Add a defcustom to control default diagnostic severity.

Previously, there was a Flycheck specific defcustom, which was used to
select a default error level for Flycheck.  However, there was nothing
for Flymake.  Additionally, there were numerous other places in
lsp-mode which query the severity attribute of the diagnostic, such as
for statistics, modeline, headerline, etc.  All of these were being
handled inconsistently, either not at all (causing an error when the
attribute was not sent by the server), ignoring it when it was
missing (causing statistics to be inaccurate) or assuming a default of
error, which might have been different than the Flycheck specific
configuration, therefore causing an inconsistency in the modeline
statistics vs what Flycheck would report.

This change creates a common defcustom which is then used anywhere the
diagnostic severity is needed, but was not provided by the server.
This should create consistent statistics between the modeline and the
back-end checkers.  Additionally, the mapping between this defcustom
and the checker specific values happens in the diagnostic package.

Since this defcustom is used outside of the lsp-diagnostic package, it
resides in the lsp-mode package and renamed more generally.
Additionally, the Flycheck specific defcustom has been obsoleted.

lsp-diagnostics.el

@@ -50,13 +50,9 @@
 (define-obsolete-variable-alias 'lsp-flycheck-default-level
   'lsp-diagnostics-flycheck-default-level  "lsp-mode 7.0.1")
 
-(defcustom lsp-diagnostics-flycheck-default-level 'error
-  "Error level to use when the server does not report back a diagnostic level."
-  :type '(choice
-          (const error)
-          (const warning)
-          (const info))
-  :group 'lsp-diagnostics)
+;;;###autoload
+(define-obsolete-variable-alias 'lsp-diagnostics-flycheck-default-level
+  'lsp-diagnostics-default-severity "lsp-mode 9.0.1")
 
 (defcustom lsp-diagnostics-attributes
   `((unnecessary :foreground "gray")
@@ -131,18 +127,19 @@ g. `error', `warning') and list of LSP TAGS."
 
 (defun lsp-diagnostics--flycheck-calculate-level (severity tags)
   "Calculate flycheck level by SEVERITY and TAGS."
-  (let ((level (pcase severity
-                 (1 'error)
-                 (2 'warning)
-                 (3 'info)
-                 (4 'info)
-                 (_ lsp-flycheck-default-level)))
-        ;; materialize only first tag.
-        (tags (seq-map (lambda (tag)
-                         (cond
-                          ((= tag lsp/diagnostic-tag-unnecessary) 'unnecessary)
-                          ((= tag lsp/diagnostic-tag-deprecated) 'deprecated)))
-                       tags)))
+  (let* ((severity (or severity
+                       (lsp-diagnostics-severity->numeric
+                        lsp-diagnostics-default-severity)))
+         (level (cond ((= severity lsp/diagnostic-severity-error)       'error)
+                      ((= severity lsp/diagnostic-severity-warning)     'warning)
+                      ((= severity lsp/diagnostic-severity-information) 'info)
+                      ((= severity lsp/diagnostic-severity-hint)        'info)))
+         ;; materialize only first tag.
+         (tags (seq-map (lambda (tag)
+                          (cond
+                           ((= tag lsp/diagnostic-tag-unnecessary) 'unnecessary)
+                           ((= tag lsp/diagnostic-tag-deprecated) 'deprecated)))
+                        tags)))
     (if tags
         (lsp-diagnostics--flycheck-level level tags)
       level)))
@@ -305,14 +302,14 @@ See https://github.com/emacs-lsp/lsp-mode."
                             (goto-char (point-min))
                             (setq start (line-beginning-position (1+ start-line))
                                   end (line-end-position (1+ end-line))))))
-                      (flymake-make-diagnostic (current-buffer)
-                                               start
-                                               end
-                                               (cl-case severity?
-                                                 (1 :error)
-                                                 (2 :warning)
-                                                 (t :note))
-                                               message))))
+                      (let* ((severity (or severity?
+                                           (lsp-diagnostics-severity->numeric
+                                            lsp-diagnostics-default-severity)))
+                             (type (cond ((= severity lsp/diagnostic-severity-error)       :error)
+                                         ((= severity lsp/diagnostic-severity-warning)     :warning)
+                                         ((= severity lsp/diagnostic-severity-information) :note)
+                                         ((= severity lsp/diagnostic-severity-hint)        :note))))
+                        (flymake-make-diagnostic (current-buffer) start end type message)))))
            ;; This :region keyword forces flymake to delete old diagnostics in
            ;; case the buffer hasn't changed since the last call to the report
            ;; function. See https://github.com/joaotavora/eglot/issues/159

