Merge pull request 'Serve reset-failed and wanted-by in the systemd module (hq issue 332)' (#137) from feat/systemd-reset-failed-why-started into main

modules/systemd/cmd/systemd-tools/client.go

@@ -98,7 +98,7 @@ func execRunner(cmd string, args []string, env []string) Ran {
 const MeshUnitHeader = "# Generated by the mesh."
 
 // acts are the verbs that change the system manager's state, which polkit keeps from a non-root account.
-var acts = map[string]bool{"start": true, "stop": true, "restart": true, "enable": true, "disable": true}
+var acts = map[string]bool{"start": true, "stop": true, "restart": true, "enable": true, "disable": true, "reset-failed": true}
 
 // escalated is the command as it is run: as given when this process is root, or in the user scope, or
 // when the call is a systemctl read; else through sudo without a prompt — an act on the system manager,
@@ -137,6 +137,10 @@ type Manager struct {
 	Read func(path string) (string, error)
 	// Env is this process's environment, the base of a user-scope call's.
 	Env []string
+	// Home is the operator account's home, whose configuration holds its own enable links.
+	Home string
+	// ReadDir lists a directory, to find the enable links naming a unit (wanted.go).
+	ReadDir func(dir string) ([]Entry, error)
 }
 
 var userBus = regexp.MustCompile(`(?i)Failed to connect to (user scope )?bus`)
@@ -240,11 +244,11 @@ func (m *Manager) Status(scope Scope, unit string) (map[string]any, error) {
 		return nil, err
 	}
 	props := []string{"LoadState", "ActiveState", "SubState", "UnitFileState", "MainPID", "ExecMainStatus", "Description", "FragmentPath"}
-	args := []string{"show", unit, "--no-pager"}
+	args := []string{"show", "--no-pager"}
 	for _, p := range props {
 		args = append(args, "--property="+p)
 	}
-	out, err := m.call(scope, "systemctl", args...)
+	out, err := m.call(scope, "systemctl", append(args, "--", unit)...)
 	if err != nil {
 		return nil, err
 	}
@@ -267,12 +271,13 @@ func (m *Manager) writtenByMesh(path string) bool {
 	return err == nil && strings.HasPrefix(text, MeshUnitHeader)
 }
 
-// Act starts, stops, restarts, enables or disables one unit, and answers with the state after.
+// Act starts, stops, restarts, enables or disables one unit, or resets its failed record, and answers with
+// the state after.
 func (m *Manager) Act(scope Scope, verb, unit string) (map[string]any, error) {
 	if err := unitArg(unit); err != nil {
 		return nil, err
 	}
-	if _, err := m.call(scope, "systemctl", verb, unit); err != nil {
+	if _, err := m.call(scope, "systemctl", verb, "--", unit); err != nil {
 		return nil, err
 	}
 	after, err := m.Status(scope, unit)
@@ -363,7 +368,7 @@ func (m *Manager) Journal(scope Scope, unit string, q JournalQuery) (map[string]
 // unitSecrets are the values of the unit's own Environment= that must not be answered. Read with
 // systemctl show, which needs no escalation; a unit that does not exist has none.
 func (m *Manager) unitSecrets(scope Scope, unit string) ([]knownSecret, error) {
-	out, err := m.call(scope, "systemctl", "show", unit, "--no-pager", "--property=Environment", "--value")
+	out, err := m.call(scope, "systemctl", "show", "--no-pager", "--property=Environment", "--value", "--", unit)
 	if err != nil {
 		return nil, err
 	}
@@ -397,11 +402,16 @@ func (m *Manager) Failed(scopes ...Scope) map[string]any {
 }
 
 // unitArg refuses a unit name systemctl or journalctl would read as an option — which under sudo would be
-// root's option.
+// root's option — and **a glob** (novox/hq issue 332): systemctl expands *, ? and [ in a unit argument to
+// every loaded unit matching it, so `stop` or `reset-failed` of "*" would act on all of them. Every verb
+// names one unit; `units` alone takes a pattern, as its own argument. The name is also given after "--".
 func unitArg(unit string) error {
 	if unit == "" || strings.HasPrefix(unit, "-") || strings.ContainsAny(unit, " \t\n\r\x00") {
 		return fmt.Errorf("%q is not a unit's name", unit)
 	}
+	if strings.ContainsAny(unit, "*?[") {
+		return fmt.Errorf("%q is a pattern, not one unit's name: the service manager would act on every unit it matches", unit)
+	}
 	return nil
 }
 

modules/systemd/cmd/systemd-tools/client_test.go

@@ -139,7 +139,7 @@ func TestASystemActEscalatesAndAnswersTheStateAfter(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if got := append([]string{calls[0].cmd}, calls[0].args...); !reflect.DeepEqual(got, []string{"sudo", "-n", "systemctl", "restart", "sshd.service"}) {
+	if got := append([]string{calls[0].cmd}, calls[0].args...); !reflect.DeepEqual(got, []string{"sudo", "-n", "systemctl", "restart", "--", "sshd.service"}) {
 		t.Fatalf("%v", got)
 	}
 	if r["ok"] != true || r["active"] != "active" || r["mesh_declared"] != false || r["note"] != nil {
@@ -242,7 +242,7 @@ func TestAUnitsNameIsNeverAnOption(t *testing.T) {
 	}
 }
 
