all: adopt strings, errors, and os helpers

cmd/headscale/cli/mockoidc.go

@@ -3,6 +3,7 @@ package cli
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net"
 	"net/http"
@@ -16,19 +17,15 @@ import (
 	"github.com/spf13/cobra"
 )
 
-// Error is used to compare errors as per https://dave.cheney.net/2016/04/07/constant-errors
-type Error string
-
-func (e Error) Error() string { return string(e) }
-
-const (
-	errMockOidcClientIDNotDefined     = Error("MOCKOIDC_CLIENT_ID not defined")
-	errMockOidcClientSecretNotDefined = Error("MOCKOIDC_CLIENT_SECRET not defined")
-	errMockOidcPortNotDefined         = Error("MOCKOIDC_PORT not defined")
-	errMockOidcUsersNotDefined        = Error("MOCKOIDC_USERS not defined")
-	refreshTTL                        = 60 * time.Minute
+var (
+	errMockOidcClientIDNotDefined     = errors.New("MOCKOIDC_CLIENT_ID not defined")
+	errMockOidcClientSecretNotDefined = errors.New("MOCKOIDC_CLIENT_SECRET not defined")
+	errMockOidcPortNotDefined         = errors.New("MOCKOIDC_PORT not defined")
+	errMockOidcUsersNotDefined        = errors.New("MOCKOIDC_USERS not defined")
 )
 
+const refreshTTL = 60 * time.Minute
+
 var accessTTL = 2 * time.Minute
 
 func init() {

cmd/headscale/cli/nodes.go

@@ -384,13 +384,7 @@ func nodesToPtables(nodes []*v1.Node) (pterm.TableData, error) {
 			expired = pterm.LightGreen("no")
 		}
 
-		var tagsBuilder strings.Builder
-
-		for _, tag := range node.GetTags() {
-			tagsBuilder.WriteString("\n" + tag)
-		}
-
-		tags := strings.TrimLeft(tagsBuilder.String(), "\n")
+		tags := strings.Join(node.GetTags(), "\n")
 
 		var user string
 		if node.GetUser() != nil {

cmd/hi/doctor.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"os"
 	"os/exec"
 	"strings"
 
@@ -283,7 +284,7 @@ func checkGitRepository(ctx context.Context) DoctorResult {
 }
 
 // checkRequiredFiles verifies required files exist.
-func checkRequiredFiles(ctx context.Context) DoctorResult {
+func checkRequiredFiles(_ context.Context) DoctorResult {
 	requiredFiles := []string{
 		"go.mod",
 		"integration/",
@@ -293,9 +294,7 @@ func checkRequiredFiles(ctx context.Context) DoctorResult {
 	var missingFiles []string
 
 	for _, file := range requiredFiles {
-		cmd := exec.CommandContext(ctx, "test", "-e", file)
-
-		err := cmd.Run()
+		_, err := os.Stat(file)
 		if err != nil {
 			missingFiles = append(missingFiles, file)
 		}

hscontrol/derp/derp.go

@@ -22,19 +22,12 @@ import (
 )
 
 func loadDERPMapFromPath(path string) (*tailcfg.DERPMap, error) {
-	derpFile, err := os.Open(path)
+	b, err := os.ReadFile(path)
 	if err != nil {
 		return nil, err
 	}
-	defer derpFile.Close()
 
 	var derpMap tailcfg.DERPMap
-
-	b, err := io.ReadAll(derpFile)
-	if err != nil {
-		return nil, err
-	}
-
 	err = yaml.Unmarshal(b, &derpMap)
 
 	return &derpMap, err

hscontrol/grpcv1.go

@@ -420,7 +420,7 @@ func (api headscaleV1APIServer) SetApprovedRoutes(
 }
 
 func validateTag(tag string) error {
-	if strings.Index(tag, "tag:") != 0 {
+	if !strings.HasPrefix(tag, "tag:") {
 		return errors.New("tag must start with the string 'tag:'")
 	}
 	if strings.ToLower(tag) != tag {
@@ -935,7 +935,7 @@ func (api headscaleV1APIServer) AuthReject(
 	}
 
 	authReq.FinishAuth(types.AuthVerdict{
-		Err: fmt.Errorf("auth request rejected"),
+		Err: errors.New("auth request rejected"),
 	})
 
 	return &v1.AuthRejectResponse{}, nil

hscontrol/policy/v2/filter.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"net/netip"
 	"slices"
-	"strconv"
 	"strings"
 	"time"
 
@@ -597,14 +596,7 @@ func groupSourcesByUser(
 // filterRuleKey generates a unique key for merging based on [tailcfg.FilterRule.SrcIPs]
 // and [tailcfg.FilterRule.IPProto].
 func filterRuleKey(rule tailcfg.FilterRule) string {
-	srcKey := strings.Join(rule.SrcIPs, ",")
-
-	protoStrs := make([]string, len(rule.IPProto))
-	for i, p := range rule.IPProto {
-		protoStrs[i] = strconv.Itoa(p)
-	}
-
-	return srcKey + "|" + strings.Join(protoStrs, ",")
+	return fmt.Sprintf("%s|%v", strings.Join(rule.SrcIPs, ","), rule.IPProto)
 }
 
 // mergeFilterRules merges rules with identical [tailcfg.FilterRule.SrcIPs] and

integration/dockertestutil/auth.go

@@ -162,10 +162,10 @@ func credentialsFromConfig() (string, string, bool) {
 		return "", "", false
 	}
 
-	parts := strings.SplitN(string(decoded), ":", 2)
-	if len(parts) != 2 {
+	user, pass, ok := strings.Cut(string(decoded), ":")
+	if !ok {
 		return "", "", false
 	}
 
-	return parts[0], parts[1], true
+	return user, pass, true
 }