Add "lpn" checking in _ListPlot

"lpn" is "list of points" checking on ListPlot[] and ListLinePlot[]

mathics/builtin/drawing/plot.py

@@ -291,6 +291,7 @@ class _ListPlot(Builtin, ABC):
             "an appropriate list of range specifications."
         ),
         "joind": "Value of option Joined -> `1` is not True or False.",
+        "lpn": "`1` is not a list of numbers or pairs of numbers.",
     }
 
     use_log_scale = False
@@ -300,6 +301,17 @@ def eval(self, points, evaluation: Evaluation, options: dict):
 
         class_name = self.__class__.__name__
 
+        if not isinstance(points, ListExpression):
+            evaluation.message(class_name, "lpn", points)
+            return
+
+        if not all(
+            not isinstance(point_pair, ListExpression) or len(point_pair.elements) == 2
+            for point_pair in points.elements
+        ):
+            evaluation.message(class_name, "lpn", points)
+            return
+
         # Scale point values down by Log 10. Tick mark values will be adjusted to be 10^n in GraphicsBox.
         if self.use_log_scale:
             points = ListExpression(

test/builtin/drawing/test_plot.py

@@ -3,13 +3,40 @@
 Unit tests from mathics.builtin.drawing.plot
 """
 
-import sys
-import time
-from test.helper import check_evaluation, evaluate
+from test.helper import check_evaluation
 
 import pytest
 
 
+def test__listplot():
+    """tests for module builtin.drawing.plot._ListPlot"""
+    for str_expr, msgs, str_expected, fail_msg in (
+        (
+            "ListPlot[5]",
+            ("5 is not a list of numbers or pairs of numbers.",),
+            "ListPlot[5]",
+            "ListPlot with invalid list of point",
+        ),
+        (
+            "ListLinePlot[{{}, {{1., 1.}}, {{1., 2.}}, {}}]",
+            (
+                "{{}, {{1., 1.}}, {{1., 2.}}, {}} is not a list of numbers or pairs of numbers.",
+            ),
+            "ListLinePlot[{{}, {{1., 1.}}, {{1., 2.}}, {}}]",
+            "ListLinePlot with invalid list of point",
+        ),
+    ):
+        check_evaluation(
+            str_expr,
+            str_expected,
+            to_string_expr=True,
+            to_string_expected=True,
+            hold_expected=True,
+            failure_message=fail_msg,
+            expected_messages=msgs,
+        )
+
+
 @pytest.mark.parametrize(
     ("str_expr", "msgs", "str_expected", "fail_msg"),
     [
@@ -159,8 +186,8 @@
         ),
     ],
 )
-def test_private_doctests_plot(str_expr, msgs, str_expected, fail_msg):
-    """builtin.drawing.plot"""
+def test_plot(str_expr, msgs, str_expected, fail_msg):
+    """tests for module builtin.drawing.plot"""
     check_evaluation(
         str_expr,
         str_expected,

test/helper.py

@@ -38,7 +38,7 @@ def evaluate(str_expr: str):
 def check_evaluation(
     str_expr: Optional[str],
     str_expected: Optional[str] = None,
-    failure_message: str = "",
+    failure_message: Optional[str] = "",
     hold_expected: bool = False,
     to_string_expr: Optional[bool] = True,
     to_string_expected: bool = True,