Fix RegexpError 500 in search highlighting when a term contains regex metacharacters

app/helpers/searches_helper.rb

@@ -22,7 +22,10 @@ def highlight_searched_content(leaf, content, query)
   end
 
   private
+    # Terms come from FTS5 highlight() spans, which can include document
+    # punctuation (e.g. a phrase match spanning "foo) bar"). Escape them so
+    # metacharacters are matched literally instead of raising a RegexpError.
     def whole_word_matchers(terms)
-      terms.map { |term| /\b#{term}\b/ }
+      terms.map { |term| /\b#{Regexp.escape(term)}\b/ }
     end
 end

test/controllers/leafables_controller_test.rb

@@ -30,6 +30,20 @@ class LeafablesControllerTest < ActionDispatch::IntegrationTest
     assert_select "mark", "great"
   end
 
+  test "show highlights a phrase match whose span contains regex metacharacters" do
+    sign_out
+    books(:handbook).update!(published: true)
+
+    section = Section.new(body: "alpha) omega in the body")
+    books(:handbook).press(section, title: "Punctuated")
+    section.leaf.reindex
+
+    get leafable_slug_path(section.leaf), params: { search: '"alpha omega"' }
+
+    assert_response :success
+    assert_select "mark", text: /alpha\) omega/
+  end
+
   test "show does not allow public access to an unpublished book" do
     sign_out
 

test/helpers/searches_helper_test.rb

@@ -1,6 +1,7 @@
 require "test_helper"
 
 class SearchesHelperTest < ActionView::TestCase
+  include PagesHelper
   test "sanitize_search_result preserves mark tags" do
     assert_equal "<mark>findme</mark> text", sanitize_search_result("<mark>findme</mark> text")
   end
@@ -16,4 +17,14 @@ class SearchesHelperTest < ActionView::TestCase
   test "sanitize_search_result strips attributes from mark tags" do
     assert_equal "<mark>findme</mark> text", sanitize_search_result('<mark class="hidden">findme</mark> text')
   end
+
+  test "highlight_searched_content handles matched terms containing regex metacharacters" do
+    leaf = Struct.new(:terms) do
+      def matches_for_highlight(_query) = terms
+    end.new([ "foo) bar" ])
+
+    result = highlight_searched_content(leaf, "foo) bar in the body", "foo bar")
+
+    assert_includes result, "<mark>foo) bar</mark>"
+  end
 end