Bug #20518
closed
Escaped-newline in %W
Description
I found an escaped-newline in %W literal is interpreted as a newline character.
% ./ruby -e '
p %W[a\
b]'
["a\nb"]
I expected it to be interpreted as a line continuation but actually not.
I'm considering to describe \<newline> as a kind of escape sequence in the document.
(Related to https://bugs.ruby-lang.org/issues/20503#note-4 )
Unfortunately, this behavior contradicts: \<newline> doesn't behave as usual escape sequences.
Note that %W is interpolable string-array literal.
https://docs.ruby-lang.org/en/master/syntax/literals_rdoc.html#label-25w+and+-25W-3A+String-Array+Lite
"interpolable" means that interpolation and escape sequences are enabled.
Other escape sequences and interpolation work well.
% ./ruby -e '
p %W[a\
b c\x21d e#{6*7}f]'
["a\nb", "c!d", "e42f"]
\x21 is interpreted as "!" and #{6*7} is iterpreted as "42".
It is the usual interpretation of escape sequences and interpolation.
But \<newline> is interpreted as "\n".
It is not the usual interpretation of escape sequences (line continuation).
It is interpreted as a line continuation in a double-quoted string:
% ./ruby -e '
p %Q[a\
b c\x21d e#{6*7}f]'
"ab c!d e42f"
\<newline> is interpreted as empty (line continuation) as expected.
\x21 is interpreted as "!" and #{6*7} is interpreted as "42".
I found this behavior changed between Ruby 1.8.0 and 1.8.1.
Ruby 1.8.0 interprets \<newline> as line continuation.
% ruby-1.8.0 -e '
p %W[a\
b c\x21d e#{6*7}f]'
["ab", "c!d", "e42f"]
% ruby-1.8.1 -e '
p %W[a\
b c\x21d e#{6*7}f]'
["a\nb", "c!d", "e42f"]
I think this is the commit to change the behavior.
commit e168b64b03403fb4efbd8dcbbdaeed83710b4d39 0d1896a88fe091000ce0d9c8ef3cf7ef1e2e991b
Author: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: 2003-09-04 14:59:43 +0000
* parse.y (tokadd_string): newlines have no special meanings in
%w/%W, otherwise they are ignored only when interpolation is
enabled. [ruby-dev:21325]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@4496 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
I read the discussion from [ruby-dev:21325].
https://public-inbox.org/ruby-dev/5FD2F0CF7F5D7F44B00F36870B9E78B508DE5071@SBG-EX4/
It discusses about %w.
%W is not considered well.
The behavior of %w is also changed between Ruby 1.8.0 and 1.8.1.
% ruby-1.8.0 -e '
p %w[a\
b c\x21d e#{6*7}f]'
["ab", "c\\x21d", "e#{6*7}f"]
% ruby-1.8.1 -e '
p %w[a\
b c\x21d e#{6*7}f]'
["a\nb", "c\\x21d", "e#{6*7}f"]
I understand the intent of this behavior for %w: it makes it possible to include white spaces in the word.
Without this behavior, there is no way to include a newline character in the word.
But I don't understand the intent for %W.
Including a newline character using \n is possible because escape sequences are enabled.
% ./ruby -v
ruby 3.4.0dev (2024-05-25T10:15:25Z master 0bae2f0002) [x86_64-linux]
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