Merge pull request 'The indexer writes no fingerprint from a packages state it did not read, and computes fingerprints again by hand (issue 1966, recovery)' (#191) from fix/1966-indexer-packages-read into main

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/integration_test.go

@@ -1233,7 +1233,18 @@ func TestAProposalIsAnsweredApprovedAndWritten(t *testing.T) {
 			t.Fatal("anchor in the form before was not converted")
 		}
 	}
-	verbs := newSeatTools(bedStore{b}, func(string, any) (json.RawMessage, error) { return json.RawMessage(`{"ok":true}`), nil })
+	// The verbs ask the indexer's first views of modules and manifests (ADR 0615 §1), as the tool runner answers them from the
+	// indexer's buckets; every other ask the controller's, answered ok.
+	verbs := newSeatTools(bedStore{b}, func(tool string, _ any) (json.RawMessage, error) {
+		if state, ok := strings.CutPrefix(tool, buckets.IndexerModule+"."); ok && indexerFirstViews[state] != "" {
+			a, err := views.FirstView(buckets.IndexerModule, state, bedSource{b.ctx, b.buckets[indexerFirstViews[state]]}, nil, "", time.Now())
+			if err != nil {
+				return nil, err
+			}
+			return json.Marshal(map[string]any{"result": a})
+		}
+		return json.RawMessage(`{"ok":true}`), nil
+	})
 	propose := func() mma.Proposal {
 		t.Helper()
 		got, err := verbs.doPropose(map[string]any{"why": "move web", "changes": `[{"op":"take-off","node":"anchor","module":"web"},` +

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer-tools/main.go

@@ -278,6 +278,10 @@ func main() {
 	tools = append(tools, catalogTools()...)
 	tools = append(tools, viewTools(os.Getenv, keptSource, time.Now)...)
 	tools = append(tools, index.PendingTools(keptRead{stdio.State(index.PendingState)}, keptRead{stdio.State(index.OwnBuildStateName)}, asks, time.Now)...)
+	tools = append(tools, index.FingerprintsTools(asks, time.Now, func(what, why string) error {
+		_, err := acts.Record(meshhandactsclient.Request{What: what, Why: why, Cause: index.FingerprintsAgainTool, Verb: "fingerprints-again"})
+		return err
+	}, 10*time.Second)...)
 	tools = append(tools, index.TryCandidateTools(keptRead{stdio.State("candidates")}, keptRead{stdio.State(index.TryRecoveryState)}, asks, time.Now)...)
 	tools = append(tools, configReadersTool(stdio.NewWatchedStates()), busStateTool(keptSource), requirementsTool(keptSource),
 		packageUsersTool(keptSource), seatDefinitionTool(keptSource), outOfStepTool(keptSource),

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/main.go

@@ -52,7 +52,14 @@ func main() {
 
 // awaitedStore is a state bound when it appears (process.AwaitBucket) as the indexer's store: until then every call is
 // process.ErrNotYet.
-type awaitedStore struct{ b *process.AwaitedBucket }
+type awaitedStore struct {
+	b *process.AwaitedBucket
+	// js and name, when set, tell a bucket that does not exist from one that cannot be reached: the awaited bucket is nil for
+	// both (the SDK drops the bus's error), and only the first is "not yet". The packages state is read this way: an unreached
+	// state is no package published, and the version line written over every import form (issue 1966).
+	js   process.BucketOpener
+	name string
+}
 
