lsp: only send buf requests to servers that support the request (#12764)

Refactors how required capabilities are detected and validated, and make
sure requests are only sent to clients that support it (and only fail if
no clients support the provided method).

The validation happens at the buf_request level, because we assume that
if someone is sending the request directly through the client, they know
what they're doing. Also, let unknown methods go through.

This is extracted from #12518 and closes #12755.

Co-authored-by: francisco souza <fsouza@users.noreply.github.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/test/functional/plugin/lsp_spec.lua b/test/functional/plugin/lsp_spec.lua
index f07a2d18a2..067a13ce68 100644
--- a/test/functional/plugin/lsp_spec.lua
+++ b/test/functional/plugin/lsp_spec.lua
@@ -270,6 +270,70 @@ describe('LSP', function()
         test_name = "basic_check_capabilities";
         on_init = function(client)
           client.stop()
+          local full_kind = exec_lua("return require'vim.lsp.protocol'.TextDocumentSyncKind.Full")
+          eq(full_kind, client.resolved_capabilities().text_document_did_change)
+        end;
+        on_exit = function(code, signal)
+          eq(0, code, "exit code", fake_lsp_logfile)
+          eq(0, signal, "exit signal", fake_lsp_logfile)
+        end;
+        on_callback = function(...)
+          eq(table.remove(expected_callbacks), {...}, "expected callback")
+        end;
+      }
+    end)
+
+    it('client.supports_methods() should validate capabilities', function()
+      local expected_callbacks = {
+        {NIL, "shutdown", {}, 1};
+      }
+      test_rpc_server {
+        test_name = "capabilities_for_client_supports_method";
+        on_init = function(client)
+          client.stop()
+          local full_kind = exec_lua("return require'vim.lsp.protocol'.TextDocumentSyncKind.Full")
+          eq(full_kind, client.resolved_capabilities().text_document_did_change)
+          eq(true, client.resolved_capabilities().completion)
+          eq(true, client.resolved_capabilities().hover)
+          eq(false, client.resolved_capabilities().goto_definition)
+          eq(false, client.resolved_capabilities().rename)
+
+          -- known methods for resolved capabilities
+          eq(true, client.supports_method("textDocument/hover"))
+          eq(false, client.supports_method("textDocument/definition"))
+
+          -- unknown methods are assumed to be supported.
+          eq(true, client.supports_method("unknown-method"))
+        end;
+        on_exit = function(code, signal)
+          eq(0, code, "exit code", fake_lsp_logfile)
+          eq(0, signal, "exit signal", fake_lsp_logfile)
+        end;
+        on_callback = function(...)
+          eq(table.remove(expected_callbacks), {...}, "expected callback")
+        end;
+      }
+    end)
+
+    it('should call unsupported_method when trying to call an unsupported method', function()
+      local expected_callbacks = {
+        {NIL, "shutdown", {}, 1};
+      }
+      test_rpc_server {
+        test_name = "capabilities_for_client_supports_method";
+        on_setup = function()
+            exec_lua([=[
+              vim.lsp._unsupported_method = function(method)
+                vim.lsp._last_unsupported_method = method
+                return 'fake-error'
+              end
+              vim.lsp.buf.hover()
+            ]=])
+        end;
+        on_init = function(client)
+          client.stop()
+          local method = exec_lua("return vim.lsp._last_unsupported_method")
+          eq("textDocument/hover", method)
         end;
         on_exit = function(code, signal)
           eq(0, code, "exit code", fake_lsp_logfile)