fix(flycheck): wrap languagetool checker definition in eval+backquote

flycheck's `flycheck-define-checker' macro requires the `:command'
executable to be a string literal at macro-expansion time -- it does
`(stringp (car command))' and errors otherwise.  The previous
`(eval (expand-file-name ...))' form (commit a8290c3b, the
externalization fix) put a `(eval FORM)' wrapper in the executable
position, which flycheck rejected at load:

  Error (use-package): recentf/:config: Command executable for
  syntax checker languagetool must be a string:
  (eval (expand-file-name "scripts/languagetool-flycheck"
                          user-emacs-directory))

`(eval FORM)' is only valid for SUBSEQUENT command-list elements
(arguments), not the executable.

Wrap the entire `flycheck-define-checker' invocation in `eval' +
backquote so the expanded path is spliced in as a string literal
before the macro sees it.  The hardcoded `~/.emacs.d/...' path is
gone for the same reason the original externalization wanted it
gone: survives a non-standard `user-emacs-directory'.

1 files changed, 15 insertions, 10 deletions

diff --git a/modules/flycheck-config.el b/modules/flycheck-config.el
index ba408b52f..f064cb137 100644
--- a/modules/flycheck-config.el
+++ b/modules/flycheck-config.el
@@ -66,17 +66,22 @@
   ;; use the load-path of the currently running Emacs instance
   (setq flycheck-emacs-lisp-load-path 'inherit)
 
-  ;; Define LanguageTool checker for comprehensive grammar checking
-  (flycheck-define-checker languagetool
-    "A grammar checker using LanguageTool.
+  ;; Define LanguageTool checker for comprehensive grammar checking.
+  ;; The :command executable must be a string literal at macro-expansion
+  ;; time (flycheck rejects `(eval ...)' in the first position), so we
+  ;; backquote-splice the expanded path into the form and eval it
+  ;; explicitly.  Survives a non-standard `user-emacs-directory'.
+  (eval
+   `(flycheck-define-checker languagetool
+      "A grammar checker using LanguageTool.
 Uses a wrapper script to format output for flycheck."
-    :command ((eval (expand-file-name "scripts/languagetool-flycheck"
-                                      user-emacs-directory))
-              source-inplace)
-    :error-patterns
-    ((warning line-start (file-name) ":" line ":" column ": "
-              (message) line-end))
-    :modes (text-mode markdown-mode gfm-mode org-mode))
+      :command (,(expand-file-name "scripts/languagetool-flycheck"
+                                   user-emacs-directory)
+                source-inplace)
+      :error-patterns
+      ((warning line-start (file-name) ":" line ":" column ": "
+                (message) line-end))
+      :modes (text-mode markdown-mode gfm-mode org-mode)))
   (add-to-list 'flycheck-checkers 'languagetool)
 
   (defun cj/flycheck-list-errors ()