fix: decode URL-encoded credentials in MongoDB connection config

.changeset/calm-doors-shine.md

@@ -0,0 +1,5 @@
+---
+'@powersync/lib-service-mongodb': patch
+---
+
+Fix authentication failure when MongoDB password contains URL-encoded characters.

libs/lib-mongodb/src/types/types.ts

@@ -129,8 +129,11 @@ export function normalizeMongoConfig(options: BaseMongoConfigDecoded): Normalize
   }
 
   const database = options.database ?? uri.pathname.split('/')[1] ?? '';
-  const username = options.username ?? uri.username;
-  const password = options.password ?? uri.password;
+  // ConnectionURI's username/password getters return URL-encoded values.
+  // Decode them so SCRAM auth uses the actual credentials, not the encoded form.
+  // Without this, passwords containing characters like '=', '@', '+' fail authentication.
+  const username = options.username ?? decodeURIComponent(uri.username);
+  const password = options.password ?? decodeURIComponent(uri.password);
 
   uri.password = '';
   uri.username = '';

libs/lib-mongodb/test/src/config.test.ts

@@ -57,6 +57,16 @@ describe('config', () => {
     expect(normalized.password).equals('pass');
   });
 
+  test('Should decode URL-encoded credentials', () => {
+    const uri = 'mongodb://user:pass%3Dword%40host@localhost:27017/powersync_test';
+    const normalized = normalizeMongoConfig({
+      type: 'mongodb',
+      uri
+    });
+    expect(normalized.username).equals('user');
+    expect(normalized.password).equals('pass=word@host');
+  });
+
   test('Should normalize a +srv URI', () => {
     const uri = 'mongodb+srv://user:pass@localhost/powersync_test';
     const normalized = normalizeMongoConfig({