Enable modernize linter (#4750)

Enable the golangci-lint modernize linter.
* Add exception for the omitempty struct issue.
* Apply modernize fixes.

Signed-off-by: SuperQ <superq@gmail.com>

.golangci.yml

@@ -5,6 +5,7 @@ linters:
     - errorlint
     - godot
     - misspell
+    - modernize
     - revive
     - sloglint
     - testifylint
@@ -77,6 +78,9 @@ linters:
       - linters:
           - errcheck
         path: _test.go
+      - linters:
+          - modernize
+        text: "omitzero: Omitempty has no effect on nested struct fields"
     warn-unused: true
 issues:
   max-issues-per-linter: 0

api/api.go

@@ -118,10 +118,7 @@ func New(opts Options) (*API, error) {
 	}
 	concurrency := opts.Concurrency
 	if concurrency < 1 {
-		concurrency = runtime.GOMAXPROCS(0)
-		if concurrency < 8 {
-			concurrency = 8
-		}
+		concurrency = max(runtime.GOMAXPROCS(0), 8)
 	}
 
 	v2, err := apiv2.NewAPI(

api/v2/api.go

@@ -20,6 +20,7 @@ import (
 	"log/slog"
 	"net/http"
 	"regexp"
+	"slices"
 	"sort"
 	"sync"
 	"time"
@@ -286,7 +287,7 @@ func (api *API) getAlertsHandler(params alert_ops.GetAlertsParams) middleware.Re
 			receivers = append(receivers, r.RouteOpts.Receiver)
 		}
 
-		if receiverFilter != nil && !receiversMatchFilter(receivers, receiverFilter) {
+		if receiverFilter != nil && !slices.ContainsFunc(receivers, receiverFilter.MatchString) {
 			continue
 		}
 
@@ -474,16 +475,6 @@ func removeEmptyLabels(ls prometheus_model.LabelSet) {
 	}
 }
 
-func receiversMatchFilter(receivers []string, filter *regexp.Regexp) bool {
-	for _, r := range receivers {
-		if filter.MatchString(r) {
-			return true
-		}
-	}
-
-	return false
-}
-
 func alertMatchesFilterLabels(a *prometheus_model.Alert, matchers []*labels.Matcher) bool {
 	sms := make(map[string]string)
 	for name, value := range a.Labels {

cluster/cluster.go

@@ -216,10 +216,7 @@ func Create(
 
 	p.register(reg, name)
 
-	retransmit := len(knownPeers) / 2
-	if retransmit < 3 {
-		retransmit = 3
-	}
+	retransmit := max(len(knownPeers)/2, 3)
 	p.delegate = newDelegate(l, reg, p, retransmit)
 
 	cfg := memberlist.DefaultLANConfig()

cmd/alertmanager/main_test.go

@@ -79,7 +79,6 @@ func TestExternalURL(t *testing.T) {
 			err:      true,
 		},
 	} {
-		tc := tc
 		if tc.hostnameResolver == nil {
 			tc.hostnameResolver = func() (string, error) {
 				return hostname, nil

config/config_test.go

@@ -1398,7 +1398,6 @@ func TestUnmarshalHostPort(t *testing.T) {
 			err: true,
 		},
 	} {
-		tc := tc
 		t.Run(tc.in, func(t *testing.T) {
 			hp := HostPort{}
 			err := yaml.Unmarshal([]byte(tc.in), &hp)

