[elpa] externals/eglot a5b7b7d933 04/33: Fix #688: Support multiple servers out-of-box for same mode

[Stefan Kangas]

branch: externals/eglot
commit a5b7b7d933b97db9ce5f8b7dcc8c866f7c35b220
Author: João Távora <joaotavora@gmail.com>
Commit: João Távora <joaotavora@gmail.com>

    Fix #688: Support multiple servers out-of-box for same mode
    
    Also per #537.
    
    * eglot.el (eglot-alternatives): new helper.
    (eglot-server-programs): Use it.  Use clangd and pylsp.
    
    * NEWS.md: Mention feature.
    
    * README.md (Connecting to a server): Mention pylsp and clangd.
---
 NEWS.md   |  6 ++++++
 README.md |  5 +++--
 eglot.el  | 28 +++++++++++++++++++++++++---
 3 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 03a22bcc53..ec39654929 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,10 @@
 # (upcoming)
 
+##### Multiple servers supported out-of-box for same major mdoe 
([#688][github#688])
+
+In practice, this removes the need for Eglot to "officially" bless one
+server over another.  Thanks to Felicián Németh for the original idea.
+
 ##### TRAMP support ([#637][github#637], ([#463][github#463], 
([#84][github#84])
 
 Thanks to Brian Cully for the minimalist approach.
@@ -272,4 +277,5 @@ and now said bunch of references-->
 [github#637]: https://github.com/joaotavora/eglot/issues/637
 [github#643]: https://github.com/joaotavora/eglot/issues/643
 [github#686]: https://github.com/joaotavora/eglot/issues/686
+[github#688]: https://github.com/joaotavora/eglot/issues/688
 [github#695]: https://github.com/joaotavora/eglot/issues/695
diff --git a/README.md b/README.md
index e367b0fd97..ca78603474 100644
--- a/README.md
+++ b/README.md
@@ -39,12 +39,12 @@ find-library` can help you tell if that happened.
 
 * Javascript's [TS & JS Language Server ][typescript-language-server]
 * Rust's [rls][rls]
-* Python's [pyls][pyls]
+* Python's [pylsp][pylsp] or [pyls][pyls] 
 * Ruby's [solargraph][solargraph]
 * Java's [Eclipse JDT Language Server][eclipse-jdt]
 * Bash's [bash-language-server][bash-language-server]
 * PHP's [php-language-server][php-language-server]
-* C/C++'s [ccls][ccls]  ([cquery][cquery] and [clangd][clangd] also work)
+* C/C++'s [clangd][clangd] or [ccls][ccls]
 * Haskell's [haskell-language-server][haskell-language-server]
 * Elm's [elm-language-server][elm-language-server]
 * Kotlin's [kotlin-language-server][kotlin-language-server]
@@ -540,6 +540,7 @@ Under the hood:
 [lsp]: https://microsoft.github.io/language-server-protocol/
 [rls]: https://github.com/rust-lang-nursery/rls
 [pyls]: https://github.com/palantir/python-language-server
+[pylsp]: https://github.com/python-lsp/python-lsp-server
 [gnuelpa]: https://elpa.gnu.org/packages/eglot.html
 [melpa]: http://melpa.org/#/eglot
 [typescript-language-server]: 
https://github.com/theia-ide/typescript-language-server
diff --git a/eglot.el b/eglot.el
index 13d9952494..a739419e9d 100644
--- a/eglot.el
+++ b/eglot.el
@@ -95,15 +95,37 @@
   :prefix "eglot-"
   :group 'applications)
 
-(defvar eglot-server-programs '((rust-mode . (eglot-rls "rls"))
-                                (python-mode . ("pyls"))
+(defun eglot-alternatives (alternatives)
+  "Compute server-choosing function for `eglot-server-programs'.
+Each element of ALTERNATIVES is a string PROGRAM or a list of
+strings (PROGRAM ARGS...) where program names an LSP server
+program to start with ARGS.  Returns a function of one
+argument."
+  (lambda (&optional interactive)
+    (let* ((listified (cl-loop for a in alternatives
+                               collect (if (listp a) a (list a))))
+           (available (cl-remove-if-not #'executable-find listified :key 
#'car)))
+      (cond ((and interactive (cdr available))
+             (let ((chosen (completing-read
+                            "[eglot] More than one server executable 
available:"
+                            (mapcar #'car available)
+                            nil t nil nil (car (car available)))))
+               (assoc chosen available #'equal)))
+            ((car available))
+            (t
+             (car listified))))))
+
+(defvar eglot-server-programs `((rust-mode . (eglot-rls "rls"))
+                                (python-mode
+                                 . ,(eglot-alternatives '("pyls" "pylsp")))
                                 ((js-mode typescript-mode)
                                  . ("typescript-language-server" "--stdio"))
                                 (sh-mode . ("bash-language-server" "start"))
                                 ((php-mode phps-mode)
                                  . ("php" "vendor/felixfbecker/\
 language-server/bin/php-language-server.php"))
-                                ((c++-mode c-mode) . ("ccls"))
+                                ((c++-mode c-mode) . ,(eglot-alternatives
+                                                       '("clangd" "ccls")))
                                 (((caml-mode :language-id "ocaml")
                                   (tuareg-mode :language-id "ocaml") 
reason-mode)
                                  . ("ocamllsp"))