Fallback to default profile when profiles file is empty (#16119)

src/prefect/settings/sources.py

@@ -121,7 +121,7 @@ def _load_profile_settings(self) -> Dict[str, Any]:
         """Helper method to load the profile settings from the profiles.toml file"""
 
         if not self.profiles_path.exists():
-            return {}
+            return self._get_default_profile()
 
         try:
             all_profile_data = toml.load(self.profiles_path)
@@ -146,9 +146,16 @@ def _load_profile_settings(self) -> Dict[str, Any]:
         profiles_data = all_profile_data.get("profiles", {})
 
         if not active_profile or active_profile not in profiles_data:
-            return {}
+            return self._get_default_profile()
         return profiles_data[active_profile]
 
+    def _get_default_profile(self) -> Dict[str, Any]:
+        """Helper method to get the default profile"""
+        default_profile_data = toml.load(DEFAULT_PROFILES_PATH)
+        default_profile = default_profile_data.get("active", "ephemeral")
+        assert isinstance(default_profile, str)
+        return default_profile_data.get("profiles", {}).get(default_profile, {})
+
     def get_field_value(
         self, field: FieldInfo, field_name: str
     ) -> Tuple[Any, str, bool]:

tests/test_settings.py

@@ -694,6 +694,8 @@ def test_loads_when_profile_path_does_not_exist(self, monkeypatch):
         monkeypatch.delenv("PREFECT_TESTING_TEST_MODE", raising=False)
         monkeypatch.delenv("PREFECT_TESTING_UNIT_TEST_MODE", raising=False)
         assert Settings().testing.test_setting == "FOO"
+        # Should default to ephemeral profile
+        assert Settings().server.ephemeral.enabled
 
     def test_loads_when_profile_path_is_not_a_toml_file(self, monkeypatch, tmp_path):
         monkeypatch.setenv("PREFECT_PROFILES_PATH", str(tmp_path / "profiles.toml"))
@@ -1444,6 +1446,69 @@ def test_environment_variables_take_precedence_over_toml_settings(
         assert not Settings().server.ephemeral.enabled
         assert not PREFECT_SERVER_ALLOW_EPHEMERAL_MODE.value()
 
+    def test_handle_profile_settings_without_active_profile(
+        self, monkeypatch, tmp_path
+    ):
+        profiles_path = tmp_path / "profiles.toml"
+
+        monkeypatch.delenv("PREFECT_TESTING_TEST_MODE", raising=False)
+        monkeypatch.delenv("PREFECT_TESTING_UNIT_TEST_MODE", raising=False)
+        monkeypatch.setenv("PREFECT_PROFILES_PATH", str(profiles_path))
+
+        profiles_path.write_text(
+            textwrap.dedent(
+                """
+                """
+            )
+        )
+
+        # Should default to ephemeral profile
+        assert Settings().server.ephemeral.enabled
+
+    def test_handle_profile_settings_with_invalid_active_profile(
+        self, monkeypatch, tmp_path
+    ):
+        profiles_path = tmp_path / "profiles.toml"
+
+        monkeypatch.delenv("PREFECT_TESTING_TEST_MODE", raising=False)
+        monkeypatch.delenv("PREFECT_TESTING_UNIT_TEST_MODE", raising=False)
+        monkeypatch.setenv("PREFECT_PROFILES_PATH", str(profiles_path))
+
+        profiles_path.write_text(
+            textwrap.dedent(
+                """
+                active = "foo"
+
+                [profiles.bar]
+                PREFECT_LOGGING_LEVEL = "DEBUG"
+                """
+            )
+        )
+
+        # Should default to ephemeral profile
+        assert Settings().server.ephemeral.enabled
+        assert Settings().logging.level != "DEBUG"
+
+    def test_handle_profile_settings_with_missing_profile_data(
+        self, monkeypatch, tmp_path
+    ):
+        profiles_path = tmp_path / "profiles.toml"
+
+        monkeypatch.delenv("PREFECT_TESTING_TEST_MODE", raising=False)
+        monkeypatch.delenv("PREFECT_TESTING_UNIT_TEST_MODE", raising=False)
+        monkeypatch.setenv("PREFECT_PROFILES_PATH", str(profiles_path))
+
+        profiles_path.write_text(
+            textwrap.dedent(
+                """
+                active = "bar"
+                """
+            )
+        )
+
+        # Should default to ephemeral profile
+        assert Settings().server.ephemeral.enabled
+
 
 class TestLoadProfiles:
     @pytest.fixture(autouse=True)