when a custom domain is default and has random_prefix_generation enabled, use the random_prefix as the first choice

app/dashboard/views/custom_alias.py

@@ -52,20 +52,27 @@ def get_available_suffixes(user: User) -> [SuffixInfo]:
     # put custom domain first
     # for each user domain, generate both the domain and a random suffix version
     for custom_domain in user_custom_domains:
+        if custom_domain.random_prefix_generation:
+            suffix = "." + random_word() + "@" + custom_domain.domain
+            suffix_info = SuffixInfo(True, suffix, signer.sign(suffix).decode(), False)
+            if user.default_alias_custom_domain_id == custom_domain.id:
+                suffixes.insert(0, suffix_info)
+            else:
+                suffixes.append(suffix_info)
+
         suffix = "@" + custom_domain.domain
         suffix_info = SuffixInfo(True, suffix, signer.sign(suffix).decode(), False)
 
         # put the default domain to top
-        if user.default_alias_custom_domain_id == custom_domain.id:
+        # only if random_prefix_generation isn't enabled
+        if (
+            user.default_alias_custom_domain_id == custom_domain.id
+            and not custom_domain.random_prefix_generation
+        ):
             suffixes.insert(0, suffix_info)
         else:
             suffixes.append(suffix_info)
 
-        if custom_domain.random_prefix_generation:
-            suffix = "." + random_word() + "@" + custom_domain.domain
-            suffix_info = SuffixInfo(True, suffix, signer.sign(suffix).decode(), False)
-            suffixes.append(suffix_info)
-
     # then SimpleLogin domain
     for sl_domain in user.get_sl_domains():
         suffix = (

tests/dashboard/test_custom_alias.py

@@ -135,6 +135,27 @@ def test_available_suffixes_default_domain(flask_client):
     assert first_suffix.suffix == "@test.com"
 
 
+def test_available_suffixes_random_prefix_generation(flask_client):
+    user = login(flask_client)
+
+    CustomDomain.create(user_id=user.id, domain="test.com", verified=True, commit=True)
+    cd2 = CustomDomain.create(
+        user_id=user.id, domain="test2.com", verified=True, commit=True
+    )
+
+    user.default_alias_custom_domain_id = cd2.id
+
+    # first suffix is test2.com
+    first_suffix = get_available_suffixes(user)[0]
+    assert first_suffix.suffix == "@test2.com"
+
+    cd2.random_prefix_generation = True
+    # e.g. .meo@test2.com
+    first_suffix = get_available_suffixes(user)[0]
+    assert first_suffix.suffix.endswith("@test2.com")
+    assert first_suffix.suffix.startswith(".")
+
+
 def test_add_already_existed_alias(flask_client):
     user = login(flask_client)
     db.session.commit()