From 5de82e6dc219e51d2c270cc7f4c54e8b9ab7de49 Mon Sep 17 00:00:00 2001
From: zimbatm <zimbatm@zimbatm.com>
Date: Mon, 2 Mar 2015 16:08:09 +0000
Subject: [PATCH] Add a default empty string to string replacements

New usages:

    "foo".sub("o") #=> "fo"
    "foo".gsub("o") #=> "f"

Applies to the bang versions as well.

This commit changes the return values of String#gsub! call with a single
argument and no block from an Enumerator to a String.

Before:

    "foo".gsub("o") #=> #<Enumerator: "foo":gsub("o")>
---
 string.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/string.c b/string.c
index 9419e31..6fca843 100644
--- a/string.c
+++ b/string.c
@@ -4087,7 +4087,7 @@ rb_pat_search(VALUE pat, VALUE str, long pos, int set_backref_str)
 
 /*
  *  call-seq:
- *     str.sub!(pattern, replacement)          -> str or nil
+ *     str.sub!(pattern, replacement='')       -> str or nil
  *     str.sub!(pattern) {|match| block }      -> str or nil
  *
  *  Performs the same substitution as String#sub in-place.
@@ -4103,12 +4103,16 @@ rb_str_sub_bang(int argc, VALUE *argv, VALUE str)
     int iter = 0;
     int tainted = 0;
     long plen;
-    int min_arity = rb_block_given_p() ? 1 : 2;
     long beg;
 
-    rb_check_arity(argc, min_arity, 2);
+    rb_check_arity(argc, 1, 2);
     if (argc == 1) {
-	iter = 1;
+       if (rb_block_given_p()) {
+          iter = 1;
+       }
+       else {
+          repl = rb_str_new("", 0);
+       }
     }
     else {
 	repl = argv[1];
@@ -4210,7 +4214,7 @@ rb_str_sub_bang(int argc, VALUE *argv, VALUE str)
 
 /*
  *  call-seq:
- *     str.sub(pattern, replacement)         -> new_str
+ *     str.sub(pattern, replacement='')      -> new_str
  *     str.sub(pattern, hash)                -> new_str
  *     str.sub(pattern) {|match| block }     -> new_str
  *
@@ -4271,8 +4275,13 @@ str_gsub(int argc, VALUE *argv, VALUE str, int bang)
 
     switch (argc) {
       case 1:
-	RETURN_ENUMERATOR(str, argc, argv);
-	mode = ITER;
+        if (rb_block_given_p()) {
+          RETURN_ENUMERATOR(str, argc, argv);
+          mode = ITER;
+        }
+        else {
+          repl = rb_str_new("", 0);
+        }
 	break;
       case 2:
 	repl = argv[1];
-- 
2.3.1