Found this in the source code which should answer your question: https://github.com/bitcoin/bitcoin/blob/b05a89b2def301704df8f22f05a45ccf891c2b83/src/rpcserver.cpp#L268-380

It's the internal register of RPC commands that bitcoind should serve, and even includes which ought to be hidden from the help command. invalidateblock is in the hidden section with three others.