Auto-run: try harder to avoid networkx issues (#3457)

* auto-run: try harder to avoid networkx issues
* fix auto-run transforms

2 files changed, 37 insertions, 5 deletions

diff --git a/lib/stitches/auto_run.py b/lib/stitches/auto_run.py
index 28da5482..760d0393 100644
--- a/lib/stitches/auto_run.py
+++ b/lib/stitches/auto_run.py
@@ -121,6 +121,7 @@ class LineSegments:
 
 def autorun(elements, preserve_order=False, break_up=None, starting_point=None, ending_point=None, trim=False):
     graph = build_graph(elements, preserve_order, break_up)
+
     graph = add_jumps(graph, elements, preserve_order)
 
     starting_point, ending_point = get_starting_and_ending_nodes(
@@ -132,7 +133,7 @@ def autorun(elements, preserve_order=False, break_up=None, starting_point=None,
     new_elements, trims, original_parents = path_to_elements(graph, path, trim)
 
     if preserve_order:
-        preserve_original_groups(new_elements, original_parents)
+        preserve_original_groups(new_elements, original_parents, transform=False)
     else:
         parent = elements[0].node.getparent()
         insert_index = parent.index(elements[0].node)
diff --git a/lib/stitches/utils/autoroute.py b/lib/stitches/utils/autoroute.py
index a83e8002..b10ae21c 100644
--- a/lib/stitches/utils/autoroute.py
+++ b/lib/stitches/utils/autoroute.py
@@ -30,7 +30,7 @@ def find_path(graph, starting_node, ending_node):
     #
     # Visiting the edges again on the way back allows us to set up
     # "underpathing".
-    path = nx.shortest_path(graph, starting_node, ending_node)
+    path = _get_shortest_path(graph, starting_node, ending_node)
 
     check_stop_flag()
 
@@ -77,6 +77,17 @@ def find_path(graph, starting_node, ending_node):
     return final_path
 
 
+def _get_shortest_path(graph, starting_node, ending_node):
+    try:
+        path = nx.shortest_path(graph, starting_node, ending_node)
+    except nx.exception.NetworkXNoPath:
+        # They did something strange, let's add a jump from start to end
+        # so at least we don't have to end with an error
+        _insert_jump(graph, graph.nodes[starting_node]['point'], graph.nodes[ending_node]['point'])
+        path = nx.shortest_path(graph, starting_node, ending_node)
+    return path
+
+
 def add_jumps(graph, elements, preserve_order):
     """Add jump stitches between elements as necessary.
 
@@ -94,9 +105,18 @@ def _add_ordered_jumps(graph, elements):
     # For each sequential pair of elements, find the shortest possible jump
     # stitch between them and add it.  The directions of these new edges
     # will enforce stitching the elements in order.
+    last_element = None
     for element1, element2 in zip(elements[:-1], elements[1:]):
+        # Try to fix missing links
+        if last_element is not None:
+            success = _insert_smallest_jump(graph, last_element, element2)
+            if success:
+                last_element = None
+
         check_stop_flag()
-        _insert_smallest_jump(graph, element1, element2)
+        success = _insert_smallest_jump(graph, element1, element2)
+        if not success:
+            last_element = element1
 
     # add jumps between subpath too, we do not care about directions here
     for element in elements:
@@ -130,6 +150,11 @@ def _insert_smallest_jump(graph, element1, element2):
     if potential_edges:
         edge = min(potential_edges, key=lambda p1_p2: p1_p2[0].distance(p1_p2[1]))
         graph.add_edge(str(edge[0]), str(edge[1]), jump=True)
+        return True
+    else:
+        # return False if we haven't successfully inserted a jump
+        # so we can try again later
+        return False
 
 
 def _insert_jump(graph, node1, node2):
@@ -195,6 +220,9 @@ def find_node(graph, point, extreme_function, constrain_to_satin=False, satin=No
     else:
         nodes = graph.nodes()
 
+    if not nodes:
+        return list(graph.nodes)[0]
+
     if point is None:
         return extreme_function(nodes, key=lambda node: graph.nodes[node]['point'].x)
     else:
@@ -241,7 +269,7 @@ def create_new_group(parent, insert_index, label, correction_transform=True):
     return group
 
 
-def preserve_original_groups(elements, original_parent_nodes):
+def preserve_original_groups(elements, original_parent_nodes, transform=True):
     """Ensure that all elements are contained in the original SVG group elements.
 
     When preserve_order is True, no elements will be reordered in the XML tree.
@@ -251,9 +279,12 @@ def preserve_original_groups(elements, original_parent_nodes):
     """
 
     for element, parent in zip(elements, original_parent_nodes):
+        transform = ''
+        if transform:
+            transform = get_correction_transform(parent, child=True)
         if parent is not None:
             parent.append(element.node)
-            element.node.set('transform', get_correction_transform(parent, child=True))
+            element.node.set('transform', transform)
 
 
 def add_elements_to_group(elements, group):