in src/main/java/org/apache/maven/resolver/internal/ant/types/Artifact.java [48:61]
public void validate(final Task task) {
if (isReference()) {
getRef().validate(task);
} else {
if (file == null) {
throw new BuildException("You must specify the 'file' for the artifact");
} else if (!file.isFile()) {
throw new BuildException("The artifact file " + file + " does not exist");
}
if (type == null || type.length() <= 0) {
throw new BuildException("You must specify the 'type' for the artifact");
}
}
}