config/notifiers.go

@@ -569,7 +569,7 @@ type IncidentioConfig struct {
 }
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface.
-func (c *IncidentioConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
+func (c *IncidentioConfig) UnmarshalYAML(unmarshal func(any) error) error {
 	*c = DefaultIncidentioConfig
 	type plain IncidentioConfig
 	if err := unmarshal((*plain)(c)); err != nil {
@@ -1102,7 +1102,7 @@ type MattermostField struct {
 }
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface for MattermostField.
-func (c *MattermostField) UnmarshalYAML(unmarshal func(interface{}) error) error {
+func (c *MattermostField) UnmarshalYAML(unmarshal func(any) error) error {
 	type plain MattermostField
 	if err := unmarshal((*plain)(c)); err != nil {
 		return err
@@ -1157,7 +1157,7 @@ type MattermostConfig struct {
 }
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface.
-func (c *MattermostConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
+func (c *MattermostConfig) UnmarshalYAML(unmarshal func(any) error) error {
 	*c = DefaultMattermostConfig
 	type plain MattermostConfig
 	if err := unmarshal((*plain)(c)); err != nil {

config/receiver/receiver_test.go

@@ -69,7 +69,6 @@ func TestBuildReceiverIntegrations(t *testing.T) {
 			err: true,
 		},
 	} {
-		tc := tc
 		t.Run("", func(t *testing.T) {
 			integrations, err := BuildReceiverIntegrations(tc.receiver, nil, nil)
 			if tc.err {

dispatch/dispatch_test.go

@@ -700,7 +700,7 @@ func TestDispatcherRaceOnFirstAlertNotDeliveredWhenGroupWaitIsZero(t *testing.T)
 	defer dispatcher.Stop()
 
 	// Push all alerts.
-	for i := 0; i < numAlerts; i++ {
+	for i := range numAlerts {
 		alert := newAlert(model.LabelSet{"alertname": model.LabelValue(fmt.Sprintf("Alert_%d", i))})
 		require.NoError(t, alerts.Put(alert))
 	}

featurecontrol/featurecontrol.go

@@ -113,7 +113,7 @@ func NewFlags(logger *slog.Logger, features string) (Flagger, error) {
 		return NoopFlags{}, nil
 	}
 
-	for _, feature := range strings.Split(features, ",") {
+	for feature := range strings.SplitSeq(features, ",") {
 		switch feature {
 		case FeatureReceiverNameInMetrics:
 			opts = append(opts, enableReceiverNameInMetrics())

matcher/parse/lexer_test.go

@@ -759,7 +759,7 @@ func TestLexer_Peek(t *testing.T) {
 // error has occurred.
 func TestLexer_PeekError(t *testing.T) {
 	l := lexer{input: "\"hello"}
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		tok, err := l.peek()
 		require.Equal(t, token{}, tok)
 		require.EqualError(t, err, "0:6: \"hello: missing end \"")

matcher/parse/token.go

@@ -16,6 +16,7 @@ package parse
 import (
 	"errors"
 	"fmt"
+	"slices"
 	"strconv"
 	"unicode/utf8"
 )
@@ -73,12 +74,7 @@ func (t token) isEOF() bool {
 
 // isOneOf returns true if the token is one of the specified kinds.
 func (t token) isOneOf(kinds ...tokenKind) bool {
-	for _, k := range kinds {
-		if k == t.kind {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(kinds, t.kind)
 }
 
 // unquote the value in token. If unquoted returns it unmodified.

nflog/nflog.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"io"
 	"log/slog"
+	"maps"
 	"math/rand"
 	"os"
 	"sync"
@@ -159,9 +160,7 @@ type state map[string]*pb.MeshEntry
 
 func (s state) clone() state {
 	c := make(state, len(s))
-	for k, v := range s {
-		c[k] = v
-	}
+	maps.Copy(c, s)
 	return c
 }
 

notify/email/email.go

@@ -80,7 +80,7 @@ func (n *Email) auth(mechs string) (smtp.Auth, error) {
 	}
 
 	err := &types.MultiError{}
-	for _, mech := range strings.Split(mechs, " ") {
+	for mech := range strings.SplitSeq(mechs, " ") {
 		switch mech {
 		case "CRAM-MD5":
 			secret := string(n.conf.AuthSecret)

