fix(client): use connection db option as default database name (#223)

src/client.ts

@@ -7,6 +7,7 @@ import { assert } from "../deps.ts";
 
 export class MongoClient {
   #cluster?: Cluster;
+  #defaultDbName = "admin";
 
   async connect(
     options: ConnectOptions | string,
@@ -15,6 +16,8 @@ export class MongoClient {
       const parsedOptions = typeof options === "string"
         ? await parse(options)
         : options;
+
+      this.#defaultDbName = parsedOptions.db;
       const cluster = new Cluster(parsedOptions);
       await cluster.connect();
       await cluster.authenticate();
@@ -49,7 +52,7 @@ export class MongoClient {
     return await this.#cluster.protocol.commandSingle(db, body);
   }
 
-  database(name: string): Database {
+  database(name = this.#defaultDbName): Database {
     assert(this.#cluster);
     return new Database(this.#cluster, name);
   }

tests/cases/02_connect.ts

@@ -1,4 +1,4 @@
-import { assert } from "../test.deps.ts";
+import { assert, assertEquals } from "../test.deps.ts";
 import { MongoClient } from "../../src/client.ts";
 
 const hostname = "127.0.0.1";
@@ -13,7 +13,7 @@ export default function connectTests() {
     client.close();
   });
 
-  Deno.test("testconnect With Options", async () => {
+  Deno.test("test connect With Options", async () => {
     const client = new MongoClient();
     await client.connect({
       servers: [{ host: hostname, port: 27017 }],
@@ -24,4 +24,12 @@ export default function connectTests() {
     assert(names.length > 0);
     client.close();
   });
+
+  Deno.test("test default database name from connection options", async () => {
+    const client = new MongoClient();
+    await client.connect(`mongodb://${hostname}:27017/my-db`);
+    const db = client.database();
+    assertEquals(db.name, "my-db");
+    client.close();
+  });
 }