Report the invalid values of the attachmentGalleryPicker and attachmentSelector macros instead of showing nothing

The attachment picker macros accept a target page, a class, a property and an object that may not exist. When one is wrong, they show nothing, "No result." or an unrelated message, so the user cannot tell what to fix.

The macros to change, with the file where most of the fix is done:

• attachmentGalleryPicker: AttachmentGalleryPickerMacro.java and its UI, AttachmentGalleryPicker.xml.
• attachmentSelector: defined in its wiki macro, AttachmentSelector.xml.

The main problems:

• attachmentGalleryPicker: a negative limit gives the notification "The attachments search query failed.", an unknown filter shows "No result.", and a target page that does not exist shows "No result." for the current page, with no message about the page.
• attachmentSelector: a class, a property or a target page that does not exist displays nothing, an object number that does not exist shows nothing, or silently the first object for object="abc", and a defaultValue that is not an attachment is shown as an attachment name. Only a missing classname gives a message naming the parameter.

The fix is to check the target page, class, property and object before showing the picker, and to show an error naming the parameter when one does not exist.

Depends on

• XCOMMONS-3847, which refuses the boolean and number values that do not convert.
• XRENDERING-823, which makes the error of an invalid parameter name the parameter and the expected value.
• XWIKI-25197, which lets a wiki macro parameter declare a range or a format, checked when the macro runs.

KOs covered

Impact found on macro fluidity

These 2 KOs come from the WYSIWYG usability audit of the macros, under the criterion E2 errors of its usability criteria, which asks that an invalid parameter value produces a message that says what is wrong and how to fix it, not a stack trace. The page of each macro, linked in the table, has the full notes and the steps to reproduce.

Each of these KOs is only partly covered here, for the problems specific to the macro. The same KOs also report invalid values that the macro system handles for every macro: XCOMMONS-3847 refuses the booleans and numbers that do not convert, and XRENDERING-823 makes the error name the parameter and the expected value. The number and format constraints, like width, height and filter, are covered by XWIKI-25197.