A lost take-in hold passes the take-in event's check, so it is said (issue 1966)

holdLost builds a pending take-in naming neither WaitsFor nor Unknown, which TakeIn's check refused, so the hold stayed
in the journal and the watchman never saw it.

Quick fix: set Unknown on holdLost's event. Thorough fix (chosen): the check accepts a pending revision that names Lost,
the field made for it; one naming nothing is still refused. Tests: a row accepting Lost, the refusal row kept, and the
lost-hold scenario encodes its said event.

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

modules/mesh-delivery-forge-bridge/cmd/mesh-delivery-forge-bridge-tools/main_test.go

@@ -186,6 +186,8 @@ func TestTheBridgeToolsReadTheGroupsAndAskTheEndAgain(t *testing.T) {
 				api: forgeAnswers(t, "/repos/novox/a/pulls/9", true, "refs/pull/9/head", h2, c2, "main"), fail: "no head branch"},
 			{name: "a forge answer that is the bare body, no wrapper", raws: map[string][]byte{}, repository: "novox/a", merge: c2, number: 9,
 				api: func(string) (json.RawMessage, error) { return json.RawMessage(`{"number":9,"merged":true}`), nil }, fail: `{"result"`},
+			{name: "a forge answer with no pull request number", raws: map[string][]byte{}, repository: "novox/a", merge: c2, number: 9,
+				api: func(string) (json.RawMessage, error) { return json.RawMessage(`{"result":{"merged":true}}`), nil }, fail: "no number"},
 			{name: "a forge that does not answer", raws: map[string][]byte{}, repository: "novox/a", merge: c2,
 				api: func(string) (json.RawMessage, error) { return nil, errors.New("the forge is down") }, fail: "the forge is down"},
 		} {

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

@@ -99,8 +99,9 @@ type PendingEntry struct {
 	Forge    forgemsg.Forge
 	Light    bool
 	Holds    []string
-	// Covered says a newer merge of the same repository is in the same revision: its message is not read or applied, since
-	// applying the newest writes every module whose manifest differs from what is held (modules.go).
+	// Covered says its message is not read or applied: either a newer merge of the same repository is in the same revision
+	// (applying the newest writes every module whose manifest differs from what is held, modules.go), or its repository's
+	// taken merge is at or ahead of it (loadNewest, takenAlready), so applying it would write nothing.
 	Covered bool
 }
 
@@ -613,7 +614,8 @@ func (ix *Indexer) headTaken(ctx context.Context, m meshdeliveryclient.Head) (bo
 	return in, err
 }
 
-// takenAlready says whether a group member's merge is at or behind its repository's taken merge.
+// takenAlready says whether a merge (a group member's, or the newest pending merge of a repository in loadNewest) is at or
+// behind its repository's taken merge.
 func (ix *Indexer) takenAlready(ctx context.Context, m forgemsg.GroupMerge) (bool, error) {
 	if ix.Taken == nil {
 		return false, nil
@@ -978,8 +980,11 @@ func (ix *Indexer) takeInWholeBy(ctx context.Context, entries []PendingEntry, ow
 	}
 	for _, e := range claimed {
 		if e.Covered {
-			by := newest[strings.ToLower(e.Forge.Repository)]
-			ix.logf("take-in: %s (%s#%d) is covered by %s, the newest merge of %s in this revision: its message is not read, and it is ended with it", e.Key, e.Forge.Repository, e.Forge.Number, by.Key, e.Forge.Repository)
+			by := "the taken merge"
+			if n, ok := newest[strings.ToLower(e.Forge.Repository)]; ok {
+				by = n.Key + ", the newest merge"
+			}
+			ix.logf("take-in: %s (%s#%d) is covered by %s of %s in this revision: its message is not read, and it is ended with it", e.Key, e.Forge.Repository, e.Forge.Number, by, e.Forge.Repository)
 			// Its pull request leaves its group's candidate as a merged message takes it out; nothing else of it is applied.
 			if err := ix.removeCandidate(ctx, e.Forge); err != nil {
 				ix.release(ctx, claimed)

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

@@ -172,8 +172,8 @@ func (t TakeIn) check() error {
 		if !strings.HasPrefix(t.Key, "m.") {
 			return fmt.Errorf("delivery: a revision's take-in key is its oldest merge's m.<sequence>, not %q", t.Key)
 		}
-		if t.Kind == TakeInPending && t.WaitsFor == "" && t.Unknown == "" {
-			return fmt.Errorf("delivery: a pending revision %s names the indexer build it waits for, or why the indexer does not know its own", t.Key)
+		if t.Kind == TakeInPending && t.WaitsFor == "" && t.Unknown == "" && len(t.Lost) == 0 {
+			return fmt.Errorf("delivery: a pending revision %s names the indexer build it waits for, why the indexer does not know its own, or the merges it lost", t.Key)
 		}
 	case TakeInGroup:
 		if t.Group == "" {

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

@@ -70,7 +70,7 @@ func TestTakeInEvents(t *testing.T) {
 	}{
 		{"group take-in without its group", "names its group", 1, func(t *TakeIn) { t.Group = "" }},
 		{"group take-in under another group's key", "g.other", 1, func(t *TakeIn) { t.Key = GroupTakeInKey("other") }},
-		{"pending revision waiting for no build", "waits for", 0, func(t *TakeIn) { t.WaitsFor = "" }},
+		{"pending revision waiting for no build", "lost", 0, func(t *TakeIn) { t.WaitsFor = "" }},
 		{"pending with a hand act", "only a taken event", 0, func(t *TakeIn) { t.By = "someone@node" }},
 		{"hand act without its by", "by", 2, func(t *TakeIn) { t.By = "" }},
 		{"take-in without merges", "no merge", 0, func(t *TakeIn) { t.Merges = nil }},
@@ -84,6 +84,13 @@ func TestTakeInEvents(t *testing.T) {
 			t.Errorf("%s: %v, want a refusal naming %q", c.name, err, c.want)
 		}
 	}
+	// A revision held for a merge the forge bridge could not give waits for no build and names what it lost (issue 1966: it was never said).
+	if held := sampleTakeIns(since)[0]; true {
+		held.WaitsFor, held.Lost = "", []string{PendingKey(12)}
+		if _, err := EncodeTakeIn(held); err != nil {
+			t.Errorf("a lost hold is refused: %v", err)
+		}
+	}
 	// indexer_pending's answer reads back; a wait of neither kind is refused.
 	pa := PendingAnswer{Waits: []PendingWait{{Key: PendingKey(12), What: TakeInRevision, Merges: sampleTakeIns(since)[0].Merges,
 		Keys: []string{PendingKey(12)}, WaitsFor: "src2:abc", Since: since, Holds: []string{"mesh-delivery-indexer"}, Said: "take-in.pending." + PendingKey(12), SaidAt: since}}}