fixed out of bound panic in substring filter

scraping.go

@@ -379,9 +379,9 @@ func getFilterResultXPath(filter *Filter) {
 					}
 				default:
 					{
-				var b bytes.Buffer
-				html.Render(&b, node)
-				filter.Results = append(filter.Results, html.UnescapeString(b.String()))
+						var b bytes.Buffer
+						html.Render(&b, node)
+						filter.Results = append(filter.Results, html.UnescapeString(b.String()))
 						break
 					}
 				}
@@ -446,9 +446,9 @@ func getFilterResultCSS(filter *Filter) {
 					}
 				default:
 					{
-				var b bytes.Buffer
-				html.Render(&b, node)
-				filter.Results = append(filter.Results, html.UnescapeString(b.String()))
+						var b bytes.Buffer
+						html.Render(&b, node)
+						filter.Results = append(filter.Results, html.UnescapeString(b.String()))
 						break
 					}
 				}
@@ -514,6 +514,11 @@ func getFilterResultSubstring(filter *Filter) {
 					} else if from < 0 {
 						from = len(asRunes) + from
 					}
+					if from < 0 {
+						filter.log("Out of bounds:", from_to)
+						continue
+					}
+
 					toStr := from_to[1]
 					var hasTo bool = true
 					if toStr == "" {
@@ -527,8 +532,15 @@ func getFilterResultSubstring(filter *Filter) {
 					} else if to < 0 {
 						to = len(asRunes) + to
 					}
+					if to < 0 {
+						filter.log("Out of bounds:", from_to)
+						continue
+					}
 					if hasFrom && hasTo {
-						sb.WriteString(string(asRunes[from:to]))
+						_, err := sb.WriteString(string(asRunes[from:to]))
+						if err != nil {
+							filter.log("Could not substring: ", err)
+						}
 					} else if hasFrom {
 						sb.WriteString(string(asRunes[from:]))
 					} else if hasTo {

scraping_test.go

@@ -277,6 +277,34 @@ func TestFilterSubstring(t *testing.T) {
 	}
 }
 
+func TestFilterSubstringOutOfBounds(t *testing.T) {
+	var tests = []struct {
+		Input string
+		Query string
+	}{
+		{"01234", ":-6"},
+		{"01234", "-6:"},
+	}
+
+	for _, test := range tests {
+		testname := fmt.Sprintf("%s %s", test.Input, test.Query)
+		t.Run(testname, func(t *testing.T) {
+			filter := Filter{
+				Parents: []*Filter{
+					{Results: []string{test.Input}},
+				},
+				Var1: test.Query,
+			}
+			getFilterResultSubstring(
+				&filter,
+			)
+			if len(filter.Logs) == 0 {
+				t.Errorf("No log message, expected one for OoB")
+			}
+		})
+	}
+}
+
 func TestFilterContains(t *testing.T) {
 	var tests = []struct {
 		Input  []string

todo.md

@@ -13,6 +13,4 @@
     - ~~inner~~
     - ~~attributes~~
     - ~~node~~
-    - tests for all of it
-- substring out of range?
-    - test it
+    - tests for all of it