refactor: plot the dependency graphs with an optional pydot

docs/requirements.txt

@@ -3,7 +3,7 @@ requests
 networkx
 meson
 ninja
-pydotplus
+pydot
 nbsphinx
 nbsphinx_link
 Ipython

pixi.toml

@@ -20,7 +20,7 @@ networkx = "*"
 ninja = "*"
 numpy = ">=1.20.3,<3"
 pip = "*"
-pydotplus = "*"
+pydot = "*"
 pytest = "!=8.1.0"
 pytest-benchmark = "*"
 pytest-cov = "*"

pymake/plot/__init__.py

@@ -1,3 +1,4 @@
 """Functions to plot source code dependencies determined using a directed
-acyclic graph (DAG). pydotplus is used to plot the DAG.
+acyclic graph (DAG). pydot, which is an optional dependency, is used to
+plot the DAG.
 """

pymake/plot/dependency_graphs.py

@@ -21,14 +21,26 @@
 
 from pathlib import Path
 
-import pydotplus.graphviz as pydot
-
 from ..utils._compiler_language_files import (
     _get_ordered_srcfiles,
     _get_srcfiles,
 )
 from ..utils._dag import _get_f_nodelist
 
+try:
+    import pydot
+except ImportError:
+    pydot = None
+
+
+def _check_pydot():
+    """Raise an error if pydot, which is an optional dependency, is missing."""
+    if pydot is None:
+        raise ImportError(
+            "pydot is required to plot dependency graphs, install it with "
+            "'pip install mfpymake[plot]'"
+        )
+
 
 def to_pydot(dag, filename="mygraph.png"):
     """Create a png file of a Directed Acyclic Graph.
@@ -44,6 +56,8 @@ def to_pydot(dag, filename="mygraph.png"):
     -------
 
     """
+    _check_pydot()
+
     # Create the graph
     graph = pydot.Dot(graph_type="digraph")
 
@@ -156,6 +170,8 @@ def make_plots(
     -------
 
     """
+    _check_pydot()
+
     srcfiles = _get_ordered_srcfiles(_get_srcfiles(srcdir, include_subdir))
     nodelist = _get_f_nodelist(srcfiles)
     for idx, n in enumerate(nodelist):

pyproject.toml

@@ -32,17 +32,19 @@ dependencies = [
     "networkx",
     "meson>=1.3.1",
     "ninja",
-    "pydotplus",
 ]
 dynamic = ["version"]
 
 [project.optional-dependencies]
+plot = [
+    "pydot",
+]
 lint = [
     "cffconvert",
     "ruff",
 ]
 test = [
-    "mfpymake[lint]",
+    "mfpymake[lint,plot]",
     "coverage!=7.6.5",
     "flaky",
     "filelock",