I hope this question hasn't been asked before: I searched and couldn't directly find it. It is known that in specific applications, compression followed by encryption leaks information of the length of the compressed message, which, combined with the possibility to inject known plain text in the message, can leak sufficient information as to break the encryption entirely. There are real-world examples where such plain text injection is a possibility, and there, compression+encryption is a bad idea. There are other applications, like VoIP, where data packets have comparable length before compression, but compression will change these lengths in ways that betray sufficient aspects of the data to allow, again, for a leakage of plain text information.
In all these cases, the vector is the variable length of the compressed plain text that is leaked.
This counter-intuitive result is opposite to the old cryptographic idea that "pre-whitening" which is also an effect of compression, is beneficial.
So, my question is: are there cryptographic applications where compression + encryption is beneficial over simply encryption (as old wisdom would have had it), or is compression in several cases dangerous, and at best, sometimes harmless, but never beneficial to encryption ? In other words, is "pre-whitening" still sometimes an advantage, or not ? I'm not talking about the gain in room or bandwidth. I'm talking on the cryptographic side only.