Support configuring model.config.freshness.build_after.update_on without period or count (#12027)

Author: MichelleArk

.changes/unreleased/Features-20250917-164941.yaml

@@ -0,0 +1,6 @@
+kind: Features
+body: Support configuring model.config.freshness.build_after.updates_on without period or count
+time: 2025-09-17T16:49:41.528385-04:00
+custom:
+    Author: michelleark
+    Issue: "12019"

core/dbt/artifacts/resources/v1/model.py

@@ -13,7 +13,11 @@
 from dbt_common.contracts.config.base import MergeBehavior
 from dbt_common.contracts.constraints import ModelLevelConstraint
 from dbt_common.contracts.util import Mergeable
-from dbt_common.dataclass_schema import ExtensibleDbtClassMixin, dbtClassMixin
+from dbt_common.dataclass_schema import (
+    ExtensibleDbtClassMixin,
+    ValidationError,
+    dbtClassMixin,
+)
 
 
 class ModelFreshnessUpdatesOnOptions(enum.Enum):
@@ -23,8 +27,8 @@ class ModelFreshnessUpdatesOnOptions(enum.Enum):
 
 @dataclass
 class ModelBuildAfter(ExtensibleDbtClassMixin):
-    count: int
-    period: TimePeriod
+    count: Optional[int] = None
+    period: Optional[TimePeriod] = None
     updates_on: ModelFreshnessUpdatesOnOptions = ModelFreshnessUpdatesOnOptions.any
 
 
@@ -75,6 +79,25 @@ class ModelConfig(NodeConfig):
     )
     freshness: Optional[ModelFreshness] = None
 
+    def __post_init__(self):
+        super().__post_init__()
+        if (
+            self.freshness
+            and self.freshness.build_after.period
+            and not self.freshness.build_after.count
+        ):
+            raise ValidationError(
+                "`freshness.build_after` must have a value for `count` if a `period` is provided"
+            )
+        elif (
+            self.freshness
+            and self.freshness.build_after.count
+            and not self.freshness.build_after.period
+        ):
+            raise ValidationError(
+                "`freshness.build_after` must have a value for `period` if a `count` is provided"
+            )
+
     @classmethod
     def __pre_deserialize__(cls, data):
         data = super().__pre_deserialize__(data)

tests/functional/model_config/test_freshness_config.py

@@ -1,6 +1,7 @@
 import pytest
 
 from dbt.tests.util import run_dbt
+from dbt_common.dataclass_schema import ValidationError
 
 # Seed data for source tables
 seeds__source_table_csv = """id,_loaded_at
@@ -77,6 +78,39 @@
 """
 
 
+models__model_freshness_schema_yml_build_after_only = """
+models:
+  - name: model_a
+    description: Model with only model freshness defined
+    config:
+      freshness:
+        build_after:
+          updates_on: all
+"""
+
+
+models__model_freshness_schema_yml_build_period_requires_count = """
+models:
+  - name: model_a
+    description: Model with only model freshness defined
+    config:
+      freshness:
+        build_after:
+          period: day
+"""
+
+
+models__model_freshness_schema_yml_build_count_requires_period = """
+models:
+  - name: model_a
+    description: Model with only model freshness defined
+    config:
+      freshness:
+        build_after:
+          count: 1
+"""
+
+
 class TestModelFreshnessConfig:
 
     @pytest.fixture(scope="class")
@@ -94,3 +128,49 @@ def test_model_freshness_configs(self, project):
         run_dbt(["parse"])
         compile_results = run_dbt(["compile"])
         assert len(compile_results) == 5  # All 4 models compiled successfully
+
+
+class TestModelFreshnessConfigParseBuildAfterOnly:
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "schema.yml": models__model_freshness_schema_yml_build_after_only,
+            "model_a.sql": models__no_freshness_sql,
+        }
+
+    def test_model_freshness_configs(self, project):
+        run_dbt(["parse"])
+
+
+class TestModelFreshnessConfigParseBuildPeriodRequiresCount:
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "schema.yml": models__model_freshness_schema_yml_build_period_requires_count,
+            "model_a.sql": models__no_freshness_sql,
+        }
+
+    def test_model_freshness_configs(self, project):
+        with pytest.raises(ValidationError) as excinfo:
+            run_dbt(["parse"])
+        expected_msg = (
+            "`freshness.build_after` must have a value for `count` if a `period` is provided"
+        )
+        assert expected_msg in str(excinfo.value)
+
+
+class TestModelFreshnessConfigParseBuildCountRequiresPeriod:
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "schema.yml": models__model_freshness_schema_yml_build_count_requires_period,
+            "model_a.sql": models__no_freshness_sql,
+        }
+
+    def test_model_freshness_configs(self, project):
+        with pytest.raises(ValidationError) as excinfo:
+            run_dbt(["parse"])
+        expected_msg = (
+            "`freshness.build_after` must have a value for `period` if a `count` is provided"
+        )
+        assert expected_msg in str(excinfo.value)