[ruby-core:26450] [Bug #2313] Incomplete encoding conversion?

Issue #2313 has been updated by Yui NARUSE.


> >> "元気".encode('UTF-8').force_encoding('ASCII-8BIT').encode('UTF-8')
> Encoding::UndefinedConversionError: "\xE5" from ASCII-8BIT to UTF-8
> 	from (irb):24:in `encode'
> 	from (irb):24
> 	from /opt/local/bin/irb:12:in `<main>'
> 
> Is that a bug in the UTF-8 encoding parser? Or is it related to this problem?

OK, I'll explain step by step:

str = "元気"
# You make a String which contains "元気" encode by some encoding
# str's byte data is some byte string which means "元気"
# str's encoding is a source encoding
str = str.encode('UTF-8')
# str is encoded to UTF-8, so
# str's byte data is "\xE5\x85\x83\xE6\xB0\x97"
# str's encoding is UTF-8
str.force_encoding('ASCII-8BIT')
# change str's encoding to ASCII-8BIT, so
# str's byte data is "\xE5\x85\x83\xE6\xB0\x97"
# str's encoding is now ASCII-8BIT

Then you try str.encode('UTF-8') and this String#encode converts byte data:
String#encode try to convert "\xE5" from ASCII-8BIT to UTF-8, but there is no mapping.
What you want to do is not a conversion, it should be setting encoding.

str.force_encoding('UTF-8')
# change str's encoding to UTF-8, so
# str's byte data is "\xE5\x85\x83\xE6\xB0\x97"
# str's encoding is now UTF-8
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http://redmine.ruby-lang.org/issues/show/2313

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