Add support for inlay hints from TypeScript language server

CHANGELOG.org

@@ -28,6 +28,7 @@
   * Add [[https://github.com/aca/emmet-ls][emmet-ls]]
   * Support all ~initializationOptions~ in ~typescript-language-server~
   * Update rust-analyzer's inlay hint protocol support.
+  * Add support for ~typescript-language-server~’s inlay hints.
 ** Release 8.0.0
   * Add ~lsp-clients-angular-node-get-prefix-command~ to get the Angular server from another location which is still has ~/lib/node_modules~ in it.
   * Set ~lsp-clients-angular-language-server-command~ after the first connection to speed up subsequent connections.

clients/lsp-javascript.el

@@ -600,12 +600,88 @@ TypeScript 3.0 or newer in the workspace."
   :type 'boolean
   :package-version '(lsp-mode . "6.1"))
 
+;; inlay hints
+
+(defface lsp-javascript-inlay-face
+  '((t :inherit font-lock-comment-face))
+  "The face to use for the JavaScript inlays."
+  :group 'lsp-javascript
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defface lsp-javascript-inlay-type-face
+  '((t :inherit lsp-javascript-inlay-face))
+  "Face for inlay type hints (e.g. inferred variable types)."
+  :group 'lsp-javascript
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defcustom lsp-javascript-inlay-type-format ": %s"
+  "Format string for variable inlays (part of the inlay face)."
+  :type '(string :tag "String")
+  :group 'lsp-javascript
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defface lsp-javascript-inlay-parameter-face
+  '((t :inherit lsp-javascript-inlay-face))
+  "Face for inlay parameter hints (e.g. function parameter names at
+call-site)."
+  :group 'lsp-javascript
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defcustom lsp-javascript-inlay-param-format "%s:"
+  "Format string for parameter inlays (part of the inlay face)."
+  :type '(string :tag "String")
+  :group 'lsp-javascript
+  :package-version '(lsp-mode . "8.0.1"))
+
 (defcustom lsp-typescript-surveys-enabled t
   "Enabled/disable occasional surveys that help us improve VS
 Code's JavaScript and TypeScript support."
   :type 'boolean
   :package-version '(lsp-mode . "6.1"))
 
+(defcustom lsp-javascript-display-inlay-hints nil
+  "Whether to display inlay hints."
+  :type 'boolean
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defcustom lsp-javascript-display-enum-member-value-hints nil
+  "Show inlay hints for enum member values."
+  :type 'boolean
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defcustom lsp-javascript-display-return-type-hints nil
+  "Show inlay hints for function return types."
+  :type 'boolean
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defcustom lsp-javascript-display-parameter-type-hints nil
+  "Show inlay hints for function parameters."
+  :type 'boolean
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defcustom lsp-javascript-display-parameter-name-hints "none"
+  "Level of hinting for parameter types."
+  :type '(choice (const :tag "none" "none")
+                 (const :tag "literals" "literals")
+                 (const :tag "all" "all"))
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defcustom lsp-javascript-display-parameter-name-hints-when-argument-matches-name nil
+  "Show inlay hints for function parameters even when argument matches
+name (e.g. `data' variable passed as `data' parameter)."
+  :type 'boolean
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defcustom lsp-javascript-display-property-declaration-type-hints nil
+  "Show inlay hints for property declaration types."
+  :type 'boolean
+  :package-version '(lsp-mode . "8.0.1"))
+
+(defcustom lsp-javascript-display-variable-type-hints nil
+  "Show inlay hints for variable types."
+  :type 'boolean
+  :package-version '(lsp-mode . "8.0.1"))
+
 (lsp-register-custom-settings
  '(("javascript.autoClosingTags" lsp-javascript-auto-closing-tags t)
    ("javascript.implicitProjectConfig.checkJs" lsp-javascript-implicit-project-config-check-js t)
@@ -678,7 +754,21 @@ Code's JavaScript and TypeScript support."
    ("typescript.format.insertSpaceBeforeAndAfterBinaryOperators" lsp-typescript-format-insert-space-before-and-after-binary-operators t)
    ("typescript.format.insertSpaceBeforeFunctionParenthesis" lsp-typescript-format-insert-space-before-function-parenthesis t)
    ("typescript.format.placeOpenBraceOnNewLineForControlBlocks" lsp-typescript-format-place-open-brace-on-new-line-for-control-blocks t)
-   ("typescript.format.placeOpenBraceOnNewLineForFunctions" lsp-typescript-format-place-open-brace-on-new-line-for-functions t)))
+   ("typescript.format.placeOpenBraceOnNewLineForFunctions" lsp-typescript-format-place-open-brace-on-new-line-for-functions t)
+   ("typescript.inlayHints.includeInlayEnumMemberValueHints" lsp-javascript-display-enum-member-value-hints t)
+   ("typescript.inlayHints.includeInlayFunctionLikeReturnTypeHints" lsp-javascript-display-return-type-hints t)
+   ("typescript.inlayHints.includeInlayFunctionParameterTypeHints" lsp-javascript-display-parameter-type-hints t)
+   ("typescript.inlayHints.includeInlayParameterNameHints" lsp-javascript-display-parameter-name-hints nil)
+   ("typescript.inlayHints.includeInlayParameterNameHintsWhenArgumentMatchesName" lsp-javascript-display-parameter-name-hints-when-argument-matches-name t)
+   ("typescript.inlayHints.includeInlayPropertyDeclarationTypeHints" lsp-javascript-display-property-declaration-type-hints t)
+   ("typescript.inlayHints.includeInlayVariableTypeHints" lsp-javascript-display-variable-type-hints t)
+   ("javascript.inlayHints.includeInlayEnumMemberValueHints" lsp-javascript-display-enum-member-value-hints t)
+   ("javascript.inlayHints.includeInlayFunctionLikeReturnTypeHints" lsp-javascript-display-return-type-hints t)
+   ("javascript.inlayHints.includeInlayFunctionParameterTypeHints" lsp-javascript-display-parameter-type-hints t)
+   ("javascript.inlayHints.includeInlayParameterNameHints" lsp-javascript-display-parameter-name-hints nil)
+   ("javascript.inlayHints.includeInlayParameterNameHintsWhenArgumentMatchesName" lsp-javascript-display-parameter-name-hints-when-argument-matches-name t)
+   ("javascript.inlayHints.includeInlayPropertyDeclarationTypeHints" lsp-javascript-display-property-declaration-type-hints t)
+   ("javascript.inlayHints.includeInlayVariableTypeHints" lsp-javascript-display-variable-type-hints t)))
 
