Mailchimp API v2.0 filter campaigns by list id doesn't filter if there is no match - api

Question

http://apidocs.mailchimp.com/api/2.0/campaigns/list.php
I would expect that something like
{
"apikey": "12345",
"filters": {
"list_id": "abcde",
"exact": true
}
}
to return a list of total=1 if there is one campaign with list_id = "abcde", or total=0 if there isn't (using exact=true). However, instead I get the full list. Is this by design? Am I missing some other setting to filter out all mismatches? Is there a way to deal with this?

Answer 1

OK, so this is what I have come up with, barring some other resolution:
When the result set is returned, do a sanity check on the first result (data.data[0]).
If there is a true match, then data.data[0].list_id = list_id
If there was no match, and the full set has come back, then data.data[0].list_id cannot = list_id
This extra step is not ideal, imo, but it does do the trick.
if data.data[0].list_id === list_id
// the list is a match, return the results
else
// the list is not a match, do something else

Answer 2

Here's another solution:
The full-response will provide an error object if no match
"errors": [{
"filter": "list_id",
"value": "abcde",
"code": 200,
"error": "Invalid MailChimp List ID: abcde"
}]
and an empty object for a set of matches
"errors": []
So you can first process your result by looking for this error object and making the appropriate decision.
I received some clarification from MailChimp (and post it here with permission) that this is as-intended:
To provide some more information, the behavior with the campaigns/list call completing, even with an invalid filter, is expected behavior. As you mention, an error array is included in the return, and it would be possible to check that array for any errors received to determine whether or not the call completed as expected.
I can certainly see how that may be unexpected, to receive the full list of campaigns when attempting to filter. If you'd prefer that an error would be returned, without the campaign data returned, we'd recommend adding that suggestion to our feedback form here: http://mailchimp.com/contact/feedback/ That's certainly something our developers could consider for future versions of the API.
I'm still not sure why they do it this way, but I've added feedback suggesting that they return an empty result (so as not to bulk up the response with irrelevant data), or to improve the documentation.