Feature #5558: String#% strange arity errors

• Status: Assigned
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[trans (Thomas Sawyer)]

When the number of arguments do not match the number of % parameters, the String#% method has some odd behavior.

When too many, it seems to work fine, ignoring the extra arguments.

"%s" % [1,2] #=> "1"

But if $DEBUG = true,

"%s" % [1,2] #=> ArgumentError: too many arguments for format string

That doesn't seem right. Is it an error or isn't it?

For too few arguments it is always an error:

"%s" % [] #=> ArgumentError: too few arguments

Personally, I think it should use '' for missing arguments. That would make it more flexible in practice.

I consider the first $DEBUG issue a bug, and the later a feature. But I'll just call it a feature altogether to make things easier.

[mame (Yusuke Endoh)]

• Status changed from Open to Assigned
• Assignee set to matz (Yukihiro Matsumoto)

This behavior is certainly intended. See [ruby-core:5161].

There is another example that behavior changes whether it is
debug mode or not: Thread#abort_on_exception.

Thread.new { raise }
sleep 1

The above will terminate normally without -d.
But it will blow up with -d.
So, we should know that -d affects the behavior, IMO.

--
Yusuke Endoh [e-mail]

[mame (Yusuke Endoh)]

• Target version set to 2.6

[naruse (Yui NARUSE)]

• Target version deleted (2.6)