notify/email/email_test.go

@@ -300,7 +300,6 @@ func TestEmailNotifyWithErrors(t *testing.T) {
 			hasEmail: true,
 		},
 	} {
-		tc := tc
 		t.Run(tc.title, func(t *testing.T) {
 			if len(tc.errMsg) == 0 {
 				t.Fatal("please define the expected error message")
@@ -579,7 +578,6 @@ func TestEmailNotifyWithAuthentication(t *testing.T) {
 			retry:  true,
 		},
 	} {
-		tc := tc
 		t.Run(tc.title, func(t *testing.T) {
 			emailCfg := &config.EmailConfig{
 				Smarthost: c.Smarthost,

notify/jira/jira_test.go

@@ -142,7 +142,6 @@ func TestSearchExistingIssue(t *testing.T) {
 			expectedJQL: `statusCategory != Done and project="PROJ" and labels="ALERT{1}" order by status ASC,resolutiondate DESC`,
 		},
 	} {
-		tc := tc
 		t.Run(tc.title, func(t *testing.T) {
 			expectedJQL = tc.expectedJQL
 			tc.cfg.APIURL = &config.URL{URL: u}
@@ -300,7 +299,6 @@ func TestPrepareSearchRequest(t *testing.T) {
 			expectedURLPath: "/rest/api/2",
 		},
 	} {
-		tc := tc
 		t.Run(tc.title, func(t *testing.T) {
 			tc.cfg.HTTPConfig = &commoncfg.HTTPClientConfig{}
 
@@ -402,8 +400,6 @@ func TestJiraTemplating(t *testing.T) {
 			errMsg: "template: :1: unclosed action",
 		},
 	} {
-		tc := tc
-
 		t.Run(tc.title, func(t *testing.T) {
 			capturedBody = nil
 
@@ -778,8 +774,6 @@ func TestJiraNotify(t *testing.T) {
 			errMsg:             "can't find transition REOPEN for issue OPS-3",
 		},
 	} {
-		tc := tc
-
 		t.Run(tc.title, func(t *testing.T) {
 			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 				switch r.URL.Path {
@@ -1118,8 +1112,6 @@ func TestJiraPriority(t *testing.T) {
 			"Medium",
 		},
 	} {
-		tc := tc
-
 		t.Run(tc.title, func(t *testing.T) {
 			t.Parallel()
 			u, err := url.Parse("http://example.com/")

notify/jira/types.go

@@ -15,6 +15,7 @@ package jira
 
 import (
 	"encoding/json"
+	"maps"
 )
 
 type issue struct {
@@ -97,9 +98,7 @@ func (i issueFields) MarshalJSON() ([]byte, error) {
 		jsonFields["status"] = i.Status
 	}
 
-	for key, field := range i.Fields {
-		jsonFields[key] = field
-	}
+	maps.Copy(jsonFields, i.Fields)
 
 	return json.Marshal(jsonFields)
 }

notify/mattermost/mattermost_test.go

@@ -58,7 +58,7 @@ func TestMattermostTemplating(t *testing.T) {
 	// Create a fake HTTP server to simulate the Mattermost webhook
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		dec := json.NewDecoder(r.Body)
-		out := make(map[string]interface{})
+		out := make(map[string]any)
 		err := dec.Decode(&out)
 		if err != nil {
 			panic(err)

notify/opsgenie/opsgenie.go

@@ -19,6 +19,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"log/slog"
+	"maps"
 	"net/http"
 	"os"
 	"strings"
@@ -141,9 +142,7 @@ func (n *Notifier) createRequests(ctx context.Context, as ...*types.Alert) ([]*h
 
 	details := make(map[string]string)
 
