Fix out of bounds access in parse_snippet

src/lib.rs

@@ -114,11 +114,20 @@ fn parse_snippet(span: &DiagnosticSpan) -> Option<Snippet> {
     }
     let mut tail = String::new();
     let last = &span.text[span.text.len() - 1];
+
+    // If we get a DiagnosticSpanLine where highlight_end > text.len(), we prevent an 'out of
+    // bounds' access by using text.len() - 1 instead.
+    let last_tail_index = if (last.highlight_end - 1) > last.text.len() {
+        last.text.len() - 1
+    } else {
+        last.highlight_end - 1
+    };
+
     if span.text.len() > 1 {
         body.push('\n');
-        body.push_str(&last.text[indent..last.highlight_end - 1]);
+        body.push_str(&last.text[indent..last_tail_index]);
     }
-    tail.push_str(&last.text[last.highlight_end - 1..]);
+    tail.push_str(&last.text[last_tail_index..]);
     Some(Snippet {
         file_name: span.file_name.clone(),
         line_range: LineRange {

tests/edge-cases/out_of_bounds.recorded.json

@@ -0,0 +1,43 @@
+{
+  "message": "unterminated double quote string",
+  "code": null,
+  "level": "error",
+  "spans": [
+    {
+      "file_name": "./tests/everything/tab_2.rs",
+      "byte_start": 485,
+      "byte_end": 526,
+      "line_start": 12,
+      "line_end": 13,
+      "column_start": 7,
+      "column_end": 3,
+      "is_primary": true,
+      "text": [
+        {
+          "text": "    \"\"\"; //~ ERROR unterminated double quote",
+          "highlight_start": 7,
+          "highlight_end": 45
+        },
+        {
+          "text": "}",
+          "highlight_start": 1,
+          "highlight_end": 3
+        }
+      ],
+      "label": null,
+      "suggested_replacement": null,
+      "suggestion_applicability": null,
+      "expansion": null
+    }
+  ],
+  "children": [],
+  "rendered": "error: unterminated double quote string\n  --> ./tests/everything/tab_2.rs:12:7\n   |\n12 |       \"\"\"; //~ ERROR unterminated double quote\n   |  _______^\n13 | | }\n   | |__^\n\n"
+}
+{
+  "message": "aborting due to previous error",
+  "code": null,
+  "level": "error",
+  "spans": [],
+  "children": [],
+  "rendered": "error: aborting due to previous error\n\n"
+}

tests/edge_cases.rs

@@ -10,3 +10,12 @@ fn multiple_fix_options_yield_no_suggestions() {
             .unwrap();
     assert!(expected_suggestions.is_empty());
 }
+
+#[test]
+fn out_of_bounds_test() {
+    let json = fs::read_to_string("./tests/edge-cases/out_of_bounds.recorded.json").unwrap();
+    let expected_suggestions =
+        rustfix::get_suggestions_from_json(&json, &HashSet::new(), rustfix::Filter::Everything)
+            .unwrap();
+    assert!(expected_suggestions.is_empty());
+}