A checker that hands no seat digests gets the heads' definitions with only each seat's own description (issue 1921, milestone 47/G, review round 2)

G's own check is made by the running B0 checker, which hands no digests, so the
program answers every head definition: 342 KB, over the 256 KiB a run's answer may
be. Without digests the descriptions of verbs, events and their schemas are left
out (171 KB for the group's heads); neither the manifest validator nor the composer
reads one, and the validator's verdicts over the group are the same either way.

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

modules/mesh-delivery-checker/cmd/mesh-checking-program/main_test.go

@@ -14,6 +14,7 @@ import (
 
 	"git.novox.be/novox/mesh-delivery/contracts/go/clients/meshdeliverycheckerclient"
 	"git.novox.be/novox/mesh-delivery/sdk/buildstep"
+	"git.novox.be/novox/mesh-sdk/go/seatdef"
 )
 
 // 1921 (B0, D2): the checking program answers, on its last line, the verdict the rules give the facts in its input, and
@@ -146,7 +147,8 @@ func TestTheCheckingProgramAnswersTheVerdictOfItsFacts(t *testing.T) {
 	t.Run("heads carrying every definition the reader holds unchanged answer none of them, within the bound", func(t *testing.T) {
 		real := under{prefix: "novox/mesh-delivery", fs: os.DirFS("../../../..")}
 		group := rules.Facts{V: rules.FactsVersion, Members: []rules.Member{{Repository: "novox/mesh-delivery", Head: "h"}}}
-		whole, err := rules.SeatsOf(real, group)
+		// An empty list of digests answers every definition whole (a checker that hands its list's digests, holding none).
+		whole, err := rules.SeatsOf(real, rules.Facts{V: rules.FactsVersion, Members: group.Members, SeatDigests: map[string]string{}})
 		if err != nil || len(whole.Seats) < 10 {
 			t.Fatalf("the repository's own definitions: %d, %v", len(whole.Seats), err)
 		}
@@ -162,6 +164,34 @@ func TestTheCheckingProgramAnswersTheVerdictOfItsFacts(t *testing.T) {
 			t.Errorf("unchanged heads answer %d definitions (%d the same), %d bytes; want none, all %d the same, within %d: %v",
 				len(same.Seats), same.Same, len(answer), len(whole.Seats), buildstep.RunInputBound, err)
 		}
+		// Review round 2 of G: a checker from before G (B0's, which makes G's own check) hands no digests, and the answer
+		// then keeps each seat's own description only, so a group's whole list stays within the bound; each still parses.
+		b0, err := rules.SeatsOf(real, rules.Facts{V: rules.FactsVersion, Members: group.Members})
+		if err != nil || len(b0.Seats) != len(whole.Seats) {
+			t.Fatalf("B0-shaped facts: %d definitions, %v", len(b0.Seats), err)
+		}
+		for i, raw := range b0.Seats {
+			var own struct {
+				Description string `json:"description"`
+			}
+			_ = json.Unmarshal(whole.Seats[i], &own)
+			var d struct {
+				Description string            `json:"description"`
+				Verbs       []json.RawMessage `json:"verbs"`
+				Events      []json.RawMessage `json:"events"`
+			}
+			_ = json.Unmarshal(raw, &d)
+			inner := 0
+			for _, m := range append(d.Verbs, d.Events...) {
+				inner += strings.Count(string(m), `"description":"`)
+			}
+			if _, perr := seatdef.Parse(raw); inner > 0 || d.Description != own.Description || perr != nil {
+				t.Errorf("B0-shaped facts answer %s with %d inner descriptions, its own %q: %v; want only its own", raw[:min(len(raw), 80)], inner, d.Description, perr)
+			}
+		}
+		if answer, _ := json.Marshal(b0); len(answer) > buildstep.RunInputBound || len(answer) >= len(mustJSON(t, whole))*3/4 {
+			t.Errorf("B0-shaped facts answer %d bytes (whole %d), want within %d and far below the whole", len(answer), len(mustJSON(t, whole)), buildstep.RunInputBound)
+		}
 		// One definition the heads change is answered alone.
 		for seat := range group.SeatDigests {
 			group.SeatDigests[seat] = "changed"
@@ -214,3 +244,12 @@ func (u under) Open(name string) (fs.File, error) {
 	}
 	return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
 }
+
+func mustJSON(t *testing.T, v any) []byte {
+	t.Helper()
+	out, err := json.Marshal(v)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return out
+}