 // expiringKeys is index.Bounds on a state whose keys take a time to live (key-ttl in the manifest): a key armed expires
 // at its end, which its watcher hears as a purge; one standing keeps its end.
@@ -88,6 +95,11 @@ func (e expiringKeys) Disarm(ctx context.Context, key string) error {
 func (s awaitedStore) store() (kvStore, error) {
 	kv := s.b.KV()
 	if kv == nil {
+		if s.js != nil {
+			if _, err := s.js.KeyValue(context.Background(), s.name); err != nil && !errors.Is(err, jetstream.ErrBucketNotFound) {
+				return kvStore{}, fmt.Errorf("the bucket %s cannot be reached: %w", s.name, err)
+			}
+		}
 		return kvStore{}, process.ErrNotYet
 	}
 	return kvStore{kv}, nil
@@ -411,17 +423,17 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	seatBus := &seatBus{defs: awaitedSource{ctx, seatDefs}, marks: awaitedSource{ctx, marks}}
 	seatReader, saySeats := followSeatList(seatBus, saySeatDefinition(js, cred), logger.Printf)
 	readWhenBound(seatReader, seatDefs, marks)
-	ix := &index.Indexer{Findings: awaitedStore{findings}, OldSections: awaitedStore{oldSections}, Requirements: awaitedStore{requirements}, Store: kvStore{candidates}, Modules: kvStore{modules}, Manifests: kvStore{manifests}, Taken: awaitedStore{taken}, Builds: known,
-		Verdicts: awaitedStore{verdicts}, SayRefused: sayRefused(conn, cred, logger.Printf), SayAccepted: sayAccepted(conn, cred),
-		Predefined: awaitedStore{predefined}, ConfigCandidates: awaitedStore{configCandidates}, Logf: logger.Printf,
+	ix := &index.Indexer{Findings: awaitedStore{b: findings}, OldSections: awaitedStore{b: oldSections}, Requirements: awaitedStore{b: requirements}, Store: kvStore{candidates}, Modules: kvStore{modules}, Manifests: kvStore{manifests}, Taken: awaitedStore{b: taken}, Builds: known,
+		Verdicts: awaitedStore{b: verdicts}, SayRefused: sayRefused(conn, cred, logger.Printf), SayAccepted: sayAccepted(conn, cred),
+		Predefined: awaitedStore{b: predefined}, ConfigCandidates: awaitedStore{b: configCandidates}, Logf: logger.Printf,
 		Named: namedVia(calls.Call), Trunk: trunkVia(calls.Call), Contains: containsVia(calls.Call), Read: readVia(calls.Call),
-		ReadOpen: openVia(calls.Call), Packages: awaitedStore{packages}, Files: filesVia(calls.Call), GoSum: goSumVia(calls.Call), GoMod: goModVia(calls.Call),
-		OwnBuild: ownBuildVia(calls.Call, cred.Node), OpenTries: openTriesVia(calls.Call), OwnBuildState: awaitedStore{ownBuildState}, TryRecovery: awaitedStore{tryRecovery}, Graph: awaitedStore{graph},
-		SeatDefinitions: awaitedStore{seatDefs}, ReadFile: readFileVia(calls.Call), SaySeatDefinition: saySeats,
+		ReadOpen: openVia(calls.Call), Packages: awaitedStore{b: packages, js: js, name: index.PackagesBucket}, Files: filesVia(calls.Call), GoSum: goSumVia(calls.Call), GoMod: goModVia(calls.Call),
+		OwnBuild: ownBuildVia(calls.Call, cred.Node), OpenTries: openTriesVia(calls.Call), OwnBuildState: awaitedStore{b: ownBuildState}, TryRecovery: awaitedStore{b: tryRecovery}, Graph: awaitedStore{b: graph},
+		SeatDefinitions: awaitedStore{b: seatDefs}, ReadFile: readFileVia(calls.Call), SaySeatDefinition: saySeats,
 		Message: messageVia(calls.Call),
 		// The take-in step (ADR 0633): its state pending and its stream take-in, both this delivery's, bound when they appear;
 		// until then every merge is taken in at once, as before.
-		Pending:   awaitedStore{process.AwaitBucket(ctx, js, conn, index.PendingBucket, "no merge is held for the indexer its revision names: each is taken in at once", logger.Printf)},
+		Pending:   awaitedStore{b: process.AwaitBucket(ctx, js, conn, index.PendingBucket, "no merge is held for the indexer its revision names: each is taken in at once", logger.Printf)},
 		SayTakeIn: sayTakeIn(js, cred)}
 	// Which build this program is, fixed here once, before it hears any merge and never asked again (index.FixOwnBuild): the
 	// node-engine names the successor while it replaces this process, and an old process that learnt it later would take
@@ -483,7 +495,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	// The holds, new with ADR 0632 (issue 1790's kind), bound when they appear: until then a merge that would hold a
 	// manifest is left for redelivery, said, rather than write what a counted engine cannot read.
 	holds := process.AwaitBucket(ctx, js, conn, index.HoldsBucket, "a merge whose manifest every node reads, needing what not every counted node-engine states, is left for redelivery", logger.Printf)
-	ix.Holds = awaitedStore{holds}
+	ix.Holds = awaitedStore{b: holds}
 	holds.Ready(func(jetstream.KeyValue) { ix.KickHolds(ctx) })
 	// Each standing hold's bound, a key that expires at its end (ADR 0632 §2, the indexer's own state): its expiry weighs
 	// the holds again, which raises manifest-held; until the state is bound a hold past its bound is raised at its next
@@ -696,7 +708,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	taken.Ready(func(jetstream.KeyValue) { ix.KickFill(ctx) })
 	// What the indexer heard of FORGE (issue 1126 note 76) is bound when its state appears, as every state a delivery adds
 	// (issue 1790): until then no message is written there, and the rest of the indexer runs.
-	heard := awaitedStore{process.AwaitBucket(ctx, js, conn, index.HeardBucket, "no FORGE message the indexer handles is written for indexer_heard", logger.Printf)}
+	heard := awaitedStore{b: process.AwaitBucket(ctx, js, conn, index.HeardBucket, "no FORGE message the indexer handles is written for indexer_heard", logger.Printf)}
 	// Each change of the states its readers read is said on its views family (ADR 0615 §5), from the mark each state was
 	// said up to; a first view (the tools bundle) answers at that mark.
 	startViews(ctx, js, cred, marks,

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/main_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"log"
 	"strings"
 	"testing"
@@ -151,8 +152,28 @@ func TestAMessageIsIndexedAndAcked(t *testing.T) { // 1238/AC2 (unit part)
 			t.Errorf("forge/group's merged message read as a group's end: %q", logs.String())
 		}
 	})
+	// Issue 1966: a bucket the bus has not made is "not yet"; one it cannot reach (jetstream not enabled, no responders) is the
+	// bus's own error, which stops a pass instead of reading as nothing published.
+	t.Run("a bucket not found is not yet, one the bus cannot reach is its error", func(t *testing.T) {
+		for _, c := range []struct {
+			name   string
+			err    error
+			notYet bool
+		}{{"not found", jetstream.ErrBucketNotFound, true}, {"not reachable", jetstream.ErrJetStreamNotEnabled, false}} {
+			b := process.AwaitBucket(context.Background(), opener{c.err}, nil, "packages", "none", t.Logf)
+			_, err := awaitedStore{b: b, js: opener{c.err}, name: "packages"}.Keys(context.Background())
+			if errors.Is(err, process.ErrNotYet) != c.notYet || err == nil || (!c.notYet && !errors.Is(err, c.err)) {
+				t.Errorf("%s: Keys answered %v, want not-yet %v", c.name, err, c.notYet)
+			}
+		}
+	})
 }
 
