fix: warn on contract.enforced=true for materialized_view (#1279)

Upstream dbt doesn't support column-equivalence contracts on materialized
views (per https://docs.getdbt.com/docs/mesh/govern/model-contracts).
Previously dbt-databricks silently accepted the flag, letting yml/SQL
column drift go undetected. Now emit a user-visible warning pointing at
the dbt docs.

The change is strictly additive — a warning, not an error — so no
existing build's pass/fail outcome changes. Model-level constraint
behavior (#1343) is preserved; column-level NOT NULL enforcement on MVs
is preserved and covered by a new regression-guard test.

Co-authored-by: Isaac

Author: sd-db

CHANGELOG.md

@@ -1,3 +1,9 @@
+## dbt-databricks 1.11.8 (TBD)
+
+### Fixes
+
+- Warn when `contract.enforced: true` is set on a `materialized_view` model — contracts are not supported for this materialization per upstream dbt ([#1279](https://github.com/databricks/dbt-databricks/issues/1279))
+
 ## dbt-databricks 1.11.7 (Apr 17, 2026)
 
 ### Features

dbt/include/databricks/macros/relations/materialized_view/create.sql

@@ -22,8 +22,19 @@
 
   {%- set columns = adapter.get_columns_in_relation(temp_relation) -%}
   {%- set model_columns = model.get('columns', {}) -%}
+  {#
+    Contracts are not supported for materialized views (see
+    https://docs.getdbt.com/docs/mesh/govern/model-contracts). We still read
+    `contract.enforced` here because it gates whether model-level constraints
+    (PK/FK — informational-only on MVs) are emitted into the DDL. Column-level
+    constraints from `model_columns` (e.g. NOT NULL) flow through
+    unconditionally and ARE enforced by Databricks at runtime.
+  #}
   {%- set contract_config = config.get('contract') -%}
   {%- if contract_config and contract_config.enforced -%}
+    {%- do exceptions.warn(
+         "model '" ~ model.name ~ "' has contract.enforced=true but contracts are not supported for materialized_view — see https://docs.getdbt.com/docs/mesh/govern/model-contracts"
+       ) -%}
     {%- set model_constraints = model.get('constraints', []) -%}
   {%- else -%}
     {%- set model_constraints = [] -%}

tests/functional/adapter/materialized_view_tests/test_contract.py

@@ -0,0 +1,127 @@
+"""
+Tests for contract/constraint behavior on materialized_view models.
+
+Context: https://github.com/databricks/dbt-databricks/issues/1279
+
+Contracts (column-equivalence checks) are not supported for materialized views
+by design (see https://docs.getdbt.com/docs/mesh/govern/model-contracts).
+Before this fix, dbt-databricks silently accepted `contract.enforced: true` on
+MVs, letting yml/SQL drift go undetected. This test file verifies:
+
+1. Setting `contract.enforced: true` on an MV emits a user-visible warning.
+2. Column-level NOT NULL constraints on MVs ARE enforced by Databricks at
+   runtime (regression guard — the MV create macro's constraint plumbing
+   must not be removed).
+"""
+
+import pytest
+from dbt.tests import util
+
+
+MY_SEED = """
+id,value
+1,100
+2,200
+3,300
+""".strip()
+
+
+MV_CONTRACT_ENFORCED_SQL = """
+{{ config(materialized='materialized_view') }}
+select id, value from {{ ref('my_seed') }}
+"""
+
+MV_CONTRACT_ENFORCED_SCHEMA = """
+version: 2
+
+models:
+  - name: mv_contract_enforced
+    config:
+      contract:
+        enforced: true
+    columns:
+      - name: id
+        data_type: bigint
+      - name: value
+        data_type: bigint
+"""
+
+
+MV_NOT_NULL_SQL = """
+{{ config(materialized='materialized_view') }}
+select
+    case when id = 2 then cast(null as bigint) else id end as id,
+    value
+from {{ ref('my_seed') }}
+"""
+
+MV_NOT_NULL_SCHEMA = """
+version: 2
+
+models:
+  - name: mv_not_null
+    columns:
+      - name: id
+        data_type: bigint
+        constraints:
+          - type: not_null
+      - name: value
+        data_type: bigint
+"""
+
+
+@pytest.mark.dlt
+@pytest.mark.skip_profile("databricks_cluster", "databricks_uc_cluster")
+class TestMVContractEnforcedEmitsWarning:
+    """`contract.enforced: true` on a materialized_view should emit a warning
+    pointing at the dbt docs, since the column-equivalence contract is not
+    supported for this materialization."""
+
+    @pytest.fixture(scope="class")
+    def seeds(self):
+        return {"my_seed.csv": MY_SEED}
+
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "mv_contract_enforced.sql": MV_CONTRACT_ENFORCED_SQL,
+            "schema.yml": MV_CONTRACT_ENFORCED_SCHEMA,
+        }
+
+    def test_contract_enforced_warning(self, project):
+        util.run_dbt(["seed"])
+        _, log_output = util.run_dbt_and_capture(
+            ["run", "--select", "mv_contract_enforced"]
+        )
+        assert "contracts are not supported for materialized_view" in log_output.lower()
+        assert "docs.getdbt.com" in log_output.lower()
+
+
+@pytest.mark.dlt
+@pytest.mark.skip_profile("databricks_cluster", "databricks_uc_cluster")
+class TestMVColumnConstraintsAreEnforced:
+    """Column-level NOT NULL constraints on materialized views ARE enforced by
+    Databricks at runtime. Regression guard: the MV create macro's constraint
+    plumbing must not be stripped on the assumption that MV constraints are
+    informational-only (that's true only for model-level PK/FK)."""
+
+    @pytest.fixture(scope="class")
+    def seeds(self):
+        return {"my_seed.csv": MY_SEED}
+
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "mv_not_null.sql": MV_NOT_NULL_SQL,
+            "schema.yml": MV_NOT_NULL_SCHEMA,
+        }
+
+    def test_not_null_constraint_enforced_at_runtime(self, project):
+        util.run_dbt(["seed"])
+        results = util.run_dbt(
+            ["run", "--select", "mv_not_null"],
+            expect_pass=False,
+        )
+        assert len(results) == 1
+        assert results[0].status == "error"
+        assert "NOT_NULL_CONSTRAINT_VIOLATED" in str(results[0].message)