feat(nimbus): Use lax Gecko pref validation in FmlClient (#15091)

Beacuse:

- Fenix is adding support for settings prefs in Gecko;
- there was a now-invalid manifest published in v149;
- nimbus-cli now requires enforces stricter validation around gecko
prefs unless `--lax-gecko-pref-validation` is passed; and
- similarily, the `FmlClient` will perform the same validation unless
disabled via the loader config

this commit:

- updates application-services to the latest nightly;
- runs nimbus-cli with `--lax-gecko-pref-validation`; and
- updates our FmlClient to use lax Gecko pref validation as well.

Fixes #15073

Author: freshstrangemusic

application-services/application-services.env

@@ -1 +1 @@
-APPLICATION_SERVICES_BUILD_ID=151.20260328050234
+APPLICATION_SERVICES_BUILD_ID=151.20260330183750

experimenter/experimenter/features/manifests/nimbus_fml_loader.py

@@ -4,7 +4,7 @@
 from typing import Optional
 
 from django.conf import settings
-from nimbus_megazord.fml import FmlClient, FmlError
+from nimbus_megazord.fml import FmlClient, FmlError, FmlLoaderConfig
 
 from experimenter.experiments.constants import NimbusConstants
 from experimenter.experiments.models import NimbusFeatureVersion
@@ -66,9 +66,16 @@ def fml_client(self, version: Optional[NimbusFeatureVersion] = None) -> FmlClien
     @staticmethod
     def get_fml_client_uncached(file_path: Path, channel: str) -> FmlClient:
         try:
-            return FmlClient(
+            # TODO(15100): Remove lax gecko pref validation
+            return FmlClient.new_with_config(
                 str(file_path),
                 channel,
+                FmlLoaderConfig(
+                    cache=None,
+                    refs={},
+                    ref_files=[],
+                    lax_gecko_pref_validation=True,
+                ),
             )
         except FmlError:
             logger.exception(

experimenter/experimenter/features/tests/fixtures/fml/versioned_features/fenix/v119.0.0/release.fml.yaml

@@ -5,17 +5,6 @@ about:
 channels:
   - release
 features:
-  cookie-banners:
-    description: Features for cookie banner handling.
-    variables:
-      sections-enabled:
-        description: This property provides a lookup table of whether or not the given section should be enabled.
-        type: "Map<CookieBannersSection, Int>"
-        default:
-          dialog-re-engage-time: 4
-          feature-setting-value: 0
-          feature-setting-value-pbm: 0
-          feature-ui: 0
   extensions-process:
     description: A feature to rollout the extensions process.
     variables:

experimenter/experimenter/features/tests/test_nimbus_fml_loader.py

@@ -51,12 +51,8 @@ def test_intiate_new_fml_loader_app_and_channel_do_not_exist(self):
         self.assertIsNone(loader.application)
         self.assertIsNone(loader.channel)
 
-    @patch(
-        "nimbus_megazord.fml.FmlClient.__init__",
-    )
     @mock_fml_versioned_features
-    def test_create_fml_client(self, new_client):
-        new_client.return_value = None
+    def test_create_fml_client(self):
         application = "fenix"
         channel = "release"
         version = "119.0.0"
@@ -70,10 +66,10 @@ def test_create_fml_client(self, new_client):
             / f"{channel}.fml.yaml"
         )
 
-        client = loader.fml_client(version=version)
+        self.assertEqual(loader.file_path(version), expected_path)
+
+        client = loader.fml_client(version)
         self.assertIsNotNone(client)
-        new_client.assert_called()
-        new_client.assert_called_with(str(expected_path), channel)
 
     @mock_fml_features
     def test_get_local_file_path_no_version(self):
@@ -215,7 +211,7 @@ def test_return_no_errors_for_invalid_application(
             self.assertIn("Nimbus FML Loader: Invalid application", log.output[0])
 
     @patch(
-        "nimbus_megazord.fml.FmlClient.__init__",
+        "nimbus_megazord.fml.FmlClient.new_with_config",
         side_effect=FmlError("gecko-pref and default are mutually exclusive"),
     )
     @mock_fml_features
@@ -230,7 +226,7 @@ def test_fml_client_returns_none_when_manifest_fails_to_parse(self, _mock_client
             )
 
     @patch(
-        "nimbus_megazord.fml.FmlClient.__init__",
+        "nimbus_megazord.fml.FmlClient.new_with_config",
         side_effect=FmlError("gecko-pref and default are mutually exclusive"),
     )
     @mock_fml_features

experimenter/manifesttool/nimbus_cli.py

@@ -90,6 +90,7 @@ def download_single_file(
             "fml",
             "--",
             "single-file",
+            "--lax-gecko-pref-validation",
             "--channel",
             channel,
             *_repo_path_cli_args(app_config.repo, ref, fml_path),
@@ -110,6 +111,7 @@ def generate_experimenter_yaml(
             "fml",
             "--",
             "generate-experimenter",
+            "--lax-gecko-pref-validation",
             str(_get_fml_path(manifest_dir, app_config, channel, version)),
             str(_get_experimenter_yaml_path(manifest_dir, app_config, version)),
         ],

experimenter/manifesttool/tests/test_nimbus_cli.py

@@ -124,6 +124,7 @@ def test_download_single_file(self, repo_type, version, fml_path):
                     "fml",
                     "--",
                     "single-file",
+                    "--lax-gecko-pref-validation",
                     "--channel",
                     "channel",
                     *(
@@ -172,6 +173,7 @@ def test_generate_experimenter_yaml(
                     "fml",
                     "--",
                     "generate-experimenter",
+                    "--lax-gecko-pref-validation",
                     str(manifest_dir / fml_path),
                     str(manifest_dir / experimenter_yaml_path),
                 ],