enh(plot) pink-ify null pandas & np-arrays

Author: ankostis

graphtik/plot.py

@@ -58,6 +58,28 @@
 
 log = logging.getLogger(__name__)
 
+## Gracefully import numpy & pandas to check for null values
+#  (probable mistakes in function definitions).
+#
+_null_checks = []
+try:
+    import numpy as np
+
+    def is_empty_array(val):
+        return isinstance(val, np.ndarray) and not np.any()
+
+    _null_checks.append(is_empty_array)
+except ImportError:
+    pass
+try:
+    from pandas.core.generic import NDFrame
+
+    def is_empty_frame(val):
+        return isinstance(val, NDFrame) and not val.any()
+
+    _null_checks.append(is_empty_frame)
+except ImportError:
+    pass
 
 #: A nested dictionary controlling the rendering of graph-plots in Jupyter cells,
 #:
@@ -1468,8 +1490,16 @@ def _make_node(self, plot_args: PlotArgs) -> pydot.Node:
             if solution is not None:
                 if nx_node in solution:
                     styles.add("kw_data_in_solution")
-                    if solution[nx_node] is None:
-                        styles.add("kw_data_in_solution_null")
+                    val = solution[nx_node]
+                    for check in _null_checks:
+                        try:
+                            if check(val):
+                                styles.add("kw_data_in_solution_null")
+                                break
+                        except Exception:
+                            log.debug(
+                                "Skipping null-check error on %s", val, exc_info=1
+                            )
 
                     if nx_node in getattr(solution, "overwrites", ()):
                         styles.add("kw_data_overwritten")

test/test_plot.py

@@ -622,7 +622,7 @@ def test_node_dot_str1(dot_str_pipeline, monkeypatch):
                 </TABLE>>, shape=invhouse, style=filled, tooltip="(input)\n(int) 2"];
         <&lt;graph&gt;> [fillcolor=SkyBlue, fixedsize=shape, label=<<TABLE CELLBORDER="0" CELLSPACING="0" BORDER="0">
                     <TR><TD><graph></TD></TR>
-                </TABLE>>, shape=house, style=filled, tooltip="(output)\n(None)\n(null-result)\n(x2 overwrites) 1. 3&#10;  0. None"];
+                </TABLE>>, shape=house, style=filled, tooltip="(output)\n(None)\n(x2 overwrites) 1. 3&#10;  0. None"];
         <cu&#58;sto&#58;m> [label=<<TABLE CELLBORDER="0" CELLSPACING="0" STYLE="rounded" BGCOLOR="wheat">
             <TR>
                 <TD BORDER="1" SIDES="b" ALIGN="left" TOOLTIP="FnOp(name=&#x27;cu:sto:m&#x27;, needs=[&#x27;edge&#x27;, &#x27;digraph: strict&#x27;], provides=[&#x27;&lt;graph&gt;&#x27;], fn=&#x27;func&#x27;)" TARGET="_top"