Hello,
ErrorResult has two kinds of exception-throwing APIs on it: the older
ones that don't allow specifying a custom message string, and newer ones
that do. People should use the newer ones where possible.
That means not using the following when throwing nsresults/DOMExceptions:
ErrorResult::Throw(nsresult)
ErrorResult::operator=(nsresult)
and instead using:
ErrorResult::ThrowDOMException(nsresult, const nsACString&)
which allows passing a message string that explains why the exception is
being thrown. Web developers will thank you and not post tweets like
https://twitter.com/sebmck/status/1155709250225573889
When throwing TypeError or RangeError, ThrowTypeError/ThrowRangeError
already require a message string, though I am making some changes in
https://phabricator.services.mozilla.com/D45932 to make it a bit simpler
to pass in custom message strings there.
Thank you all for making web developers' lives better,
Boris
P.S. We currently have a _lot_ of uses of the
no-informative-error-message APIs. Some of these might be things we
don't really expect web pages to hit (e.g. exceptions when in the wrong
type of global). But generally speaking all ~560 uses of
operator=(nsresult) are code smells, as are the ~1000 uses of
Throw(NS_ERROR_DOM_*).
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