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Backport #8341

closed

block_given? (and the actual block) persist between calls to a proc created from a method (using method().to_proc()).

Added by pythonesque (Joshua Yanovski) about 9 years ago. Updated almost 9 years ago.

Status:
Closed
Priority:
Normal
[ruby-core:54626]

Description

Confirmed on both 2.0.0 and 1.9.2-p290. A testcase (utilizing RSpec) is attached, but the behavior is easy to demonstrate without a testcase or RSpec.

First, we define a method that can optionally accept a block.
def foo
if block_given?
yield
else
puts "No block given."
end
end

Then, we convert the method to a proc and store it in a variable.
method_to_proc = method(:foo).to_proc

Now, we try calling method_to_proc without a block, getting the expected result:
method_to_proc.call

=> No block given.

We call it again, this time with a block, and again get the expected result:
method_to_proc.call { puts "Block given." }

=> Block given.

But when we call it a third time, again with no block...
method_to_proc.call

=> Block given.

...it remembers the previous proc that was passed in.

If we then call it with a new proc, it overwrites the old proc as expected (this is not tested in the testcase, which only tests block_given?):
method_to_proc.call { puts "New block given." }

=> New block given.

The testcase verifies this behavior, and also that the behavior does not occur when calling a method in the usual way, or when using method() but not to_proc(), or when using method().to_proc() but not storing the result in the same variable (the last of which isn't that surprising but is included for completeness).

I cannot see any reason that this should be expected behavior. Either block_given? should work the same way in method.to_proc()s as it does in method()s, or it should always return false, and it certainly shouldn't "remember" the last block used.


Files

testcase.rb (1.67 KB) testcase.rb pythonesque (Joshua Yanovski), 04/28/2013 06:32 AM
8341.patch (2.32 KB) 8341.patch ktsj (Kazuki Tsujimoto), 06/16/2013 03:29 AM

Related issues 1 (0 open1 closed)

Related to Backport193 - Backport #8531: ifuncに渡したブロックが共有されるClosedusa (Usaku NAKAMURA)06/16/2013Actions
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