String#dup returns copy when no modification made. Fixes #3633.

rubinius · Apr 4, 2016 · 42fb295 · 42fb295
1 parent cfd3f08
commit 42fb295
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Showing 2 changed files with 10 additions and 2 deletions.
diff --git a/core/string.rb b/core/string.rb
@@ -1388,7 +1388,7 @@ def sub(pattern, replacement=undefined)
       ret.append(match.post_match)
       tainted ||= val.tainted?
     else
-      return self
+      ret = dup
     end
 
     ret.taint if tainted

diff --git a/spec/ruby/core/string/sub_spec.rb b/spec/ruby/core/string/sub_spec.rb
@@ -2,6 +2,14 @@
 require File.expand_path('../fixtures/classes.rb', __FILE__)
 
 describe "String#sub with pattern, replacement" do
+  it "returns a copy of self when no modification is made" do
+    a = "hello"
+    b = a.sub /w.*$/, "*"
+
+    b.should_not equal(a)
+    b.should == "hello"
+  end
+
   it "returns a copy of self with all occurrences of pattern replaced with replacement" do
     "hello".sub(/[aeiou]/, '*').should == "h*llo"
     "hello".sub(//, ".").should == ".hello"
@@ -562,4 +570,4 @@
   it "raises a ArgumentError" do
     lambda { "abca".sub!(/a/) }.should raise_error(ArgumentError)
   end
-end
+end