Re: perltidy and UTF-8 BOM

[haukex]

It seems that Perl::Tidy only supports UTF-8 and the default ("none") encodings, and it does not recognize the BOM - when I run it with the -utf8 switch on a UTF-8 file with a BOM, I get "unexpected character decimal 65279 () in script".

While the UTF-8 BOM might be useful to your text editor, it isn't really useful to Perl: it is completely ignored, and you still need an explicit use utf8; (see the caveats at the beginning of perlunicode). Note this is different for UTF-16, where the BOM will cause Perl to automatically use that encoding. But anyway, you might want to consider whether you need the BOM, since many text editors default to UTF-8 anyway, and if you're worried someone might take your UTF-8 encoded Perl source and open it with an incorrect encoding, remember that there's still the use utf8; at the top of the file. In fact, I sometimes write "use utf8; # Euro Symbol: €" so that I have an immediate visual clue as to whether the text editor used the right encoding (why I like that symbol, plus it's easy to type on my German keyboard :-) ).

Other than filing a bug in the issue tracker and/or writing a patch, you could work around the issue by writing a small wrapper for perltidy that strips the BOM first and adds it back in again after:

perl -wM5.012 -CDS -pe '$.==1 && s/\A\x{FEFF}//' utf8_bom.pl \
    | perltidy -utf8 \
    | perl -wM5.012 -CDS -pe 'INIT{print "\x{FEFF}"}' \
    > utf8_bom_tidy.pl

[AnomalousMonk]

... s/\A\x{FEFF}// ... print "\x{FEFF}" ...

Again, a total UTF-8 n00b (or maybe nob) here, but isn't the UTF-8 BOM  "\xEF\xBB\xBF" (239 187 191) (see this and the perltidy complaint cited in the OP)? (And  \x{FEFF} works out to decimal 65279.)

[haukex]

The Byte order mark is the Unicode character U+FEFF, and depending on the encoding it is encoded as different bytes - see "Byte order marks by encoding" on the same Wikipedia page. Because I've changed STDIN and STDOUT to be UTF-8 with the command-line switch -CS, I can use the Unicode representation and don't need to look at the bytes (although I could do that too, but I figured since everything is UTF-8 already anyway...).

$ perl -wMstrict -CSD -e 'print "\x{FEFF}"' | hexdump -C
00000000  ef bb bf                                          |...|
$ perl -wMstrict -e 'binmode STDOUT, ":raw:encoding(UTF-8)";     print
+ "\x{FEFF}"' | hexdump -C
00000000  ef bb bf                                          |...|
$ perl -wMstrict -e 'binmode STDOUT, ":raw:encoding(UTF-16-LE)"; print
+ "\x{FEFF}"' | hexdump -C
00000000  ff fe                                             |..|
$ perl -wMstrict -e 'binmode STDOUT, ":raw:encoding(UTF-16-BE)"; print
+ "\x{FEFF}"' | hexdump -C
00000000  fe ff                                             |..|
$ perl -wMstrict -e 'binmode STDOUT, ":raw:encoding(UTF-32-LE)"; print
+ "\x{FEFF}"' | hexdump -C
00000000  ff fe 00 00                                       |....|
$ perl -wMstrict -e 'binmode STDOUT, ":raw:encoding(UTF-32-BE)"; print
+ "\x{FEFF}"' | hexdump -C
00000000  00 00 fe ff                                       |....|