-// The manifest owns the systemd package, claims the seat's nine verbs, and lists exactly the tools served.
+// The manifest owns the systemd package, claims the seat's eleven verbs, and lists exactly the tools served.
 func TestTheManifestOwnsThePackageAndListsWhatIsServed(t *testing.T) {
 	raw, err := os.ReadFile("../../module.json")
 	if err != nil {

modules/systemd/cmd/systemd-tools/main.go

@@ -1,6 +1,6 @@
-// systemd's tools: the node-service-manager seat's nine verbs — the units on this machine in both scopes,
-// read and acted on by name, their journal, and what has failed (novox/hq ADR 0177). The node
-// tools runtime launches this bundle as a process of its own and serves what it serves (ADR 0188, ADR 0193);
+// systemd's tools: the node-service-manager seat's eleven verbs — the units on this machine in both scopes,
+// read and acted on by name, their journal, what has failed, what wants a unit, and a failed record cleared
+// (novox/hq ADR 0177, issue 332). The node tools runtime launches this bundle as a process of its own and serves what it serves (ADR 0188, ADR 0193);
 // it runs as the operator account, so acts on the system manager, and reads of its journal, escalate with
 // sudo -n, and the user scope is the account's own manager (client.go). The host applies units; this answers
 // about them. stdout is the MCP channel; this says nothing else.
@@ -123,6 +123,28 @@ func tools(m *Manager) []stdio.Tool {
 				}
 				return m.Journal(scope, unit, q)
 			}},
+		// **Clearing a failed record** (novox/hq issue 332): a unit whose file is gone keeps its failed state,
+		// and its start-limit count, in its manager until it is reset. A unit's name is required, so the
+		// verb never resets every failed unit at once.
+		act("reset-failed", "Clear one unit's failed record in its manager — its failed state and its start-limit count — and answer its state after. It removes no file and starts nothing."),
+		{Name: seat + ".wanted-by",
+			Description: "What wants, requires or triggers one unit, read-only: the manager's reverse dependencies " +
+				"(WantedBy, RequiredBy, UpheldBy, BoundBy, TriggeredBy and the rest, and the units that pull those in) and every " +
+				"enable link naming it in the scope's configuration directories (*.wants, *.requires, *.upholds) — the " +
+				"operator account's own ~/.config/systemd/user in user scope — each with where it points, whether it " +
+				"dangles and whose directory it is in; and what that means, in words.",
+			Input: map[string]any{"scope": scopeArg, "unit": unitArgS},
+			Run: func(a map[string]any) (any, error) {
+				scope, err := scopeOf(a)
+				if err != nil {
+					return nil, err
+				}
+				unit, err := unitOf(a)
+				if err != nil {
+					return nil, err
+				}
+				return m.WantedBy(scope, unit)
+			}},
 		// Was the module's own systemd_failed; on the seat since the operator's direction of 2026-10-07, so
 		// whatever holds the role answers it and every machine is asked the same way.
 		{Name: seat + ".failed",
@@ -157,7 +179,12 @@ func fromEnv() *Manager {
 			uid = n
 		}
 	}
-	return &Manager{Account: account, UID: uid, User: name, Run: execRunner, Read: readFile, Env: os.Environ()}
+	home := strings.TrimSpace(os.Getenv("MESH_OPERATOR_HOME"))
+	if home == "" && account == name {
+		home, _ = os.UserHomeDir()
+	}
+	return &Manager{Account: account, UID: uid, User: name, Run: execRunner, Read: readFile, Env: os.Environ(),
+		Home: home, ReadDir: readDir}
 }
 
