Fix issue with GitOps incorrectly wiping policy stats (#43282)

<!-- Add the related story/sub-task/bug number, like Resolves #123, or
remove if NA -->
**Related issue:** Resolves #43273

# Checklist for submitter

If some of the following don't apply, delete the relevant line.

- [X] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
See [Changes
files](https://github.com/fleetdm/fleet/blob/main/docs/Contributing/guides/committing-changes.md#changes-files)
for more information.

## Testing

- [X] Added/updated automated tests
- Added new test for this case (policies without software automation
being pushed by two different users), verified it fails on main and
passes on this branch
- [X] QA'd all new/changed functionality manually
- [X] Verified that changing `webhooks_and_tickets_enabled` on a policy
AND running gitops as another user doesn't wipe stats
- [X] Verified that changing `query` on a policy and running gitops does
wipe stats
- [X] Verified that changing `query` on a policy and running gitops does
wipe stats

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Fixed an issue where policy stats were incorrectly reset during GitOps
policy updates. Policy statistics now remain accurate when policies are
re-applied without modification to installation or script
configurations.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

43273-fix-policy-stats-wipe

@@ -0,0 +1 @@
+- Fixed an issue where policy stats may be wiped incorrectly after a GitOps run.

server/datastore/mysql/policies.go

@@ -1519,29 +1519,19 @@ func (ds *Datastore) ApplyPolicySpecs(ctx context.Context, authorID uint, specs
 					removePolicyStats                bool
 				)
 				if insertOnDuplicateDidInsertOrUpdate(res) {
-					// Figure out if the query, platform, software installer, or VPP app changed.
-					var softwareInstallerID *uint
-					if spec.SoftwareTitleID != nil {
-						softwareInstallerID = softwareInstallerIDs[teamID][*spec.SoftwareTitleID]
-					}
+					// Figure out if the query, platform, software installer, VPP app, or script changed.
 					if prev, ok := teamIDToPoliciesByName[teamID][spec.Name]; ok {
 						switch {
 						case prev.Query != spec.Query:
 							shouldRemoveAllPolicyMemberships = true
 							removePolicyStats = true
-						case teamID != nil &&
-							((prev.SoftwareInstallerID == nil && spec.SoftwareTitleID != nil) ||
-								(prev.SoftwareInstallerID != nil && softwareInstallerID != nil && *prev.SoftwareInstallerID != *softwareInstallerID)):
+						case teamID != nil && softwareInstallerID != nil && !ptr.Equal(prev.SoftwareInstallerID, softwareInstallerID):
 							shouldRemoveAllPolicyMemberships = true
 							removePolicyStats = true
-						case teamID != nil &&
-							((prev.VPPAppsTeamsID == nil && spec.SoftwareTitleID != nil) ||
-								(prev.VPPAppsTeamsID != nil && vppAppsTeamsID != nil && *prev.VPPAppsTeamsID != *vppAppsTeamsID)):
+						case teamID != nil && vppAppsTeamsID != nil && !ptr.Equal(prev.VPPAppsTeamsID, vppAppsTeamsID):
 							shouldRemoveAllPolicyMemberships = true
 							removePolicyStats = true
-						case teamID != nil &&
-							((prev.ScriptID == nil && spec.ScriptID != nil) ||
-								(prev.ScriptID != nil && spec.ScriptID != nil && *prev.ScriptID != *spec.ScriptID)):
+						case teamID != nil && scriptID != nil && !ptr.Equal(prev.ScriptID, scriptID):
 							shouldRemoveAllPolicyMemberships = true
 							removePolicyStats = true
 						case prev.Platforms != spec.Platform:

