A package may be declared absent, and an uninstalled front end is retired for good (hq ADR 0175)

absent: true on a package has the host remove it through the machine's own
package manager when it is installed and leave alone a machine that never had
it; read back either way. Undeclaring a package still removes nothing. A
found firewall whose command is gone is recorded as removed, said once, and
asked nothing of.

internal/apply/opening_test.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/novox/mesh-host/internal/declaration"
 	"github.com/novox/mesh-host/internal/store"
@@ -522,3 +523,33 @@ func TestUfwIsNotRetiredUntilTheMeshsOwnFilterIsLoaded(t *testing.T) {
 		t.Errorf("ufw was not retired once the mesh's filter was loaded: active %v, %+v", u.active, state.Firewall)
 	}
 }
+
+// A front end that is no longer installed is recorded as removed, said once, and asked nothing of
+// (novox/hq ADR 0175).
+func TestAnUninstalledFrontEndIsRetiredForGood(t *testing.T) {
+	dir := t.TempDir()
+	u := &ufwMachine{installed: false, ruleset: "table inet mesh\n"}
+	known := store.State{Firewall: &store.FoundFirewall{Kind: "ufw", WasActive: true, DisabledByMesh: true,
+		RetiredBy: "mesh", FoundAt: time.Now()}}
+	converged := parse(t, `{"declaration":1,"resources":[`+withConf(dir)+`]}`)
+	report, state, err := applyWith(t, converged, known, u.run)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if state.Firewall.RetiredBy != "removed" || !strings.Contains(report.Firewall, "no longer installed") {
+		t.Fatalf("record %+v, said %q", state.Firewall, report.Firewall)
+	}
+	u.asked = nil
+	report, _, err = applyWith(t, converged, state, u.run)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if report.Firewall != "" {
+		t.Errorf("said again: %q", report.Firewall)
+	}
+	for _, a := range u.asked {
+		if strings.HasPrefix(a, "ufw") && a != "ufw status" {
+			t.Errorf("asked something of a front end that is not there: %v", u.asked)
+		}
+	}
+}