Support rename for global symbols

[olafurpg]

Following up from offline discussions at ScalaSphere.

Currently, metals supports rename for local symbols only. This means it's possible to rename a variable inside a block, but not possible to rename a top-level class/object/def.

The way I imagine rename will work is that we'll use the symbol index to find all references to the symbol being renamed. We already have a symbol index, however several challenges need to be addressed first before we blindly start using it

• Validate that SemanticDB files are up-to-date to prevent half-complete renames
  • use token edit distance for slightly stale SemanticDBs
  • abort rename if compilation is required
• Rename companion object/class together
• Rename synthetic apply/copy parameters for case classes when renaming case class fields
• Rename filename when renaming the only top-level symbol in a file
  • LSP does not support this by default, investigate what extension to use to make it work in vscode/atom.

@ShaneDelmore would you be interested to take on this ticket?

[ShaneDelmore]

I'll take this ticket.

[olafurpg]

The current VS Code milestone has a proposal to allow WorkspaceEdit to create/rename/delete files https://code.visualstudio.com/updates/v1_25#_workspaceedit-can-createrenamedelete-files

WorkspaceEdit can create/rename/delete Files We have added a proposed API that extends WorkspaceEdit so that it can be used to create, rename, and delete files or folders. This is useful for complex refactorings, for example renaming a file when a type is being renamed, but should also enable other scenarios.

I suspect this will eventually make it into LSP once validated.

[ShaneDelmore]

I completely forgot about this, so sorry! I’m not working on LSP this quarter and won’t be tackling this after all, or at least not in the next few months.

[olafurpg]

Metals doesn't support rename anymore. Rename may get added back in the future but for now I think it's best to close this ticket to keep the issue tracker focused. We can revisit this once we have solid "find all references" working.