-	for k, v := range data.CommonLabels {
-		details[k] = v
-	}
+	maps.Copy(details, data.CommonLabels)
 
 	for k, v := range n.conf.Details {
 		details[k] = tmpl(v)

notify/pagerduty/pagerduty_test.go

@@ -313,7 +313,6 @@ func TestErrDetails(t *testing.T) {
 			exp: "",
 		},
 	} {
-		tc := tc
 		t.Run("", func(t *testing.T) {
 			err := errDetails(tc.status, tc.body)
 			require.Contains(t, err, tc.exp)

notify/sns/sns_test.go

@@ -113,7 +113,6 @@ func TestNotifyWithInvalidTemplate(t *testing.T) {
 			},
 		},
 	} {
-		tc := tc
 		t.Run(tc.title, func(t *testing.T) {
 			snsCfg := &config.SNSConfig{
 				HTTPConfig: &commoncfg.HTTPClientConfig{},

pkg/labels/parse.go

@@ -127,8 +127,8 @@ func ParseMatcher(s string) (_ *Matcher, err error) {
 		expectTrailingQuote bool
 	)
 
-	if strings.HasPrefix(rawValue, "\"") {
-		rawValue = strings.TrimPrefix(rawValue, "\"")
+	if after, ok := strings.CutPrefix(rawValue, "\""); ok {
+		rawValue = after
 		expectTrailingQuote = true
 	}
 

provider/mem/mem.go

@@ -166,13 +166,6 @@ func (a *Alerts) Close() {
 	}
 }
 
-func max(a, b int) int {
-	if a > b {
-		return a
-	}
-	return b
-}
-
 // Subscribe returns an iterator over active alerts that have not been
 // resolved and successfully notified about.
 // They are not guaranteed to be in chronological order.

provider/mem/mem_test.go

@@ -221,8 +221,7 @@ func TestAlertsPut(t *testing.T) {
 func TestAlertsSubscribe(t *testing.T) {
 	marker := types.NewMarker(prometheus.NewRegistry())
 
-	ctx, cancel := context.WithCancel(context.Background())
-	defer cancel()
+	ctx := t.Context()
 	alerts, err := NewAlerts(ctx, marker, 30*time.Minute, noopCallback{}, promslog.NewNopLogger(), prometheus.NewRegistry())
 	if err != nil {
 		t.Fatal(err)
@@ -246,7 +245,7 @@ func TestAlertsSubscribe(t *testing.T) {
 		wg     sync.WaitGroup
 	)
 	wg.Add(nb)
-	for i := 0; i < nb; i++ {
+	for i := range nb {
 		go func(i int) {
 			defer wg.Done()
 
@@ -576,7 +575,7 @@ func TestAlertsConcurrently(t *testing.T) {
 	}()
 	expire := 10 * time.Millisecond
 	wg := sync.WaitGroup{}
-	for i := 0; i < 100; i++ {
+	for range 100 {
 		wg.Add(1)
 		go func() {
 			defer wg.Done()

silence/silence.go

@@ -25,6 +25,7 @@ import (
 	"os"
 	"reflect"
 	"regexp"
+	"slices"
 	"sort"
 	"sync"
 	"time"
@@ -932,10 +933,8 @@ func QState(states ...types.SilenceState) QueryParam {
 		f := func(sil *pb.Silence, _ *Silences, now time.Time) (bool, error) {
 			s := getState(sil, now)
 
-			for _, ps := range states {
-				if s == ps {
-					return true, nil
-				}
+			if slices.Contains(states, s) {
+				return true, nil
 			}
 			return false, nil
 		}

silence/silence_bench_test.go

@@ -422,7 +422,7 @@ func benchmarkQueryWithConcurrentAdds(b *testing.B, initialSilences int, addRati
 	lset := model.LabelSet{"aaaa": "AAAA", "bbbb": "BBBB", "cccc": "CCCC"}
 
