Problem installing HTTP::UserAgent after Bailador

[nige123]

I recently upgraded to Rakudo 2017.07 - after installing Bailador with zef I installed HTTP::UserAgent.

Starting Bailador now gives the error:

===SORRY!===
P6M Merging GLOBAL symbols failed: duplicate definition of symbol Response

Is it possible there is a symbol clash with 'Response'?

[jonathanstowe]

yes, there may well be if Bailador or one of its dependencies has an HTTP::Response or possibly even just a Response in some other namespace. I think it may be because Bailador doesn't specify an "auth" in its META6. HTTP::UserAgent itself goes out of its way to fully qualify its own HTTP::Response and HTTP::Request with the appropriate auth and ISTR I sent a patch for HTTP::Server to avoid the clash with the similarly named modules that it provides. I guess that you'd probably see the same problem if you installed HTTP::Server.

Unfortunately there's not much that can be done in HTTP::UserAgent itself to prevent this short of renaming the modules, which might be a good idea in the medium term but not without some deprecation cycle as the module is a dependency of other modules.

It might be good if you could provide the actual code that is failing so we can test however.

[nige123]

Hi,

Thanks for the explanation. 👍

Here is some code that shows the problem ...

shell> rakudobrew build moar 2017.07
shell> rakudobrew build zef
shell> zef install Bailador
shell> zef install HTTP::UserAgent
shell> echo 'use Bailador; use HTTP::UserAgent' > boom.p6
shell> perl6 boom.p6
===SORRY!===
P6M Merging GLOBAL symbols failed: duplicate definition of symbol Response
shell> echo 'use HTTP::UserAgent; use Bailador' > works.p6
shell> perl6 works.p6
shell>

HTH

[ugexe]

The problem seems to be related to 3 things:

1. HTTP::UserAgent has a X::HTTP::Response
2. HTTP::Response has a X::HTTP::Response
3. Bailador has put something in either the X:: or ::Response namespace

1 and 2 seems to be trying to avoid circular dependency re X::HTTP base class. But by removing X::HTTP::Response from HTTP::UserAgent it no longer has merge failures (although it fails its test, since X::HTTP::Response in HTTP::Response does not have all the members of the one in HTTP::UserAgent).

The fact this only happens when loading Bailador first points at a rakudo bug.

[jonathanstowe]

Yeah I was hesitating on calling it as a rakudo bug without collecting some tangible evidence but yeah I was inclining toward that position. But this observation gives a starting point to make a standalone reproducer/

I'll take a look at the weekend to see if we can work around this.

[jonathanstowe]

Having had a quick look I think the sensible thing to do would to move all the exception classes into a single module and rationalise the names somewhat as this is not ideal by any standard :) Even if there is a bug in the Stash merge somewhere it will be neater and prevent any future problems.

Unless anyone has any strong objections, I will do this today.

[jonathanstowe]

For what it's worth, doing what I described above and using the more complex version of X::HTTP::Response just works and fixes the problem with Bailador. The just working thing may however may be due to insufficient testing of the exceptions, I'll try and improve this as well.

[jonathanstowe]

I'll merge the above branch in a bit unless someone finds a problem with it.

[nige123]

Thanks for sorting this ! 👍