feat(lsp): support workspace/foldingRange/refresh #41780

Problem:
Servers cannot request refreshing stale LSP folding ranges after a
project-wide change.

Solution:
Advertise `workspace.foldingRange.refreshSupport` and re-request folding
ranges for active buffers when handling `workspace/foldingRange/refresh`.

AI-assisted

runtime/lua/vim/lsp/_folding_range.lua

@@ -289,6 +289,26 @@ function State:foldclose(kind, winid)
   end)
 end
 
+--- |lsp-handler| for the method `workspace/foldingRange/refresh`
+---
+--- Refresh requests are sent by the server to indicate a project-wide change
+--- that requires all folding ranges to be re-requested by the client.
+---@param ctx lsp.HandlerContext
+---@internal
+function M.on_refresh(err, _, ctx)
+  if err then
+    return vim.NIL
+  end
+
+  for _, state in pairs(State.active) do
+    if state.client_state[ctx.client_id] then
+      state:refresh(ctx.client_id)
+    end
+  end
+
+  return vim.NIL
+end
+
 ---@param kind lsp.FoldingRangeKind
 ---@param winid? integer
 function M.foldclose(kind, winid)

runtime/lua/vim/lsp/handlers.lua

@@ -673,6 +673,11 @@ RSC['workspace/diagnostic/refresh'] = function(err, result, ctx)
   return vim.lsp.diagnostic.on_refresh(err, result, ctx)
 end
 
+---@see https://microsoft.github.io/language-server-protocol/specification/#workspace_foldingRange_refresh
+RSC['workspace/foldingRange/refresh'] = function(err, result, ctx)
+  return vim.lsp._folding_range.on_refresh(err, result, ctx)
+end
+
 ---@see https://microsoft.github.io/language-server-protocol/specification/#workspace_inlayHint_refresh
 RSC['workspace/inlayHint/refresh'] = function(err, result, ctx)
   return vim.lsp.inlay_hint.on_refresh(err, result, ctx)

runtime/lua/vim/lsp/protocol.lua

@@ -639,6 +639,9 @@ function protocol.make_client_capabilities()
       diagnostics = {
         refreshSupport = true,
       },
+      foldingRange = {
+        refreshSupport = true,
+      },
       fileOperations = {
         dynamicRegistration = false,
         didCreate = false,