+// opener is a bus that answers every bucket with err.
+type opener struct{ err error }
+
+func (o opener) KeyValue(context.Context, string) (jetstream.KeyValue, error) { return nil, o.err }
+
 func TestTheSourceMainKeyIsTakenAtItsRevision(t *testing.T) { // 1344/AC1 (the watch's side: key, revision, value)
 	var logs bytes.Buffer
 	logger := log.New(&logs, "", 0)

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/takein.go

@@ -24,6 +24,7 @@ type takerIn interface {
 	TakeInMerge(ctx context.Context, repository, merge string, seq uint64, by, why string) index.TakenIn
 	DropTryCandidate(ctx context.Context, id, by, why string) index.TakenIn
 	RecoverTriesByHand(ctx context.Context, by, why string) index.TakenIn
+	FingerprintsAgain(ctx context.Context, module string) index.TakenIn
 }
 
 // takenIn answers one value of the takeins state (the tool indexer_take_in, issue 1945): a value not yet answered takes the
@@ -42,7 +43,9 @@ func takenIn(ctx context.Context, ix takerIn, kv jetstream.KeyValue, e jetstream
 		return
 	}
 	asked, r := "take-in", index.TakenIn{}
-	if a.RecoverTries {
+	if a.Fingerprints {
+		asked, r = "computing of fingerprints again", ix.FingerprintsAgain(ctx, a.Module)
+	} else if a.RecoverTries {
 		asked, r = "recovery of the tries", ix.RecoverTriesByHand(ctx, a.By, a.Why)
 		a.Module = "tries"
 	} else if a.TryCandidate != "" && a.Drop {

modules/mesh-delivery-indexer/internal/index/candidates.go

@@ -150,13 +150,15 @@ type Indexer struct {
 	retrying   atomic.Bool                                                       // a RetryUnread runs in the background (kickRetry)
 	retryAgain atomic.Bool                                                       // an event asked for one more RetryUnread after the running one
 	retryWG    sync.WaitGroup                                                    // the background RetryUnread, for tests to wait on
-	recompute  sync.Mutex                                                        // one Recompute at a time
-	untaken    map[string]string                                                 // repository to the latest merge applied while the taken state was missing (taken.go)
-	filling    atomic.Bool                                                       // a FillTaken runs in the background (KickFill)
-	fillAgain  atomic.Bool                                                       // a kick arrived while it ran
-	atHeads    map[string]map[string]meshcatalog.PackagesByModuleValue           // a member head's published Go modules, by repository@head (candidatePublished)
-	saidAt     map[string]string                                                 // the head of a repository whose failed read was said, by repository: said once per head
-	failedAt   map[string]string                                                 // the head of a repository whose tree lacks a directory asked, by repository: not asked again until the head changes
+	fresh      map[string]bool                                                   // modules whose import form is computed again by hand (FingerprintsAgain), "*" for every one; under freshMu
+	freshMu    sync.Mutex
+	recompute  sync.Mutex                                              // one Recompute at a time
+	untaken    map[string]string                                       // repository to the latest merge applied while the taken state was missing (taken.go)
+	filling    atomic.Bool                                             // a FillTaken runs in the background (KickFill)
+	fillAgain  atomic.Bool                                             // a kick arrived while it ran
+	atHeads    map[string]map[string]meshcatalog.PackagesByModuleValue // a member head's published Go modules, by repository@head (candidatePublished)
+	saidAt     map[string]string                                       // the head of a repository whose failed read was said, by repository: said once per head
+	failedAt   map[string]string                                       // the head of a repository whose tree lacks a directory asked, by repository: not asked again until the head changes
 	// OwnBuild answers the fingerprint of the build this program runs, from the node-engine's seat; nil knows none.
 	OwnBuild   func(ctx context.Context) (string, error)
 	underSeats bool       // a dry run inside judge.WithSeats: its judge passes do not hold the seat list (verdicts.go)