 func main() {

modules/systemd/cmd/systemd-tools/wanted.go

@@ -0,0 +1,345 @@
+package main
+
+// What wants, requires or triggers one unit (novox/hq issue 332), read-only. Two sources, because each misses
+// what the other sees:
+//
+//   - **the manager**, asked for the unit's reverse dependencies (systemctl show's WantedBy, RequiredBy and
+//     the rest, and list-dependencies --reverse for what pulls it in through another unit). It knows what is
+//     loaded now, including a dependency a unit file states in its own [Unit] section;
+//   - **the configuration directories**, read for an enable link naming the unit in a *.wants, *.requires or
+//     *.upholds directory. A link outlives the unit file it pointed at: once the package that shipped the unit
+//     is gone, the link dangles, and the manager asks for a unit it cannot find at every boot or login. That
+//     is the case a failed record of a unit whose load state is not-found comes from, and the answer says
+//     each link's target and whether it dangles.
+//
+// Nothing here changes anything. Clearing the record is `reset-failed`'s.
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// reverseProperties are the unit's properties that name a unit depending on it.
+var reverseProperties = []string{"WantedBy", "RequiredBy", "RequisiteOf", "BoundBy", "UpheldBy", "ConsistsOf", "TriggeredBy", "PartOf"}
+
+// stateProperties say what the manager knows of the unit itself, so a not-found unit is recognised.
+var stateProperties = []string{"LoadState", "ActiveState", "SubState", "UnitFileState", "FragmentPath"}
+
+// dependencyDirs are the suffixes of the directories an enable link sits in, and the dependency each makes.
+var dependencyDirs = map[string]string{".wants": "Wants", ".requires": "Requires", ".upholds": "Upholds"}
+
+// Entry is one name in a directory as lstat sees it: a link is never followed to say what it is.
+type Entry struct {
+	Name string
+	// Dir is whether the name is itself a directory; a link to one is not.
+	Dir bool
+	// Link is where a symbolic link points, as written; empty when the name is not a link.
+	Link string
+	// Dangles is whether a link points at nothing: what it names does not exist.
+	Dangles bool
+	// Error is why a link's target could not be looked at, when that is anything but its not existing.
+	Error string
+}
+
+// ConfigDir is one directory a manager reads units and enable links from, and whose it is.
+type ConfigDir struct {
+	Path  string `json:"path"`
+	Whose string `json:"whose"`
+	// Removable is whether a dangling link here is a person's or an administrator's to remove: their own
+	// configuration, not a package's, a generator's or the runtime's, which put theirs back.
+	Removable bool `json:"-"`
+}
+
+// EnableLink is one link in a dependency directory that names the unit.
+type EnableLink struct {
+	Path string `json:"path"`
+	// Of is the unit that wants (or requires, or upholds) this one: the directory's name less its suffix.
+	Of         string `json:"of"`
+	Dependency string `json:"dependency"`
+	Target     string `json:"target,omitempty"`
+	Dangles    bool   `json:"dangles"`
+	// Error is why the target could not be looked at, other than its not existing: neither dangling nor not.
+	Error string `json:"error,omitempty"`
+	// Link is false for a plain file in a dependency directory, which the manager reads the same way.
+	Link  bool   `json:"link"`
+	Whose string `json:"whose"`
+
+	removable bool
+}
+
+// configDirs are the directories a scope's manager reads unit files and enable links from, in its own order
+// of precedence (systemd.unit(5), "Unit File Load Path"). The account's own are left out, and said, when its
+// home is not known.
+func (m *Manager) configDirs(scope Scope) []ConfigDir {
+	if scope == User {
+		account := "the operator account's own configuration"
+		dirs := []ConfigDir{}
+		if m.Home != "" {
+			dirs = append(dirs, ConfigDir{filepath.Join(m.Home, ".config", "systemd", "user.control"), account + " (set by a program through the manager)", true})
+		}
+		dirs = append(dirs, ConfigDir{fmt.Sprintf("/run/user/%d/systemd/user", m.UID), "made at runtime, gone at the next login", false})
+		if m.Home != "" {
+			dirs = append(dirs, ConfigDir{filepath.Join(m.Home, ".config", "systemd", "user"), account, true})
+		}
+		dirs = append(dirs,
+			ConfigDir{"/etc/systemd/user", "the machine's configuration, for every account", true},
+			ConfigDir{"/etc/xdg/systemd/user", "the machine's configuration, for every account", true})
+		if m.Home != "" {
+			dirs = append(dirs, ConfigDir{filepath.Join(m.Home, ".local", "share", "systemd", "user"), "a program installed in the account's own home", false})
+		}
+		return append(dirs,
+			ConfigDir{"/usr/local/lib/systemd/user", "a program installed by hand, for every account", false},
+			ConfigDir{"/usr/lib/systemd/user", "a package's", false})
+	}
+	return []ConfigDir{
+		{"/etc/systemd/system.control", "the machine's configuration (set by a program through the manager)", true},
+		{"/run/systemd/transient", "made at runtime, gone at the next boot", false},
+		{"/run/systemd/generator.early", "a generator's, made again at every boot and reload", false},
+		{"/etc/systemd/system", "the machine's configuration", true},
+		{"/run/systemd/system", "made at runtime, gone at the next boot", false},
+		{"/run/systemd/generator", "a generator's, made again at every boot and reload", false},
+		{"/usr/local/lib/systemd/system", "a program installed by hand", false},
+		{"/usr/lib/systemd/system", "a package's", false},
+		{"/run/systemd/generator.late", "a generator's, made again at every boot and reload", false},
+	}
+}
+
+// within is whether a path lies in one of the directories.
+func within(path string, dirs []ConfigDir) bool {
+	path = filepath.Clean(path)
+	for _, d := range dirs {
+		if path == d.Path || strings.HasPrefix(path, d.Path+string(filepath.Separator)) {
+			return true
+		}
+	}
+	return false
+}
+
+// links finds every enable link naming the unit under the scope's configuration directories: by its own
+// name, or by the name of the file it points at. A directory that cannot be read is said, never skipped as
+// empty; one that does not exist is the ordinary case and is not. **A dependency directory that is itself a
+// link is followed only when it leads into the searched directories**: elsewhere it is said, and not read,
+// so a link cannot point the search, or a removal after it, at any directory on the machine.
+func (m *Manager) links(scope Scope, unit string) ([]EnableLink, []string) {
+	found, unread := []EnableLink{}, []string{}
+	dirs := m.configDirs(scope)
+	for _, dir := range dirs {
+		entries, err := m.ReadDir(dir.Path)
+		if err != nil {
+			if !errors.Is(err, fs.ErrNotExist) {
+				unread = append(unread, dir.Path+": "+err.Error())
+			}
+			continue
+		}
+		for _, e := range entries {
+			dependency, of := "", ""
+			for suffix, dep := range dependencyDirs {
+				if strings.HasSuffix(e.Name, suffix) {
+					dependency, of = dep, strings.TrimSuffix(e.Name, suffix)
+				}
