warn about links with empty href destination

I often make blank links as a note to myself to remember to fill in
a URL. If I forget, though, there will be a link that just brings the
user to the top of the page, which isn't what I want. So now, we warn on
these empty links. If you want to bring the user to the top of the page,
use an explicit `#` character.

Fixes #492

lib/Statocles/Plugin/LinkCheck.pm

@@ -39,6 +39,7 @@ sub check_pages {
 
     my %page_paths = ();
     my %links = ();
+    my %empty = (); # Pages with empty links
     for my $page ( @{ $event->pages } ) {
         $page_paths{ $page->path } = 1;
         if ( $page->DOES( 'Statocles::Page::Document' ) ) {
@@ -47,8 +48,13 @@ sub check_pages {
             for my $attr ( qw( src href ) ) {
                 for my $el ( $dom->find( "[$attr]" )->each ) {
                     my $url = $el->attr( $attr );
+
+                    if ( !$url ) {
+                        push @{ $empty{ $page->path } }, $el;
+                    }
+
                     $url =~ s{#.*$}{};
-                    next unless $url;
+                    next unless $url; # Skip checking fragment-internal links for now
                     next if $url =~ m{^(?:[a-z][a-z0-9+.-]*):}i;
                     next if $url =~ m{^//};
                     if ( $url !~ m{^/} ) {
@@ -68,18 +74,25 @@ sub check_pages {
         }
     }
 
-    my @missing; # Array of arrayrefs of [ link => page ] pairs
+    my @missing; # Array of arrayrefs of [ link_url, page_path, link_element ]
     for my $link_url ( keys %links ) {
         $link_url .= 'index.html' if $link_url =~ m{/$};
         next if $page_paths{ $link_url } || $page_paths{ "$link_url/index.html" };
         next if grep { $link_url =~ /^$_/ } @{ $self->ignore };
         push @missing, [ $link_url, $_ ] for keys %{ $links{ $link_url } };
     }
 
+    for my $page_url ( keys %empty ) {
+        push @missing, map { [ '', $page_url, $_ ] } @{ $empty{ $page_url } };
+    }
+
     if ( @missing ) {
         # Sort by page url and then missing link url
         for my $m ( sort { $a->[1] cmp $b->[1] || $a->[0] cmp $b->[0] } @missing ) {
-            $event->emitter->log->warn( "URL broken on $m->[1]: '$m->[0]' not found" );
+            my $msg = $m->[0] ? sprintf( q{'%s' not found}, $m->[0] )
+                    : sprintf( q{Link with text "%s" has no destination}, $m->[2]->text )
+                    ;
+            $event->emitter->log->warn( "URL broken on $m->[1]: $msg" );
         }
     }
 }

t/app/blog/pages.t

@@ -66,6 +66,7 @@ my @page_tests = (
                 "Full URLs without schema are not broken" => '//example.com',
                 "Fixed relative URL" => '/blog/2014/06/02/more_tags/docs.html',
                 "Test a mailto: link" => 'mailto:[email protected]',
+                'No link destination' => '/blog/2014/06/02/more_tags/',
             );
             my @links = $dom->find( 'article .content a' )->each;
             is scalar @links, scalar keys %links, 'all links found';
@@ -813,6 +814,7 @@ my @page_tests = (
             "Full URLs without schema are not broken" => '//example.com',
             "Fixed relative URL" => 'docs.html',
             "Test a mailto: link" => 'mailto:[email protected]',
+            'No link destination' => '',
         );
         my @links = $dom->find( 'section a' )->each;
         is scalar @links, scalar keys %links, 'all links found';

t/plugin/link_check.t

@@ -41,6 +41,7 @@ subtest 'check links' => sub {
             [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/docs.html: '/missing/favicon.png' not found} ) ],
             [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/docs.html: '/missing/script.js' not found} ) ],
             [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/docs.html: '/missing/stylesheet.css' not found} ) ],
+            [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/index.html: Link with text "No link destination" has no destination}) ],
             [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/index.html: '/blog/2014/06/02/does_not_exist' not found}) ],
             [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/index.html: '/blog/2014/06/02/more_tags/current_does_not_exist' not found}) ],
             [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/index.html: '/blog/2014/06/02/more_tags/does_not_exist' not found}) ],
@@ -89,6 +90,7 @@ subtest 'ignore patterns' => sub {
 
         cmp_deeply $site->log->history,
             bag(
+                [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/index.html: Link with text "No link destination" has no destination}) ],
                 [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/index.html: '/blog/2014/06/02/does_not_exist' not found}) ],
                 [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/index.html: '/blog/2014/06/02/more_tags/current_does_not_exist' not found}) ],
                 [ ignore(), 'warn', re(qr{\QURL broken on $page: '/blog/2014/06/02/more_tags/does_not_exist' not found}) ],
@@ -116,7 +118,10 @@ subtest 'ignore patterns' => sub {
 
         my $page = '/blog/2014/06/02/more_tags/index.html';
 
-        cmp_deeply $site->log->history, [],
+        cmp_deeply $site->log->history, 
+            [
+                [ ignore(), warn => re(qr{\QURL broken on /blog/2014/06/02/more_tags/index.html: Link with text "No link destination" has no destination}) ],
+            ],
             'all broken links ignored'
                 or diag explain $site->log->history;
     };

t/share/app/blog/2014/06/02/more_tags/index.markdown

@@ -31,3 +31,6 @@ links:
 [Fixed relative URL](docs.html)
 
 [Test a mailto: link](mailto:[email protected])
+
+[No link destination]()
+

t/share/theme/site/layout.html.ep

@@ -23,7 +23,7 @@
         </nav>
         <%= $content %>
         <footer>
-            <a href="<%= $site->data->{profile_url} // '' %>">Profile</a>
+            <a href="<%= $site->data->{profile_url} // '#' %>">Profile</a>
             <div id="app-info"><%= $self->app->data->{info} // '' %></div>
         </footer>
     </body>