modules/mesh-delivery-indexer/internal/index/fingerprints.go

@@ -0,0 +1,167 @@
+package index
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"maps"
+	"slices"
+	"strings"
+	"time"
+
+	"git.novox.be/novox/mesh-delivery/contracts/go/clients/meshcatalogclient"
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// FingerprintsAgainTool computes the fingerprints again now (issue 1966; the instruction "tools are how a module is spoken
+// to"): the indexer reads the packages state, takes no held fingerprint for the build's, and writes the import form for
+// every module whose imports are all published, as a merge's recompute would. For the module whose fingerprint a pass
+// wrote while the packages state was unread (the version line over the import form) and that nothing else moves.
+const FingerprintsAgainTool = "indexer_fingerprints_again"
+
+// FingerprintMove is one module's fingerprint before and after a recompute by hand.
+type FingerprintMove struct {
+	Module string `json:"module"`
+	Old    string `json:"old"`
+	New    string `json:"new"`
+}
+
+// FingerprintsAgain computes the fingerprints of module again ("all" or empty: every held module) from the published
+// packages as they are read now, and answers each fingerprint that moved. A read of the packages state that failed
+// writes nothing, and says so.
+func (ix *Indexer) FingerprintsAgain(ctx context.Context, module string) TakenIn {
+	module = strings.TrimSpace(module)
+	if module == "" {
+		module = "all"
+	}
+	out := TakenIn{Module: module}
+	if ix.Modules == nil || ix.Manifests == nil {
+		out.Answer = "the indexer writes no fingerprints"
+		return out
+	}
+	before, err := ix.fingerprintsHeld(ctx)
+	if err != nil {
+		out.Answer = "the modules state cannot be read: " + err.Error()
+		return out
+	}
+	if module != "all" {
+		if _, ok := before[module]; !ok {
+			out.Answer = "the indexer holds no fingerprint of " + module
+			return out
+		}
+	}
+	key := module
+	if module == "all" {
+		key = "*"
+	}
+	ix.freshMu.Lock()
+	ix.fresh = map[string]bool{key: true}
+	ix.freshMu.Unlock()
+	// The path of a merge's recompute: the modules, then the candidates their fingerprints reach (recomputeWith), then the
+	// pending merges a changed fingerprint settles (PendingAgain, as after a toolchain report).
+	err = ix.recomputeWith(ctx, nil, nil)
+	ix.freshMu.Lock()
+	ix.fresh = nil
+	ix.freshMu.Unlock()
+	if err != nil {
+		out.Answer = "nothing was written: " + err.Error()
+		return out
+	}
+	if err := ix.PendingAgain(ctx); err != nil {
+		ix.logf("the pending merges are not evaluated again after the fingerprints were computed again: %v", err)
+	}
+	after, err := ix.fingerprintsHeld(ctx)
+	if err != nil {
+		out.Answer = "computed, but the modules state cannot be read back: " + err.Error()
+		return out
+	}
+	for _, m := range slices.Sorted(maps.Keys(after)) {
+		if module != "all" && m != module {
+			continue
+		}
+		if before[m] != after[m] {
+			out.Fingerprints = append(out.Fingerprints, FingerprintMove{Module: m, Old: before[m], New: after[m]})
+		}
+	}
+	out.Stored = true
+	out.Answer = fmt.Sprintf("%d fingerprint(s) moved", len(out.Fingerprints))
+	return out
+}
+
+// isFresh says the module's import form is computed again by hand in this pass.
+func (ix *Indexer) isFresh(module string) bool {
+	ix.freshMu.Lock()
+	defer ix.freshMu.Unlock()
+	return ix.fresh[module] || ix.fresh["*"]
+}
+
+// fingerprintsHeld is each held module's fingerprint of the new form.
+func (ix *Indexer) fingerprintsHeld(ctx context.Context) (map[string]string, error) {
+	keys, err := ix.Modules.Keys(ctx)
+	if err != nil {
+		return nil, err
+	}
+	out := map[string]string{}
+	for _, k := range keys {
+		value, _, found, err := ix.Modules.Get(ctx, k)
+		if err != nil {
+			return nil, err
+		}
+		if !found {
+			continue
+		}
+		if m, err := meshcatalogclient.DecodeModule(value); err == nil {
+			out[k] = m.Fp2
+		}
+	}
+	return out, nil
+}
+
+// FingerprintsTools is the tool indexer_fingerprints_again over ask (the takeins state). It acts first and says the hand
+// act after: record is told what was done and answers an error when it could not be recorded, which the answer says and
+// which never refuses or delays the recovery beyond bound.
+func FingerprintsTools(ask func(key string, value []byte) (TakeInAsk, error), now func() time.Time, record func(what, why string) error, bound time.Duration) []stdio.Tool {
+	return []stdio.Tool{{Name: FingerprintsAgainTool,
+		Description: "Compute the fingerprints of one module (or all) again now from the published packages as the indexer reads them: " +
+			"the import form is written for every module whose imports are all published, whatever fingerprint the module holds. For the " +
+			"fingerprints a pass wrote while the packages state was unread (the version line over the import form: builds then fail on an " +
+			"older package). Answers each module whose fingerprint moved, old and new; when the packages state cannot be read it writes " +
+			"nothing and says why. Runs as a merge's recompute does (the modules, the candidates they reach, the pending merges they settle). Acts first, then records the hand act through mesh-hand-acts; when that cannot be recorded the answer says so.",
+		Input: map[string]any{"type": "object", "required": []string{"why"}, "properties": map[string]any{
+			"module": map[string]any{"type": "string", "description": "the module's name, or all (the default)"},
+			"why":    map[string]any{"type": "string", "description": "why it is computed again now, in plain words"}}},
+		Run: func(args map[string]any) (any, error) {
+			module, _ := args["module"].(string)
+			why, _ := args["why"].(string)
+			module, why = strings.TrimSpace(module), strings.TrimSpace(why)
+			if why == "" {
+				return nil, errors.New("say why: a hand act is said in the journal")
+			}
+			if module == "" {
+				module = "all"
+			}
+			data, err := json.Marshal(TakeInAsk{V: 1, Module: module, Fingerprints: true, Why: why, By: stdio.CallerOf(args), At: now().UTC()})
+			if err != nil {
+				return nil, err
+			}
+			a, err := ask("fingerprints."+module+"."+now().UTC().Format("20060102T150405.000000000"), data)
+			if err != nil {
+				return nil, err
+			}
+			res := map[string]any{"result": a.Result}
+			done := make(chan error, 1)
+			go func() { done <- record("computed the fingerprints of "+module+" again by hand", why) }()
+			wait, cancel := context.WithTimeout(context.Background(), bound) // a context's bound, no timer (ADR 0437 §8)
+			defer cancel()
+			select {
+			case err := <-done:
+				if err != nil {
+					res["hand-act"] = "not recorded: " + err.Error()
+				}
+			case <-wait.Done(): // a bound on the record, never on the recovery
+				res["hand-act"] = fmt.Sprintf("not recorded within %s: mesh-hand-acts did not answer", bound)
+			}
+			return res, nil
+		}}}
+}

