Why don't I get a defined value from LWP::UserAgent->new()?

Question

I get this error while using cookie_jar method:

Can't call method cookie_jar on an undefined value

Here is my code:

my $cookie_jar= new HTTP::Cookies;
my $ua=new LWP::UserAgent;
my %cookies= fetch CGI::Cookie;
my $encoded=$cookies{'SCred'};
$cookie_jar->set_cookie(1, "SCred", $encoded, "/", $SSO_DOMAIN,  "", 0, 0, 60*60, 0);
$ua->cookie_jar($cookie_jar); # I get error on this line

Any idea why I get this error?

Answer 1

I've tried your code (with strict, warnings and what I think are the required modules, with turning the free variables into strings):

kyle@indigo64 ~[home*]$ cat x.pl
use strict;
use warnings;
use HTTP::Cookies;
use LWP::UserAgent;
use CGI::Cookie;

my $ua         = new LWP::UserAgent;
my %cookies    = fetch CGI::Cookie;
my $encoded    = $cookies{'SCred'};

my $cookie_jar = new HTTP::Cookies;
$cookie_jar->set_cookie(
  1, "SCred", '$encoded',
  "/", '$SSO_DOMAIN',  "",
  0, 0, 60*60, 0
);
$ua->cookie_jar($cookie_jar);

print "ua: ",$ua,"\n";
print "ua->cookie_jar: ",$ua->cookie_jar,"\n";
mortis@indigo64 ~[home*]$ perl x.pl
ua: LWP::UserAgent=HASH(0x82f8cc8)
ua->cookie_jar: HTTP::Cookies=HASH(0x82f8b84)
kyle@indigo64 ~[home*]$ 

and it works. You might want to either post a fuller example, or are there lines between the '$ua = new...' and the '$ua->cookie_jar' lines where $ua is re-assigned or otherwise set to undef? If you print the value of '$ua' just before the call to cookie_jar you should see that it's undef, it must be being reset somewhere between the first assignment and where you are calling that method.

Answer 2

Just to rule out any weird interactions, try the following:

my $cookie_jar = HTTP::Cookies->new;
my $ua = LWP::UserAgent->new;
my %cookies = CGI::Cookie->fetch;
my $encoded = $cookies{'SCred'};
$cookie_jar->set_cookie(
    1, "SCred", $encoded, "/", $SSO_DOMAIN,  "", 0, 0, 60*60, 0
);
$ua->cookie_jar($cookie_jar); # I get error on this line

Now, for some reason, $ua is undefined, which means the constructor call:

my $ua = LWP::UserAgent->new;

failed. I am not too familiar with fastcgi. However, LWP::UserAgent croaks on any failure in the constructor: I am not sure how you are reaching the line in question.

Have you checked the server logs? Total shot in the dark: Does the following add any useful information to the error log?

my $ua = eval { LWP::UserAgent->new }
    or warn "LWP::UserAgent->new failed: $@";

Answer 3

If that is the actual error you get, it's not a problem with cookie_jar. That just happens to be the first method you try to call. Check that you actually get an object when when make the user-agent.

Remove all the cookie stuff and try the agent method:

use strict;
my $ua = eval { LWP::UserAgent->new }
    or die "Could not make user-agent! $@";
$ua->agent("TestAgent");

If anything goes wrong in the constructor, you should be able to catch it. However, if your script isn't already die-ing, I think you have something else wrong. If LWP::UserAgent::new runs into a problem, it already croaks. The only thing it can return is a defined value that it has already called methods on.