Brackets in LWP Post

Bod has asked for the wisdom of the Perl Monks concerning the following question:

A while ago I asked about Data::Dumper output which was silly error on my part that was obscuring what was really going on!

The real problem is that LinkedIn is generating an error when I attempt to post. The error is: Illegal character VCHAR='(' So, instead of struggling with LWP::Authen::OAuth2, I thought I'd write my own module using LWP::Authen::OAuth2 to do the authentication and my own method to post to LinkedIn.

But I still get the same problem. I have tried debugging all the variables I use and these are all as expected.
This is the method I have to post to LinkedIn

sub post {
    my ($self, $text) = @_;
    my $ua     = $self->{'auth'}->user_agent;
    my $token  = $self->{'auth'}->access_token;
    my $header = {
        'Authorization:'             => 'Bearer ' . $token->{'access_t
+oken'},
        'X-Restli-Protocol-Version:' => '2.0.0',
        'Content-type:'              => 'text/json',
    };

    my $user = $self->get_id;
    my $json = {
        'owner'     => "urn:li:person:$user",
        'text'      => {
            'text'  => $text,
        },
    };
    
    $ua->default_header('Content-type' => 'text/json');
    return $ua->post(
        $self->{'auth'}->api_url_base . 'shares',
        Content => encode_json($json),
        $header,
    );
}
[download]

First off we get the underlaying User Agent from $self->{'auth'}. This is an instance of LWP::Authen::OAuth2 which has been authorised. I have checked that authorisation is happening correctly by calling the me endpoint which returns the authenticated user. The underlaying User Agent is an instance of LWP::UserAgent.
Next we get the user string which again I have checked to ensure it is correct - it is!

We have to call $ua->default_header('Content-type' => 'text/json'); as, for some reason, it doesn't set in $header earlier.

The call to $ua->post is going to the right place and sending the right data. The JSON payload might be a bit light to work as I have stripped it down to the bare minimum for testing. However, that would almost certainly produce a different error. When I call the method:

my $post = $linkedin->post("Some test text to post");
print Dumper $post;
[download]

I get a long JSON output back from LinkedIn. Here is the bit I think it is complaining about...

'_request' => bless( {
                                        '_content' => '{"owner":"urn:l
+i:person:GKiAGefMOA","text":{"text":"Some test text to post"}}',
                                        '_uri' => bless( do{\(my $o = 
+'https://api.linkedin.com/v2/shares')}, 'URI::https' ),
                                        '_headers' => bless( {
                                                               'user-a
+gent' => 'libwww-perl/6.49',
                                                               'hash(0
+x29bc430)' => undef,
                                                               'conten
+t-type' => 'text/json',
                                                               'conten
+t-length' => 77,
                                                               '::std_
+case' => {
                                                                      
+           'hash(0x29bc430)' => 'HASH(0x29bc430)',
                                                                      
+           'if-ssl-cert-subject' => 'If-SSL-Cert-Subject'
                                                                      
+         }
                                                             }, 'HTTP:
+:Headers' ),
                                        '_method' => 'POST',
                                        '_uri_canonical' => $VAR1->{'_
+request'}{'_uri'}
                                      }, 'HTTP::Request' )
[download]

I do not understand where ::std_case is coming from or why it contains un expanded hash references. Is this a bug in LWP perhaps?

Any ideas on how I can debug this problem further please?

If it helps, here is the full JSON response from LinkedIn:

$VAR1 = bless( {
                 '_msg' => 'Illegal character VCHAR=\'(\'',
                 '_content' => '<h1>Bad Message 400</h1><pre>reason: I
+llegal character VCHAR=\'(\'</pre>',
                 '_protocol' => 'HTTP/1.1',
                 '_headers' => bless( {
                                        'x-li-fabric' => 'prod-lva1',
                                        'set-cookie' => [
                                                          'bcookie="v=
+2&101cb44b-4229-4298-8a92-c5269a7fc04b"; Domain=.linkedin.com; Expire
+s=Fri, 12-May-2023 04:30:20 GMT; Path=/; Secure; SameSite=None',
                                                          'li_gc=MTswO
+zE2MjA3NTE5Njg7MjswMjH/a8hG8abKjZCHC2n5JOsrQCRqNMUbA1a8yBjKcfaoAw==; 
+Domain=.linkedin.com; Expires=Fri, 05 May 2023 19:16:27 GMT; Path=/; 
+Secure; SameSite=None',
                                                          'lidc="b=VB1
+7:s=V:r=V:a=V:p=V:g=3729:u=1:i=1620751968:t=1620838368:v=2:sig=AQEnd1
+nC7PL_5JIHPskD72XlQtoH5ub6"; Expires=Wed, 12 May 2021 16:52:48 GMT; d
+omain=.linkedin.com; Path=/; SameSite=None; Secure'
                                                        ],
                                        'date' => 'Tue, 11 May 2021 16
+:52:48 GMT',
                                        'client-ssl-cert-issuer' => '/
+C=US/O=DigiCert Inc/CN=DigiCert SHA2 Secure Server CA',
                                        'client-ssl-cipher' => 'ECDHE-
+RSA-AES128-GCM-SHA256',
                                        'client-peer' => '108.174.11.8
+4:443',
                                        'client-date' => 'Tue, 11 May 
+2021 16:52:48 GMT',
                                        'content-type' => 'text/html;c
+harset=iso-8859-1',
                                        'client-ssl-socket-class' => '
+IO::Socket::SSL',
                                        'client-response-num' => 1,
                                        'x-li-uuid' => 'FCL5EFQRfhZA0A
+HZiSsAAA==',
                                        'content-length' => 70,
                                        '::std_case' => {
                                                          'x-li-fabric
+' => 'X-Li-Fabric',
                                                          'client-resp
+onse-num' => 'Client-Response-Num',
                                                          'set-cookie'
+ => 'Set-Cookie',
                                                          'x-li-uuid' 
+=> 'X-LI-UUID',
                                                          'client-ssl-
+cert-issuer' => 'Client-SSL-Cert-Issuer',
                                                          'client-ssl-
+cipher' => 'Client-SSL-Cipher',
                                                          'client-peer
+' => 'Client-Peer',
                                                          'client-date
+' => 'Client-Date',
                                                          'x-li-pop' =
+> 'X-Li-Pop',
                                                          'client-ssl-
+cert-subject' => 'Client-SSL-Cert-Subject',
                                                          'x-li-proto'
+ => 'X-LI-Proto',
                                                          'client-ssl-
+socket-class' => 'Client-SSL-Socket-Class'
                                                        },
                                        'x-li-pop' => 'prod-edc2',
                                        'client-ssl-cert-subject' => '
+/C=US/ST=California/L=Sunnyvale/O=LinkedIn Corporation/CN=tablet.link
+edin.com',
                                        'x-li-proto' => 'http/1.1'
                                      }, 'HTTP::Headers' ),
                 '_rc' => 400,
                 '_request' => bless( {
                                        '_content' => '{"owner":"urn:l
+i:person:GKiAGefMOA","text":{"text":"Some test text to post"}}',
                                        '_uri' => bless( do{\(my $o = 
+'https://api.linkedin.com/v2/shares')}, 'URI::https' ),
                                        '_headers' => bless( {
                                                               'user-a
+gent' => 'libwww-perl/6.49',
                                                               'hash(0
+x29bc430)' => undef,
                                                               'conten
+t-type' => 'text/json',
                                                               'conten
+t-length' => 77,
                                                               '::std_
+case' => {
                                                                      