+			}
+			if dependency == "" || (!e.Dir && e.Link == "") {
+				continue
+			}
+			sub := filepath.Join(dir.Path, e.Name)
+			read := sub
+			if e.Link != "" {
+				target := e.Link
+				if !filepath.IsAbs(target) {
+					target = filepath.Join(dir.Path, target)
+				}
+				if !within(target, dirs) {
+					unread = append(unread, sub+": a link to "+e.Link+", outside the directories searched, not followed")
+					continue
+				}
+				read = filepath.Clean(target)
+			}
+			inside, err := m.ReadDir(read)
+			if err != nil {
+				if !errors.Is(err, fs.ErrNotExist) {
+					unread = append(unread, sub+": "+err.Error())
+				}
+				continue
+			}
+			for _, l := range inside {
+				if l.Name != unit && (l.Link == "" || filepath.Base(l.Link) != unit) {
+					continue
+				}
+				found = append(found, EnableLink{Path: filepath.Join(sub, l.Name), Of: of, Dependency: dependency,
+					Target: l.Link, Dangles: l.Link != "" && l.Dangles, Error: l.Error, Link: l.Link != "",
+					Whose: dir.Whose, removable: dir.Removable && e.Link == ""})
+			}
+		}
+	}
+	sort.Slice(found, func(i, j int) bool { return found[i].Path < found[j].Path })
+	return found, unread
+}
+
+// WantedBy is what wants, requires or triggers one unit: the manager's reverse dependencies and the enable
+// links naming it, with a finding in words. A manager that does not answer is said beside the links, which
+// are read from disk and do not need it.
+func (m *Manager) WantedBy(scope Scope, unit string) (map[string]any, error) {
+	if err := unitArg(unit); err != nil {
+		return nil, err
+	}
+	answer := map[string]any{"unit": unit, "scope": string(scope)}
+
+	manager := map[string]any{}
+	args := []string{"show", "--no-pager"}
+	for _, p := range append(append([]string{}, stateProperties...), reverseProperties...) {
+		args = append(args, "--property="+p)
+	}
+	loadState := ""
+	dependents := 0
+	if out, err := m.call(scope, "systemctl", append(args, "--", unit)...); err != nil {
+		manager["error"] = err.Error()
+	} else {
+		for _, line := range strings.Split(out, "\n") {
+			k, v, ok := strings.Cut(line, "=")
+			if !ok || k == "" {
+				continue
+			}
+			if isReverse(k) {
+				if names := strings.Fields(v); len(names) > 0 {
+					manager[k] = names
+					dependents += len(names)
+				}
+				continue
+			}
+			manager[k] = v
+		}
+		loadState, _ = manager["LoadState"].(string)
+	}
+	// Through other units: list-dependencies --reverse follows the same edges from the units that pull in
+	// those that pull this one in. Its first line is the unit itself.
+	if out, err := m.call(scope, "systemctl", "list-dependencies", "--reverse", "--plain", "--no-legend", "--no-pager", "--", unit); err != nil {
+		manager["reverse_error"] = err.Error()
+	} else {
+		chain := []string{}
+		for i, line := range strings.Split(out, "\n") {
+			name := strings.TrimSpace(strings.TrimLeft(line, " │├└─●○×*"))
+			if i == 0 || name == "" || name == unit {
+				continue
+			}
+			chain = append(chain, name)
+		}
+		if len(chain) > 0 {
+			manager["reverse"] = chain
+		}
+	}
+	answer["manager"] = manager
+
+	links, unread := m.links(scope, unit)
+	answer["links"] = links
+	answer["searched"] = m.configDirs(scope)
+	if len(unread) > 0 {
+		answer["unread"] = unread
+	}
+	answer["findings"] = findings(scope, unit, loadState, dependents, links, unread, manager["error"] != nil, m.Home == "")
+	return answer, nil
+}
+
+func isReverse(property string) bool {
+	for _, p := range reverseProperties {
+		if p == property {
+			return true
+		}
+	}
+	return false
+}
+
+// findings say what the answer means, so a caller does not have to put the parts together.
+func findings(scope Scope, unit, loadState string, dependents int, links []EnableLink, unread []string, managerFailed, noHome bool) []string {
+	out := []string{}
+	dangling, removable, unknown := 0, 0, 0
+	for _, l := range links {
+		switch {
+		case l.Dangles:
+			dangling++
+			if l.removable {
+				removable++
+			}
+			out = append(out, l.Path+" makes "+l.Of+" "+strings.TrimSuffix(strings.ToLower(l.Dependency), "s")+" "+unit+" and points at "+l.Target+", which does not exist ("+l.Whose+")")
+		case l.Error != "":
+			unknown++
+			out = append(out, l.Path+" points at "+l.Target+", which could not be looked at: "+l.Error)
+		}
+	}
+	if loadState == "not-found" && len(links) > 0 && dangling == 0 && unknown == 0 {
+		out = append(out, "the unit's file is not found, and "+plural(len(links), "enable link")+" still name it")
+	}
+	if removable > 0 {
+		out = append(out, "`disable` does not remove a link whose unit file is gone, and no verb of this seat removes one yet "+
+			"(novox/hq issue 332); once it is gone, `reset-failed` clears the unit's failed record")
+	} else if dangling > 0 {
+		out = append(out, "the dangling links are in a package's, a generator's or the runtime's directory, which puts them back: they are not the person's to remove")
+	}
+	incomplete := managerFailed || len(unread) > 0 || unknown > 0 || (scope == User && noHome)
+	if len(links) == 0 && dependents == 0 {
+		where := "in the directories searched"
+		if incomplete {
+			where += ", which are not all of them (below)"
+		}
+		if loadState == "not-found" {
+			out = append(out, "nothing names "+unit+" "+where+": a failed record of it is stale, and `reset-failed` clears it")
+		} else if !managerFailed {
+			out = append(out, "no unit and no enable link pulls "+unit+" in "+where+": it starts only when asked by name, by a timer, socket or path unit the manager does not list, or by a program")
+		}
+	}
+	if managerFailed {
+		out = append(out, "the manager did not answer, so only the links on disk are known")
+	}
+	if scope == User && noHome {
+		out = append(out, "the account's home is not known to this process, so its own directories were not searched")
+	}
+	if len(unread) > 0 {
+		out = append(out, "some directories could not be read, so a link may be missing from this answer")
+	}
+	return out
+}
+
+func plural(n int, what string) string {
+	if n == 1 {
+		return "1 " + what
+	}
+	return strconv.Itoa(n) + " " + what + "s"
+}
+
+// readDir lists a directory as enable links need it, by lstat: each name, whether it is itself a directory,
+// where a link points, and whether what it points at does not exist — any other failure to look is said as
+// the error it was, never as dangling.
+func readDir(dir string) ([]Entry, error) {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return nil, err
+	}
+	out := make([]Entry, 0, len(entries))
+	for _, e := range entries {
+		out = append(out, entryOf(filepath.Join(dir, e.Name()), e.Name(), e.Type()))
+	}
+	return out, nil
+}
+
+func entryOf(full, name string, mode fs.FileMode) Entry {
+	entry := Entry{Name: name, Dir: mode.IsDir()}
+	if mode&fs.ModeSymlink == 0 {
+		return entry
+	}
+	target, err := os.Readlink(full)
+	if err != nil {
+		target, entry.Error = "(unreadable)", err.Error()
+	}
+	entry.Link = target
+	if _, err := os.Stat(full); errors.Is(err, fs.ErrNotExist) {
+		entry.Dangles = true
+	} else if err != nil {
+		entry.Error = err.Error()
+	}
+	return entry
+}

