Tim Hunt authored Apr 05, 2020 and Eloy Lafuente committed Apr 24, 2020

A bit off-topic for this issue number, but I noticed it while
working on this, and though it was not worth creating a
separate MDL for.

This information is not really meaningful for users, and takes up prime
real-estate, so we are removing it.

Having had one subtle bug cased be this, I decided to do a search and
fix all of these.

Now any question using extra_question_fields can overload make_answer
(just as make_hint), instead of overloading whole initialise_question_answers.

question_type::save_question_answers function added, supporting
saving answers and extra answer fields. It can be called from
save_question_options function for the questions, using
question_answers table. Special functions created for overloading
so that every question could tune it to it's own form.

Shortanswer qtype save_question_options() converted as a proof of
concept and for testing purposes.

Extra answer data may be optional, saving DB space - i.e. not every row in
question_answers will have respective row in extra answers table. Current
implementation of question_type::get_question_options() won't return such
answers at all. This commit fix that, changing join type for db query.

Also fixed coding style violation in the variable name in get_question_options.

where there are very many variants

This adds 3 new methods, called from question_type::save_hints,
to make it easier for different question types to overload this
functionality without duplicating code.

Question types that will benefit from this change include
oumultiresponse, ddmarker, preg and correctwriting.

Correct bad formated infiles in question/type directories

$a->field = null; isset($a->field) returns false, which is typical PHP.
I also improve the error handling a bit.

Without this, images in answers were not being written to the export
file for questions using extra_answer_fields.

The files that belong to the question hints are neither moved when the
question is moved to another context, nor deleted when the question is
deleted.

Oops! How come no one noticed that until today.

Will let us make more of qtype backup and restore work automatically.

Shortanswer question type converted to use extra question fields.
Signed-off-by: Oleg Sychev <oasychev@gmail.com>

AMOS BEGIN
 MOV [calculated,qtype_calculated],[pluginname,qtype_calculated]
 MOV [calculated_help,qtype_calculated],[pluginname_help,qtype_calculated]
 MOV [calculated_link,qtype_calculated],[pluginname_link,qtype_calculated]
 MOV [addingcalculated,qtype_calculated],[pluginnameadding,qtype_calculated]
 MOV [editingcalculated,qtype_calculated],[pluginnameediting,qtype_calculated]
 MOV [calculatedsummary,qtype_calculated],[pluginnamesummary,qtype_calculated]

 MOV [calculatedmulti,qtype_calculatedmulti],[pluginname,qtype_calculatedmulti]
 MOV [calculatedmulti_help,qtype_calculatedmulti],[pluginname_help,qtype_calculatedmulti]
 MOV [calculatedmulti_link,qtype_calculatedmulti],[pluginname_link,qtype_calculatedmulti]
 MOV [addingcalculatedmulti,qtype_calculatedmulti],[pluginnameadding,qtype_calculatedmulti]
 MOV [editingcalculatedmulti,qtype_calculatedmulti],[pluginnameediting,qtype_calculatedmulti]
 MOV [calculatedmultisummary,qtype_calculatedmulti],[pluginnamesummary,qtype_calculatedmulti]

 MOV [calculatedsimple,qtype_calculatedsimple],[pluginname,qtype_calculatedsimple]
 MOV [calculatedsimple_help,qtype_calculatedsimple],[pluginname_help,qtype_calculatedsimple]
 MOV [calculatedsimple_link,qtype_calculatedsimple],[pluginname_link,qtype_calculatedsimple]
 MOV [addingcalculatedsimple,qtype_calculatedsimple],[pluginnameadding,qtype_calculatedsimple]
 MOV [editingcalculatedsimple,qtype_calculatedsimple],[pluginnameediting,qtype_calculatedsimple]
 MOV [calculatedsimplesummary,qtype_calculatedsimple],[pluginnamesummary,qtype_calculatedsimple]

 MOV [description,qtype_description],[pluginname,qtype_description]
 MOV [description_help,qtype_description],[pluginname_help,qtype_description]
 MOV [addingdescription,qtype_description],[pluginnameadding,qtype_description]
 MOV [editingdescription,qtype_description],[pluginnameediting,qtype_description]
 MOV [descriptionsummary,qtype_description],[pluginnamesummary,qtype_description]

