Auto detect macos clangd (#2161)

* Auto detect Xcode clangd

* Fix lsp-clients-clangd-executable defcustom type error

* Move executable-find util function to lsp-mode

* fix quoting

* Add return values to docstring

* Fix typo and formatting

Author: wyuenho

clients/lsp-clangd.el

@@ -165,7 +165,8 @@ available in your path to use. Otherwise the system will try to
 find a suitable one. Set this variable before loading lsp."
   :group 'lsp-clangd
   :risky t
-  :type 'file)
+  :type '(choice (file :tag "Path")
+                 (const :tag "Auto" nil)))
 
 (defvar lsp-clients--clangd-default-executable nil
   "Clang default executable full path when found.
@@ -181,10 +182,12 @@ This must be set only once after loading the clang client.")
   "Generate the language server startup command."
   (unless lsp-clients--clangd-default-executable
     (setq lsp-clients--clangd-default-executable
-          (-first #'executable-find
-                  (-map (lambda (version)
-                          (concat "clangd" version))
-                        '("" "-12" "-11" "-10" "-9" "-8" "-7" "-6")))))
+          (or (-first #'executable-find
+                      (-map (lambda (version)
+                              (concat "clangd" version))
+                            '("" "-12" "-11" "-10" "-9" "-8" "-7" "-6")))
+              (lsp-clients-executable-find "xcodebuild" "-find-executable" "clangd")
+              (lsp-clients-executable-find "xcrun" "--find" "clangd"))))
 
   `(,(or lsp-clients-clangd-executable lsp-clients--clangd-default-executable "clangd")
     ,@lsp-clients-clangd-args))

lsp-mode.el

@@ -1520,6 +1520,26 @@ BODY should never return `t' value."
   download-in-progress?
   buffers)
 
+(defun lsp-clients-executable-find (find-command &rest args)
+  "Finds an executable by invoking a search command.
+
+FIND-COMMAND is the executable finder that searches for the
+actual language server executable. ARGS is a list of arguments to
+give to FIND-COMMAND to find the language server.  Returns the
+output of FIND-COMMAND if it exits successfully, nil otherwise.
+
+Typical uses include finding an executable by invoking 'find' in
+a project, finding LLVM commands on macOS with 'xcrun', or
+looking up project-specific language servers for projects written
+in the various dynamic languages, e.g. 'nvm', 'pyenv' and 'rbenv'
+etc."
+  (when-let* ((find-command-path (executable-find find-command))
+              (executable-path
+               (with-temp-buffer
+                 (when (zerop (apply 'call-process find-command-path nil t nil args))
+                   (buffer-substring-no-properties (point-min) (point-max))))))
+    (string-trim executable-path)))
+
 (defvar lsp--already-widened nil)
 
 (defmacro lsp-save-restriction-and-excursion (&rest form)