modules/systemd/cmd/systemd-tools/wanted_test.go

@@ -0,0 +1,444 @@
+package main
+
+// What wants a unit, and a failed record cleared (novox/hq issue 332): over a fake runner and a fake
+// directory listing, so no link is made to test them (the mesh makes no symbolic links, its tests
+// included); the real listing is tested on what a temporary directory holds without one.
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// tree is a fake file system of directories, each a list of entries; a directory not in it does not exist.
+type tree map[string][]Entry
+
+func (t tree) readDir(dir string) ([]Entry, error) {
+	if e, ok := t[dir]; ok {
+		if e == nil {
+			return nil, fs.ErrPermission
+		}
+		return e, nil
+	}
+	return nil, fs.ErrNotExist
+}
+
+const home = "/home/operator"
+
+func withTree(m *Manager, t tree) *Manager {
+	m.Home, m.ReadDir = home, t.readDir
+	return m
+}
+
+// The leftover of a removed package: its file is gone, an enable link in the account's own configuration
+// still names it, and the manager still has default.target wanting it.
+func greenclip() tree {
+	user := home + "/.config/systemd/user"
+	return tree{
+		user: {{Name: "default.target.wants", Dir: true}, {Name: "timers.target.wants", Dir: true}, {Name: "clip.service"}},
+		user + "/default.target.wants": {
+			{Name: "greenclip.service", Link: "/usr/lib/systemd/user/greenclip.service", Dangles: true},
+			{Name: "pipewire.service", Link: "/usr/lib/systemd/user/pipewire.service"},
+		},
+		user + "/timers.target.wants":                {{Name: "backup.timer", Link: "/usr/lib/systemd/user/backup.timer"}},
+		"/usr/lib/systemd/user":                      {{Name: "pipewire.service"}, {Name: "sockets.target.wants", Dir: true}},
+		"/usr/lib/systemd/user/sockets.target.wants": {{Name: "pipewire.socket", Link: "../pipewire.socket"}},
+	}
+}
+
+func showAndReverse(show, reverse string) func(c call) Ran {
+	return func(c call) Ran {
+		for _, a := range c.args {
+			if a == "show" {
+				return Ran{Stdout: show}
+			}
+			if a == "list-dependencies" {
+				return Ran{Stdout: reverse}
+			}
+		}
+		return Ran{}
+	}
+}
+
+func TestWantedByFindsADanglingEnableLinkInTheAccountsOwnConfiguration(t *testing.T) {
+	var calls []call
+	run := fake(showAndReverse(
+		"LoadState=not-found\nActiveState=failed\nSubState=failed\nUnitFileState=\nFragmentPath=\nWantedBy=default.target\nRequiredBy=\nTriggeredBy=\n",
+		"greenclip.service\n  default.target\n"), &calls)
+	answer, err := withTree(operator(run), greenclip()).WantedBy(User, "greenclip.service")
+	if err != nil {
+		t.Fatal(err)
+	}
+	links := answer["links"].([]EnableLink)
+	want := []EnableLink{{Path: home + "/.config/systemd/user/default.target.wants/greenclip.service", Of: "default.target",
+		Dependency: "Wants", Target: "/usr/lib/systemd/user/greenclip.service", Dangles: true, Link: true,
+		Whose: "the operator account's own configuration", removable: true}}
+	if !reflect.DeepEqual(links, want) {
+		t.Fatalf("links %+v", links)
+	}
+	manager := answer["manager"].(map[string]any)
+	if !reflect.DeepEqual(manager["WantedBy"], []string{"default.target"}) || manager["LoadState"] != "not-found" {
+		t.Fatalf("manager %+v", manager)
+	}
+	if _, empty := manager["RequiredBy"]; empty {
+		t.Fatal("an empty property is answered as a dependency")
+	}
+	if !reflect.DeepEqual(manager["reverse"], []string{"default.target"}) {
+		t.Fatalf("reverse %v", manager["reverse"])
+	}
+	said := strings.Join(answer["findings"].([]string), "\n")
+	if !strings.Contains(said, "default.target.wants/greenclip.service makes default.target want greenclip.service") ||
+		!strings.Contains(said, "which does not exist") || !strings.Contains(said, "reset-failed") {
+		t.Fatalf("findings %q", said)
+	}
+	if _, has := answer["unread"]; has {
+		t.Fatalf("a directory that does not exist was said as unread: %v", answer["unread"])
+	}
+	// Read-only: the manager is only asked.
+	for _, c := range calls {
+		if c.args[1] != "show" && c.args[1] != "list-dependencies" {
+			t.Fatalf("WantedBy ran %v", c.args)
+		}
+		if c.args[0] != "--user" {
+			t.Fatalf("a user-scope question went to the system manager: %v", c.args)
+		}
+	}
+	// The unit comes after "--", so a name that slipped past would still not be an option.
+	last := calls[len(calls)-1].args
+	if last[len(last)-2] != "--" {
+		t.Fatalf("%v", last)
+	}
+}
+
+func TestWantedByMatchesALinkByWhatItPointsAt(t *testing.T) {
+	user := home + "/.config/systemd/user"
+	fsys := tree{
