Fix panic

Author: Hendrik van Antwerpen

stack-graphs/CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## v0.14.1 -- Unpublished
+
+### Fixed
+
+- A panic when using `StackGraph::incoming_edge_degree` on some nodes without incoming edges.
+
 ## v0.14.0 -- 2024-07-09
 
 ### Changed

stack-graphs/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "stack-graphs"
-version = "0.14.0"
+version = "0.14.1"
 description = "Name binding for arbitrary programming languages"
 homepage = "https://github.com/github/stack-graphs/tree/main/stack-graphs"
 repository = "https://github.com/github/stack-graphs/"

stack-graphs/src/graph.rs

@@ -1334,7 +1334,10 @@ impl StackGraph {
 
     /// Returns the number of edges that end at a particular sink node.
     pub fn incoming_edge_degree(&self, sink: Handle<Node>) -> Degree {
-        self.incoming_edges[sink]
+        self.incoming_edges
+            .get(sink)
+            .cloned()
+            .unwrap_or(Degree::Zero)
     }
 }
 

stack-graphs/tests/it/graph.rs

@@ -8,7 +8,7 @@
 use std::collections::HashSet;
 
 use maplit::hashset;
-use stack_graphs::graph::StackGraph;
+use stack_graphs::graph::{Degree, StackGraph};
 
 use crate::test_graphs;
 use crate::test_graphs::CreateStackGraph;
@@ -196,3 +196,22 @@ fn can_add_graph_to_empty_graph() {
         );
     }
 }
+
+#[test]
+fn can_get_incoming_edges() {
+    let mut graph = StackGraph::new();
+    let file = graph.get_or_create_file("test.py");
+    let h1 = graph.internal_scope(file, 0);
+    let h2 = graph.internal_scope(file, 1);
+    let h3 = graph.internal_scope(file, 2);
+    assert_eq!(Degree::Zero, graph.incoming_edge_degree(h1));
+    assert_eq!(Degree::Zero, graph.incoming_edge_degree(h2));
+    assert_eq!(Degree::Zero, graph.incoming_edge_degree(h3));
+    graph.add_edge(h1, h2, 0);
+    graph.add_edge(h3, h2, 0);
+    assert_eq!(Degree::Zero, graph.incoming_edge_degree(h1));
+    assert_eq!(Degree::Multiple, graph.incoming_edge_degree(h2));
+    assert_eq!(Degree::Zero, graph.incoming_edge_degree(h3));
+    graph.add_edge(h3, h1, 0);
+    assert_eq!(Degree::One, graph.incoming_edge_degree(h1));
+}