$0 donations not allowed in CiviContribute import (but are for manual contribution entry)

When importing contributions, any contribution with total amount $0 gives an error, "Mandatory key(s) missing from params array: total_amount".

Yet entering an contribution amount of $0 is allowed when manually entering contributions.

The function that throws this error is civicrm/api/v3/utils.php in function civicrm_api3_verify_mandatory(), about line 125, where it uses the php function empty() to evaluate whether the key exists or not.

PHP empty() returns true when the value =

I don't know how civicrm_api3_verify_mandatory() is used, but generally for numerical and money fields, a field with value zero is not considered empty. Particularly for contributions, a $0 contribution may be entered for a wide variety of reasons and it is perfectly valid.

So I don't know if it is best to address the problem civicrm_api3_verify_mandatory() (my suggestion is to add || (empty($params[$key]) && $params[$key]!=0)) in line 125 and similarly for the similar line involving $subkey at about line 112) or to back up to the import routine itself and not use civicrm_api3_verify_mandatory for the total amount field.

Either way, it should be possible to import a contribution with total amount set to $0.