+		user: {{Name: "graphical-session.target.requires", Dir: true}},
+		user + "/graphical-session.target.requires": {{Name: "clipboard.service", Link: "/usr/lib/systemd/user/greenclip.service"}},
+	}
+	answer, err := withTree(operator(fake(showAndReverse("LoadState=loaded\n", "greenclip.service\n"), nil)), fsys).WantedBy(User, "greenclip.service")
+	if err != nil {
+		t.Fatal(err)
+	}
+	links := answer["links"].([]EnableLink)
+	if len(links) != 1 || links[0].Dependency != "Requires" || links[0].Of != "graphical-session.target" || links[0].Dangles {
+		t.Fatalf("%+v", links)
+	}
+}
+
+func TestWantedBySaysWhenNothingNamesTheUnit(t *testing.T) {
+	answer, err := withTree(operator(fake(showAndReverse("LoadState=not-found\nActiveState=failed\nWantedBy=\n", "gone.service\n"), nil)), greenclip()).WantedBy(User, "gone.service")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(answer["links"].([]EnableLink)) != 0 {
+		t.Fatalf("%v", answer["links"])
+	}
+	said := strings.Join(answer["findings"].([]string), "\n")
+	if !strings.Contains(said, "nothing names gone.service in the directories searched:") {
+		t.Fatalf("%q", said)
+	}
+}
+
+func TestWantedBySaysAnUnreadableDirectoryAndAManagerThatDoesNotAnswer(t *testing.T) {
+	fsys := greenclip()
+	fsys["/etc/systemd/user"] = nil // unreadable
+	run := fake(func(call) Ran { return Ran{Status: 1, Stderr: "Failed to connect to bus: No such file or directory"} }, nil)
+	answer, err := withTree(operator(run), fsys).WantedBy(User, "greenclip.service")
+	if err != nil {
+		t.Fatalf("an unreachable manager failed the whole answer: %v", err)
+	}
+	manager := answer["manager"].(map[string]any)
+	if e, _ := manager["error"].(string); !strings.Contains(e, "does not answer") {
+		t.Fatalf("%+v", manager)
+	}
+	if len(answer["links"].([]EnableLink)) != 1 {
+		t.Fatal("the links on disk were not read without the manager")
+	}
+	unread, _ := answer["unread"].([]string)
+	if len(unread) != 1 || !strings.HasPrefix(unread[0], "/etc/systemd/user: ") {
+		t.Fatalf("%v", unread)
+	}
+	said := strings.Join(answer["findings"].([]string), "\n")
+	if !strings.Contains(said, "only the links on disk are known") || !strings.Contains(said, "could not be read") {
+		t.Fatalf("%q", said)
+	}
+	if strings.Contains(said, "nothing names") {
+		t.Fatal("an incomplete answer said nothing names the unit")
+	}
+}
+
+func TestWantedByInTheSystemScopeReadsTheMachinesDirectoriesUnescalated(t *testing.T) {
+	var calls []call
+	fsys := tree{
+		"/etc/systemd/system":                         {{Name: "multi-user.target.wants", Dir: true}},
+		"/etc/systemd/system/multi-user.target.wants": {{Name: "sshd.service", Link: "/usr/lib/systemd/system/sshd.service"}},
+	}
+	m := withTree(operator(fake(showAndReverse("LoadState=loaded\nWantedBy=multi-user.target\n", "sshd.service\nmulti-user.target\ngraphical.target\n"), &calls)), fsys)
+	answer, err := m.WantedBy(System, "sshd.service")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, c := range calls {
+		if c.cmd != "systemctl" {
+			t.Fatalf("a read was escalated: %s %v", c.cmd, c.args)
+		}
+	}
+	links := answer["links"].([]EnableLink)
+	if len(links) != 1 || links[0].Whose != "the machine's configuration" {
+		t.Fatalf("%+v", links)
+	}
+	if !reflect.DeepEqual(answer["manager"].(map[string]any)["reverse"], []string{"multi-user.target", "graphical.target"}) {
+		t.Fatalf("%v", answer["manager"])
+	}
+	for _, d := range answer["searched"].([]ConfigDir) {
+		if strings.HasPrefix(d.Path, home) {
+			t.Fatal("the system scope searched the account's home")
+		}
+	}
+}
+
+func TestWantedByRefusesAUnitThatReadsAsAnOption(t *testing.T) {
+	m := withTree(operator(fake(func(call) Ran { t.Fatal("ran"); return Ran{} }, nil)), tree{})
+	if _, err := m.WantedBy(User, "--all"); err == nil {
+		t.Fatal("an option was taken as a unit")
+	}
+}
+
+func TestResetFailedClearsOneUnitEscalatedOnlyInTheSystemScope(t *testing.T) {
+	if p, a := escalated("systemctl", []string{"reset-failed", "x.mount"}, System, 1000); p != "sudo" || !reflect.DeepEqual(a, []string{"-n", "systemctl", "reset-failed", "x.mount"}) {
+		t.Fatalf("%s %v", p, a)
+	}
+	var calls []call
+	m := operator(fake(func(c call) Ran {
+		if c.args[1] == "show" {
+			return Ran{Stdout: "LoadState=not-found\nActiveState=inactive\nSubState=dead\nUnitFileState=\nFragmentPath=\n"}
+		}
+		return Ran{}
+	}, &calls))
+	var reset stdioTool
+	for _, tool := range tools(m) {
+		if tool.Name == seat+".reset-failed" {
+			reset = stdioTool{tool.Run}
+		}
+	}
+	if reset.run == nil {
