all: fix staticcheck issues

- Apply De Morgan's law to simplify condition in types.go
- Simplify return statement in batcher_test.go
- Fix potential nil pointer dereference by using t.Fatal in util_test.go
- Remove unused variable assignment in auth_oidc_test.go
- Remove duplicate tarReader assignment in hsic.go
- Add empty line after embedded field in batcher_test.go and types.go

Note: Many staticcheck SA4006 warnings are false positives due to
Go 1.26's new `new(value)` syntax which creates a pointer to a value.
The staticcheck tool hasn't been updated to understand this syntax.

hscontrol/mapper/batcher_test.go

@@ -36,6 +36,7 @@ type batcherTestCase struct {
 // that would normally be sent by poll.go in production.
 type testBatcherWrapper struct {
 	Batcher
+
 	state *state.State
 }
 
@@ -81,12 +82,7 @@ func (t *testBatcherWrapper) RemoveNode(id types.NodeID, c chan<- *tailcfg.MapRe
 	}
 
 	// Finally remove from the real batcher
-	removed := t.Batcher.RemoveNode(id, c)
-	if !removed {
-		return false
-	}
-
-	return true
+	return t.Batcher.RemoveNode(id, c)
 }
 
 // wrapBatcherForTest wraps a batcher with test-specific behavior.

hscontrol/policy/v2/types.go

@@ -596,6 +596,7 @@ type Alias interface {
 
 type AliasWithPorts struct {
 	Alias
+
 	Ports []tailcfg.PortRange
 }
 
@@ -2107,7 +2108,7 @@ func validateProtocolPortCompatibility(protocol Protocol, destinations []AliasWi
 	for _, dst := range destinations {
 		for _, portRange := range dst.Ports {
 			// Check if it's not a wildcard port (0-65535)
-			if !(portRange.First == 0 && portRange.Last == 65535) {
+			if portRange.First != 0 || portRange.Last != 65535 {
 				return fmt.Errorf("protocol %q does not support specific ports; only \"*\" is allowed", protocol)
 			}
 		}

hscontrol/util/util_test.go

@@ -1103,7 +1103,7 @@ func TestEnsureHostnameWithHostinfo(t *testing.T) {
 			wantHostname: "test-node",
 			checkHostinfo: func(t *testing.T, hi *tailcfg.Hostinfo) {
 				if hi == nil {
-					t.Error("hostinfo should not be nil")
+					t.Fatal("hostinfo should not be nil")
 				}
 
 				if hi.Hostname != "test-node" {
@@ -1149,7 +1149,7 @@ func TestEnsureHostnameWithHostinfo(t *testing.T) {
 			wantHostname: "node-nkey1234",
 			checkHostinfo: func(t *testing.T, hi *tailcfg.Hostinfo) {
 				if hi == nil {
-					t.Error("hostinfo should not be nil")
+					t.Fatal("hostinfo should not be nil")
 				}
 
 				if hi.Hostname != "node-nkey1234" {
@@ -1165,7 +1165,7 @@ func TestEnsureHostnameWithHostinfo(t *testing.T) {
 			wantHostname: "unknown-node",
 			checkHostinfo: func(t *testing.T, hi *tailcfg.Hostinfo) {
 				if hi == nil {
-					t.Error("hostinfo should not be nil")
+					t.Fatal("hostinfo should not be nil")
 				}
 
 				if hi.Hostname != "unknown-node" {
@@ -1183,7 +1183,7 @@ func TestEnsureHostnameWithHostinfo(t *testing.T) {
 			wantHostname: "unknown-node",
 			checkHostinfo: func(t *testing.T, hi *tailcfg.Hostinfo) {
 				if hi == nil {
-					t.Error("hostinfo should not be nil")
+					t.Fatal("hostinfo should not be nil")
 				}
 
 				if hi.Hostname != "unknown-node" {

integration/auth_oidc_test.go

@@ -1052,7 +1052,7 @@ func TestOIDCMultipleOpenedLoginUrls(t *testing.T) {
 	require.NotEqual(t, redirect1.String(), redirect2.String())
 
 	// complete auth with the first opened "browser tab"
-	_, redirect1, err = doLoginURLWithClient(ts.Hostname(), redirect1, loginClient, true)
+	_, _, err = doLoginURLWithClient(ts.Hostname(), redirect1, loginClient, true)
 	require.NoError(t, err)
 
 	listUsers, err = headscale.ListUsers()

integration/hsic/hsic.go

@@ -721,8 +721,6 @@ func extractTarToDirectory(tarData []byte, targetDir string) error {
 		return fmt.Errorf("failed to create directory %s: %w", targetDir, err)
 	}
 
-	tarReader := tar.NewReader(bytes.NewReader(tarData))
-
 	// Find the top-level directory to strip
 	var topLevelDir string
 
@@ -743,7 +741,7 @@ func extractTarToDirectory(tarData []byte, targetDir string) error {
 		}
 	}
 
-	tarReader = tar.NewReader(bytes.NewReader(tarData))
+	tarReader := tar.NewReader(bytes.NewReader(tarData))
 	for {
 		header, err := tarReader.Next()
 		if err == io.EOF {