Treat an escaped caret in JSONPath patterns as a literal (dpp-criteria issue 7)

app/services/i_regexp.rb

@@ -7,7 +7,8 @@
 # outside a character class (RFC 9485 lists them as ordinary characters, its
 # mappings in section 5 and the JSONPath Compliance Test Suite treat them as
 # anchors): such a pattern is unusable (Anchored), like an invalid one
-# (Invalid); `\^` counts as well. Differences to Ruby and ECMA-262 that
+# (Invalid). An escaped `\^` is a literal ^ (dpp-criteria issue #7); `\$` is
+# not valid I-Regexp (use `[$]`). Differences to Ruby and ECMA-262 that
 # matter: `.` matches any character except LF and CR; only the escapes \( \) \*
 # \+ \- \. \? \[ \\ \] \n \r \t \{ \| \} and the category escapes \p{..} and \P{..} exist (no \d,
 # \w, \s); there are no lazy quantifiers, no {,m} and no non-capturing or other
@@ -155,7 +156,6 @@ def escape_outside
 
     c = take
     return category(c) if %w[p P].include?(c)
-    raise Anchored, "\\^" if c == "^"
 
     char(single_escape(c))
   end

test/services/i_regexp_test.rb

@@ -22,12 +22,19 @@ class IRegexpTest < ActiveSupport::TestCase
   end
 
   test "^ or $ outside a character class makes the pattern unusable (dpp-criteria 4b17bb8)" do
-    ["^ab.*", ".*bc$", "^[Bb]atter", "59040|PCDS$", "(^a)", "a\\^b"].each do |pattern|
-      assert_match(/\Acontains (\^|\$|\\\^) outside a character class/, IRegexp.problem(pattern), pattern)
+    ["^ab.*", ".*bc$", "^[Bb]atter", "59040|PCDS$", "(^a)"].each do |pattern|
+      assert_match(/\Acontains (\^|\$) outside a character class/, IRegexp.problem(pattern), pattern)
       refute IRegexp.search?(pattern, pattern.delete("^$\\")), pattern
     end
   end
 
+  test "an escaped \\^ is a literal ^, an escaped \\$ is not I-Regexp (dpp-criteria issue #7)" do
+    assert_nil IRegexp.problem("a\\^b")
+    assert IRegexp.match?("a\\^b", "a^b")
+    refute IRegexp.search?("a\\^b", "ab")
+    assert_match(/not an I-Regexp escape/, IRegexp.problem("a\\$"))
+  end
+
   test "^ and $ inside a character class are allowed" do
     assert_nil IRegexp.problem("[^a]")
     assert_nil IRegexp.problem("[a^]")