Add setboolcheck linter: flag map[T]bool used as sets

.claude/CLAUDE.md

@@ -13,3 +13,13 @@ MYSQL_TEST=1 go test -run TestFunctionName ./server/datastore/mysql/...
 
 # Generate boilerplate for a new frontend component, including associated stylesheet, tests, and storybook
 ./frontend/components/generate -n RequiredPascalCaseNameOfTheComponent -p optional/path/to/desired/parent/directory
+```
+
+## Go code style
+
+- Prefer `map[T]struct{}` over `map[T]bool` when the map represents a set.
+- Convert a map's keys to a slice with `slices.Collect(maps.Keys(m))` instead of manually appending in a loop.
+- Avoid `time.Sleep` in tests. Prefer `testing/synctest` to run code in a fake-clock bubble, or use polling helpers, channels, or `require.Eventually`.
+- Use `require` and `assert` from `github.com/stretchr/testify` in tests.
+- Use `t.Context()` in tests instead of `context.Background()`.
+- Use `any` instead of `interface{}`

.custom-gcl.yml

@@ -6,3 +6,6 @@ plugins:
   - module: "go.uber.org/nilaway"
     import: "go.uber.org/nilaway/cmd/gclplugin"
     version: v0.0.0-20260126174828-99d94caaf043 # fixed version for reproducible builds - latest as of 2026-01-29
+  - module: "github.com/fleetdm/fleet/v4/tools/ci/setboolcheck"
+    import: "github.com/fleetdm/fleet/v4/tools/ci/setboolcheck/cmd/gclplugin"
+    path: "tools/ci/setboolcheck"

.golangci-incremental.yml

@@ -13,6 +13,7 @@ linters:
     - gosec
     - modernize
     - nilaway
+    - setboolcheck
   settings:
     gosec:
       # Only enable rules that are too noisy on existing code but valuable for new code.
@@ -37,6 +38,9 @@ linters:
           # Settings must be a "map from string to string" to mimic command line flags: the keys are
           # flag names and the values are the values to the particular flags.
           include-pkgs: "github.com/fleetdm/fleet/v4"
+      setboolcheck:
+        type: module
+        description: Flags map[T]bool used as sets; suggests map[T]struct{} instead.
   exclusions:
     generated: strict
     rules:

tools/ci/setboolcheck/cmd/gclplugin/plugin.go

@@ -0,0 +1,27 @@
+// Package gclplugin provides the golangci-lint module plugin entry point.
+package gclplugin
+
+import (
+	"github.com/fleetdm/fleet/v4/tools/ci/setboolcheck"
+	"github.com/golangci/plugin-module-register/register"
+	"golang.org/x/tools/go/analysis"
+)
+
+func init() {
+	register.Plugin("setboolcheck", New)
+}
+
+// New returns the golangci-lint plugin for the setboolcheck analyzer.
+func New(_ any) (register.LinterPlugin, error) {
+	return &plugin{}, nil
+}
+
+type plugin struct{}
+
+func (p *plugin) BuildAnalyzers() ([]*analysis.Analyzer, error) {
+	return []*analysis.Analyzer{setboolcheck.Analyzer}, nil
+}
+
+func (p *plugin) GetLoadMode() string {
+	return register.LoadModeTypesInfo
+}

tools/ci/setboolcheck/go.mod

@@ -0,0 +1,13 @@
+module github.com/fleetdm/fleet/v4/tools/ci/setboolcheck
+
+go 1.26.1
+
+require (
+	github.com/golangci/plugin-module-register v0.1.2
+	golang.org/x/tools v0.42.0
+)
+
+require (
+	golang.org/x/mod v0.33.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
+)

tools/ci/setboolcheck/go.sum

@@ -0,0 +1,10 @@
+github.com/golangci/plugin-module-register v0.1.2 h1:e5WM6PO6NIAEcij3B053CohVp3HIYbzSuP53UAYgOpg=
+github.com/golangci/plugin-module-register v0.1.2/go.mod h1:1+QGTsKBvAIvPvoY/os+G5eoqxWn70HYDm2uvUyGuVw=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+golang.org/x/mod v0.33.0 h1:tHFzIWbBifEmbwtGz65eaWyGiGZatSrT9prnU8DbVL8=
+golang.org/x/mod v0.33.0/go.mod h1:swjeQEj+6r7fODbD2cqrnje9PnziFuw4bmLbBZFrQ5w=
+golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
+golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
+golang.org/x/tools v0.42.0 h1:uNgphsn75Tdz5Ji2q36v/nsFSfR/9BRFvqhGBaJGd5k=
+golang.org/x/tools v0.42.0/go.mod h1:Ma6lCIwGZvHK6XtgbswSoWroEkhugApmsXyrUmBhfr0=