Various changes have been done to ValueSpec and its subclasses,
improving maintainability and robustness. If you don't write your own
complicated ValueSpec subclasses and you don't have any self-written
complicated check parameters, you are probably not affected.
ValueSpec's constructor doesn't accept any random unspecifed
keyword arguments anymore. It is better to raise an exception at the
incorrect call site than silently accepting every typo. To fix any problems
with this change, just remove the offending keyword arguments, they served
no purpose after all.
ValueSpec.canonical_value() is an abstract method now, otherwise we
force lots of places to handle None. Previously quite a few things
worked only more or less by accident. If you implement your own
ValueSpec subclass, you have to implement that method now, unless
an intermediate class already does it for you.
DropdownChoice and CascadingDropdown don't have a
no_preselect keyword argument anymore. It was redundant, because
no_preselect_title is enough: If this keyword argument is not
None, no_preselect=True is implied. Previously one could
specify nonsensical combinations of those arguments. To fix any problems
with this change, just drop the no_preselect keyword argument.
Alternative, UploadOrPasteTextFile, TextOrRegExp,
and CAorCAChain don't have a style keyword argument
anymore. It didn't serve any purpose since Checkmk 2.0. Just remove it.
TimeofdayRanges has been removed, simply use
ListOfTimeRanges instead. The former has been deprecated since
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