 	// Create initial silences
-	for i := 0; i < initialSilences; i++ {
+	for i := range initialSilences {
 		id := strconv.Itoa(i)
 		patA := "A{4}|" + id
 		patB := id

template/template.go

@@ -435,7 +435,7 @@ type TemplateFunc func(string) (string, error)
 // deepCopyWithTemplate returns a deep copy of a map/slice/array/string/int/bool or combination thereof, executing the
 // provided template (with the provided data) on all string keys or values. All maps are connverted to
 // map[string]interface{}, with all non-string keys discarded.
-func DeepCopyWithTemplate(value interface{}, tmplTextFunc TemplateFunc) (interface{}, error) {
+func DeepCopyWithTemplate(value any, tmplTextFunc TemplateFunc) (any, error) {
 	if value == nil {
 		return value, nil
 	}
@@ -446,7 +446,7 @@ func DeepCopyWithTemplate(value interface{}, tmplTextFunc TemplateFunc) (interfa
 	case reflect.String:
 		parsed, ok := tmplTextFunc(value.(string))
 		if ok == nil {
-			var inlineType interface{}
+			var inlineType any
 			err := yaml.Unmarshal([]byte(parsed), &inlineType)
 			if err != nil || (inlineType != nil && reflect.TypeOf(inlineType).Kind() == reflect.String) {
 				// ignore error, thus the string is not an interface
@@ -458,8 +458,8 @@ func DeepCopyWithTemplate(value interface{}, tmplTextFunc TemplateFunc) (interfa
 
 	case reflect.Array, reflect.Slice:
 		arrayLen := valueMeta.Len()
-		converted := make([]interface{}, arrayLen)
-		for i := 0; i < arrayLen; i++ {
+		converted := make([]any, arrayLen)
+		for i := range arrayLen {
 			var err error
 			converted[i], err = DeepCopyWithTemplate(valueMeta.Index(i).Interface(), tmplTextFunc)
 			if err != nil {
@@ -470,7 +470,7 @@ func DeepCopyWithTemplate(value interface{}, tmplTextFunc TemplateFunc) (interfa
 
 	case reflect.Map:
 		keys := valueMeta.MapKeys()
-		converted := make(map[string]interface{}, len(keys))
+		converted := make(map[string]any, len(keys))
 
 		for _, keyMeta := range keys {
 			var err error

template/template_test.go

@@ -278,7 +278,6 @@ func TestData(t *testing.T) {
 			},
 		},
 	} {
-		tc := tc
 		t.Run("", func(t *testing.T) {
 			got := tmpl.Data(tc.receiver, tc.groupLabels, tc.alerts...)
 			require.Equal(t, tc.exp, got)
@@ -403,7 +402,6 @@ func TestTemplateExpansion(t *testing.T) {
 			exp: "[key2 key4]",
 		},
 	} {
-		tc := tc
 		t.Run(tc.title, func(t *testing.T) {
 			f := tmpl.ExecuteTextString
 			if tc.html {
@@ -465,7 +463,6 @@ func TestTemplateExpansionWithOptions(t *testing.T) {
 			exp: "bar",
 		},
 	} {
-		tc := tc
 		t.Run(tc.title, func(t *testing.T) {
 			tmpl, err := FromGlobs([]string{}, tc.options...)
 			require.NoError(t, err)
@@ -579,10 +576,9 @@ func TestTemplateFuncs(t *testing.T) {
 		data:  time.Now().Add(-1 * time.Hour),
 		exp:   "1h 0m 0s",
 	}} {
-		tc := tc
 		t.Run(tc.title, func(t *testing.T) {
 			wg := sync.WaitGroup{}
-			for i := 0; i < 10; i++ {
+			for range 10 {
 				wg.Add(1)
 				go func() {
 					defer wg.Done()
@@ -656,7 +652,6 @@ func TestDeepCopyWithTemplate(t *testing.T) {
 			want:  nil,
 		},
 	} {
-		tc := tc
 		t.Run(tc.title, func(t *testing.T) {
 			got, err := DeepCopyWithTemplate(tc.input, tc.fn)
 			require.NoError(t, err)

test/cli/acceptance.go

@@ -19,6 +19,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"maps"
 	"net"
 	"net/http"
 	"os"
@@ -485,9 +486,7 @@ func (am *Alertmanager) addAlertCommand(omitEquals bool, alert *TestAlert) ([]by
 	args := []string{amURLFlag, "alert", "add"}
 	// Make a copy of the labels
 	labels := make(models.LabelSet, len(alert.labels))
-	for k, v := range alert.labels {
-		labels[k] = v
-	}
+	maps.Copy(labels, alert.labels)
 	if omitEquals {
 		// If alertname is present and omitEquals is true then the command should
 		// be `amtool alert add foo ...` and not `amtool alert add alertname=foo ...`.

