mruby-regexp: add /regex/ literal support, $~, Regexp.compile

- /regex/ literal syntax now works (compiler generates Regexp.compile)
- Regexp#match and Regexp#=~ set $~ global variable
- Regexp.last_match(n) for accessing capture groups
- Regexp.compile as alias for Regexp.new
- Regexp#options

Co-authored-by: Claude <noreply@anthropic.com>

mrbgems/mruby-regexp/mrblib/regexp.rb

@@ -0,0 +1,16 @@
+class Regexp
+  def self.compile(pattern, *args)
+    new(pattern, *args)
+  end
+
+  def options
+    @flags.to_i
+  end
+
+  # $1-$9 convenience methods via $~
+  def self.last_match(n = nil)
+    md = $~
+    return md if n.nil?
+    md ? md[n] : nil
+  end
+end

mrbgems/mruby-regexp/src/re_compile.c

@@ -429,7 +429,6 @@ compile_quantified(re_compiler *c)
     mrb_bool nongreedy = (peek(c) == '?');
     if (nongreedy) next_char(c);
 
-    uint32_t atom_len = c->code_len - start;
 
     if (ch == '*') {
       /* e* → L: SPLIT(body, end); body; JMP L; end:

mrbgems/mruby-regexp/src/regexp.c

@@ -105,6 +105,7 @@ create_matchdata(mrb_state *mrb, mrb_value str, int *captures, int ncap)
 
   mrb_value obj = mrb_obj_value(mrb_data_object_alloc(mrb, md_class, md, &matchdata_type));
   /* store in $~ */
+  mrb_gv_set(mrb, mrb_intern_lit(mrb, "$~"), obj);
   return obj;
 }
 
@@ -127,7 +128,10 @@ regexp_match(mrb_state *mrb, mrb_value self)
   int ncap = re_exec(mrb, pat, RSTRING_PTR(str), RSTRING_LEN(str), pos,
                      captures, pat->num_captures * 2);
 
-  if (ncap == 0) return mrb_nil_value();
+  if (ncap == 0) {
+    mrb_gv_set(mrb, mrb_intern_lit(mrb, "$~"), mrb_nil_value());
+    return mrb_nil_value();
+  }
 
   return create_matchdata(mrb, str, captures, pat->num_captures * 2);
 }
@@ -171,7 +175,11 @@ regexp_match_op(mrb_state *mrb, mrb_value self)
   int ncap = re_exec(mrb, pat, RSTRING_PTR(str), RSTRING_LEN(str), 0,
                      captures, pat->num_captures * 2);
 
-  if (ncap == 0) return mrb_nil_value();
+  if (ncap == 0) {
+    mrb_gv_set(mrb, mrb_intern_lit(mrb, "$~"), mrb_nil_value());
+    return mrb_nil_value();
+  }
+  create_matchdata(mrb, str, captures, pat->num_captures * 2);
   return mrb_int_value(mrb, captures[0]);
 }
 
@@ -393,7 +401,7 @@ mrb_mruby_regexp_gem_init(mrb_state *mrb)
 
   /* Class methods */
   mrb_define_method(mrb, re, "initialize", regexp_init, MRB_ARGS_ARG(1, 2));
-  mrb_define_class_method(mrb, re, "compile", regexp_init, MRB_ARGS_ARG(1, 2));
+  /* compile is defined in Ruby (mrblib) as alias for new */
   mrb_define_class_method(mrb, re, "escape", regexp_escape, MRB_ARGS_REQ(1));
   mrb_define_class_method(mrb, re, "quote", regexp_escape, MRB_ARGS_REQ(1));
 

mrbgems/mruby-regexp/test/regexp.rb

@@ -139,3 +139,27 @@ end
 assert("String#scan") do
   assert_equal ["1", "2", "3"], "a1b2c3".scan(Regexp.new("\\d"))
 end
+
+assert("Regexp literal /regex/") do
+  assert_true /abc/.match?("abc")
+  assert_equal "123", /\d+/.match("abc123")[0]
+  assert_true /hello/i.match?("HELLO")
+end
+
+assert("$~ global variable") do
+  /(\w+)@(\w+)/ =~ "user@host"
+  assert_kind_of MatchData, $~
+  assert_equal "user", $~[1]
+  assert_equal "host", $~[2]
+end
+
+assert("$~ is nil on no match") do
+  /xyz/ =~ "abc"
+  assert_nil $~
+end
+
+assert("Regexp.last_match") do
+  /(\d+)/ =~ "abc123"
+  assert_equal "123", Regexp.last_match(1)
+  assert_equal "123", Regexp.last_match(0)
+end