SEP-1319: Decouple Request Payloads, Remove passthrough iteration, Typecheck fixes (#1086)

src/shared/metadataUtils.ts

@@ -10,18 +10,15 @@ import { BaseMetadata } from '../types.js';
  * For other objects: title → name
  * This implements the spec requirement: "if no title is provided, name should be used for display purposes"
  */
-export function getDisplayName(metadata: BaseMetadata): string {
+export function getDisplayName(metadata: BaseMetadata & { annotations?: { title?: string } }): string {
     // First check for title (not undefined and not empty string)
     if (metadata.title !== undefined && metadata.title !== '') {
         return metadata.title;
     }
 
     // Then check for annotations.title (only present in Tool objects)
-    if ('annotations' in metadata) {
-        const metadataWithAnnotations = metadata as BaseMetadata & { annotations?: { title?: string } };
-        if (metadataWithAnnotations.annotations?.title) {
-            return metadataWithAnnotations.annotations.title;
-        }
+    if (metadata.annotations?.title) {
+        return metadata.annotations.title;
     }
 
     // Finally fall back to name

src/shared/protocol.test.ts

@@ -666,11 +666,13 @@ describe('mergeCapabilities', () => {
 
         const additional: ClientCapabilities = {
             experimental: {
-                feature: true
+                feature: {
+                    featureFlag: true
+                }
             },
             elicitation: {},
             roots: {
-                newProp: true
+                listChanged: true
             }
         };
 
@@ -679,11 +681,12 @@ describe('mergeCapabilities', () => {
             sampling: {},
             elicitation: {},
             roots: {
-                listChanged: true,
-                newProp: true
+                listChanged: true
             },
             experimental: {
-                feature: true
+                feature: {
+                    featureFlag: true
+                }
             }
         });
     });
@@ -701,7 +704,7 @@ describe('mergeCapabilities', () => {
                 subscribe: true
             },
             prompts: {
-                newProp: true
+                listChanged: true
             }
         };
 
@@ -709,8 +712,7 @@ describe('mergeCapabilities', () => {
         expect(merged).toEqual({
             logging: {},
             prompts: {
-                listChanged: true,
-                newProp: true
+                listChanged: true
             },
             resources: {
                 subscribe: true

src/shared/protocol.ts

@@ -693,16 +693,24 @@ export abstract class Protocol<SendRequestT extends Request, SendNotificationT e
     }
 }
 
-export function mergeCapabilities<T extends ServerCapabilities | ClientCapabilities>(base: T, additional: T): T {
-    return Object.entries(additional).reduce(
-        (acc, [key, value]) => {
-            if (value && typeof value === 'object') {
-                acc[key] = acc[key] ? { ...acc[key], ...value } : value;
-            } else {
-                acc[key] = value;
-            }
-            return acc;
-        },
-        { ...base }
-    );
+function isPlainObject(value: unknown): value is Record<string, unknown> {
+    return value !== null && typeof value === 'object' && !Array.isArray(value);
+}
+
+export function mergeCapabilities(base: ServerCapabilities, additional: Partial<ServerCapabilities>): ServerCapabilities;
+export function mergeCapabilities(base: ClientCapabilities, additional: Partial<ClientCapabilities>): ClientCapabilities;
+export function mergeCapabilities<T extends ServerCapabilities | ClientCapabilities>(base: T, additional: Partial<T>): T {
+    const result: T = { ...base };
+    for (const key in additional) {
+        const k = key as keyof T;
+        const addValue = additional[k];
+        if (addValue === undefined) continue;
+        const baseValue = result[k];
+        if (isPlainObject(baseValue) && isPlainObject(addValue)) {
+            result[k] = { ...(baseValue as Record<string, unknown>), ...(addValue as Record<string, unknown>) } as T[typeof k];
+        } else {
+            result[k] = addValue as T[typeof k];
+        }
+    }
+    return result;
 }

src/shared/transport.ts

@@ -71,7 +71,7 @@ export interface Transport {
      *
      * The requestInfo can be used to get the original request information (headers, etc.)
      */
-    onmessage?: (message: JSONRPCMessage, extra?: MessageExtraInfo) => void;
+    onmessage?: <T extends JSONRPCMessage>(message: T, extra?: MessageExtraInfo) => void;
 
     /**
      * The session ID generated for this connection.