Emacs lsp-mode bugfix related to dash package

[sshine]

Even though the behavior I'm about to describe relates to Emacs' lsp-mode package, and not Emacs' lsp-haskell package or even ghcide directly, I thought it might be valuable in Google search results since it may provide hindrance for those who want to get ghcide up and running with Emacs:

As described here and here, the default installation of lsp-mode, lsp-ui, lsp-ui-mode and lsp-haskell as described in ghcide's "Using with Emacs" section may result in the following error message:

Symbol’s value as variable is void: capability

This can be caused by either an old version of the Emacs package dash, or a cached .elc file for an old version. A fix consists of (re)moving the old package from ~/.emacs.d/elpa/ and installing it again, e.g. via M-x package-list-packages RET and M-x package-install RET dash RET. If this is not enough,

find ~/.emacs.d -name '*.elc' -exec rm {} \;

(which causes recompilation of all bytecode-compiled scripts.)

[ndmitchell]

Useful info! I copied it to the setup guide in haskell/ghcide#164.

[sshine]

Cool!