Post-review-fixes

src/snowflake/cli/api/project/schemas/entities/common.py

@@ -17,7 +17,7 @@
 from abc import ABC
 from typing import Generic, List, Optional, TypeVar, Union
 
-from pydantic import Field, PrivateAttr
+from pydantic import Field, PrivateAttr, field_validator
 from snowflake.cli.api.identifiers import FQN
 from snowflake.cli.api.project.schemas.identifier_model import Identifier
 from snowflake.cli.api.project.schemas.native_app.application import (
@@ -41,11 +41,20 @@ class MetaField(UpdatableModel):
         title="Actions that will be executed after the application object is created/upgraded",
         default=None,
     )
-    use_mixins: Optional[str | List[str]] = Field(
+    use_mixins: Optional[List[str]] = Field(
         title="Name of the mixin used to fill the entity fields",
         default=None,
     )
 
+    @field_validator("use_mixins", mode="before")
+    @classmethod
+    def ensure_use_mixins_is_a_list(
+        cls, mixins: Optional[str | List[str]]
+    ) -> Optional[List[str]]:
+        if isinstance(mixins, str):
+            return [mixins]
+        return mixins
+
 
 class DefaultsField(UpdatableModel):
     schema_: Optional[str] = Field(

src/snowflake/cli/api/project/schemas/project_definition.py

@@ -201,18 +201,23 @@ def apply_mixins(cls, data: Dict) -> Dict:
         """
         Applies mixins to those entities, whose meta field contains the mixin name.
         """
-        if "mixins" in data and "entities" in data:
-            for entity in data["entities"].values():
-                entity_mixins = entity_mixins_to_list(
-                    entity.get("meta", {}).get("use_mixins")
-                )
-                entity_fields = get_allowed_fields_for_entity(entity)
-                if entity_fields and entity_mixins:
-                    for mixin_name in entity_mixins:
-                        if mixin_name in data["mixins"]:
-                            for key, value in data["mixins"][mixin_name].items():
-                                if key in entity_fields:
-                                    entity[key] = value
+        if "mixins" not in data or "entities" not in data:
+            return data
+
+        for entity in data["entities"].values():
+            entity_mixins = entity_mixins_to_list(
+                entity.get("meta", {}).get("use_mixins")
+            )
+
+            entity_fields = get_allowed_fields_for_entity(entity)
+            if entity_fields and entity_mixins:
+                for mixin_name in entity_mixins:
+                    if mixin_name in data["mixins"]:
+                        for key, value in data["mixins"][mixin_name].items():
+                            if key in entity_fields:
+                                entity[key] = value
+                    else:
+                        raise ValueError(f"Mixin {mixin_name} not found in mixins")
         return data
 
     def get_entities_by_type(self, entity_type: str):

tests/project/test_project_definition_v2.py

@@ -385,6 +385,9 @@ def test_v1_to_v2_conversion(
             _assert_entities_are_equal(v1_function, v2_function)
 
 
+# TODO:
+# 1. rewrite projects to have one big definition covering all complex positive cases
+# 2. Add negative case - entity uses non-existent mixin
 @pytest.mark.parametrize(
     "project_name,stage1,stage2",
     [("mixins_basic", "foo", "bar"), ("mixins_defaults_hierarchy", "foo", "baz")],