plot: check field exists (#3742)

dvc/repo/plot/template.py

@@ -24,6 +24,13 @@ class NoDataForTemplateError(DvcException):
         )
 
 
+class NoFieldInDataError(DvcException):
+    def __init__(self, field_name):
+        super().__init__(
+            "Field '{}' does not exist in provided data.".format(field_name)
+        )
+
+
 class Template:
     INDENT = 4
     SEPARATORS = (",", ": ")
@@ -91,6 +98,11 @@ class Template:
         with open(template_path, "r") as fobj:
             result_content = fobj.read()
 
+        if x_field:
+            Template._check_field_exists(data, x_field)
+        if y_field:
+            Template._check_field_exists(data, y_field)
+
         result_content = Template._replace_data_anchors(
             result_content, data, priority_datafile
         )
@@ -101,6 +113,14 @@ class Template:
 
         return result_content
 
+    @staticmethod
+    def _check_field_exists(data, field):
+        for file, data_points in data.items():
+            if not any(
+                field in data_point.keys() for data_point in data_points
+            ):
+                raise NoFieldInDataError(field)
+
     @staticmethod
     def _replace_metadata_anchors(
         result_content, title, x_field, x_title, y_field, y_title

tests/func/test_plot.py

@@ -18,6 +18,7 @@ from dvc.repo.plot.data import (
 from dvc.repo.plot.template import (
     TemplateNotFoundError,
     NoDataForTemplateError,
+    NoFieldInDataError,
 )
 from dvc.repo.plot import NoDataOrTemplateProvided
 
@@ -502,3 +503,15 @@ def test_plot_yaml(tmp_dir, scm, dvc):
         {"val": 2, PlotData.INDEX_FIELD: 0, "rev": "workspace"},
         {"val": 3, PlotData.INDEX_FIELD: 1, "rev": "workspace"},
     ]
+
+
+def test_raise_on_wrong_field(tmp_dir, scm, dvc):
+    metric = [{"val": 2}, {"val": 3}]
+    _write_json(tmp_dir, metric, "metric.json")
+    _run_with_metric(tmp_dir, "metric.json", "first run")
+
+    with pytest.raises(NoFieldInDataError):
+        dvc.plot("metric.json", x_field="no_val")
+
+    with pytest.raises(NoFieldInDataError):
+        dvc.plot("metric.json", y_field="no_val")