Bug #18955
Updated by andrykonchin (Andrew Konchin) over 2 years ago
I haven't found any similar existing issue to decided to create a new one.
I noticed that `sprintf("%c", string)` doesn't handle (in an expected way) a case when encodings of format sequence and string argument aren't the same and string contains non-ASCII character.
In this case it seems to me that `sprintf` uses just binary representation of a character and assigns (or interprets with) encoding of the format sequence string.
I would expect that `sprintf` negotiates encoding and converts everything (the the character and from the format string) string's encoding to the chosen one. format's encoding.
Examples to illustrate this behavior:
```ruby
format = "%c".encode("Windows-1251")
string = "Й".encode(Encoding::KOI8_U)
r = sprintf(format, string)
r.encoding
# => #<Encoding:Windows-1251>
r == "Й".encode("Windows-1251")
# => false
r.codepoints
# => [234]
string.codepoints
# => [234]
```
In this example the result's encoding is a format's encoding. But codepoint isn't changed and equals a codepoint of the character in the original string's encoding. But it should be different:
```ruby
"Й".encode("Windows-1251").codepoints
# => [201]
```
Another example:
```ruby
string = "À".encode(Encoding::CP1252)
sprintf("%c", string)
# => in `sprintf': invalid byte sequence in UTF-8 (ArgumentError)
```
In this example the error means that `sprintf` doesn't encode properly a codepoint (of string's encoding) in UTF-8. It uses just raw bytes.