 MOV [essay,qtype_essay],[pluginname,qtype_essay]
 MOV [essay_help,qtype_essay],[pluginname_help,qtype_essay]
 MOV [essay_link,qtype_essay],[pluginname_link,qtype_essay]
 MOV [addingessay,qtype_essay],[pluginnameadding,qtype_essay]
 MOV [editingessay,qtype_essay],[pluginnameediting,qtype_essay]
 MOV [essaysummary,qtype_essay],[pluginnamesummary,qtype_essay]

 MOV [match,qtype_match],[pluginname,qtype_match]
 MOV [match_help,qtype_match],[pluginname_help,qtype_match]
 MOV [match_link,qtype_match],[pluginname_link,qtype_match]
 MOV [addingmatch,qtype_match],[pluginnameadding,qtype_match]
 MOV [editingmatch,qtype_match],[pluginnameediting,qtype_match]
 MOV [matchsummary,qtype_match],[pluginnamesummary,qtype_match]

 MOV [missingtype,qtype_missingtype],[pluginname,qtype_missingtype]
 MOV [addingmissingtype,qtype_missingtype],[pluginnameadding,qtype_missingtype]
 MOV [editingmissingtype,qtype_missingtype],[pluginnameediting,qtype_missingtype]

 MOV [multianswer,qtype_multianswer],[pluginname,qtype_multianswer]
 MOV [multianswer_help,qtype_multianswer],[pluginname_help,qtype_multianswer]
 MOV [multianswer_link,qtype_multianswer],[pluginname_link,qtype_multianswer]
 MOV [addingmultianswer,qtype_multianswer],[pluginnameadding,qtype_multianswer]
 MOV [editingmultianswer,qtype_multianswer],[pluginnameediting,qtype_multianswer]
 MOV [multianswersummary,qtype_multianswer],[pluginnamesummary,qtype_multianswer]

 MOV [multichoice,qtype_multichoice],[pluginname,qtype_multichoice]
 MOV [multichoice_help,qtype_multichoice],[pluginname_help,qtype_multichoice]
 MOV [multichoice_link,qtype_multichoice],[pluginname_link,qtype_multichoice]
 MOV [addingmultichoice,qtype_multichoice],[pluginnameadding,qtype_multichoice]
 MOV [editingmultichoice,qtype_multichoice],[pluginnameediting,qtype_multichoice]
 MOV [multichoicesummary,qtype_multichoice],[pluginnamesummary,qtype_multichoice]

 MOV [numerical,qtype_numerical],[pluginname,qtype_numerical]
 MOV [numerical_help,qtype_numerical],[pluginname_help,qtype_numerical]
 MOV [numerical_link,qtype_numerical],[pluginname_link,qtype_numerical]
 MOV [addingnumerical,qtype_numerical],[pluginnameadding,qtype_numerical]
 MOV [editingnumerical,qtype_numerical],[pluginnameediting,qtype_numerical]
 MOV [numericalsummary,qtype_numerical],[pluginnamesummary,qtype_numerical]

 MOV [random,qtype_random],[pluginname,qtype_random]
 MOV [random_help,qtype_random],[pluginname_help,qtype_random]
 MOV [editingrandom,qtype_random],[pluginnameediting,qtype_random]

 MOV [shortanswer,qtype_shortanswer],[pluginname,qtype_shortanswer]
 MOV [shortanswer_help,qtype_shortanswer],[pluginname_help,qtype_shortanswer]
 MOV [shortanswer_link,qtype_shortanswer],[pluginname_link,qtype_shortanswer]
 MOV [addingshortanswer,qtype_shortanswer],[pluginnameadding,qtype_shortanswer]
 MOV [editingshortanswer,qtype_shortanswer],[pluginnameediting,qtype_shortanswer]
 MOV [shortanswersummary,qtype_shortanswer],[pluginnamesummary,qtype_shortanswer]

 MOV [truefalse,qtype_truefalse],[pluginname,qtype_truefalse]
 MOV [truefalse_help,qtype_truefalse],[pluginname_help,qtype_truefalse]
 MOV [truefalse_link,qtype_truefalse],[pluginname_link,qtype_truefalse]
 MOV [addingtruefalse,qtype_truefalse],[pluginnameadding,qtype_truefalse]
 MOV [editingtruefalse,qtype_truefalse],[pluginnameediting,qtype_truefalse]
 MOV [truefalsesummary,qtype_truefalse],[pluginnamesummary,qtype_truefalse]
AMOS END

Fix based on Roger Moore's patch.