[GR-19220] Fix broken UTF-8 inspect (#1842).

PullRequest: truffleruby/1175

Author: aardvark179

CHANGELOG.md

@@ -33,6 +33,7 @@ Bug fixes:
 * Arrays backed by native storage now allocate the correct amount of memory (#1828).
 * Fixed issue in `ConditionVariable#wait` that could lose a `ConditionVariable#signal`.
 * Do not leak TruffleRuby specific method Array#swap (#1816)
+* Fixed `#inspect` on broken UTF-8 sequences (#1842, @chrisseaton).
 
 Compatibility:
 

spec/ruby/core/string/inspect_spec.rb

@@ -319,6 +319,10 @@
     0.chr.inspect.should == '"\\x00"'
   end
 
+  it "uses \\x notation for broken UTF-8 sequences" do
+    "\xF0\x9F".inspect.should == '"\\xF0\\x9F"'
+  end
+
   describe "when default external is UTF-8" do
     before :each do
       @extenc, Encoding.default_external = Encoding.default_external, Encoding::UTF_8

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

@@ -571,7 +571,7 @@ def inspect
       if char
         index += inspect_char(enc, result_encoding, ascii, unicode, index, char, array)
       else
-        array << "\\x#{getbyte(index).to_s(16)}"
+        array << "\\x#{getbyte(index).to_s(16).upcase}"
         index += 1
       end
     end