lsp-headerline.el

@@ -306,7 +306,11 @@ PATH is the current folder to be checked."
   (let ((range-severity 10))
     (mapc (-lambda ((&Diagnostic :range (&Range :start) :severity?))
             (when (lsp-point-in-range? start range)
-              (setq range-severity (min range-severity severity?))))
+              (setq range-severity
+                    (min range-severity
+                         (or severity?
+                             (lsp-diagnostics-severity->numeric
+                              lsp-diagnostics-default-severity))))))
           (lsp--get-buffer-diagnostics))
     range-severity))
 

lsp-mode.el

@@ -634,6 +634,15 @@ diagnostics have changed."
   :type 'hook
   :group 'lsp-mode)
 
+(defcustom lsp-diagnostics-default-severity 'error
+  "Error level to use when the server does not report one."
+  :type '(choice (const :tag "Error"       error)
+                 (const :tag "Warning"     warning)
+                 (const :tag "Information" info)
+                 (const :tag "Hint"        hint))
+  :group 'lsp-mode
+  :package-version '(lsp-mode . "9.0.1"))
+
 (define-obsolete-variable-alias 'lsp-workspace-folders-changed-hook
   'lsp-workspace-folders-changed-functions "lsp-mode 6.3")
 
@@ -2277,6 +2286,14 @@ Common usecase are:
                         result)))
       (ht)))
 
+(defun lsp-diagnostics-severity->numeric (severity)
+  "Determine numeric severity from symbolic SEVERITY."
+  (pcase severity
+    ('error   lsp/diagnostic-severity-error)
+    ('warning lsp/diagnostic-severity-warning)
+    ('info    lsp/diagnostic-severity-information)
+    ('hint    lsp/diagnostic-severity-hint)))
+
 (defun lsp-diagnostics-stats-for (path)
   "Get diagnostics statistics for PATH.
 The result format is vector [_ errors warnings infos hints] or nil."
@@ -2296,11 +2313,15 @@ The result format is vector [_ errors warnings infos hints] or nil."
   (let ((path (lsp--fix-path-casing (lsp--uri-to-path uri)))
         (new-stats (make-vector 5 0)))
     (mapc (-lambda ((&Diagnostic :severity?))
-            (cl-incf (aref new-stats (or severity? 1))))
+            (cl-incf (aref new-stats (or severity?
+                                         (lsp-diagnostics-severity->numeric
+                                          lsp-diagnostics-default-severity)))))
           diagnostics)
     (when-let ((old-diags (gethash path (lsp--workspace-diagnostics workspace))))
       (mapc (-lambda ((&Diagnostic :severity?))
-              (cl-decf (aref new-stats (or severity? 1))))
+              (cl-decf (aref new-stats (or severity?
+                                           (lsp-diagnostics-severity->numeric
+                                            lsp-diagnostics-default-severity)))))
             old-diags))
     (lsp-diagnostics--update-path path new-stats)
     (while (not (string= path (setf path (file-name-directory

lsp-modeline.el

@@ -229,8 +229,10 @@ The `:global' workspace is global one.")
     (mapc (lambda (buf-diags)
             (mapc (lambda (diag)
                     (-let [(&Diagnostic? :severity?) diag]
-                      (when severity?
-                        (cl-incf (aref stats severity?)))))
+                      (cl-incf (aref stats
+                                     (or severity?
+                                         (lsp-diagnostics-severity->numeric
+                                          lsp-diagnostics-default-severity))))))
                   buf-diags))
           diagnostics)
     (while (< i lsp/diagnostic-severity-max)