RR-1: the reader refuses a callers entry that is no form of the format

An entry is operator, healers, persons, sessions, invokers, seat:<seat>, module:<module> or holder:<seat>@same-node;
a bare name or one of the earlier classes (holder, invokes, reviewers) is refused naming the entry.

Builds: design 47 G §336, §392, §409

Claude-Session: https://claude.ai/code/session_01JG73KEq4zoDfM9WtYpcQgZ

go/seatdef/callers.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"strings"
 )
 
 // Callers says who may call a verb or send an accepted kind. It is read as text (the form every definition on main
@@ -53,13 +54,53 @@ func checkCallers(where string, c *Callers) Problems {
 	}
 	var ps Problems
 	for i, e := range c.List {
-		if e == "" {
-			ps = append(ps, Problem{fmt.Sprintf("%s[%d]", where, i), "is empty"})
+		if why := CallerEntryProblem(e); why != "" {
+			ps = append(ps, Problem{fmt.Sprintf("%s[%d]", where, i), why})
 		}
 	}
 	return ps
 }
 
+// The entries of a list of callers that are not a name (design 47 G §336).
+const (
+	CallerOperator = "operator"
+	CallerHealers  = "healers"
+	CallerPersons  = "persons"
+	CallerSessions = "sessions"
+	CallerInvokers = "invokers"
+)
+
+// The prefixes of the entries that name a seat's holder or a module (design 47 G §392, §336).
+const (
+	CallerSeatPrefix   = "seat:"
+	CallerModulePrefix = "module:"
+	CallerHolderPrefix = "holder:"
+	CallerSameNode     = "@same-node"
+)
+
+// CallerEntryProblem says why an entry of a list of callers is none of the forms of design 47 G §336, §392; empty
+// when it is one: `operator`, `healers`, `persons`, `sessions`, `invokers`, `seat:<seat>`, `module:<module>` and
+// `holder:<seat>@same-node`. A bare name is refused, since a name such as `mesh-grants` is both a seat and a module.
+func CallerEntryProblem(e string) string {
+	switch e {
+	case CallerOperator, CallerHealers, CallerPersons, CallerSessions, CallerInvokers:
+		return ""
+	}
+	if n, ok := strings.CutPrefix(e, CallerSeatPrefix); ok && wordName.MatchString(n) {
+		return ""
+	}
+	if n, ok := strings.CutPrefix(e, CallerModulePrefix); ok && wordName.MatchString(n) {
+		return ""
+	}
+	if n, ok := strings.CutPrefix(e, CallerHolderPrefix); ok {
+		if seat, ok := strings.CutSuffix(n, CallerSameNode); ok && wordName.MatchString(seat) {
+			return ""
+		}
+	}
+	return fmt.Sprintf("%q is none of operator, healers, persons, sessions, invokers, seat:<seat>, module:<module> and "+
+		"holder:<seat>@same-node", e)
+}
+
 // The classes of a verb (design 47 G §391).
 const (
 	ClassRead    = "read"

go/seatdef/seatdef_test.go

@@ -118,7 +118,12 @@ func TestADefinitionIsReadStrictlyNamingWhatIsWrong(t *testing.T) {
 		{"callers as text", strings.Replace(whole, `"name":"list",`, `"name":"list","callers":"a person",`, 1), ""},
 		{"callers as a list", strings.Replace(whole, `"name":"list",`, `"name":"list","callers":["operator","seat:mesh-grants","invokers"],"class":"read",`, 1), ""},
 		{"callers as neither", strings.Replace(whole, `"name":"list",`, `"name":"list","callers":7,`, 1), "callers is a text or a list"},
-		{"a list with an empty entry", strings.Replace(whole, `"name":"list",`, `"name":"list","callers":["operator",""],`, 1), "verbs[0].callers[1]: is empty"},
+		{"a list with an empty entry", strings.Replace(whole, `"name":"list",`, `"name":"list","callers":["operator",""],`, 1), "verbs[0].callers[1]"},
+		{"a bare name among callers", strings.Replace(whole, `"name":"list",`, `"name":"list","callers":["mesh-grants"],`, 1), `"mesh-grants" is none of operator`},
+		{"a class of the old branches", strings.Replace(whole, `"name":"list",`, `"name":"list","callers":["holder","invokes","reviewers"],`, 1), `"holder" is none of operator`},
+		{"every form among callers", strings.Replace(whole, `"name":"list",`,
+			`"name":"list","callers":["operator","healers","persons","sessions","invokers","seat:mesh-grants","module:mesh-grants","holder:node-backup@same-node"],`, 1), ""},
+		{"a holder not on the same node", strings.Replace(whole, `"name":"list",`, `"name":"list","callers":["holder:node-backup"],`, 1), "none of operator"},
 		{"a class that is none", strings.Replace(whole, `"name":"list",`, `"name":"list","class":"free",`, 1), `verbs[0].class: "free" is not a class (read, act, warrant)`},
 		{"an accepted kind's callers", strings.Replace(whole, `"events":`, `"accepts":[{"name":"step","body":{},"callers":["seat:mesh-pipeline-runner"]}],"events":`, 1), ""},
 		{"an event's callers", strings.Replace(whole, `"name":"created"`, `"name":"created","callers":["operator"]`, 1), "only an accepted kind carries callers"},