metrics show: allow falsey values (#4642)

* metrics show: allow falsey values

Fixes #4630

* metrics show: bug in logging to console. Fixes #4630

* repro: fix incorrect usage of _show_metrics

* fix formatting/styling

* metrics: add a simple func test

Co-authored-by: Ruslan Kuprieiev <[email protected]>

tests/func/metrics/test_show.py

@@ -160,3 +160,10 @@ def test_non_metric_and_recurisve_show(tmp_dir, dvc, run_copy_metrics):
             "metrics_t.yaml": {"foo": 1.1},
         }
     }
+
+
+def test_show_falsey(tmp_dir, dvc):
+    tmp_dir.gen("metrics.json", '{"foo": 0, "bar": 0.0, "baz": {}}')
+    assert dvc.metrics.show(targets=["metrics.json"]) == {
+        "": {"metrics.json": {"foo": 0, "bar": 0.0}}
+    }

tests/unit/command/test_metrics.py

@@ -1,7 +1,12 @@
 import textwrap
 
 from dvc.cli import parse_args
-from dvc.command.metrics import CmdMetricsDiff, CmdMetricsShow, _show_diff
+from dvc.command.metrics import (
+    CmdMetricsDiff,
+    CmdMetricsShow,
+    _show_diff,
+    _show_metrics,
+)
 
 
 def test_metrics_diff(dvc, mocker):
@@ -233,3 +238,17 @@ def test_metrics_diff_with_old():
         metrics.yaml  a.d.e     3      4      1
         metrics.yaml  x.b       5      6      1"""
     )
+
+
+def test_metrics_show_with_valid_falsey_values():
+    assert _show_metrics(
+        {"branch_1": {"metrics.json": {"a": 0, "b": {"ad": 0.0, "bc": 0.0}}}},
+        all_branches=True,
+    ) == textwrap.dedent(
+        """\
+        branch_1:
+        \tmetrics.json:
+        \t\ta: 0
+        \t\tb.ad: 0.0
+        \t\tb.bc: 0.0"""
+    )