review: rebuild a file the mesh once wrote whole, keep links, give back a missing line end, and release a hold only after the write (hq issue 128)

2026-09-27 00:09:34 +02:00
parent 1cb895346d
commit fdc768c476
7 changed files with 338 additions and 34 deletions
@@ -469,3 +469,150 @@ func TestTheRecordOfABlockSurvivesTheStateFile(t *testing.T) {
 		t.Errorf("undeclaring from a saved state left %q", got)
 	}
 }
+
+// The mesh's old whole hosts file, as the controller composed it before issue 128.
+const oldWholeHosts = "# Generated by the mesh. Do not edit — this file is replaced whenever a machine\n" +
+	"# joins or leaves, and an edit would survive until then and vanish.\n\n" +
+	"127.0.0.1\tlocalhost\n" +
+	"::1\t\tlocalhost ip6-localhost ip6-loopback\n" +
+	"127.0.1.1\tg14\n" +
+	"\n" +
+	"10.42.0.1\tace.internal\tace\n" +
+	"10.42.0.9\tg14.internal\tg14\t# this machine\n"
+
+func wholeDecl(path, content string) string {
+	return fmt.Sprintf(`{"declaration":1,"resources":[
+	  {"id":%q,"type":"file","path":%q,"content":%q}
+	]}`, namesID, path, content)
+}
+
+func applyKeepingIn(t *testing.T, raw string, known store.State, keepDir string) (Report, store.State) {
+	t.Helper()
+	report, state, err := ApplyKeeping(context.Background(), archHost(t), parse(t, raw), known,
+		store.OriginDeclared, (&machine{}).run, nil, nil, KeepIn(keepDir))
+	if err != nil {
+		t.Fatalf("apply failed: %v", err)
+	}
+	return report, state
+}
+
+func TestAFileTheMeshWroteWholeAndMadeItselfKeepsOnlyItsLoopbackLines(t *testing.T) {
+	// Written whole into a file that was not there, then declared as a block under the same id:
+	// the old names must not stay above the region, where a resolver would answer from them first.
+	path := filepath.Join(t.TempDir(), "hosts")
+	_, state := applyKeepingIn(t, wholeDecl(path, oldWholeHosts), store.State{}, t.TempDir())
+	report, state := applyKeepingIn(t, blockDecl(t, path, meshNames), state, t.TempDir())
+	floor := "127.0.0.1\tlocalhost\n::1\t\tlocalhost ip6-localhost ip6-loopback\n127.0.1.1\tg14\n"
+	if got := readText(t, path); got != floor+"\n"+marked(namesID, meshNames) {
+		t.Fatalf("the old whole file became:\n%q", got)
+	}
+	o := outcomeOf(report, namesID)
+	if o.Action != "updated" || !strings.Contains(o.Detail, "loopback lines") {
+		t.Errorf("the rebuild was reported as %q: %s", o.Action, o.Detail)
+	}
+	if rec, _ := state.Find(namesID); !rec.Into.Created {
+		t.Error("a file the mesh made itself was not recorded as the mesh's")
+	}
+	report, _ = applyKeepingIn(t, blockDecl(t, path, meshNames), state, t.TempDir())
+	if got := outcomeOf(report, namesID).Action; got != "unchanged" {
+		t.Errorf("applied again, the rebuilt file was %q", got)
+	}
+	undeclare(t, state)
+	if got := readText(t, path); got != floor {
+		t.Errorf("undeclared, the file holds %q", got)
+	}
+}
+
+func TestAFileTheMeshWroteWholeOverAnOriginalGetsTheOriginalBack(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "hosts")
+	_ = os.WriteFile(path, []byte(workstationHosts), 0o644)
+	keep := t.TempDir()
+	_, state := applyKeepingIn(t, wholeDecl(path, oldWholeHosts), store.State{}, keep)
+	if rec, _ := state.Find(namesID); rec.Kept == "" {
+		t.Fatal("where the original was kept was not recorded")
+	}
+	report, state := applyKeepingIn(t, blockDecl(t, path, meshNames), state, keep)
+	if got := readText(t, path); got != workstationHosts+"\n"+marked(namesID, meshNames) {
+		t.Fatalf("the old whole file became:\n%q", got)
+	}
+	if d := outcomeOf(report, namesID).Detail; !strings.Contains(d, "original kept at") {
