1823aae891Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com> Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com> Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
90 lines
3.9 KiB
TypeScript
90 lines
3.9 KiB
TypeScript
/**
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* Drives the `subscriptions/listen` server (`./server.ts`) two ways on a
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* 2026-07-28 connection:
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*
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* 1. **auto-open via `ClientOptions.listChanged`** — the same option a
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* 2025-era client sets; on a modern connection the SDK auto-opens a
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* listen stream with the filter derived from which sub-options were set,
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* so the configured `onChanged` handlers fire on every published change;
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* 2. **manual `client.listen()`** — opens a stream explicitly, registers a
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* `notifications/tools/list_changed` handler the stream feeds, and closes
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* after a few notifications.
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*
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* The example calls `flip_tools` to mutate the server's tool set on demand
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* (rather than a timer), then asserts the change notification arrived.
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*/
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import { check, parseExampleArgs, siblingPath } from '@mcp-examples/shared';
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import type { ClientOptions, McpSubscription } from '@modelcontextprotocol/client';
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import { Client, StreamableHTTPClientTransport } from '@modelcontextprotocol/client';
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import { StdioClientTransport } from '@modelcontextprotocol/client/stdio';
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/** Wait until `pred()` is true or `timeoutMs` elapses. */
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async function until(pred: () => boolean, timeoutMs = 5000): Promise<void> {
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const deadline = Date.now() + timeoutMs;
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while (!pred()) {
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if (Date.now() > deadline) throw new Error('timed out waiting for change notification');
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await new Promise(r => setTimeout(r, 25));
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}
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}
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const { transport, url } = parseExampleArgs();
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// Both legs connect identically and differ only in ClientOptions; the local
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// helper keeps the SDK transport setup visible in THIS file (the canonical
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// shape) while avoiding duplicating it for each leg. Modern-only —
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// `subscriptions/listen` is a 2026-07-28 protocol feature.
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const connect = async (options?: ClientOptions): Promise<Client> => {
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const client = new Client(
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{ name: 'subscriptions-example-client', version: '1.0.0' },
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{ versionNegotiation: { mode: 'auto' }, ...options }
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);
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await (transport === 'stdio'
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? client.connect(new StdioClientTransport({ command: 'npx', args: ['-y', 'tsx', siblingPath(import.meta.url, 'server.ts')] }))
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: client.connect(new StreamableHTTPClientTransport(new URL(url))));
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return client;
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};
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// --- auto-open via ClientOptions.listChanged ---
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{
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let count = 0;
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const client = await connect({
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listChanged: {
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tools: {
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autoRefresh: false,
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// The default debounce coalesces bursts; this example asserts
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// raw delivery, so disable it.
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debounceMs: 0,
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onChanged: () => void count++
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}
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}
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});
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check.ok(client.autoOpenedSubscription, 'a listChanged option should auto-open a subscription on a modern connection');
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check.ok(client.autoOpenedSubscription?.honoredFilter.toolsListChanged, 'auto-opened filter should include toolsListChanged');
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await client.callTool({ name: 'flip_tools' });
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await until(() => count >= 1);
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await client.callTool({ name: 'flip_tools' });
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await until(() => count >= 2);
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await client.autoOpenedSubscription?.close();
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await client.close();
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check.ok(count >= 2, 'auto-open leg should receive at least two tools/list_changed');
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}
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// --- manual client.listen() ---
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{
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const client = await connect();
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let count = 0;
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client.setNotificationHandler('notifications/tools/list_changed', () => void count++);
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const sub: McpSubscription = await client.listen({ toolsListChanged: true });
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check.ok(sub.honoredFilter.toolsListChanged, 'manual listen should honor toolsListChanged');
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await client.callTool({ name: 'flip_tools' });
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await until(() => count >= 1);
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await client.callTool({ name: 'flip_tools' });
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await until(() => count >= 2);
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await sub.close();
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await client.close();
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check.ok(count >= 2, 'manual leg should receive at least two tools/list_changed');
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}
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