+		t.Fatal("reset-failed is not served")
+	}
+	out, err := reset.run(map[string]any{"unit": "greenclip.service", "scope": "user"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(calls[0].args, []string{"--user", "reset-failed", "--", "greenclip.service"}) || calls[0].cmd != "systemctl" {
+		t.Fatalf("%s %v", calls[0].cmd, calls[0].args)
+	}
+	answer := out.(map[string]any)
+	if answer["active"] != "inactive" || answer["verb"] != "reset-failed" {
+		t.Fatalf("%v", answer)
+	}
+	if _, err := reset.run(map[string]any{"scope": "user"}); err == nil {
+		t.Fatal("reset-failed without a unit would reset every failed unit")
+	}
+	if _, err := reset.run(map[string]any{"unit": "-a", "scope": "user"}); err == nil {
+		t.Fatal("an option was taken as a unit")
+	}
+}
+
+type stdioTool struct {
+	run func(map[string]any) (any, error)
+}
+
+// **A glob is not a unit** (the review of mesh-catalog #137): systemctl expands it to every loaded unit it
+// matches, so `reset-failed` or `stop` of "*" would act on all of them. Refused before anything runs, for
+// every verb taking a unit.
+func TestAGlobIsRefusedAsAUnitByEveryVerb(t *testing.T) {
+	for _, bad := range []string{"*", "*.service", "foo?.service", "a[bc].mount"} {
+		if unitArg(bad) == nil {
+			t.Errorf("%q accepted", bad)
+		}
+	}
+	var calls []call
+	m := withTree(operator(fake(func(call) Ran { return Ran{} }, &calls)), tree{})
+	for _, tool := range tools(m) {
+		verb := strings.TrimPrefix(tool.Name, seat+".")
+		if verb == "units" || verb == "failed" {
+			continue // a pattern, and no unit
+		}
+		_, err := tool.Run(map[string]any{"unit": "*", "scope": "user", "why": "test"})
+		if err == nil {
+			t.Errorf("%s accepted {\"unit\":\"*\"}", verb)
+		}
+	}
+	if len(calls) != 0 {
+		t.Fatalf("a glob reached the manager: %v", calls)
+	}
+}
+
+// The unit is given after "--" to show as well as to an act, so nothing after it is read as an option.
+func TestTheUnitComesAfterTheEndOfOptions(t *testing.T) {
+	var calls []call
+	m := operator(fake(func(call) Ran { return Ran{Stdout: "LoadState=loaded\n"} }, &calls))
+	if _, err := m.Status(System, "sshd.service"); err != nil {
+		t.Fatal(err)
+	}
+	a := calls[0].args
+	if a[0] != "show" || a[len(a)-2] != "--" || a[len(a)-1] != "sshd.service" {
+		t.Fatalf("%v", a)
+	}
+}
+
+// A target that could not be looked at, for any reason but its not existing, is neither dangling nor not:
+// it is said as the error it was, and the answer does not say nothing names the unit.
+func TestALinkWhoseTargetCannotBeLookedAtIsNotSaidToDangle(t *testing.T) {
+	user := home + "/.config/systemd/user"
+	fsys := tree{
+		user:                           {{Name: "default.target.wants", Dir: true}},
+		user + "/default.target.wants": {{Name: "x.service", Link: "/mnt/away/x.service", Error: "stat /mnt/away/x.service: permission denied"}},
+	}
+	answer, err := withTree(operator(fake(showAndReverse("LoadState=loaded\n", "x.service\n"), nil)), fsys).WantedBy(User, "x.service")
+	if err != nil {
+		t.Fatal(err)
+	}
+	links := answer["links"].([]EnableLink)
+	if len(links) != 1 || links[0].Dangles || links[0].Error == "" {
+		t.Fatalf("%+v", links)
+	}
+	said := strings.Join(answer["findings"].([]string), "\n")
+	if !strings.Contains(said, "could not be looked at: stat /mnt/away/x.service: permission denied") || strings.Contains(said, "does not exist") {
+		t.Fatalf("%q", said)
+	}
+}
+
+// A *.wants directory that is itself a link is followed only into the directories searched: one leading
+// elsewhere is said and not read, so neither the search nor a removal after it can be pointed anywhere.
+func TestALinkedDependencyDirectoryIsFollowedOnlyIntoTheSearchedDirectories(t *testing.T) {
+	user := home + "/.config/systemd/user"
+	fsys := tree{
+		user: {
+			{Name: "default.target.wants", Link: "/srv/elsewhere"},
+			{Name: "graphical-session.target.wants", Link: "/etc/systemd/user/shared.wants"},
+		},
+		"/srv/elsewhere":                 {{Name: "x.service", Link: "/gone/x.service", Dangles: true}},
+		"/etc/systemd/user/shared.wants": {{Name: "x.service", Link: "/gone/x.service", Dangles: true}},
+	}
+	read := []string{}
+	m := withTree(operator(fake(showAndReverse("LoadState=not-found\n", "x.service\n"), nil)), fsys)
+	inner := m.ReadDir
+	m.ReadDir = func(dir string) ([]Entry, error) { read = append(read, dir); return inner(dir) }
+	answer, err := m.WantedBy(User, "x.service")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, d := range read {
