Add "lpn" checking in _ListPlot

mathics/builtin/drawing/plot.py

@@ -286,11 +286,12 @@ class _ListPlot(Builtin, ABC):
     attributes = A_PROTECTED | A_READ_PROTECTED
 
     messages = {
+        "joind": "Value of option Joined -> `1` is not True or False.",
+        "lpn": "`1` is not a list of numbers or pairs of numbers.",
         "prng": (
             "Value of option PlotRange -> `1` is not All, Automatic or "
             "an appropriate list of range specifications."
         ),
-        "joind": "Value of option Joined -> `1` is not True or False.",
     }
 
     use_log_scale = False
@@ -309,6 +310,21 @@ def eval(self, points, evaluation: Evaluation, options: dict):
                 )
             )
 
+        points = points.evaluate(evaluation)
+        if not isinstance(points, ListExpression):
+            evaluation.message(class_name, "lpn", points)
+            return
+
+        if not all(
+            element.is_numeric(evaluation)
+            or isinstance(element, ListExpression)
+            or (1 <= len(element.elements) <= 2)
+            or (len(element.elements) == 1 and isinstance(element[0], ListExpression))
+            for element in points.elements
+        ):
+            evaluation.message(class_name, "lpn", points)
+            return
+
         # If "points" is a literal value with a Python representation,
         # it has a ".value" attribute with a non-None value. So here,
         # we don't have to eval_N().to_python().

mathics/core/expression.py

@@ -1410,8 +1410,13 @@ def rules():
                 if not isinstance(result, EvalMixin):
                     return result, False
                 if result.sameQ(new):
-                    new._timestamp_cache(evaluation)
-                    return new, False
+                    # Even though result and new may be the same,
+                    # new can be a Expression[SymbolConstant: System`List...]
+                    # while "result' might be ListExpression!?
+                    # So make sure to use "result", not "new".
+                    if isinstance(result, Expression):
+                        result._timestamp_cache(evaluation)
+                    return result, False
                 else:
                     return result, True
 

mathics/eval/drawing/plot.py

@@ -201,19 +201,21 @@ def eval_ListPlot(
             [xx for xx, yy in plot_groups], [xx for xx, yy in plot_groups], x_range
         )
         plot_groups = [plot_groups]
-    elif all(isinstance(line, list) for line in plot_groups):
-        if not all(isinstance(line, list) for line in plot_groups):
+    elif all(isinstance(line, (list, tuple)) for line in plot_groups):
+        if not all(isinstance(line, (list, tuple)) for line in plot_groups):
             return
 
         # He have a list of plot groups
         if all(
-            isinstance(point, list) and len(point) == 2
-            for plot_group in plot_groups
+            isinstance(point, (list, tuple)) and len(point) == 2
+            for _ in plot_groups
             for point in plot_groups
         ):
             pass
         elif not is_discrete_plot and all(
-            not isinstance(point, list) for line in plot_groups for point in line
+            not isinstance(point, (list, tuple))
+            for line in plot_groups
+            for point in line
         ):
             # FIXME: is this right?
             y_min = min(plot_groups)[0]
@@ -229,7 +231,7 @@ def eval_ListPlot(
     # Split into plot segments
     plot_groups = [[plot_group] for plot_group in plot_groups]
     if isinstance(x_range, (list, tuple)):
-        x_min, m_max = x_range
+        x_min, x_max = x_range
         y_min, y_max = y_range
 
     for lidx, plot_group in enumerate(plot_groups):

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,