Unify metrics behavior with dirs

dvc/command/run.py

@@ -133,16 +133,15 @@ def add_parser(subparsers, parent_parser):
         "--metrics",
         action="append",
         default=[],
-        help="Declare output metric file or directory.",
+        help="Declare output metric file.",
         metavar="<path>",
     )
     run_parser.add_argument(
         "-M",
         "--metrics-no-cache",
         action="append",
         default=[],
-        help="Declare output metric file or directory "
-        "(do not put into DVC cache).",
+        help="Declare output metric file (do not put into DVC cache).",
         metavar="<path>",
     )
     run_parser.add_argument(

dvc/output/base.py

@@ -246,10 +246,11 @@ def save(self):
 
         self.ignore()
 
+        if self.metric or self.plot:
+            self.verify_metric()
+
         if not self.use_cache:
             self.info = self.save_info()
-            if self.metric or self.plot:
-                self.verify_metric()
             if not self.IS_DEPENDENCY:
                 logger.debug(
                     "Output '%s' doesn't use cache. Skipping saving.", self

dvc/output/local.py

@@ -81,7 +81,7 @@ def verify_metric(self):
         name = "metrics" if self.metric else "plot"
         if os.path.isdir(path):
             msg = "directory '{}' cannot be used as {}."
-            raise DvcException(msg.format(self.path_info, name))
+            raise IsADirectoryError(msg.format(self.path_info, name))
 
         if not istextfile(path):
             msg = "binary file '{}' cannot be used as {}."

tests/func/test_run_single_stage.py

@@ -989,3 +989,31 @@ def test_should_raise_on_stage_output(tmp_dir, dvc, run_copy):
 
     with pytest.raises(OutputIsStageFileError):
         run_copy("foo", "name.dvc", single_stage=True)
+
+
+class TestRunDirMetrics:
+    @pytest.fixture(autouse=True)
+    def setup(self, dvc):
+        with open("script.py", "w+") as fobj:
+            fobj.write("import sys\n")
+            fobj.write("import os\n")
+            fobj.write("os.makedirs(sys.argv[1])\n")
+            fobj.write(
+                "with open(os.path.join(sys.argv[1], "
+                "'metrics.json'), 'a+') as fobj:\n"
+            )
+            fobj.write("    fobj.write('foo')\n")
+
+    def test_metrics_dir_cached(self, dvc):
+        with pytest.raises(IsADirectoryError):
+            dvc.run(
+                cmd="python script.py dir", metrics=["dir"], single_stage=True,
+            )
+
+    def test_metrics_dir_not_cached(self, dvc):
+        with pytest.raises(IsADirectoryError):
+            dvc.run(
+                cmd="python script.py dir",
+                metrics_no_cache=["dir"],
+                single_stage=True,
+            )