modules/mesh-delivery-indexer/internal/index/form.go

@@ -57,6 +57,9 @@ func formOf(module, repository string, kept *meshcatalog.ModulesByModuleValueInp
 			logf("%s: no published package holds %s, so its fingerprint takes the version line", module, strings.Join(r.Missing, ", "))
 		}
 	}
+	// The fingerprint written here is the version line's, not the import form's: no import form is held for the inputs it was
+	// computed from, so a later pass whose import form computes the same does not take this one for the build's (issue 1966).
+	kept.ImportForm = ""
 	others := fingerprint.OtherPackages(kept.Packages, repository)
 	versions, unpublished := fingerprint.HeldVersionsOf(others, held)
 	for p, v := range pins { // an accepted series' newest published version (acceptedSeries, DLV-I6)

modules/mesh-delivery-indexer/internal/index/imports_test.go

@@ -2,13 +2,16 @@ package index
 
 import (
 	"context"
+	"errors"
 	"strings"
 	"testing"
 	"time"
 
 	"git.novox.be/novox/mesh-delivery/contracts/go/clients/meshcatalogclient"
 	"git.novox.be/novox/mesh-delivery/contracts/go/seats/meshcatalog"
+	"git.novox.be/novox/mesh-delivery/contracts/go/seats/meshdeliverychecker"
 	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/builds"
+	"git.novox.be/novox/mesh-sdk/go/process"
 )
 
