metric: show: xpath should override xpath set after run

dvc/repo/metrics/show.py

@@ -190,7 +190,7 @@ def _collect_metrics(repo, path, recursive, typ, xpath, branch):
 
         if not typ and isinstance(o.metric, dict):
             t = o.metric.get(o.PARAM_METRIC_TYPE, typ)
-            x = o.metric.get(o.PARAM_METRIC_XPATH, xpath)
+            x = xpath or o.metric.get(o.PARAM_METRIC_XPATH)
         else:
             t = typ
             x = xpath

tests/func/test_metrics.py

@@ -831,3 +831,16 @@ class TestShouldDisplayMetricsEvenIfMetricIsMissing(object):
             in caplog.text
         )
         assert 0 == ret
+
+
+def test_show_xpath_should_override_stage_xpath(dvc_repo):
+    metric_file = "metric"
+    metric = {"m1": 0.1, "m2": 0.2}
+    with open(metric_file, "w") as fobj:
+        json.dump(metric, fobj)
+
+    dvc_repo.run(cmd="", overwrite=True, metrics=[metric_file])
+    dvc_repo.metrics.modify(metric_file, typ="json", xpath="m2")
+
+    result = dvc_repo.metrics.show(xpath="m1")
+    assert result == {"": {metric_file: [0.1]}}