Add cquery support for c/c++ projects

Implements minimal support for the core cquery language
server. None of its extensions are implemented yet.

* eglot.el (eglot-server-programs): Add cquery to list
of guessed programs for c-mode and c++-mode.
(eglot-initialization-options eglot-cquery): Specialize init
options to pass cquery a cache directory and disable a flood
of $cquery/progress messages.
(eglot-handle-notification $cquery/publishSemanticHighlighting):
(eglot-handle-notification $cquery/setInactiveRegions):
(eglot-handle-notification $cquery/progress): New no-op functions
to avoid filling logs with "unknown message" warnings.
(eglot-cquery): New eglot-lsp-server subclass.

* README.md: Mention cquery in the README.

diff --git a/lisp/progmodes/eglot.el b/lisp/progmodes/eglot.el
index 3d363444405d6f9dd3691921af71e96f3cec88be..189ad1e5aae0b6c7657bddb8ff17dee7b061912b 100644 (file)
--- a/lisp/progmodes/eglot.el
+++ b/lisp/progmodes/eglot.el
@@ -72,6 +72,8 @@
                                 (python-mode . ("pyls"))
                                 (js-mode . ("javascript-typescript-stdio"))
                                 (sh-mode . ("bash-language-server" "start"))
+                                (c++-mode . (eglot-cquery "cquery"))
+                                (c-mode . (eglot-cquery "cquery"))
                                 (php-mode . ("php" "vendor/felixfbecker/\
 language-server/bin/php-language-server.php")))
   "How the command `eglot' guesses the server to start.
@@ -1613,6 +1615,34 @@ Proceed? "
         (funcall (or eglot--current-flymake-report-fn #'ignore)
                  eglot--unreported-diagnostics)))))
 
+\f
+;;; cquery-specific
+;;;
+(defclass eglot-cquery (eglot-lsp-server) ()
+  :documentation "cquery's C/C++ langserver.")
+
+(cl-defmethod eglot-initialization-options ((server eglot-cquery))
+  "Passes through required cquery initialization options"
+  (let* ((root (car (project-roots (eglot--project server))))
+         (cache (expand-file-name ".cquery_cached_index/" root)))
+    (vector :cacheDirectory (file-name-as-directory cache)
+            :progressReportFrequencyMs -1)))
+
+(cl-defmethod eglot-handle-notification
+  ((server eglot-cquery) (_method (eql :$cquery/progress))
+   &rest counts &key activeThreads &allow-other-keys)
+  "No-op for noisy $cquery/progress extension")
+
+(cl-defmethod eglot-handle-notification
+  ((server eglot-cquery) (_method (eql :$cquery/setInactiveRegions))
+   &key uri inactiveRegions &allow-other-keys)
+  "No-op for unsupported $cquery/setInactiveRegions extension")
+
+(cl-defmethod eglot-handle-notification
+  ((server eglot-cquery) (_method (eql :$cquery/publishSemanticHighlighting))
+   &key uri symbols &allow-other-keys)
+  "No-op for unsupported $cquery/publishSemanticHighlighting extension")
+
 (provide 'eglot)
 ;;; eglot.el ends here