Only use LSP features if the server supports them

dot-config/vim/init.vim

@@ -131,13 +131,3 @@ statusline.Init()
 # necessary.
 import "./lsp.vim"
 lsp.Configure()
-
-set formatexpr=lsp#lsp#FormatExpr()
-set keywordprg=:LspHover
-nnoremap gD <Cmd>LspGotoDeclaration<CR>
-nnoremap gd <Cmd>LspGotoDefinition<CR>
-nnoremap gi <Cmd>LspGotoImpl<CR>
-nnoremap <C-k> <Cmd>LspShowSignature<CR>
-nnoremap gr <Cmd>LspShowReferences<CR>
-xnoremap <silent> <Leader>e <Cmd>LspSelectionExpand<CR>
-xnoremap <silent> <Leader>s <Cmd>LspSelectionShrink<CR>

dot-config/vim/lsp.vim

@@ -162,7 +162,47 @@ def ListMissingServers(argLead: string, cmdLine: string, cursorPos: number): lis
 	return MissingServers()->mapnew((_, server): string => server.name)
 enddef
 
+def ServerHas(feature: string): bool
+	return lsp#buffer#CurbufGetServer(feature) != {}
+enddef
+
+def LspBufferSettings(): void
+	if ServerHas('documentFormatting')
+		setlocal formatexpr=lsp#lsp#FormatExpr()
+	endif
+
+	if ServerHas('hover')
+		setlocal keywordprg=:LspHover
+	endif
+
+	if ServerHas('declaration')
+		nnoremap <buffer> gD <Cmd>LspGotoDeclaration<CR>
+	endif
+
+	if ServerHas('definition')
+		nnoremap <buffer> gd <Cmd>LspGotoDefinition<CR>
+	endif
+
+	if ServerHas('implementation')
+		nnoremap <buffer> gi <Cmd>LspGotoImpl<CR>
+	endif
+
+	if ServerHas('references')
+		nnoremap <buffer> gr <Cmd>LspShowReferences<CR>
+	endif
+
+	if ServerHas('selectionRange')
+		xnoremap <buffer> <silent> <Leader>e <Cmd>LspSelectionExpand<CR>
+		xnoremap <buffer> <silent> <Leader>s <Cmd>LspSelectionShrink<CR>
+	endif
+enddef
+
 export def Configure(): void
+	augroup dot/vim/lsp.vim
+		autocmd!
+		autocmd User LspAttached LspBufferSettings()
+	augroup END
+
 	# We have to use final rather than const because LspAddServer() assumes it can
 	# modify the dicts it gets, rather than making a fresh copy to mess with.
 	final installedServers = InstalledServers()
@@ -173,7 +213,6 @@ export def Configure(): void
 		const missingCount = len(lspServers) - len(installedServers)
 		const warn = $'{missingCount} language server{missingCount > 1 ? "s are" : " is"} configured, but not installed. You may want to run :LspInstall.'
 		augroup dot/vim/lsp.vim
-			autocmd!
 			exe $'autocmd VimEnter * ++once echo {strings.Quote(warn)}'
 		augroup END
 	endif