feat(ingest): handling for const in json schema (#9694)

Co-authored-by: Harshal Sheth <hsheth2@gmail.com>

metadata-ingestion/src/datahub/ingestion/extractor/json_schema_util.py

@@ -316,10 +316,12 @@ class JsonSchemaTranslator:
 
     @staticmethod
     def _get_description_from_any_schema(schema: Dict) -> str:
-        # we do a redundant `if description in schema` check to guard against the scenario that schema is not a dictionary
-        description = (
-            (schema.get("description") or "") if "description" in schema else ""
-        )
+        description = ""
+        if "description" in schema:
+            description = str(schema.get("description"))
+        elif "const" in schema:
+            schema_const = schema.get("const")
+            description = f"Const value: {schema_const}"
         if JsonSchemaTranslator._INJECT_DEFAULTS_INTO_DESCRIPTION:
             default = schema.get("default")
             if default is not None:

metadata-ingestion/tests/unit/schema/test_json_schema_util.py

@@ -725,6 +725,19 @@ def test_non_str_enums():
     assert fields[0].description == 'One of: "baz", 1, null'
 
 
+def test_const_description_pulled_correctly():
+    schema = {
+        "$id": "test",
+        "$schema": "http://json-schema.org/draft-07/schema#",
+        "properties": {"bar": {"type": "string", "const": "not_defined"}},
+    }
+
+    fields = list(JsonSchemaTranslator.get_fields_from_schema(schema))
+    expected_field_paths: List[str] = ["[version=2.0].[type=object].[type=string].bar"]
+    assert_field_paths_match(fields, expected_field_paths)
+    assert fields[0].description == "Const value: not_defined"
+
+
 def test_anyof_with_properties():
     # We expect the event / timestamp fields to be included in both branches of the anyOf.