Convert source file encoding to UTF-8

[Tietew]

Fixes simplecov-ruby/simplecov-html#91

Summary

• Open the source file in encoding UTF-8 instead of ASCII-8BIT.
• Check for magic comment and call IO#set_encoding to convert encoding to UTF-8.

Background

File.open(..., "rb") will set its encoding to ASCII-8BIT instead of script encoding (UTF-8).
This means all lines are ASCII-8BIT.

In simplecov-html, following line
https://github.com/colszowka/simplecov-html/blob/7540373ed44ccd43d1347b775a69673297cc8f90/views/source_file.erb#L48
will try to convert src from ASCII-8BIT to UTF-8!
Therefore, all non-ASCII characters will be replaced by Unicode Replacement Character.

[PragTob]

👋

Hi there, thanks for your fix! 💚

I'll have to mull the best approach over in my head a bit. I think this is pretty great and sophisticated but I think I need some time to think about and play with it.

Thanks!

[PragTob]

Thanks a lot, I think this is the right approach! I created #866 to build upon this and maybe still add some more specs (as files can have many forms I'm worried about something crashing while we try to read it 😅 ).

Goal is to write the cuke this evening and package up a release for early next week or maybe even this evening depending on how long I stay out today ;)

[PragTob]

Closing in favor of #866