fix: import metrics with extra (#15047)

* fix: import metrics with extra

* Fix test

superset/datasets/commands/importers/v1/utils.py

@@ -98,11 +98,12 @@ def import_dataset(
             except TypeError:
                 logger.info("Unable to encode `%s` field: %s", key, config[key])
     for metric in config.get("metrics", []):
-        if metric.get("extra"):
+        if metric.get("extra") is not None:
             try:
                 metric["extra"] = json.dumps(metric["extra"])
             except TypeError:
                 logger.info("Unable to encode `extra` field: %s", metric["extra"])
+                metric["extra"] = None
 
     # should we delete columns and metrics not present in the current import?
     sync = ["columns", "metrics"] if overwrite else []

tests/datasets/commands_tests.py

@@ -328,7 +328,7 @@ class TestImportDatasetsCommand(SupersetTestCase):
         assert metric.expression == "count(1)"
         assert metric.description is None
         assert metric.d3format is None
-        assert metric.extra is None
+        assert metric.extra == "{}"
         assert metric.warning_text is None
 
         assert len(dataset.columns) == 1

tests/fixtures/importexport.py

@@ -384,7 +384,7 @@ dataset_config: Dict[str, Any] = {
             "expression": "count(1)",
             "description": None,
             "d3format": None,
-            "extra": None,
+            "extra": {},
             "warning_text": None,
         },
     ],