ruby rspec and strings comparison

Question

I'm not a ruby expert and may be this will seem a silly question...but I'm too courious about an oddity (I think) I've found in RSpec matcher called match.

You know match takes in input a string or a regex. Example:

"test".should match "test" #=> will pass
"test".should match /test/ #=> will pass

The strange begins when you insert special regex characters in the input string:

"*test*".should match "*test*" #=> will fail throwing a regex exception

This means (I thought) that input strings are interpreted as regex, then I should escape special regex characters to make it works:

"*test*".should match "\*test\*" #=> will fail with same exception
"*test*".should match /\*test\*/ #=> will pass

From this basic test, I understand that match treats input strings as regular expressions but it does not allow you to escape special regex characters.

Am I true? Is not this a singular behavior? I mean, it's a string or a regex!

EDIT AFTER ANSWER:

Following DigitalRoss (right) answer the following tests passed:

"*test*".should match "\\*test\\*" #=> pass
"*test*".should match '\*test\*' #=> pass
"*test*".should match /\*test\*/ #=> pass

DigitalRoss · Accepted Answer · 2011-04-24 19:07:29Z

13

What you are seeing is the different interpretation of backslash-escaped characters in String vs Regexp. In a soft (") quoted string, \* becomes a *, but /\*/ is really a backslash followed by a star.

If you use hard quotes (') for the String objects or double the backslash characters (only for the Strings, though) then your tests should produce the same results.

edited Apr 24, 2011 at 19:07

answered Apr 24, 2011 at 17:41

DigitalRoss

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3 Comments

Emiliano Poggi Over a year ago

Thanks you are right. I edited the question with the code tests you mentioned.

Ghoti Over a year ago

You can also escape regexp like strings, e.g. %r{\*test\*} Not so useful with this because you still need backslashes, but found it invaluable when matching for /

random-forest-cat Over a year ago

lightly related, but i ran into a similar issue - mine was around string comparisons containing escaped characters, `\nsome text\n' for example. fixed using double quotes to prevent rspec from double escaping.

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