H9 test: entry-again takes a shadow's not-found entry in

Builds: design 47 G §698; lead answer A-319

Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h

internal/selfcompose/entries_test.go

@@ -5,8 +5,10 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"runtime"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -128,6 +130,32 @@ func composeFromEntries(t *testing.T) {
 	if !nf || nfOther {
 		t.Errorf("entry-not-found told %v for the ghost and %v for the entry held", nf, nfOther)
 	}
+	// An entry asked again by hand is asked again in the shadow's cache too (lead answer A-319): the shadow holds the ghost as not
+	// found, the half then holds it, and the node's own composer asked again takes it in on the shadow as well.
+	var late atomic.Bool
+	shadowEnv := b.env()
+	shadowEnv.Entry = EntryCall(func(ctx context.Context, seat, verb string, args any) (json.RawMessage, error) {
+		if in := args.(meshcatalog.EntryInput); in.Fingerprint == ghost && late.Load() {
+			return json.Marshal(meshcatalog.EntryAnswer{Entry: meshcatalog.CatalogEntry{Module: "ghost", Fp: ghost}})
+		}
+		return ask(ctx, seat, verb, args)
+	})
+	shadow := NewShadow(shadowEnv, nil)
+	shadow.c.entries.Need(ctx, ghost)
+	for deadline := time.Now().Add(10 * time.Second); shadow.c.entries.Rows() == nil || shadow.c.entries.Rows()[0].State != meshcatalogclient.EntryNotFound; {
+		if time.Now().After(deadline) {
+			t.Fatal("the shadow did not hold the ghost as not found")
+		}
+		runtime.Gosched()
+	}
+	late.Store(true)
+	c.AlsoEntryAgain = shadow.EntryAgain
+	if err := c.EntryAgain(ctx, ghost); err != nil {
+		t.Fatal(err)
+	}
+	if _, state := shadow.c.entries.Need(ctx, ghost); state != meshcatalogclient.EntryAnswered {
+		t.Errorf("the shadow holds the ghost's entry as %s after entry-again, want answered", state)
+	}
 	// Each entry and want it composes from is kept in the composition state before the composition that uses them.
 	state.mu.Lock()
 	_, hasEntry := state.kv[entryKey(fp)]