Fixed String#{chomp, chomp!} issue with invalid encoded strings

(cherry picked from commit 026e983)

Author: bjfish

CHANGELOG.md

@@ -20,6 +20,7 @@ Bug fixes:
 * Fixed constant/identifier detection in lexer for non-ASCII encodings (#2079, #2102, @ivoanjo).
 * Fixed parsing of `--jvm` as an application argument (#2108).
 * Fix `rb_rescue2` to ignore the end marker `(VALUE)0` (#2127, #2130).
+* Fix `String#{chomp, chomp!}` issue with invalid encoded strings (#2133).
 
 Compatibility:
 

spec/ruby/core/string/chomp_spec.rb

@@ -55,6 +55,10 @@
       $/ = "cdef"
       "abcdef".chomp.should == "ab"
     end
+
+    it "removes one trailing newline for string with invalid encoding" do
+      "\xa0\xa1\n".chomp.should == "\xa0\xa1"
+    end
   end
 
   describe "when passed nil" do
@@ -108,6 +112,10 @@
     it "returns an empty String when self is empty" do
       "".chomp("").should == ""
     end
+
+    it "removes one trailing newline for string with invalid encoding" do
+      "\xa0\xa1\n".chomp("").should == "\xa0\xa1"
+    end
   end
 
   describe "when passed '\\n'" do

src/main/ruby/truffleruby/core/string.rb

@@ -844,7 +844,7 @@ def chomp!(sep=undefined)
         if j = Primitive.string_previous_byte_index(self, bytes)
           chr = Primitive.string_chr_at(self, j)
 
-          if chr.ord == 13
+          if !Primitive.nil?(chr) && chr.ord == 13
             bytes = j
           end
         end
@@ -857,13 +857,13 @@ def chomp!(sep=undefined)
 
       while i = Primitive.string_previous_byte_index(self, bytes)
         chr = Primitive.string_chr_at(self, i)
-        break unless chr.ord == 10
+        break unless !Primitive.nil?(chr) && chr.ord == 10
 
         bytes = i
 
         if j = Primitive.string_previous_byte_index(self, i)
           chr = Primitive.string_chr_at(self, j)
-          if chr.ord == 13
+          if !Primitive.nil?(chr) && chr.ord == 13
             bytes = j
           end
         end