+           'hash(0x29bc430)' => 'HASH(0x29bc430)',
                                                                      
+           'if-ssl-cert-subject' => 'If-SSL-Cert-Subject'
                                                                      
+         }
                                                             }, 'HTTP:
+:Headers' ),
                                        '_method' => 'POST',
                                        '_uri_canonical' => $VAR1->{'_
+request'}{'_uri'}
                                      }, 'HTTP::Request' )
               }, 'HTTP::Response' );
[download]

Comment on Brackets in LWP Post Select or Download Code

Replies are listed 'Best First'.
Re: Brackets in LWP Post by bliako (Abbot) on May 11, 2021 at 18:17 UTC
Further arguments can be given to initialize the headers of the request. These are given as separate name/value pairs. (from LWP::UserAgent) You are POSTing with the wrong headers: you are giving a meaningless hashref whereas it should be dereferenced to provide `name/value pairs`. (that said, I can not say if all else is OK) `return $ua->post( $self->{'auth'}->api_url_base . 'shares', Content => encode_json($json), %$header, #<<<<< );` [download] bw, bliako	[reply] [d/l] [select]
Re^2: Brackets in LWP Post by Bod (Parson) on May 11, 2021 at 18:42 UTC
You are POSTing with the wrong headers: Fabulous! You are spot on...dereferencing `$header` makes it work as it should :) Many, many thanks. Bizarrely, the hashref worked to authorise a GET call to a different endpoint to fetch information about the current user. I used that to check that the headers were being passed correctly. Strange how it works for a GET but not a POST.	[reply] [d/l]
Re^3: Brackets in LWP Post by bliako (Abbot) on May 11, 2021 at 20:24 UTC
Bizarrely, the hashref worked to authorise a GET call that's strange because LWP::UserAgent says that they all use the same notation to pass the headers: `Additional headers and content options are the same as for the "get" in LWP::UserAgent method.` anyway, cool project!	[reply] [d/l]
Re: Brackets in LWP Post by choroba (Cardinal) on May 11, 2021 at 18:43 UTC
The documentation of the post method of LWP::UserAgent shows `my $res = $ua->post( $url, $field_name => $value, Content => $content +);` [download] Your code uses `$ua->post( $self->{'auth'}->api_url_base . 'shares', Content => encode_json($json), $header, );` [download] So, dereference the header (I also tried to moving it before Content, but it doesn't seem to matter). This should remove the hash reference from the request. `$ua->post( $self->{'auth'}->api_url_base . 'shares', %$header, Content => encode_json($json) );` [download] The `::std_case` field just handles standard lowercasing of header keys, nothing to worry about. `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l] [select]
Re^2: Brackets in LWP Post by Bod (Parson) on May 11, 2021 at 22:36 UTC
Fantastic thanks :) That's moved me forwards significantly...	[reply]
Re: Brackets in LWP Post by 1nickt (Canon) on May 11, 2021 at 17:36 UTC
Hi, What is the value `$self->{'auth'}->api_url_base`? It looks like an object, should it not be a string? The way forward always starts with a minimal test.	[reply] [d/l]
Re^2: Brackets in LWP Post by Bod (Parson) on May 11, 2021 at 17:55 UTC
What is the value `$self->{'auth'}->api_url_base`? `$self->{'auth'}` is the authenticated instance of LWP::Authen::OAuth2. `api_url_base` is a method of that module that just returns a string with the base path of the API. In this case, the string is `https://api.linkedin.com/v2/`. documentation	[reply] [d/l] [select]