+		t.Errorf("the rebuild was reported as: %s", d)
+	}
+	undeclare(t, state)
+	if got := readText(t, path); got != workstationHosts {
+		t.Errorf("undeclared, the machine did not get its original back: %q", got)
+	}
+}
+
+func TestAFileTheMeshWroteWholeAndSomebodyChangedIsWrittenIntoAsItStands(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "hosts")
+	_, state := applyKeepingIn(t, wholeDecl(path, oldWholeHosts), store.State{}, t.TempDir())
+	edited := oldWholeHosts + "192.168.1.20 printer\n"
+	_ = os.WriteFile(path, []byte(edited), 0o644)
+	report, _ := applyKeepingIn(t, blockDecl(t, path, meshNames), state, t.TempDir())
+	if got := readText(t, path); got != edited+"\n"+marked(namesID, meshNames) {
+		t.Fatalf("an edited whole file became:\n%q", got)
+	}
+	if d := outcomeOf(report, namesID).Detail; !strings.Contains(d, "changed since; its old lines were kept") {
+		t.Errorf("the outcome does not say so: %s", d)
+	}
+}
+
+func TestALinkedFileStaysALink(t *testing.T) {
+	dir := t.TempDir()
+	real := filepath.Join(dir, "static", "hosts")
+	_ = os.MkdirAll(filepath.Dir(real), 0o755)
+	_ = os.WriteFile(real, []byte(workstationHosts), 0o644)
+	link := filepath.Join(dir, "hosts")
+	if err := os.Symlink(real, link); err != nil {
+		t.Fatal(err)
+	}
+	_, state := applyBlockDecl(t, blockDecl(t, link, meshNames), store.State{})
+	if info, err := os.Lstat(link); err != nil || info.Mode()&os.ModeSymlink == 0 {
+		t.Fatalf("the link was replaced by a file")
+	}
+	if got := readText(t, real); got != workstationHosts+"\n"+marked(namesID, meshNames) {
+		t.Errorf("the file the link names holds %q", got)
+	}
+	undeclare(t, state)
+	if info, err := os.Lstat(link); err != nil || info.Mode()&os.ModeSymlink == 0 {
+		t.Fatalf("undeclaring replaced the link with a file")
+	}
+	if got := readText(t, real); got != workstationHosts {
+		t.Errorf("undeclared, the file the link names holds %q", got)
+	}
+}
+
+func TestALastLineWithNoEndIsGivenBackWithNone(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "hosts")
+	_ = os.WriteFile(path, []byte("x"), 0o644)
+	_, state := applyBlockDecl(t, blockDecl(t, path, meshNames), store.State{})
+	if got := readText(t, path); got != "x\n\n"+marked(namesID, meshNames) {
+		t.Fatalf("got %q", got)
+	}
+	undeclare(t, state)
+	if got := readText(t, path); got != "x" {
+		t.Errorf("undeclaring left %q, the machine had %q", got, "x")
+	}
+}
+
+func TestAFailedBlockWriteKeepsItsHold(t *testing.T) {
+	// Held from when it was declared whole, then declared as a block into a file whose markers do
+	// not pair: the write is refused, and the hold — with where its original is — stays.
+	path := filepath.Join(t.TempDir(), "hosts")
+	broken := "a\n# BEGIN mesh " + namesID + "\n"
+	_ = os.WriteFile(path, []byte(broken), 0o644)
+	known := store.State{Held: []store.Held{{ID: namesID, Module: "mesh-wireguard", Kind: "file",
+		Target: path, Kept: "/var/lib/mesh/kept/hosts"}}}
+	resource := fmt.Sprintf(`{"id":%q,"type":"file","path":%q,"into":"block","content":%q}`, namesID, path, meshNames)
+	d := adopted(t, `{"taken":[],"untaken":{"mesh-wireguard":["`+namesID+`"]}}`, resource)
+	_, state, err := ApplyKeeping(context.Background(), archHost(t), d, known,
+		store.OriginDeclared, (&machine{}).run, nil, nil, KeepIn(t.TempDir()))
+	if err == nil {
+		t.Fatal("a write into unpaired markers was not refused")
+	}
+	h, held := state.HeldAt(namesID)
+	if !held || h.Kept != "/var/lib/mesh/kept/hosts" {
+		t.Errorf("a failed write released the hold: %+v", state.Held)
+	}
+}