Add a text post processing phase to the translator.

Macros or problems can add a hook by calling
`add_content_post_processor` with a subroutine that will be called after
the translator has processed answers.  For all display modes except TeX,
the subroutine will be passed the problem text parsed into a Mojo::DOM
object and a reference to the header text.  For the TeX display mode a
reference to the problem text is passed.  The subroutine can then modify
the problem DOM or text, and header text.  The resulting Mojo::DOM
object will be converted back to a string and the problem text reference
returned by the translator set to point to that string.

Note that the `$PG_PROBLEM_TEXT_ARRAY_REF` has been removed from the
translator code.  It is never used and is redundant with the
`$PG_PROBLEM_TEXT_REF` which is all that is used.  It was becoming
annoying to maintain both in a compatible manner.

The hidden MathQuill inputs for the latex string is added in this post
processing stage (see the ENDDOCUMENT method in PG.pl).

.github/workflows/unit-tests.yml

@@ -28,6 +28,7 @@ jobs:
             libhtml-parser-perl \
             libjson-perl \
             libjson-xs-perl \
+            libmojolicious-perl \
             libtest2-suite-perl \
             libtie-ixhash-perl \
             libuuid-tiny-perl \

cpanfile

@@ -17,6 +17,7 @@ on runtime => sub {
 	requires 'JSON';
 	requires 'JSON::XS';
 	requires 'Locale::Maketext';
+	requires 'Mojolicious';
 	requires 'Tie::IxHash';
 	requires 'Types::Serialiser';
 	requires 'UUID::Tiny';

docker/pg.Dockerfile

@@ -20,6 +20,7 @@ RUN apt-get update \
 		libhtml-parser-perl \
 		libjson-perl \
 		libjson-xs-perl \
+		libmojolicious-perl \
 		libtest2-suite-perl \
 		libtie-ixhash-perl \
 		libuuid-tiny-perl \

htdocs/js/InputColor/color.js

@@ -42,7 +42,7 @@
 				answerInput.focus();
 			});
 		} else {
-			answerLink.href = '';
+			answerLink.removeAttribute('href');
 		}
 	};
 

lib/PGcore.pm

@@ -97,6 +97,7 @@ sub new {
 		PG_alias                     => undef,
 		PG_problem_grader            => undef,
 		displayMode                  => undef,
+		content_post_processors      => [],
 		envir                        => $envir,
 		WARNING_messages             => [],
 		DEBUG_messages               => [],
@@ -563,6 +564,12 @@ sub get_persistent_data {
 	return $self->{PERSISTENCE_HASH}{$label};
 }
 
+sub add_content_post_processor {
+	my ($self, $handler) = @_;
+	push(@{ $self->{content_post_processors} }, $handler) if ref($handler) eq 'CODE';
+	return;
+}
+
 sub check_answer_hash {
 	my $self = shift;
 	foreach my $key (keys %{ $self->{PG_ANSWERS_HASH} }) {

lib/WeBWorK/PG.pm

@@ -139,7 +139,7 @@ sub new_helper ($invocant, %options) {
 		}
 	}
 
-	$translator->translate();
+	$translator->translate;
 
 	# IMPORTANT: The translator environment should not be trusted after the problem code runs.
 
@@ -172,6 +172,8 @@ sub new_helper ($invocant, %options) {
 		);
 	}
 
+	$translator->post_process_content;
+
 	# HTML_dpng uses an ImageGenerator. We have to render the queued equations.
 	if ($image_generator) {
 		my $sourceFile = "$options{templateDirectory}$options{sourceFilePath}";