Re^5: Moo and Spreadsheet::ParseExcel

Error reproduced! :-)

Here's a one line patch for Moo::Role that fixes your issue. I'll report it to the Moo bug tracker when I've figured out why this patch makes any difference to anything!

# Replace this sub...
sub apply_roles_to_package {
  my ($me, $to, @roles) = @_;
  $me->_inhale_if_moose($_) for @roles;
  $me->SUPER::apply_roles_to_package($to, @roles);
}

# With this instead...
sub apply_roles_to_package {
  my ($me, $to, @roles) = @_;
  for my $r (@roles) { $me->_inhale_if_moose($r) };
  $me->SUPER::apply_roles_to_package($to, @roles);
}
[download]

Update: OK, it happens because something inadvertently causes the global $_ to become undefined.

Update 2: Bug report submitted.

Update 3: patched on git.

Update 4 (about a week later): Moo 1.000006 released.

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

Comment on Re^5: Moo and Spreadsheet::ParseExcel Download Code

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Re^6: Moo and Spreadsheet::ParseExcel by karlgoethebier (Abbot) on Nov 09, 2012 at 13:06 UTC
Great! But how strange. `local $_` also fails. It would be very interesting to hear why this fails. Update: Ergo better omit `$_` in general? Thank you very much for your help and best regards, Karl ŤThe Crux of the Biscuit is the Apostropheť	[reply] [d/l] [select]
Re^7: Moo and Spreadsheet::ParseExcel by tobyink (Canon) on Nov 09, 2012 at 13:32 UTC
`my $_` should work, but `local $_` would fail. It's because the loop variable in a `for` loop is an alias to each element of the array. So the global `$_` is an alias into `@roles` in this case. Assigning to global `$_` assigns into the `@roles` array. `local` (despite the name) operates on global variables, providing a local value for them, but not really creating a new local variable. So even in the scope of `local $_` assigning to `$_` will assign into `@roles`. It's a particular combination of Perl features which is normally fairly safe to use, but because `apply_roles_to_package` also happens to load modules (and thus run third-party code - i.e. code which is not part of Moo) it causes problems. `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply] [d/l] [select]
Re^8: Moo and Spreadsheet::ParseExcel (explain?) by tye (Sage) on Nov 17, 2012 at 19:29 UTC
Could you try explaining this again? In particular, what is the code outside of Moo that causes $_ to exhibit this problem? It probably doesn't help that I'm not clear on how 'undef' ends up in @roles (is the code that does that shown anywhere in this thread?). I'm also unclear how the 'uninitialized' warning causes the Role::Tiny module to fail (leading to a "Compilation failed") without producing an error message. Thank you (in advance). - tye	[reply]
Re^9: Moo and Spreadsheet::ParseExcel (explain?) by tobyink (Canon) on Nov 17, 2012 at 23:45 UTC
Re^10: Moo and Spreadsheet::ParseExcel (explain?) by tye (Sage) on Nov 18, 2012 at 01:16 UTC
Re^6: Moo and Spreadsheet::ParseExcel by karlgoethebier (Abbot) on Nov 17, 2012 at 13:02 UTC
Thanks again for fixing this. Regards, Karl ŤThe Crux of the Biscuit is the Apostropheť	[reply]