generate_warning function in assignment external API is returning incorrect values

Create an assignment activity configured to allow only to allow only text (Submission types field set to Online text) Just under the previous setting, set the field Word limit to 1 As admin, enable "Mobile services": Site administration ► Mobile app ► Mobile settings Create a Token in the mobile app service for one student in the course: Click on Site administration ► Plugins ► Web services ► Manage tokens Next, you can do a CURL REST call simulating a WS client with the user. You need to replace the wstoken, assignmentid with the assignment activity instance id and the URL of your moodle instance curl 'http://localhost/m/stable_master/webservice/rest/server.php?moodlewsrestformat=json' --data 'assignmentid=37&plugindata%5Bonlinetext_editor%5D%5Btext%5D=%3Cp%3Easdf%20asdf%3C%2Fp%3E%0A&plugindata%5Bonlinetext_editor%5D%5Bformat%5D=1&plugindata%5Bonlinetext_editor%5D%5Bitemid%5D=0&moodlewssettingfilter=true&moodlewssettingfileurl=true&wsfunction=mod_assign_save_submission&wstoken=12a2a65aeea2a177055e233f9e303218' --compressed | python -m "json.tool" # Check that as curl response you receive a valid json. The first element of the json response array contains the field "warningcode" set to couldnotsavesubmission, and the "item" field containing a text with HTML characters encoded.