 const meshSDK = "git.novox.be/novox/mesh-sdk/go"
@@ -51,6 +54,7 @@ func (m *missingDir) Error() string { return "no directory " + m.dir }
 func TestImportsReportedMoveTheFingerprintOnlyWithAnImportedPackage(t *testing.T) {
 	t.Run("a build of an older fingerprint keeps no imports", buildOfAnOlderFingerprintKeepsNoImports)
 	t.Run("a change of a sibling directory alone moves its importer", aSiblingDirectoryAloneMovesItsImporter)
+	t.Run("an unread packages state writes no fingerprint, and they are computed again by hand (issue 1966)", anUnreadPackagesStateWritesNoFingerprintAndFingerprintsAreComputedAgain)
 	t.Run("an accepted series' newest published version pins it, by that version's contents", anAcceptedSeriesPinsItsNewest)
 	ctx := context.Background()
 	ix, mods := newFormIndexer(t, mod{"avahi", catalogueManifest(t, "avahi")})
@@ -270,3 +274,114 @@ func anAcceptedSeriesPinsItsNewest(t *testing.T) {
 		t.Errorf("a trunk merge moved avahi off its accepted series' newest: %q %v", m.Fp2, m.Packages)
 	}
 }
+
+// Issue 1966 (the indexer started while the bus's storage was down): a read of the packages state that failed, or that
+// answered no published package where held modules were computed from published ones, writes no fingerprint (the version
+// line over every import form is what an empty state computes); a version line written leaves no import form behind
+// that a later pass takes for the build's; and indexer_fingerprints_again computes the import form again by hand.
+func anUnreadPackagesStateWritesNoFingerprintAndFingerprintsAreComputedAgain(t *testing.T) {
+	ctx := context.Background()
+	// avahi at the import form, pinned to mesh-sdk at c3, as the test above leaves it.
+	setup := func(t *testing.T) (*Indexer, *memStore, meshcatalog.ModulesByModuleValue) {
+		ix, mods := newFormIndexer(t, mod{"avahi", catalogueManifest(t, "avahi")})
+		reportToolchain(t, ix, "mesh-build-go", "novox", "go", "go1.27.1")
+		ix.Packages, ix.Files = newMem(), forge{c1: sdkFiles("a1", "b1"), c3: sdkFiles("a2", "b2")}.files
+		setPackages(t, mods, "avahi", []string{meshSDK})
+		raw, err := meshcatalogclient.EncodeModule(meshcatalog.ModulesByModuleValue{Repository: "novox/mesh-sdk", Path: ".", Commit: c1, None2: "a TypeScript package"})
+		if err != nil {
+			t.Fatal(err)
+		}
+		mods.put("mesh-sdk", raw)
+		held, _ := ix.heldModules(ctx)
+		if err := ix.publish(ctx, "novox/mesh-sdk", c1, held, false); err != nil {
+			t.Fatal(err)
+		}
+		if err := ix.Recompute(ctx); err != nil {
+			t.Fatal(err)
+		}
+		first, _ := moduleOf(t, mods, "avahi")
+		if err := ix.ApplyBuildEnd(ctx, buildEnd(t, "avahi", first.Fp2, meshSDK, meshSDK+"/announce")); err != nil {
+			t.Fatal(err)
+		}
+		held, _ = ix.heldModules(ctx)
+		if err := ix.publish(ctx, "novox/mesh-sdk", c3, held, false); err != nil {
+			t.Fatal(err)
+		}
+		if err := ix.Recompute(ctx); err != nil {
+			t.Fatal(err)
+		}
+		m, _ := moduleOf(t, mods, "avahi")
+		if m.Fp2 == first.Fp2 || m.Fp2 != m.Inputs2.ImportForm {
+			t.Fatalf("setup: fp2 %q (was %q), import form %q; want the import form", m.Fp2, first.Fp2, m.Inputs2.ImportForm)
+		}
+		return ix, mods, m
+	}
+	t.Run("a pass whose read of the packages state failed or answered nothing writes no fingerprint", func(t *testing.T) {
+		for _, c := range []struct {
+			name string
+			bad  func(ix *Indexer)
+			why  string
+		}{
+			{"the listing fails", func(ix *Indexer) { ix.Packages.(*memStore).keysErr = errors.New("jetstream not enabled") }, "cannot be listed"},
+			{"the state is not on the bus yet", func(ix *Indexer) { ix.Packages.(*memStore).keysErr = process.ErrNotYet }, "answers no published package"}, // a mesh with no import form computes as before: TestIndexerWritesModulesAtAMerge
+			{"the state answers no package", func(ix *Indexer) { ix.Packages = newMem() }, "answers no published package"},
+		} {
+			t.Run(c.name, func(t *testing.T) {
+				ix, mods, _ := setup(t)
+				was, _ := moduleOf(t, mods, "avahi")
+				c.bad(ix)
+				err := ix.Recompute(ctx)
+				if err == nil || !strings.Contains(err.Error(), c.why) {
+					t.Fatalf("recompute with an unread packages state: err %v, want one saying %q", err, c.why)
+				}
+				if now, _ := moduleOf(t, mods, "avahi"); now.Fp2 != was.Fp2 {
+					t.Fatalf("a pass over an unread packages state moved avahi's fingerprint to %q (was %q)", now.Fp2, was.Fp2)
+				}
+			})
+		}
+	})
+	t.Run("a version line written keeps no import form, and a fingerprint computed again by hand is the import form", func(t *testing.T) {
+		ix, mods, good := setup(t)
+		// What the pass that read nothing wrote on novox: the version line's fingerprint, the import form still kept.
+		bad := good
+		bad.Fp2 = "src2:" + strings.Repeat("d", 64)
+		raw, err := meshcatalogclient.EncodeModule(bad)
+		if err != nil {
+			t.Fatal(err)
+		}
+		mods.put("avahi", raw)
+		if err := ix.Recompute(ctx); err != nil {
+			t.Fatal(err)
+		}
+		if now, _ := moduleOf(t, mods, "avahi"); now.Fp2 != bad.Fp2 {
+			t.Fatalf("the held version line is not kept by the build's shortcut (fp2 %q); the case the tool recovers has changed", now.Fp2)
+		}
+		r := ix.FingerprintsAgain(ctx, "avahi")
+		if !r.Stored || len(r.Fingerprints) != 1 || r.Fingerprints[0].Old != bad.Fp2 || r.Fingerprints[0].New != good.Fp2 {
+			t.Fatalf("fingerprints again: %+v, want avahi from %q to %q", r, bad.Fp2, good.Fp2)
+		}
+		if now, _ := moduleOf(t, mods, "avahi"); now.Fp2 != good.Fp2 || ix.fresh != nil {
+			t.Fatalf("avahi holds %q after it, want %q (fresh %v)", now.Fp2, good.Fp2, ix.fresh)
+		}
+		// It runs a merge's recompute, candidates included: a candidate store that cannot be listed fails it, said.
+		ix.Store, ix.previews = &memStore{keysErr: errors.New("no bus")}, map[string]meshdeliverychecker.PreviewsByRepositoryHeadTrunkValue{"k": {}}
+		if r := ix.FingerprintsAgain(ctx, "avahi"); r.Stored || !strings.Contains(r.Answer, "listing the candidates") {
+			t.Fatalf("fingerprints again over candidates that cannot be listed: %+v", r)
+		}
+		if r := ix.FingerprintsAgain(ctx, "nothing"); r.Stored {
+			t.Fatalf("fingerprints again of a module not held answered stored: %+v", r)
+		}
+	})
+	t.Run("formOf clears the import form when it writes the version line", func(t *testing.T) {
+		for _, c := range []struct {
+			name    string
+			imports []string
+		}{{"an import no package holds", []string{meshSDK + "/announce"}}, {"no import reported", nil}} {
+			kept := meshcatalog.ModulesByModuleValueInputs2{Tree: "t", Imports: c.imports, ImportForm: "src2:" + strings.Repeat("a", 64)}
+			f := formOf("avahi", "novox/mesh-catalog", &kept, nil, meshcatalog.ModulesByModuleValue{}, nil, nil, nil, nil)
+			if kept.ImportForm != "" {
+				t.Errorf("%s: kept import form %q after the version line %q", c.name, kept.ImportForm, f.fp)
+			}
+		}
+	})
+}

modules/mesh-delivery-indexer/internal/index/packages.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"git.novox.be/novox/mesh-sdk/go/process"
 	"maps"
 	"path"
 	"reflect"
@@ -31,21 +32,40 @@ import (
 
