[Rust-Analyzer] Support SnippetTextEdit (#1926)

Fixes #1907

Author: yyoncho

lsp-mode.el

@@ -4225,7 +4225,14 @@ The method uses `replace-buffer-contents'."
                  (seq-sort #'lsp--text-edit-sort-predicate)
                  (mapc (lambda (edit)
                          (progress-reporter-update reporter (cl-incf done))
-                         (funcall apply-edit edit))))
+                         (funcall apply-edit edit)
+                         (when (lsp-snippet-text-edit? edit)
+                           (-when-let ((&SnippetTextEdit :range (&RangeToPoint :start)
+                                                         :insert-text-format? :new-text) edit)
+                             (when (eq insert-text-format? lsp/insert-text-format-snippet)
+                               (let (yas-indent-line)
+                                 (yas-expand-snippet (lsp--to-yasnippet-snippet new-text)
+                                                     start (+ start (length new-text))))))))))
           (when (fboundp 'undo-amalgamate-change-group)
             (with-no-warnings (undo-amalgamate-change-group change-group)))
           (progress-reporter-done reporter))))))

lsp-protocol.el

@@ -475,6 +475,7 @@ See `-let' for a description of the destructuring mechanism."
  (TextDocumentItem (:languageId :text :uri :version) nil)
  (TextDocumentSyncOptions nil (:change :openClose :save :willSave :willSaveWaitUntil))
  (TextEdit (:newText :range) nil)
+ (SnippetTextEdit (:newText :range) (:insertTextFormat))
  (TypeDefinitionCapabilities nil (:dynamicRegistration :linkSupport))
  (TypeHierarchyCapabilities nil (:dynamicRegistration))
  (TypeHierarchyItem (:kind :name :range :selectionRange :uri) (:children :data :deprecated :detail :parents))

lsp-rust.el

@@ -568,7 +568,8 @@ The command should include `--message=format=json` or similar option."
                    (when lsp-rust-analyzer-server-display-inlay-hints
                      (lsp-rust-analyzer-inlay-hints-mode)))
   :ignore-messages nil
-  :server-id 'rust-analyzer))
+  :server-id 'rust-analyzer
+  :custom-capabilities '((experimental . ((snippetTextEdit . ,lsp-enable-snippet ))))))
 
 (defun lsp-rust-switch-server (&optional lsp-server)
   "Switch priorities of lsp servers, unless LSP-SERVER is already active."