Abstract inline CSS feature

CSS::Inliner is reused across the codebase. This abstraction eliminates
duplication and simplifies future customization.

Previously, the 1MB size limit was hard-coded. This commit replaces it with
a package variable to make it configurable.

Also update RT_Config doc as CSS::Inliner is now a core dependency.

Author: sunnavy

etc/RT_Config.pm.in

@@ -974,12 +974,12 @@ formatting look very much like the corresponding RT page, but it also
 makes the emails very large. They can be large enough that some email
 servers will trim content because of the size.
 
-To reduce the size of the emails, you can install the optional module
-C<CSS::Inliner> and enable the C<$EmailDashboardInlineCSS> option. When
-enabled, styles will be applied directly to the HTML in the email and
-the large C<style> sections are removed. This significantly reduces
-the size of dashboard emails at the cost of some detail in the styling.
-With this enabled, some parts of the email won't look exactly like RT.
+To reduce the size of the emails, you can enable the
+C<$EmailDashboardInlineCSS> option. When enabled, styles will be applied
+directly to the HTML in the email and the large C<style> sections are
+removed. This significantly reduces the size of dashboard emails at the
+cost of some detail in the styling. With this enabled, some parts of the
+email won't look exactly like RT.
 
 =cut
 

lib/RT/Dashboard/Mailer.pm

@@ -62,6 +62,7 @@ use File::Temp 'tempdir';
 use HTML::Scrubber;
 use URI::QueryParam;
 use List::MoreUtils qw( any none uniq );
+use RT::Util 'InlineCSS';
 
 sub MailDashboards {
     my $self = shift;
@@ -613,21 +614,11 @@ sub BuildEmail {
         inline_imports => 1,
     );
 
-    # Inline the CSS if CSS::Inliner is installed and can be loaded
+    # Inline the CSS
     if ( RT->Config->Get('EmailDashboardInlineCSS') ) {
-        if ( RT::StaticUtil::RequireModule('CSS::Inliner') ) {
-            # HTML::Query generates a ton of warnings about unsupported
-            # pseudoclasses. Suppress those since they don't help the person
-            # running RT.
-            local $SIG{__WARN__} = sub {};
-
-            my $inliner = CSS::Inliner->new( { encode_entities => 1, ignore_style_type_attr => 1 } );
-            $inliner->read({ html => $content });
-            $content = $inliner->inlinify();
-        }
-        else {
-            RT->Logger->warn('EmailDashboardInlineCSS is enabled but CSS::Inliner is not installed. Install the optional module CSS::Inliner to use this feature.');
-        }
+        # Mailer usually works at backend, remove the size limit
+        local $RT::Util::INLINE_CSS_MAX_SIZE;
+        $content = InlineCSS($content);
     }
 
     my $entity = MIME::Entity->build(

lib/RT/Interface/Web/Scrubber.pm

@@ -53,6 +53,7 @@ use 5.010;
 use base qw/HTML::Scrubber/;
 
 use HTML::Gumbo;
+use RT::Util 'InlineCSS';
 
 =head1 NAME
 
@@ -247,14 +248,7 @@ sub scrub {
         warn "HTML::Gumbo pre-parse failed: $@" if $@;
     }
 
-    if ( ( length($Content) < ( 1024 * 1024 ) ) && $Content =~ /<style.*>/ ) {
-        require CSS::Inliner;
-        my $css_inliner = CSS::Inliner->new( { encode_entities => 1, ignore_style_type_attr => 1, ignore_selectors => ['pre'] } );
-        $css_inliner->read( { html => $Content } );
-        $Content = $css_inliner->inlinify();
-    }
-
-    return $self->SUPER::scrub($Content);
+    return $self->SUPER::scrub( InlineCSS($Content) );
 }
 
 RT::Base->_ImportOverlays();

lib/RT/Transaction.pm

@@ -81,6 +81,7 @@ use vars qw( %_BriefDescriptions $PreferredContentType );
 use RT::Attachments;
 use RT::Scrips;
 use RT::Ruleset;
+use RT::Util 'InlineCSS';
 
 use HTML::FormatText::WithLinks::AndTables;
 use HTML::Scrubber;
@@ -379,13 +380,6 @@ sub Content {
             if ($args{Type} ne 'text/html') {
                 $content = RT::Interface::Email::ConvertHTMLToText($content);
             } else {
-                if ( ( length($content) < ( 1024 * 1024 ) ) && $content =~ /<style.*>/ ) {
-                    require CSS::Inliner;
-                    my $css_inliner = CSS::Inliner->new( { encode_entities => 1, ignore_style_type_attr => 1, ignore_selectors => ['pre'] } );
-                    $css_inliner->read( { html => $content } );
-                    $content = $css_inliner->inlinify();
-                }
-
                 # Scrub out <html>, <head>, <meta>, and <body>, and
                 # leave all else untouched.
                 my $scrubber = HTML::Scrubber->new();
@@ -396,7 +390,7 @@ sub Content {
                     body => 0,
                 );
                 $scrubber->default( 1 => { '*' => 1 } );
-                $content = $scrubber->scrub( $content );
+                $content = $scrubber->scrub( InlineCSS($content) );
             }
         }
         else {

lib/RT/Util.pm

@@ -52,7 +52,7 @@ use warnings;
 
 
 use base 'Exporter';
-our @EXPORT = qw/safe_run_child mime_recommended_filename EntityLooksLikeEmailMessage EmailContentTypes/;
+our @EXPORT = qw/safe_run_child mime_recommended_filename EntityLooksLikeEmailMessage EmailContentTypes InlineCSS/;
 
 use Scalar::Util qw/weaken/;
 use Encode qw/encode/;
@@ -287,6 +287,44 @@ sub RecursiveSub {
     return $sub;
 }
 
+=head2 InlineCSS CONTENT
+
+For html CONTENT, convert CSS <style> blocks to inline styles.
+
+=cut
+
+our $INLINE_CSS_MAX_SIZE = 1024 * 1024;
+
+sub InlineCSS {
+    my $content = shift // return;
+
+    if ( $INLINE_CSS_MAX_SIZE && length($content) > $INLINE_CSS_MAX_SIZE ) {
+        RT->Logger->debug("Content exceeds max size ($INLINE_CSS_MAX_SIZE), skipping");
+        return $content;
+    }
+
+    if ( $content !~ /<style.*>/ ) {
+        RT->Logger->debug("Content does not contain style blocks, skipping");
+        return $content;
+    }
+
+    # HTML::Query generates a ton of warnings about unsupported
+    # pseudoclasses. Suppress those since they don't help the person
+    # running RT.
+    local $SIG{__WARN__} = sub {};
+    require CSS::Inliner;
+    my $css_inliner = CSS::Inliner->new(
+        {   encode_entities        => 1,
+            ignore_style_type_attr => 1,
+            ignore_selectors       => ['pre'],
+            @_,
+        }
+    );
+    $css_inliner->read( { html => $content } );
+    return $css_inliner->inlinify();
+}
+
+
 require RT::Base;
 RT::Base->_ImportOverlays();