chore: add npm run repl with a connected client

package.json

@@ -19,6 +19,7 @@
     "lint:changed": "node scripts/lint-changed.mjs",
     "test": "npm run cleanup && npm run test --workspaces --if-present",
     "build": "tsc --build",
+    "repl": "node scripts/repl.mjs",
     "check:command-jsdoc": "tsx scripts/check-command-jsdoc.ts",
     "documentation": "typedoc --entryPointStrategy packages --entryPoints ./packages/client ./packages/bloom ./packages/json ./packages/search ./packages/time-series ./packages/entraid ./packages/redis --out ./documentation",
     "gh-pages": "gh-pages -d ./documentation -e ./documentation -u 'documentation-bot <documentation@bot>'",

scripts/repl.mjs

@@ -0,0 +1,39 @@
+// Opens a Node REPL with a connected `client` in scope.
+// Uses the built packages, so run `npm run build` after source changes.
+// Target another server with `npm run repl -- --host <host> --port <port>`
+// (either flag alone is fine) or with REDIS_URL. Flags win over REDIS_URL.
+import repl from 'node:repl';
+import { parseArgs } from 'node:util';
+import { createClient } from 'redis';
+
+const { values: { host, port } } = parseArgs({
+  options: {
+    host: { type: 'string', short: 'h' },
+    port: { type: 'string', short: 'p' }
+  }
+});
+
+const url = host || port
+  ? `redis://${host ?? 'localhost'}:${port ?? 6379}`
+  : process.env.REDIS_URL ?? 'redis://localhost:6379';
+const client = createClient({ url });
+// Connection errors such as ECONNREFUSED carry the reason in `code`, not `message`.
+const reason = err => err.code ?? err.message;
+
+// Exit if the first connect fails; after that, keep the default reconnects.
+const onConnectError = err => {
+  console.error(`Could not connect to ${url}: ${reason(err)}`);
+  process.exit(1);
+};
+client.once('error', onConnectError);
+await client.connect();
+client.off('error', onConnectError);
+client.on('error', err => console.error('Redis client error:', reason(err)));
+console.log(`Connected to ${url}. Use \`client\`, e.g. await client.ping()`);
+
+const server = repl.start('redis> ');
+server.context.client = client;
+server.on('exit', async () => {
+  client.destroy();
+  process.exit();
+});