 // publishedAll is every value of the packages state, by Go module path; empty with no state or one that does not answer.
 func (ix *Indexer) publishedAll(ctx context.Context) map[string]meshcatalog.PackagesByModuleValue {
-	out := map[string]meshcatalog.PackagesByModuleValue{}
-	if ix.Packages == nil {
-		return out
-	}
-	keys, err := ix.Packages.Keys(ctx)
+	out, err := ix.publishedRead(ctx)
 	if err != nil {
 		ix.logf("the packages state cannot be listed, so every fingerprint takes the version line: %v", err)
-		return out
+	}
+	return out
+}
+
+// publishedRead is publishedAll with a read that failed said as an error, never as an empty map: a pass that takes an
+// unread state for "no package is published" writes the version line over every module's fingerprint (issue 1966, the
+// indexer started while the bus's storage was down). No state wired is no error: nothing is published then.
+func (ix *Indexer) publishedRead(ctx context.Context) (map[string]meshcatalog.PackagesByModuleValue, error) {
+	out := map[string]meshcatalog.PackagesByModuleValue{}
+	if ix.Packages == nil {
+		return out, nil
+	}
+	keys, err := ix.Packages.Keys(ctx)
+	if errors.Is(err, process.ErrNotYet) {
+		return out, nil // the state is not on the bus yet: nothing is published, as before
+	}
+	if err != nil {
+		return out, fmt.Errorf("the packages state cannot be listed: %w", err)
 	}
 	for _, key := range keys {
 		if IsSeriesKey(key) {
 			continue // a package's series (series.go), not a Go module's digests
 		}
 		value, _, found, err := ix.Packages.Get(ctx, key)
-		if err != nil || !found {
+		if errors.Is(err, process.ErrNotYet) {
+			continue
+		}
+		if err != nil {
+			return out, fmt.Errorf("packages.%s cannot be read: %w", key, err)
+		}
+		if !found {
 			continue
 		}
 		p, err := DecodePublishedPackages(value)
@@ -55,7 +75,32 @@ func (ix *Indexer) publishedAll(ctx context.Context) map[string]meshcatalog.Pack
 		}
 		out[p.Module] = p
 	}
-	return out
+	return out, nil
+}
+
+// publishedForPass is the packages state a recompute computes fingerprints from, or why it must write none: a read that
+// failed, or that answered no published module where the held modules show packages were published before (a module
+// whose fingerprint was computed from the import form, or that holds resolved package versions). The first start of a
+// mesh, whose held modules show none, computes from an empty state as before.
+func (ix *Indexer) publishedForPass(ctx context.Context, held map[string]meshcatalog.ModulesByModuleValue) (map[string]meshcatalog.PackagesByModuleValue, error) {
+	published, err := ix.publishedRead(ctx)
+	if err != nil {
+		return nil, err
+	}
+	if len(published) > 0 {
+		return published, nil
+	}
+	var had []string
+	for key, m := range held {
+		if m.Inputs2 != nil && m.Inputs2.ImportForm != "" { // not Packages: a version line holds those too, with nothing published
+			had = append(had, key)
+		}
+	}
+	if len(had) > 0 {
+		slices.Sort(had)
+		return nil, fmt.Errorf("the packages state answers no published package, though %d held modules (%s ...) were computed from published ones", len(had), had[0])
+	}
+	return published, nil
 }
 
 // reached are, by repository, the mesh Go module paths the held modules' go.sum names and the imports their builds

modules/mesh-delivery-indexer/internal/index/pending_test.go

@@ -135,6 +135,40 @@ func sha(c byte) string { return strings.Repeat(string(c), 40) }
 
 func TestTakeIn(t *testing.T) { // 1585/T3-T13 (ADR 0633)
 	ctx := context.Background()
+	t.Run("indexer_fingerprints_again acts before it records the hand act and says a failed record", func(t *testing.T) { // issue 1966
+		for _, c := range []struct {
+			name   string
+			record func(what, why string) error
+			said   string
+		}{
+			{"recorded", func(string, string) error { return nil }, ""},
+			{"record refused", func(string, string) error { return errors.New("no ledger") }, "not recorded: no ledger"},
+			{"record never answers", func(string, string) error { select {} }, "not recorded within"},
+		} {
+			t.Run(c.name, func(t *testing.T) {
+				var asked []string
+				ask := func(key string, _ []byte) (TakeInAsk, error) {
+					asked = append(asked, key)
+					return TakeInAsk{Result: &TakenIn{Module: "all", Stored: true}}, nil
+				}
+				tool := FingerprintsTools(ask, time.Now, c.record, 10*time.Millisecond)[0]
+				if _, err := tool.Run(map[string]any{"module": "avahi"}); err == nil {
+					t.Fatal("a hand act with no why was done")
+				}
+				if len(asked) != 0 {
+					t.Fatalf("asked the indexer without a why: %v", asked)
+				}
+				got, err := tool.Run(map[string]any{"module": "avahi", "why": "the packages read came back empty"})
+				if err != nil || len(asked) != 1 || !strings.HasPrefix(asked[0], "fingerprints.avahi.") {
+					t.Fatalf("run: %v, asked %v", err, asked)
+				}
+				said, _ := got.(map[string]any)["hand-act"].(string)
+				if !strings.Contains(said, c.said) || (c.said == "") != (said == "") {
+					t.Fatalf("hand-act %q, want one saying %q", said, c.said)
+				}
+			})
+		}
+	})
 	t.Run("T6 a merge while the own build is unknown writes nothing", func(t *testing.T) {
 		b := newTakeInBed(t)
 		b.ix.ownFP, b.ix.ownFixed = "", false // this process is started again and asks the engine, which does not answer

modules/mesh-delivery-indexer/internal/index/registered.go

@@ -220,6 +220,8 @@ type TakenIn struct {
 	// and deleted.
 	Handed  []string `json:"handed,omitempty"`
 	Dropped []string `json:"dropped,omitempty"`
+	// Fingerprints are the modules whose fingerprint a recompute by hand moved (FingerprintsAgain), each old and new.
+	Fingerprints []FingerprintMove `json:"fingerprints,omitempty"`
 }
 
