[flori/json] Fix "unexpected token" offset for Infinity

Previously in the JSON::Ext parser, when we encountered an "Infinity"
token (and weren't allowing NaN/Infinity) we would try to display the
"unexpected token" at the character before.

https://github.com/flori/json/commit/42ac170712

3 files changed, 21 insertions, 2 deletions

diff --git a/ext/json/parser/parser.c b/ext/json/parser/parser.c
index 876bec5769..095dd99e50 100644
--- a/ext/json/parser/parser.c
+++ b/ext/json/parser/parser.c
@@ -587,7 +587,7 @@ tr25:
         if (json->allow_nan) {
             *result = CInfinity;
         } else {
-            rb_enc_raise(EXC_ENCODING eParserError, "unexpected token at '%s'", p - 8);
+            rb_enc_raise(EXC_ENCODING eParserError, "unexpected token at '%s'", p - 7);
         }
     }
 	goto st29;
diff --git a/ext/json/parser/parser.rl b/ext/json/parser/parser.rl
index 1ecf3317c7..2602d91f55 100644
--- a/ext/json/parser/parser.rl
+++ b/ext/json/parser/parser.rl
@@ -229,7 +229,7 @@ static char *JSON_parse_object(JSON_Parser *json, char *p, char *pe, VALUE *resu
         if (json->allow_nan) {
             *result = CInfinity;
         } else {
-            rb_enc_raise(EXC_ENCODING eParserError, "unexpected token at '%s'", p - 8);
+            rb_enc_raise(EXC_ENCODING eParserError, "unexpected token at '%s'", p - 7);
         }
     }
     action parse_string {
diff --git a/test/json/json_ext_parser_test.rb b/test/json/json_ext_parser_test.rb
index b5b18fb20b..f49f88b596 100644
--- a/test/json/json_ext_parser_test.rb
+++ b/test/json/json_ext_parser_test.rb
@@ -3,6 +3,8 @@ require_relative 'test_helper'
 
 class JSONExtParserTest < Test::Unit::TestCase
   if defined?(JSON::Ext::Parser)
+    include JSON
+
     def test_allocate
       parser = JSON::Ext::Parser.new("{}")
       assert_raise(TypeError, '[ruby-core:35079]') do
@@ -11,5 +13,22 @@ class JSONExtParserTest < Test::Unit::TestCase
       parser = JSON::Ext::Parser.allocate
       assert_raise(TypeError, '[ruby-core:35079]') { parser.source }
     end
+
+    def test_error_messages
+      ex = assert_raise(ParserError) { parse('Infinity') }
+      assert_equal "unexpected token at 'Infinity'", ex.message
+
+      unless RUBY_PLATFORM =~ /java/
+        ex = assert_raise(ParserError) { parse('-Infinity') }
+        assert_equal "unexpected token at '-Infinity'", ex.message
+      end
+
+      ex = assert_raise(ParserError) { parse('NaN') }
+      assert_equal "unexpected token at 'NaN'", ex.message
+    end
+
+    def parse(json)
+      JSON::Ext::Parser.new(json).parse
+    end
   end
 end