test/cli/collector.go

@@ -16,6 +16,7 @@ package test
 import (
 	"encoding/json"
 	"fmt"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -105,12 +106,13 @@ func (c *Collector) add(alerts ...*models.GettableAlert) {
 }
 
 func (c *Collector) Check() string {
-	report := fmt.Sprintf("\ncollector %q:\n\n", c)
+	var report strings.Builder
+	report.WriteString(fmt.Sprintf("\ncollector %q:\n\n", c))
 
 	c.mtx.RLock()
 	defer c.mtx.RUnlock()
 	for iv, expected := range c.expected {
-		report += fmt.Sprintf("interval %v\n", iv)
+		report.WriteString(fmt.Sprintf("interval %v\n", iv))
 
 		var alerts []models.GettableAlerts
 		for at, got := range c.collected {
@@ -122,10 +124,10 @@ func (c *Collector) Check() string {
 		for _, exp := range expected {
 			found := len(exp) == 0 && len(alerts) == 0
 
-			report += "---\n"
+			report.WriteString("---\n")
 
 			for _, e := range exp {
-				report += fmt.Sprintf("- %v\n", c.opts.alertString(e))
+				report.WriteString(fmt.Sprintf("- %v\n", c.opts.alertString(e)))
 			}
 
 			for _, a := range alerts {
@@ -136,10 +138,10 @@ func (c *Collector) Check() string {
 			}
 
 			if found {
-				report += "  [ ✓ ]\n"
+				report.WriteString("  [ ✓ ]\n")
 			} else {
 				c.t.Fail()
-				report += "  [ ✗ ]\n"
+				report.WriteString("  [ ✗ ]\n")
 			}
 		}
 	}
@@ -161,23 +163,23 @@ func (c *Collector) Check() string {
 	}
 	if totalExp != totalAct {
 		c.t.Fail()
-		report += fmt.Sprintf("\nExpected total of %d alerts, got %d", totalExp, totalAct)
+		report.WriteString(fmt.Sprintf("\nExpected total of %d alerts, got %d", totalExp, totalAct))
 	}
 
 	if c.t.Failed() {
-		report += "\nreceived:\n"
+		report.WriteString("\nreceived:\n")
 
 		for at, col := range c.collected {
 			for _, alerts := range col {
-				report += fmt.Sprintf("@ %v\n", at)
+				report.WriteString(fmt.Sprintf("@ %v\n", at))
 				for _, a := range alerts {
-					report += fmt.Sprintf("- %v\n", c.opts.alertString(a))
+					report.WriteString(fmt.Sprintf("- %v\n", c.opts.alertString(a)))
 				}
 			}
 		}
 	}
 
-	return report
+	return report.String()
 }
 
 // alertsToString returns a string representation of the given Alerts. Use for

test/cli/mock.go

@@ -16,6 +16,7 @@ package test
 import (
 	"encoding/json"
 	"fmt"
+	"maps"
 	"net"
 	"net/http"
 	"reflect"
@@ -293,12 +294,8 @@ func (ws *MockWebhook) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 			labels      = models.LabelSet{}
 			annotations = models.LabelSet{}
 		)
-		for k, v := range a.Labels {
-			labels[k] = v
-		}
-		for k, v := range a.Annotations {
-			annotations[k] = v
-		}
+		maps.Copy(labels, a.Labels)
+		maps.Copy(annotations, a.Annotations)
 
 		start := strfmt.DateTime(a.StartsAt)
 		end := strfmt.DateTime(a.EndsAt)

