(I posted a similar problem here, but this new question is not a duplicate).

Small reproducible problem:

b = "LxF6sé侍"

We have here a string, where one of its one bytes is illegal in UTF-8 (it’s the byte with hex F6). The encoding of the String from the Ruby viewpoint is Encoding::UTF_8. Looking at the byte sequence, we can see

p b.bytes.to_a

=>

[76, 246, 115, 195, 169, 228, 190, 141]

My goal is to remove from the string all bytes which are illegal in UTF-8. I want to get in my simple example a string with content "Lsé侍".

I tried

c1 = b.encode('UTF-8', invalid: :replace, replace: '')

but c1 has the same content as b. Then I tried

b.force_encoding(Encoding::ASCII_UTF8)
c2 = b.encode('UTF-8', invalid: :replace, replace: '')

but this also erases the characters é and 侍, since they are not valid in ASCII.

I also was thinking of putting together a hard coded list of those byte values which are invalid in UTF8, and simply delete them from the string, but this is ugly.

Any ideas how this can be done?