokenFileContentUpdate(t *testing.T) {
 	time.Sleep(5 * time.Second)
 
 	// check if request is updated with the old token
-	request = &http.Request{Method: "Get"}
+	request = &http.Request{Method: http.MethodGet}
 	resp, err = rt.RoundTrip(request)
 	assert.NoError(t, err)
 	authHeaderValue = resp.Header.Get("Authorization")

extension/opampextension/auth.go

@@ -25,7 +25,7 @@ func (h *headerCaptureRoundTripper) RoundTrip(req *http.Request) (*http.Response
 	// Dummy response is recorded here
 	return &http.Response{
 		Status:     "200 OK",
-		StatusCode: 200,
+		StatusCode: http.StatusOK,
 		Proto:      "HTTP/1.0",
 		ProtoMajor: 1,
 		ProtoMinor: 0,

extension/sumologicextension/extension.go

@@ -460,7 +460,7 @@ func (se *SumologicExtension) registerCollector(ctx context.Context, collectorNa
 
 	if res.StatusCode < 200 || res.StatusCode >= 400 {
 		return credentials.CollectorCredentials{}, se.handleRegistrationError(res)
-	} else if res.StatusCode == 301 {
+	} else if res.StatusCode == http.StatusMovedPermanently {
 		// Use the URL from Location header for subsequent requests.
 		u := strings.TrimSuffix(res.Header.Get("Location"), "/")
 		se.SetBaseURL(u)
@@ -511,7 +511,7 @@ func (se *SumologicExtension) handleRegistrationError(res *http.Response) error
 	)
 
 	// Return unrecoverable error for 4xx status codes except 429
-	if res.StatusCode >= 400 && res.StatusCode < 500 && res.StatusCode != 429 {
+	if res.StatusCode >= 400 && res.StatusCode < 500 && res.StatusCode != http.StatusTooManyRequests {
 		return backoff.Permanent(fmt.Errorf(
 			"failed to register the collector, got HTTP status code: %d",
 			res.StatusCode,