+		if d == "/srv/elsewhere" {
+			t.Fatal("a linked .wants outside the searched directories was followed")
+		}
+	}
+	links := answer["links"].([]EnableLink)
+	if len(links) != 1 || links[0].Path != user+"/graphical-session.target.wants/x.service" || links[0].removable {
+		t.Fatalf("%+v", links)
+	}
+	unread, _ := answer["unread"].([]string)
+	if len(unread) != 1 || !strings.Contains(unread[0], "outside the directories searched, not followed") {
+		t.Fatalf("%v", unread)
+	}
+}
+
+// "Nothing names it" is only ever said of the directories searched, and the account's own are not among
+// them when its home is not known — which is said.
+func TestNothingNamesItIsSaidOfTheDirectoriesSearchedAndTheHomeWhenUnknown(t *testing.T) {
+	m := withTree(operator(fake(showAndReverse("LoadState=not-found\n", "x.service\n"), nil)), tree{})
+	m.Home = ""
+	answer, err := m.WantedBy(User, "x.service")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, d := range answer["searched"].([]ConfigDir) {
+		if strings.Contains(d.Path, ".config") || strings.Contains(d.Path, ".local") || d.Path == "" {
+			t.Fatalf("searched %q without a home", d.Path)
+		}
+	}
+	said := strings.Join(answer["findings"].([]string), "\n")
+	if !strings.Contains(said, "nothing names x.service in the directories searched, which are not all of them") ||
+		!strings.Contains(said, "the account's home is not known") {
+		t.Fatalf("%q", said)
+	}
+	m.Home = home
+	answer, _ = m.WantedBy(User, "x.service")
+	said = strings.Join(answer["findings"].([]string), "\n")
+	if !strings.Contains(said, "nothing names x.service in the directories searched:") {
+		t.Fatalf("%q", said)
+	}
+}
+
+// Every directory systemd reads units from, in both scopes (systemd.unit(5)).
+func TestTheSearchedDirectoriesAreTheManagersLoadPath(t *testing.T) {
+	m := withTree(operator(nil), tree{})
+	paths := func(s Scope) string {
+		var out []string
+		for _, d := range m.configDirs(s) {
+			out = append(out, d.Path)
+		}
+		return strings.Join(out, "\n")
+	}
+	for _, want := range []string{"/etc/systemd/system.control", "/run/systemd/transient", "/run/systemd/generator.early",
+		"/etc/systemd/system", "/run/systemd/system", "/run/systemd/generator", "/usr/local/lib/systemd/system",
+		"/usr/lib/systemd/system", "/run/systemd/generator.late"} {
+		if !strings.Contains(paths(System)+"\n", want+"\n") {
+			t.Errorf("system scope does not search %s", want)
+		}
+	}
+	for _, want := range []string{home + "/.config/systemd/user.control", "/run/user/1000/systemd/user", home + "/.config/systemd/user",
+		"/etc/systemd/user", "/etc/xdg/systemd/user", home + "/.local/share/systemd/user", "/usr/local/lib/systemd/user", "/usr/lib/systemd/user"} {
+		if !strings.Contains(paths(User)+"\n", want+"\n") {
+			t.Errorf("user scope does not search %s", want)
+		}
+	}
+}
+
+// The real listing, by lstat, on what a temporary directory holds: a directory, a file, and a directory
+// that does not exist or cannot be read.
+func TestReadDirListsByLstat(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.Mkdir(filepath.Join(dir, "default.target.wants"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "x.service"), []byte("[Unit]\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	entries, err := readDir(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := []Entry{{Name: "default.target.wants", Dir: true}, {Name: "x.service"}}
+	if !reflect.DeepEqual(entries, want) {
+		t.Fatalf("%+v", entries)
+	}
+	if _, err := readDir(filepath.Join(dir, "absent")); !errors.Is(err, fs.ErrNotExist) {
+		t.Fatalf("a missing directory: %v", err)
+	}
+	if os.Getuid() != 0 {
+		locked := filepath.Join(dir, "locked")
+		if err := os.Mkdir(locked, 0o000); err != nil {
+			t.Fatal(err)
+		}
+		defer os.Chmod(locked, 0o755)
+		if _, err := readDir(locked); err == nil || errors.Is(err, fs.ErrNotExist) {
+			t.Fatalf("an unreadable directory read as %v", err)
+		}
+	}
+	// And through the search: a real tree with no link in it names nothing, and says so.
+	m := operator(fake(showAndReverse("LoadState=not-found\n", "x.service\n"), nil))
+	m.Home, m.ReadDir = dir, readDir
+	answer, err := m.WantedBy(User, "x.service")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(answer["links"].([]EnableLink)) != 0 {
+		t.Fatalf("%v", answer["links"])
+	}
+}

modules/systemd/module.json

@@ -18,7 +18,9 @@
         "enable",
         "disable",
         "journal",
-        "failed"
+        "failed",
+        "reset-failed",
+        "wanted-by"
       ]
     }
   ],