So we don't want to make exceptions for these - the only reason we did that for UsableSubnetworksAggregatedList was because 1) it was a breaking change and we wanted it to unblock the release, and 2) it doesn't seem to obey any heuristic, so we needed an exception.

But implementing a better heuristic for determining which RPCs are paginated will result in a breaking change, as we are going to enforce a new heuristic which will correct the existing RPCs which we previously missed, as well as ensure we don't miss turning RPCs into paginated lists in the future.

The PHP Heuristic should look like this:

• Check the exception dictionary. If the method is there as a key, use the value as the results field (you've done this already)
• If there is exactly one map field, that field is the results field.
• If there are no repeated fields there is no results field and we shall throw an error
• If there is exactly one repeated field, that field is the results field.
• If there is one repeated message field and any number of repeated primitives, we page on the message field

By implementing this, the above RPCs should be turned into paginated lists (without needing to add them to the exception dictionary)

I added a few minor suggestions, but the logic here looks good! We just need to add some tests (either by updating compute_small.proto or by creating a new test like rest_only_pagination.proto).