add tests and an error to make sure schema update are safe

core/dbt/artifacts/schemas/manifest/v12/manifest.py

@@ -180,3 +180,13 @@ def upgrade_schema_version(cls, data):
         if manifest_schema_version < cls.dbt_schema_version.version:
             data = upgrade_manifest_json(data, manifest_schema_version)
         return cls.from_dict(data)
+
+    @classmethod
+    def validate(cls, _):
+        # When dbt try to load an artifact with additional optional fields
+        # that are not present in the schema, from_dict will work fine.
+        # As long as validate is not called, the schema will not be enforced.
+        # This is intentional, as it allows for safer schema upgrades.
+        raise RuntimeError(
+            "The WritableManifest should never be validated directly to allow for schema upgrades."
+        )

tests/functional/artifacts/test_artifacts.py

@@ -663,6 +663,22 @@ def test_run_and_generate(self, project, manifest_schema_path, run_results_schem
             > 0
         )
 
+    # Test artifact with additional fields load fine
+    def test_load_artifact(self, project, manifest_schema_path, run_results_schema_path):
+        catcher = EventCatcher(ArtifactWritten)
+        results = run_dbt(args=["compile"], callbacks=[catcher.catch])
+        assert len(results) == 7
+        manifest_dct = get_artifact(os.path.join(project.project_root, "target", "manifest.json"))
+        # add a field that is not in the schema
+        for _, node in manifest_dct["nodes"].items():
+            node["something_else"] = "something_else"
+        # load the manifest with the additional field
+        loaded_manifest = WritableManifest.from_dict(manifest_dct)
+
+        # successfully loaded the manifest with the additional field, but the field should not be present
+        for _, node in loaded_manifest.nodes.items():
+            assert not hasattr(node, "something_else")
+
 
 class TestVerifyArtifactsReferences(BaseVerifyProject):
     @pytest.fixture(scope="class")

tests/unit/contracts/graph/test_nodes.py

@@ -236,10 +236,12 @@ def test_basic_compiled_model(basic_compiled_dict, basic_compiled_model):
     assert node.is_ephemeral is False
 
 
-def test_invalid_extra_fields_model(minimal_uncompiled_dict):
-    bad_extra = minimal_uncompiled_dict
-    bad_extra["notvalid"] = "nope"
-    assert_fails_validation(bad_extra, ModelNode)
+def test_extra_fields_model_okay(minimal_uncompiled_dict):
+    extra = minimal_uncompiled_dict
+    extra["notvalid"] = "nope"
+    # Model still load fine with extra fields
+    loaded_model = ModelNode.from_dict(extra)
+    assert not hasattr(loaded_model, "notvalid")
 
 
 def test_invalid_bad_type_model(minimal_uncompiled_dict):

tests/unit/contracts/graph/test_nodes_parsed.py

@@ -1961,6 +1961,14 @@ def test_basic_source_definition(
     pickle.loads(pickle.dumps(node))
 
 
+def test_extra_fields_source_definition_okay(minimum_parsed_source_definition_dict):
+    extra = minimum_parsed_source_definition_dict
+    extra["notvalid"] = "nope"
+    # Model still load fine with extra fields
+    loaded_source = SourceDefinition.from_dict(extra)
+    assert not hasattr(loaded_source, "notvalid")
+
+
 def test_invalid_missing(minimum_parsed_source_definition_dict):
     bad_missing_name = minimum_parsed_source_definition_dict
     del bad_missing_name["name"]