 (lsp-dependency 'typescript-language-server
                 '(:system lsp-clients-typescript-tls-path)
@@ -727,6 +817,56 @@ Code's JavaScript and TypeScript support."
       (lsp)
       (lsp--info "Renamed '%s' to '%s'." name (file-name-nondirectory new)))))
 
+(defun lsp-javascript-update-inlay-hints ()
+  (if (lsp-javascript-initialized?)
+      (lsp-request-async
+       "typescript/inlayHints"
+       (lsp-make-javascript-inlay-hints-params
+        :text-document (lsp--text-document-identifier))
+       (lambda (res)
+         (lsp--remove-overlays 'lsp-javascript-inlay-hint)
+         (-each (gethash "inlayHints" res)
+           #'(lambda (hint)
+               (-let* (((&javascript:InlayHint :text :position :kind :whitespace-before? :whitespace-after?) hint)
+                       (pos (lsp--position-to-point position))
+                       (overlay (make-overlay pos pos nil 'front-advance 'end-advance)))
+                 (overlay-put overlay 'lsp-javascript-inlay-hint t)
+                 (overlay-put overlay 'before-string
+                              (format "%s%s%s"
+                                      (if (and whitespace-before? (not (string= kind lsp/javascript-inlay-hint-kind-type-hint))) " " "")
+                                      (propertize (lsp-javascript-format-inlay text kind)
+                                                  'font-lock-face (lsp-javascript-face-for-inlay kind))
+                                      (if whitespace-after? " " ""))))))))
+    :mode 'tick))
+
+(defun lsp-javascript-format-inlay (text kind)
+  (cond
+   ((eql kind lsp/javascript-inlay-hint-kind-type-hint) (format lsp-javascript-inlay-type-format text))
+   ((eql kind lsp/javascript-inlay-hint-kind-parameter-hint) (format lsp-javascript-inlay-param-format text))
+   ;; ((eql kind lsp/javascript-inlay-hint-kind-enum-hint) (format lsp-javascript-inlay-enum-format text))
+   (t text)))
+
+(defun lsp-javascript-face-for-inlay (kind)
+  (cond
+   ((eql kind lsp/javascript-inlay-hint-kind-type-hint) 'lsp-javascript-inlay-type-face)
+   ((eql kind lsp/javascript-inlay-hint-kind-parameter-hint) 'lsp-javascript-inlay-parameter-face)
+   (t 'lsp-javascript-inlay-face)))
+
+(defun lsp-javascript-initialized? ()
+  (when-let ((workspace (lsp-find-workspace 'ts-ls (buffer-file-name))))
+    (eq 'initialized (lsp--workspace-status workspace))))
+
+(define-minor-mode lsp-javascript-inlay-hints-mode
+  "Mode for displaying inlay hints."
+  :lighter nil
+  (cond
+   (lsp-javascript-inlay-hints-mode
+    (lsp-javascript-update-inlay-hints)
+    (add-hook 'lsp-on-idle-hook #'lsp-javascript-update-inlay-hints nil t))
+   (t
+    (lsp--remove-overlays 'lsp-javascript-inlay-hint)
+    (remove-hook 'lsp-on-idle-hook #'lsp-javascript-update-inlay-hints t))))
+
 (lsp-register-client
  (make-lsp-client :new-connection (lsp-stdio-connection (lambda ()
                                                           `(,(lsp-package-path 'typescript-language-server)
@@ -748,6 +888,9 @@ Code's JavaScript and TypeScript support."
                                       (lsp--set-configuration
                                        (ht-merge (lsp-configuration-section "javascript")
                                                  (lsp-configuration-section "typescript")))))
+                  :after-open-fn (lambda ()
+                                   (when lsp-javascript-display-inlay-hints
+                                     (lsp-javascript-inlay-hints-mode)))
                   :ignore-messages '("readFile .*? requested by TypeScript but content not available")
                   :server-id 'ts-ls
                   :request-handlers (ht ("_typescript.rename" #'lsp-javascript--rename))

lsp-protocol.el

@@ -421,6 +421,12 @@ See `-let' for a description of the destructuring mechanism."
                (rust-analyzer:CommandLink (:title :command) (:arguments :tooltip))
                (rust-analyzer:CommandLinkGroup (:commands) (:title)))
 
+(defconst lsp/javascript-inlay-hint-kind-type-hint "Type")
+(defconst lsp/javascript-inlay-hint-kind-parameter-hint "Parameter")
+(defconst lsp/javascript-inlay-hint-kind-enum-hint "Enum")
+(lsp-interface (javascript:InlayHint (:text :position :kind) (:whitespaceBefore :whitespaceAfter))
+               (javascript:InlayHintsParams (:textDocument) (:range)))
+
 (lsp-interface (clojure-lsp:TestTreeParams (:uri :tree) nil)
                (clojure-lsp:TestTreeNode (:name :range :nameRange :kind) (:children)))