book/02-website-module.md

@@ -566,6 +566,14 @@ That paragraph exists because the kit's acceptance run
 ([`kit-acceptance.md`][acceptance]) built a module by following this chapter to the
 letter, and its page rendered outside the site. Everything else it wrote was right.
 
+**And check a component's prop names against [§3.4][api] rather than guessing
+them.** `PageHeader` takes `eyebrow`, `title`, `lead` and `center` — a page that
+passes `subtitle` renders its heading and nothing under it, because an unknown
+prop on a React component is silently dropped. Nothing warns, in the console or
+anywhere else; the page simply looks emptier than every core page around it. This
+template shipped exactly that mistake until a run of it against a real core was
+looked at, which is the only way that class of thing is ever found.
+
 **It is curated and closed, not a re-export of core's component library.** Adding
 to it is a minor version bump, and so is adding an optional prop to a member;
 changing an existing prop is a major one.

template/client/src/routes/public/Clan.jsx

@@ -47,7 +47,7 @@ export default function Clan() {
         <>
           <PageHeader
             title={data.name}
-            subtitle={`${data.memberCount} members${data.abbr ? ` · ${data.abbr}` : ''}`}
+            lead={`${data.memberCount} members${data.abbr ? ` · ${data.abbr}` : ''}`}
           />
 
           {/* Core's per-Team notification control lands here — ABOVE the roster,

template/client/src/routes/public/Clans.jsx

@@ -18,7 +18,7 @@ export default function Clans() {
 
   return (
     <PublicLayout shell="narrow">
-      <PageHeader title="Clans" subtitle="The companies, orders and warbands of the world" />
+      <PageHeader title="Clans" lead="The companies, orders and warbands of the world" />
 
       {loading && <Loading />}
       {error && <ErrorState error={error} />}
@@ -34,7 +34,9 @@ export default function Clans() {
               <Link to={`/examplegame/clans/${clan.externalId}`}>
                 {clan.name}{clan.abbr ? ` [${clan.abbr}]` : ''}
               </Link>
-              <span style={{ opacity: 0.7 }}> — {clan.memberCount} members</span>
+              <span style={{ opacity: 0.7 }}>
+                {' '}— {clan.memberCount} member{clan.memberCount === 1 ? '' : 's'}
+              </span>
             </li>
           ))}
         </ul>

template/client/src/routes/public/WorldStatus.jsx

@@ -48,7 +48,12 @@ export default function WorldStatus() {
     <PublicLayout shell="narrow">
       <PageHeader
         title="World status"
-        subtitle="What the game server last told us about itself"
+        // `lead`, not `subtitle`. PageHeader takes `eyebrow`, `title`, `lead` and
+        // `center`, and an unknown prop on a React component is silently dropped —
+        // so a page written with `subtitle` renders its title and nothing else, on
+        // a site where every core page has a line under its heading. Nothing warns.
+        // Found by installing this template into a real core and looking at it.
+        lead="What the game server last told us about itself"
       />
 
       {loading && <Loading />}