dbt-materialize: more gracefully handle contracts on unknown types

Backport dbt-labs/dbt-core#8887 to make data contracts work correctly
with custom PostgreSQL types that are unknown to dbt/psycopg2. The error
messages are bad when contract validation on such types fails, but the
contracts fundamentally work, which is a big improvement.

See comments within the patch for details.

misc/dbt-materialize/CHANGELOG.md

@@ -1,5 +1,10 @@
 # dbt-materialize Changelog
 
+## Unreleased
+
+* Backport [dbt-core #8887](https://github.com/dbt-labs/dbt-core/pull/8887) to
+  unblock users using any custom type with data contracts.
+
 ## 1.7.1 - 2023-12-14
 
 * Remove the dependency of data contracts pre-flight checks on the existence of

misc/dbt-materialize/dbt/adapters/materialize/connections.py

@@ -18,6 +18,7 @@
 from typing import Optional
 
 import psycopg2
+from psycopg2.extensions import string_types
 from psycopg2.extras import register_uuid
 
 import dbt.adapters.postgres.connections
@@ -31,6 +32,12 @@
 
 logger = AdapterLogger("Materialize")
 
+# NOTE(morsapaes): registering the UUID type produces nicer error messages when
+# data contracts fail on a UUID type. See comment in the
+# `data_type_code_to_name` method for details. We may be able to remove this
+# when dbt-core#8900 lands.
+register_uuid()
+
 # Override the psycopg2 connect function in order to inject Materialize-specific
 # session parameter defaults.
 #
@@ -50,10 +57,6 @@ def connect(**kwargs):
     ]
     kwargs["options"] = " ".join(options)
 
-    # NOTE(morsapaes): work around dbt-core #8353 while #8900 doesn't land to
-    # unblock users using UUID types.
-    register_uuid()
-
     return _connect(**kwargs)
 
 
@@ -135,6 +138,40 @@ def cancel(self, connection):
             # probably bad, re-raise it
             raise
 
+    # NOTE(benesch): this is a backport, with modifications, of dbt-core#8887.
+    # TODO(benesch): consider removing this when v1.8 ships with this code.
+    @classmethod
+    def data_type_code_to_name(cls, type_code: int) -> str:
+        if type_code in string_types:
+            return string_types[type_code].name
+        else:
+            # The type is unknown to psycopg2, so make up a unique name based on
+            # the type's OID. Here are the consequences for data contracts that
+            # reference unknown types:
+            #
+            #   * Data contracts that are valid work flawlessly. Take the
+            #     `mz_timestamp` type, for example, which is unknown to psycopg2
+            #     because it is a special Materialize type. It has OID 16552. If
+            #     the data contract specifies a column of type `mz_timestamp`
+            #     and the model's column is actually of type `mz_timestamp`, the
+            #     contract will validate successfully and the user will have no
+            #     idea that under the hood dbt validated these two strings
+            #     against one another:
+            #
+            #         expected: `custom type unknown to dbt (OID 16552)`
+            #           actual: `custom type unknown to dbt (OID 16552)`
+            #
+            #   * Data contracts that are invalid produce an ugly error message.
+            #     If the contract specifies the `timestamp` type but the model's
+            #     column is actually of type `mz_timestamp`, dbt will complain
+            #     with an error message like "expected type DATETIME, got custom
+            #     type unknown to dbt (OID 16552)".
+            #
+            #     Still, this is much better than the built-in behavior with dbt
+            #     1.7, which is to raise "Unhandled error while executing:
+            #     16552". See dbt-core#8353 for details.
+            return f"custom type unknown to dbt (OID {type_code})"
+
     # Disable transactions. Materialize transactions do not support arbitrary
     # queries in transactions and therefore many of dbt's internal macros
     # produce invalid transactions.

misc/dbt-materialize/tests/adapter/test_contracts.py

@@ -0,0 +1,81 @@
+import pytest
+from dbt.tests.util import run_dbt, run_dbt_and_capture
+
+# NOTE(benesch): these tests are backported, with modifications, from
+# dbt-core#8887.
+
+# TODO(benesch): consider removing these tests when v1.8 ships with these tests
+# as part of core.
+
+my_timestamp_model_sql = """
+select
+  '2023-01-01T00:00:00'::timestamp as ts
+"""
+
+my_mz_timestamp_model_sql = """
+select
+  '1672531200000'::mz_timestamp as ts
+"""
+
+model_schema_timestamp_yml = """
+models:
+  - name: my_model
+    config:
+      contract:
+        enforced: true
+    columns:
+      - name: ts
+        data_type: timestamp
+"""
+
+model_schema_mz_timestamp_yml = """
+models:
+  - name: my_model
+    config:
+      contract:
+        enforced: true
+    columns:
+      - name: ts
+        data_type: mz_timestamp
+"""
+
+
+class TestModelContractUnrecognizedTypeCode1:
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "my_model.sql": my_mz_timestamp_model_sql,
+            "schema.yml": model_schema_mz_timestamp_yml,
+        }
+
+    def test_nonstandard_data_type(self, project):
+        run_dbt(["run"], expect_pass=True)
+
+
+class TestModelContractUnrecognizedTypeCodeActualMismatch:
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "my_model.sql": my_mz_timestamp_model_sql,
+            "schema.yml": model_schema_timestamp_yml,
+        }
+
+    def test_nonstandard_data_type(self, project):
+        expected_msg = "custom type unknown to dbt (OID 16552) | DATETIME      | data type mismatch"
+        _, logs = run_dbt_and_capture(["run"], expect_pass=False)
+        assert expected_msg in logs
+
+
+class TestModelContractUnrecognizedTypeCodeExpectedMismatch:
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "my_model.sql": my_timestamp_model_sql,
+            "schema.yml": model_schema_mz_timestamp_yml,
+        }
+
+    def test_nonstandard_data_type(self, project):
+        expected_msg = "DATETIME        | custom type unknown to dbt (OID 16552) | data type mismatch"
+        _, logs = run_dbt_and_capture(["run"], expect_pass=False)
+        print(logs)
+        assert expected_msg in logs