refactor(metadata-protocol): move the object-extender fold out of protocol.ts into protocol-object-extender-fold.ts (#25467 cut 30)

packages/metadata-protocol/src/protocol-object-extender-fold.ts

@@ -0,0 +1,68 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#25467 cut 30] The object-extender fold, from
+ * `ObjectStackProtocolImplementation`, moved out of `protocol.ts` whole:
+ * `foldObjectExtendersFromRegistry`, which folds the registry's `extend`
+ * contributors onto an OBJECT body that came from the MetadataService, so the
+ * by-name read serves the object's resolved schema as the list read does
+ * (#7556).
+ *
+ * A MOVE, not a redesign. The function below is the body of the
+ * `ObjectStackProtocolImplementation` method of the same name as it stood,
+ * re-indented one level and otherwise unedited.
+ *
+ * ## How the moved body reaches the class
+ *
+ * The shape #23050 set for `rest-server.ts` (its `data-action-routes.ts`
+ * header carries the full reasoning), as `protocol-batch-data.ts` applies it.
+ * The class keeps the method — the published `dist/*.d.ts` lists its name,
+ * docblock and declared signature — and its body is one literal of exactly
+ * the {@link ObjectExtenderFoldHost} member it reads, plus a `.call`. The
+ * `engine` field is handed over as a getter, so the read finds it as it
+ * stands at call time. Every caller keeps calling the class method.
+ *
+ * What the body reads from elsewhere, it imports from where `protocol.ts`
+ * imports it. Nothing re-exports this module, so the published surface does
+ * not move.
+ */
+
+import { PLURAL_TO_SINGULAR } from '@objectstack/spec/shared';
+import type { ObjectStackProtocolImplementation } from './protocol.js';
+
+/**
+ * The `ObjectStackProtocolImplementation` member the function below reads —
+ * the only one; the function's `this` is the `Pick` of it. It is typed AS the
+ * class member (an indexed access on the class), so a change to its
+ * signature on the class is a change here too.
+ */
+export interface ObjectExtenderFoldHost {
+    readonly engine: ObjectStackProtocolImplementation['engine'];
+}
+
+/** The body of `ObjectStackProtocolImplementation#foldObjectExtendersFromRegistry`; the method's docblock there is its contract. */
+export function foldObjectExtendersFromRegistry(
+    this: Pick<ObjectExtenderFoldHost, 'engine'>,
+    type: string,
+    name: unknown,
+    body: unknown,
+): unknown {
+    const singular = PLURAL_TO_SINGULAR[type] ?? type;
+    if (singular !== 'object') return body;
+    if (body === null || typeof body !== 'object') return body;
+    // [#8027] The list caller reads the name off the ROW rather than off a
+    // request, and a row with no usable `name` has no contributor list to
+    // look up — `mergePackageAwareOverlay` skips such rows too.
+    if (typeof name !== 'string' || name === '') return body;
+    const registry = (this.engine as any)?.registry;
+    // Partial registry doubles in tests predate this method; a host that
+    // cannot fold answers exactly as it did before.
+    if (!registry || typeof registry.foldObjectExtendersOnto !== 'function') return body;
+    try {
+        return registry.foldObjectExtendersOnto(name, body);
+    } catch {
+        // The fold is a read over in-memory contributors; a failure here
+        // must not turn a served schema into a 5xx.
+        return body;
+    }
+}

packages/metadata-protocol/src/protocol.ts

@@ -423,6 +423,8 @@ import { flowRegistrationsOf, resolveFlowCanonicalizer, resolveFlowRegistrationR
 import { isDeclaredCodeDatasource, isHostCodeDatasource } from './protocol-code-datasource-predicates.js';
 // [#25467 cut 29] The legacy-organization row filters: which rows a not-yet-migrated database still holds.
 import { legacyOrganizationRowsOf, withoutLegacyOrganizationRows } from './protocol-legacy-organization-rows.js';
+// [#25467 cut 30] The object-extender fold onto a MetadataService object body.
+import { foldObjectExtendersFromRegistry } from './protocol-object-extender-fold.js';
 
 /**
  * Canonical Zod schema per metadata type lives in
@@ -8899,24 +8901,12 @@ export class ObjectStackProtocolImplementation implements
      * would duplicate both.
      */
     private foldObjectExtendersFromRegistry(type: string, name: unknown, body: unknown): unknown {
-        const singular = PLURAL_TO_SINGULAR[type] ?? type;
-        if (singular !== 'object') return body;
-        if (body === null || typeof body !== 'object') return body;
-        // [#8027] The list caller reads the name off the ROW rather than off a
-        // request, and a row with no usable `name` has no contributor list to
-        // look up — `mergePackageAwareOverlay` skips such rows too.
-        if (typeof name !== 'string' || name === '') return body;
-        const registry = (this.engine as any)?.registry;
-        // Partial registry doubles in tests predate this method; a host that
-        // cannot fold answers exactly as it did before.
-        if (!registry || typeof registry.foldObjectExtendersOnto !== 'function') return body;
-        try {
-            return registry.foldObjectExtendersOnto(name, body);
-        } catch {
-            // The fold is a read over in-memory contributors; a failure here
-            // must not turn a served schema into a 5xx.
-            return body;
-        }
+        // [#25467 cut 30] The body moved to `protocol-object-extender-fold.ts` (see `ObjectExtenderFoldHost`).
+        const readEngine = () => this.engine;
+        const host: ThisParameterType<typeof foldObjectExtendersFromRegistry> = {
+            get engine() { return readEngine(); },
+        };
+        return foldObjectExtendersFromRegistry.call(host, type, name, body);
     }
 
     /**