feat(lsp): fallback to code-action command on resolve failure (#25464)

The haskell-language-server supports resolve only for a subset of code
actions. For many code actions trying to resolve the `edit` property
results in an error, but the unresolved action already contains a
command that can be executed without issue.

The protocol specification is unfortunately a bit vague about this,
and what the haskell-language-server does seems to be valid.

Example:

    newtype Dummy = Dummy Int
    instance Num Dummy where

Triggering code actions on "Num Dummy" and choosing "Add placeholders
for all missing methods" resulted in:

    -32601: No plugin enabled for SMethod_CodeActionResolve, potentially available: explicit-fields, importLens, hlint, overloaded-record-dot

With this change it will insert the missing methods:

    instance Num Dummy where
      (+) = _
      (-) = _
      (*) = _
      negate = _
      abs = _
      signum = _
      fromInteger = _

1 files changed, 44 insertions, 0 deletions

diff --git a/test/functional/plugin/lsp_spec.lua b/test/functional/plugin/lsp_spec.lua
index 155c9ad96c..ef08860f10 100644
--- a/test/functional/plugin/lsp_spec.lua
+++ b/test/functional/plugin/lsp_spec.lua
@@ -3483,6 +3483,50 @@ describe('LSP', function()
         end
       }
     end)
+    it("Fallback to command execution on resolve error", function()
+      clear()
+      exec_lua(create_server_definition)
+      local result = exec_lua([[
+        local server = _create_server({
+          capabilities = {
+            executeCommandProvider = {
+              commands = {"command:1"},
+            },
+            codeActionProvider = {
+              resolveProvider = true
+            }
+          },
+          handlers = {
+            ["textDocument/codeAction"] = function()
+              return {
+                {
+                  title = "Code Action 1",
+                  command = {
+                    title = "Command 1",
+                    command = "command:1",
+                  }
+                }
+              }
+            end,
+            ["codeAction/resolve"] = function()
+              return nil, "resolve failed"
+            end,
+          }
+        })
+
+        local client_id = vim.lsp.start({
+          name = "dummy",
+          cmd = server.cmd,
+        })
+
+        vim.lsp.buf.code_action({ apply = true })
+        vim.lsp.stop_client(client_id)
+        return server.messages
+      ]])
+      eq("codeAction/resolve", result[4].method)
+      eq("workspace/executeCommand", result[5].method)
+      eq("command:1", result[5].params.command)
+    end)
   end)
   describe('vim.lsp.commands', function()
     it('Accepts only string keys', function()