server/datastore/mysql/policies_test.go

@@ -93,6 +93,7 @@ func TestPolicies(t *testing.T) {
 		{"BatchedPolicyMembershipCleanupOnPolicyUpdate", testBatchedPolicyMembershipCleanupOnPolicyUpdate},
 		{"ApplyPolicySpecsNeedsFullMembershipCleanupFlag", testApplyPolicySpecsNeedsFullMembershipCleanupFlag},
 		{"CleanupPolicyMembershipCrashRecovery", testCleanupPolicyMembershipCrashRecovery},
+		{"ApplyPolicySpecNoSpuriousStatsReset", testApplyPolicySpecNoSpuriousStatsReset},
 	}
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {
@@ -7948,3 +7949,87 @@ func testTeamPolicyAutomationFilter(t *testing.T, ds *Datastore) {
 	require.NoError(t, err)
 	assert.Equal(t, 3, mergedCount)
 }
+
+// testApplyPolicySpecNoSpuriousStatsReset verifies that re-applying a team
+// policy via ApplyPolicySpecs does not spuriously reset policy_stats when the
+// only change is author_id (e.g. a different user runs GitOps) and the spec
+// has SoftwareTitleID set to ptr.Uint(0) (as the GitOps client does for all
+// team policies to "unset" the installer field).
+func testApplyPolicySpecNoSpuriousStatsReset(t *testing.T, ds *Datastore) {
+	ctx := t.Context()
+
+	user1 := test.NewUser(t, ds, "StatsUser1", "statsuser1@example.com", true)
+	user2 := test.NewUser(t, ds, "StatsUser2", "statsuser2@example.com", true)
+	team, err := ds.NewTeam(ctx, &fleet.Team{Name: t.Name()})
+	require.NoError(t, err)
+
+	// Create a team policy (no software installer) as user1.
+	require.NoError(t, ds.ApplyPolicySpecs(ctx, user1.ID, []*fleet.PolicySpec{
+		{
+			Name:     "stats-test-policy",
+			Query:    "SELECT 1;",
+			Team:     team.Name,
+			Platform: "darwin",
+			Type:     fleet.PolicyTypeDynamic,
+		},
+	}))
+
+	// Create a host on the team and record a failing result.
+	hostID := fmt.Sprintf("%s-host", strings.ReplaceAll(t.Name(), "/", "_"))
+	h, err := ds.NewHost(ctx, &fleet.Host{
+		OsqueryHostID:   &hostID,
+		DetailUpdatedAt: time.Now(),
+		LabelUpdatedAt:  time.Now(),
+		PolicyUpdatedAt: time.Now(),
+		SeenTime:        time.Now(),
+		NodeKey:         &hostID,
+		UUID:            hostID,
+		Hostname:        hostID,
+		Platform:        "darwin",
+		TeamID:          &team.ID,
+	})
+	require.NoError(t, err)
+
+	// Get the policy to find its ID.
+	policies, _, err := ds.ListTeamPolicies(ctx, team.ID, fleet.ListOptions{}, fleet.ListOptions{}, "")
+	require.NoError(t, err)
+	require.Len(t, policies, 1)
+	pol := policies[0]
+
+	// Record a failing result for the host.
+	err = ds.RecordPolicyQueryExecutions(ctx, h, map[uint]*bool{pol.ID: new(false)}, time.Now(), false, nil)
+	require.NoError(t, err)
+
+	// Update aggregate counts.
+	err = ds.UpdateHostPolicyCounts(ctx)
+	require.NoError(t, err)
+
+	// Verify the policy has a failing host count of 1.
+	policies, _, err = ds.ListTeamPolicies(ctx, team.ID, fleet.ListOptions{}, fleet.ListOptions{}, "")
+	require.NoError(t, err)
+	require.Len(t, policies, 1)
+	require.Equal(t, uint(1), policies[0].FailingHostCount)
+
+	// Now re-apply the same policy as a DIFFERENT user (simulating GitOps run
+	// by a different API token), with SoftwareTitleID=ptr.Uint(0) as the GitOps
+	// client sets for all team policies. This changes author_id in the DB, which
+	// causes insertOnDuplicateDidInsertOrUpdate to return true. Before the fix,
+	// the comparison logic would see SoftwareTitleID!=nil and incorrectly
+	// conclude the software installer changed, resetting stats.
+	require.NoError(t, ds.ApplyPolicySpecs(ctx, user2.ID, []*fleet.PolicySpec{
+		{
+			Name:            "stats-test-policy",
+			Query:           "SELECT 1;",
+			Team:            team.Name,
+			Platform:        "darwin",
+			SoftwareTitleID: new(uint), // ptr to 0, as GitOps does
+			Type:            fleet.PolicyTypeDynamic,
+		},
+	}))
+
+	// Verify that policy stats were NOT reset.
+	policies, _, err = ds.ListTeamPolicies(ctx, team.ID, fleet.ListOptions{}, fleet.ListOptions{}, "")
+	require.NoError(t, err)
+	require.Len(t, policies, 1)
+	assert.Equal(t, uint(1), policies[0].FailingHostCount, "policy stats should not have been reset")
+}

server/ptr/ptr.go

@@ -91,6 +91,18 @@ func T[T any](x T) *T {
 	return &x
 }
 
+// Equal returns true if both pointers are nil, or both are non-nil and
+// point to equal values.
+func Equal[T comparable](a, b *T) bool {
+	if a == nil && b == nil {
+		return true
+	}
+	if a == nil || b == nil {
+		return false
+	}
+	return *a == *b
+}
+
 // ValOrZero returns the value of x if x is not nil, and the zero value
 // for T otherwise.
 func ValOrZero[T any](x *T) T {