Question: Should Refactoring->Rename to support multiple language servers with prepareRename/rename capabilities?

It is possible that more than one Language Server is defined for a document.

Currently, in such a case, on rename operation LSPRenameProcessor executes renaming using the only one LS - the quickest in respond to textDocument/prepareRename request. But in case of https://github.com/eclipse/wildwebdeveloper/issues/1209 it turns out that the quickest response is a null-response (received from a LS that cannot provide the rename operation for a given text region). PR #655 solves this issue by taking into account a first non-null response.

But this still leaves the only one (the quickest) prepareRename response is actually to be processed with the rename operation leaving other possible replacements (provided by the rest of LSs) not touched.

So, the question is should LSPRenameProcessor to process ALL the responses from ALL the LS in a rename operation?

Start with LSPRenameProcessor and review PR #655, then compare the behavior described in eclipse/wildwebdeveloper#1209. Determine whether rename should combine responses from all language servers or retain a single response, including how null prepareRename results are handled. Done means the expected behavior is decided and documented clearly enough to guide an implementation.