test/with_api_v2/collector.go

@@ -16,6 +16,7 @@ package test
 import (
 	"encoding/json"
 	"fmt"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -105,12 +106,13 @@ func (c *Collector) add(alerts ...*models.GettableAlert) {
 }
 
 func (c *Collector) Check() string {
-	report := fmt.Sprintf("\ncollector %q:\n\n", c)
+	var report strings.Builder
+	report.WriteString(fmt.Sprintf("\ncollector %q:\n\n", c))
 
 	c.mtx.RLock()
 	defer c.mtx.RUnlock()
 	for iv, expected := range c.expected {
-		report += fmt.Sprintf("interval %v\n", iv)
+		report.WriteString(fmt.Sprintf("interval %v\n", iv))
 
 		var alerts []models.GettableAlerts
 		for at, got := range c.collected {
@@ -122,10 +124,10 @@ func (c *Collector) Check() string {
 		for _, exp := range expected {
 			found := len(exp) == 0 && len(alerts) == 0
 
-			report += "---\n"
+			report.WriteString("---\n")
 
 			for _, e := range exp {
-				report += fmt.Sprintf("- %v\n", c.opts.alertString(e))
+				report.WriteString(fmt.Sprintf("- %v\n", c.opts.alertString(e)))
 			}
 
 			for _, a := range alerts {
@@ -136,10 +138,10 @@ func (c *Collector) Check() string {
 			}
 
 			if found {
-				report += "  [ ✓ ]\n"
+				report.WriteString("  [ ✓ ]\n")
 			} else {
 				c.t.Fail()
-				report += "  [ ✗ ]\n"
+				report.WriteString("  [ ✗ ]\n")
 			}
 		}
 	}
@@ -161,23 +163,23 @@ func (c *Collector) Check() string {
 	}
 	if totalExp != totalAct {
 		c.t.Fail()
-		report += fmt.Sprintf("\nExpected total of %d alerts, got %d", totalExp, totalAct)
+		report.WriteString(fmt.Sprintf("\nExpected total of %d alerts, got %d", totalExp, totalAct))
 	}
 
 	if c.t.Failed() {
-		report += "\nreceived:\n"
+		report.WriteString("\nreceived:\n")
 
 		for at, col := range c.collected {
 			for _, alerts := range col {
-				report += fmt.Sprintf("@ %v\n", at)
+				report.WriteString(fmt.Sprintf("@ %v\n", at))
 				for _, a := range alerts {
-					report += fmt.Sprintf("- %v\n", c.opts.alertString(a))
+					report.WriteString(fmt.Sprintf("- %v\n", c.opts.alertString(a)))
 				}
 			}
 		}
 	}
 
-	return report
+	return report.String()
 }
 
 // alertsToString returns a string representation of the given Alerts. Use for

test/with_api_v2/mock.go

@@ -16,6 +16,7 @@ package test
 import (
 	"encoding/json"
 	"fmt"
+	"maps"
 	"net/http"
 	"net/http/httptest"
 	"reflect"
@@ -306,12 +307,8 @@ func (ws *MockWebhook) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 			labels      = models.LabelSet{}
 			annotations = models.LabelSet{}
 		)
-		for k, v := range a.Labels {
-			labels[k] = v
-		}
-		for k, v := range a.Annotations {
-			annotations[k] = v
-		}
+		maps.Copy(labels, a.Labels)
+		maps.Copy(annotations, a.Annotations)
 
 		start := strfmt.DateTime(a.StartsAt)
 		end := strfmt.DateTime(a.EndsAt)

types/types_test.go

@@ -367,7 +367,6 @@ func TestAlertMerge(t *testing.T) {
 	}
 
 	for i, p := range pairs {
-		p := p
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			if res := p.A.Merge(p.B); !reflect.DeepEqual(p.Res, res) {
 				t.Errorf("unexpected merged alert %#v", res)