Flycheck reports 'the function ... is not known to be defined' for autoloaded elisp function. Why? about flycheck HOT 7 OPEN

Thanks for the detailed report 😍
The warning is computed by the Emacs bytecode compiler, not by Flycheck itself. You can use M-x flycheck-compile to see exactly how it is invoked.

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The warning is computed by the Emacs bytecode compiler, not by Flycheck itself.

Thanks for the quick reply! Any idea how to avoid the warning?

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@ktetzlaff You can use declare-function for this. See https://www.gnu.org/software/emacs/manual/html_node/elisp/Declaring-Functions.html

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You can use declare-function for this. ...

@bbatsov Yes, that works. However, I would need to add declare-function to a lot of files. Is it somehow possible to declare a function globally? I.e. make a user defined function work like a built-in/preloaded function?

Or trick flycheck into ignoring the warning for a specific function?

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See flycheck-emacs-lisp-load-path maybe?

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See flycheck-emacs-lisp-load-path maybe?

@cpitclaudel I have flycheck-emacs-lisp-load-path set to inherit and the flycheck-compile output shows that the directory containing the test files gets added (--directory /home/kail/tmp). So: No - unfortunately that doesn't help.

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I have the same issue, just with the function ‘...' might not be defined at runtime. I have code such as this:

(use-package web-mode
  :mode ("\\.vue\\'" . web-mode)
  :config
  (customize-set-variable 'web-mode-markup-indent-offset 2)
  (customize-set-variable 'web-mode-css-indent-offset 2)
  (customize-set-variable 'web-mode-code-indent-offset 2))

(defun my/twee-mode-language-at-pos ()
  "Determine language at point, defaulting to web-mode if not Twee code."
  (if (save-excursion
        (beginning-of-line)
        (looking-at "^\s*<<"))
      "twee"
    (web-mode-language-at-pos)))

I get the function ‘web-mode-language-at-pos’ might not be defined at runtime. even though if I use (require 'web-mode) it works just fine.

If I expand the use-package macro, I get:

(progn
  (defvar use-package--warning43
    (function
     (lambda
       (keyword err)
       (let
           ((msg
             (format "%s/%s: %s" 'web-mode keyword
                     (error-message-string err))))
         (display-warning 'use-package msg :error)))))
  (condition-case-unless-debug err
      (progn
        (unless
            (fboundp 'web-mode)
          (autoload
            (function web-mode)
            "web-mode" nil t))
        (eval-after-load 'web-mode
          '(condition-case-unless-debug err
               (progn
                 (customize-set-variable 'web-mode-markup-indent-offset 2)
                 (customize-set-variable 'web-mode-css-indent-offset 2)
                 (customize-set-variable 'web-mode-code-indent-offset 2)
                 t)
             (error
              (funcall use-package--warning43 :config err))))
        (add-to-list 'auto-mode-alist
                     '("\\.vue\\'" . web-mode)))
    (error
     (funcall use-package--warning43 :catch err))))

Seems like the require part is under a conditional, which is why the byte compiler may have trouble recognizing this.

Anyways, this isn't really a Flycheck bug. The byte compiler also complains. I just wish there was a way to get rid of these.

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