Show error message if file upload fails

[simontaurus]

e.g. because file type is not allowed

[ademolaomosanya]

Hello @simontaurus i would love to fix this issue
i have fixed a similar issue in cat-a-lot gadget for mediawiki, where the page is stuck at a protected file and the error is not handled properly, i created an error dialg and fix the api to handle the error properly.
I want to complete this task by making changes to the error-handling scripts, MwJson_editor.js and MwJson_api.js.
By adding of pre-upload validations for file sizes and types, the display of error messages in MwJson_editor.js before the upload even begins, and the addition of detailed messages for failure cases such as duplicate files or name conflicts in MwJson_api.js will give users better feedback on why the file upload failed.
I would appreciate feedback on whether there are other validation to be handle for file uploads or any specific detail i need to know.

[simontaurus]

Sounds great!

Uploading a file triggers mwjson.api.updatePage() of the File Page

mediawiki-extensions-MwJson/modules/ext.MwJson.editor/MwJson_editor.js

Line 1314 in ec1a32c

mwjson.api.updatePage(page).done((page) => {

whicht triggers the file uploaded if needed:

mediawiki-extensions-MwJson/modules/ext.MwJson.api/MwJson_api.js

Line 340 in ec1a32c

const hasChangedFile = ('file' in page && page.file.changed);

finally calling uploadFile()

mediawiki-extensions-MwJson/modules/ext.MwJson.api/MwJson_api.js

Line 318 in ec1a32c

}).fail(function (retStatus, data) {

Probably the error is not correctly detected there or the promise.reject() cascade is somewhere wrong.
Making a pre-upload validations to fail early sound like a good idea!