Revert: Stop using shutil.which on Windows as it still seems to have …

…issues as of Python 3.8.1

src/nxv/_graphviz.py

@@ -76,22 +76,21 @@ def get_graphviz_bins(graphviz_bin: Optional[str], algorithm: str) -> List[str]:
                 f"by the GRAPHVIZ_BIN environment variable: {graphviz_bin}"
             )
         return [graphviz_bin]
-
+
+    # Otherwise, use directory containing the result of `which {algorithm}`
+    graphviz_bin = shutil.which(algorithm)
+    if graphviz_bin:
+        graphviz_bin = os.path.dirname(graphviz_bin)
+        return [graphviz_bin]
+
+    # Otherwise, on Windows, look for the standard install locations
     if is_windows():
-        # Otherwise, on Windows, look for the standard install locations
         graphviz_bins = get_windows_graphviz_bins()
         if not graphviz_bins:
             raise GraphVizInstallationNotFoundError(
                 "No GraphViz installation was found at any of the standard Windows locations."
             )
         return graphviz_bins
-    else:
-        # Otherwise, on non-Windows, use directory containing the result of `which {algorithm}`
-        # shutil.which seems to be broken on Windows as of Python 3.8.1
-        graphviz_bin = shutil.which(algorithm)
-        if graphviz_bin:
-            graphviz_bin = os.path.dirname(graphviz_bin)
-            return [graphviz_bin]
 
     raise GraphVizInstallationNotFoundError(
         "No GraphViz installation was specified. "

src/nxv/_rendering.py

@@ -167,7 +167,7 @@ def render(
     graph: Union[nx.Graph, nx.DiGraph, nx.MultiGraph, nx.MultiDiGraph],
     style: Optional[Style] = None,
     *,
-    algorithm: str = "dot",
+    algorithm: Optional[str] = None,
     format: Optional[str] = None,
     graphviz_bin: Optional[str] = None,
     subgraph_func=None,
@@ -201,6 +201,11 @@ def render(
     :raises GraphVizAlgorithmNotFoundError: If nxv cannot find the specified algorithm in a `GraphViz`_ installation.
     :raises GraphVizError: If `GraphViz`_ failed to run on the given inputs.
     """
+    if algorithm is None:
+        algorithm = "dot"
+    if not algorithm or not isinstance(algorithm, str):
+        raise ValueError("The algorithm parameter must be the str name of a valid GraphViz algorithm.")
+
     if format is None:
         if _ipython.is_execution_context():
             format = "ipython/svg"