From @jonathanstowe

If the second grep was working on the result of the first this would not output anything​:

install/bin/perl6 -e 'Supply.from-list(<foo bar baz>).grep(/foo/).grep(/baz/).tap({say $_})'
baz

Instead it outputs "baz" which is a valid value from the original Supply.

Having bisected this was definitely introduced with a8231f14b2d5400e0653aac453496e00318142c5 which was where the majority of the changes to supplies went in.

It is still present in

This is Rakudo version 2015.12-111-gfec0619 built on MoarVM version 2015.12
implementing Perl 6.c

which is where I detected it, and HEAD as of today.

I noticed this first in trying to fix Net​::AMQP in the ecosystem, here it greps for AMQP frames which represent methods and reformats them to a hash with the method as a key, a subsequent attempt to further grep the resulting supply is fatal because it reverts to being raw AMQP frames as per the original supply.

I can add a test to roast if necessary.

From @jonathanstowe

Added a test in Raku/roast@696d50a932

It is fixed by rakudo 770d1097380822808e4597ce42d0b750dbd4909b

On Sun Jan 17 05​:10​:22 2016, jns+bc@​gellyfish.co.uk wrote​:

If the second grep was working on the result of the first this would
not output anything​:

install/bin/perl6 -e 'Supply.from-list(<foo bar
baz>).grep(/foo/).grep(/baz/).tap({say $_})'
baz

Instead it outputs "baz" which is a valid value from the original
Supply.

Having bisected this was definitely introduced with
a8231f14b2d5400e0653aac453496e00318142c5 which was where the majority
of the changes to supplies went in.

It is still present in

This is Rakudo version 2015.12-111-gfec0619 built on MoarVM version
2015.12
implementing Perl 6.c

which is where I detected it, and HEAD as of today.

I noticed this first in trying to fix Net​::AMQP in the ecosystem, here
it greps for AMQP frames which represent methods and reformats them to
a hash with the method as a key, a subsequent attempt to further grep
the resulting supply is fatal because it reverts to being raw AMQP
frames as per the original supply.

I can add a test to roast if necessary.

@jnthn - Status changed from 'new' to 'resolved'