 // TakeIn reads a registered module's manifest now, whatever was tried before, and writes it as a merge would (the tool

modules/mesh-delivery-indexer/internal/index/takein.go

@@ -56,6 +56,9 @@ type TakeInAsk struct {
 	Sequence        uint64 `json:"sequence,omitempty"`
 	// TryCandidate asks the candidate of this try's group to be dropped (indexer_drop_try_candidate), trycandidates.go.
 	TryCandidate string `json:"try-candidate,omitempty"`
+	// Fingerprints asks the fingerprints of Module ("all": every module) to be computed again now, from the published
+	// packages as they are read (indexer_fingerprints_again, fingerprints.go).
+	Fingerprints bool `json:"fingerprints,omitempty"`
 	// RecoverTries asks the open tries' candidates to be recovered now (indexer_recover_tries).
 	RecoverTries bool      `json:"recover-tries,omitempty"`
 	Drop         bool      `json:"drop,omitempty"`
@@ -77,7 +80,7 @@ func DecodeTakeIn(data []byte) (TakeInAsk, error) {
 	if a.V != 1 {
 		return a, fmt.Errorf("a takeins value of version %d, not 1", a.V)
 	}
-	if a.Module == "" && a.Repository == "" && a.Pending == "" && a.Merge == "" && a.TryCandidate == "" && !a.RecoverTries {
+	if a.Module == "" && a.Repository == "" && a.Pending == "" && a.Merge == "" && a.TryCandidate == "" && !a.RecoverTries && !a.Fingerprints {
 		return a, errors.New("a takeins value naming no module, repository, pending wait, merge or try")
 	}
 	return a, nil

modules/mesh-delivery-indexer/internal/index/toolchains.go

@@ -223,7 +223,13 @@ func (ix *Indexer) recomputeLocked(ctx context.Context, overlay map[string]meshc
 		all[key] = &known{key: key, cur: cur, manifest: m, languages: languagesOf(m), bases: basesOf(m), contexts: hasContext(m), held: before}
 	}
 	tools := ix.agreed()
-	published := ix.publishedAll(ctx)
+	published, err := ix.publishedForPass(ctx, held)
+	if err != nil {
+		// No module's fingerprint is written from a state that was not read: the version line over every import form is
+		// what an empty packages state would compute (issue 1966). The next pass, or indexer_fingerprints_again, computes them.
+		ix.logf("no fingerprint is written by this pass: %v", err)
+		return fmt.Errorf("no fingerprint is written: %w", err)
+	}
 	series := ix.SeriesAll(ctx) // each package's series, the newest a user accepting it takes (DLV-I6)
 	type result struct {
 		fp, none string
@@ -258,6 +264,9 @@ func (ix *Indexer) recomputeLocked(ctx context.Context, overlay map[string]meshc
 		chain = append(chain, module)
 		kept := *k.cur.Inputs2
 		kept.Bases, kept.Builder = nil, ""
+		if ix.isFresh(module) { // indexer_fingerprints_again: the import form is written again, the held one stands for nothing
+			kept.ImportForm = ""
+		}
 		var missing []string
 		for _, b := range k.bases {
 			if r := of(b, chain); r.fp != "" {

modules/mesh-delivery-indexer/manifest_test.go

@@ -175,8 +175,8 @@ func TestManifestDeclarations(t *testing.T) { // 1238/AC1, 1444 (reads the build
 	want = append(want, "indexer_first_views", "indexer_first_view_again", index.ConfigReadersTool, index.BusStateTool, index.RequirementsTool, index.PackageUsersTool, index.SayAcceptedTool, // DLV-F3r, DLV-I10, DLV-I11, DLV-I7, DLV-I8, DLV-I9c
 		index.SeatDefinitionTool, index.SeatDefinitionsAgainTool, index.OutOfStepTool, // DLV-I19
 		index.HoldsTool, index.EngineReadsTool, // ADR 0632 §2: the mesh-wide holds and the engines' reads they weigh
-		index.PendingTool, index.TakeInPendingTool, index.DropPendingTool, index.TryCandidatesTool, index.DropTryCandidateTool, index.RecoverTriesTool, index.TakeInMergeTool) // 1585/T12, T13 (ADR 0633 §5)
-	if !reflect.DeepEqual(m.Tools, want) || len(want) != 38 {
+		index.PendingTool, index.TakeInPendingTool, index.DropPendingTool, index.TryCandidatesTool, index.DropTryCandidateTool, index.RecoverTriesTool, index.TakeInMergeTool, index.FingerprintsAgainTool) // issue 1966;  1585/T12, T13 (ADR 0633 §5)
+	if !reflect.DeepEqual(m.Tools, want) || len(want) != 39 {
 		t.Errorf("tools = %v, want %v", m.Tools, want)
 	}
 	// Every read tool of the indexer a reader of this repository invokes is one it serves (the checker's seventh first

modules/mesh-delivery-indexer/module.json

@@ -54,7 +54,8 @@
     "indexer_try_candidates",
     "indexer_drop_try_candidate",
     "indexer_recover_tries",
-    "indexer_take_in_merge"
+    "indexer_take_in_merge",
+    "indexer_fingerprints_again"
   ],
   "consumes": [
     "go-package-registry.published",