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I've just started to use Flycheck to improve the quality of my code, and I am grateful that it is helping me to do that by pointing out assignments to free variables, and by identifying possibly undefined functions on the last line of the error display. (Actually, these two are Warnings, not errors.)

I would like to see no warnings in my error display, of course.

So is there a way for me to tell Flycheck about the global variables that I use on my project, and that I reference in multiple files? I have the appropriate defvar statements in one file, but not in all files. And I don't want to put defvar statements in every file that references them (I think, unless that's really the proper Emacs Lisp way...)

And is there a way for me to tell Flycheck about all the functions (which are defined in other files) that I reference in many files? That way only the truly undefined functions will show up in the last line of the Flycheck output. (I have so many that I don't usually want to flog through the long list of functions that I already know are defined, just to find ones that are possibly not defined.

I looked at the Flycheck manual on the home website, but it said nothing about this sort of thing. Neither could I see any sort of config variables for Lisp "include" or "prefix" files where I could point Flycheck to the file containing all my defvar statements...

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2 Answers 2

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For global variables, use (defvar foo) (with no initial value). See the Elisp manual, node Compiler Errors.

For functions, use (declare foo "myfile.el"). See the Elisp manual, node Declaring Functions.

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  • Thank you. I was kind of hoping there would be a way to tell Flycheck to prefix those declaration files to the buffer, before doing it's checking. That way I wouldn't have to maintain a pile of changing declarations in all my files. I'll play around with your suggestions, and maybe all I will need is a single declare reference at the top of each file. PS. If it helps any, I made sure that I read the entire Emacs and Elisp manuals from end to end a while ago, but was trying to solve the problem using a Flycheck feature (if one existed). Thank you again for your tireless help on this site..
    – Kevin
    Jun 27, 2016 at 15:52
  • As long as the byte-compiler sees such a vacuous defvar once, that silences it for that variable for any subsequent compilations (in that session). So if you byte-compile several files, it is enough to put the vacuous defvar in the first that you compile. Likewise, for function declarations. You can put all of them in the same file, which you byte-compile first.
    – Drew
    Jun 27, 2016 at 15:55
  • I played around with defvar, (declare..., and (declare-function .., but the only times they help Flycheck is when the declarations appear in the file explicitly. That means I would need to maintain a pile of them in every Lisp file that I use. Instead, I put a job on my TODO list to write some functions to insert a pile of such declarations into each buffer on the find-file-hook and to remove them on the before-save-hook. Maybe that approach will accomplish my goals (low maintenance) while keeping Flycheck happy.
    – Kevin
    Jun 27, 2016 at 16:37
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    @kevin Another possibility is to require the files with the definitions.
    – npostavs
    Jun 27, 2016 at 16:41
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    I googled "flycheck elisp load-path" and it showed me github.com/flycheck/flycheck/issues/174 among other explanations, including a duplicate here at E.S.: emacs.stackexchange.com/q/10244
    – phils
    Jun 28, 2016 at 14:29
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The outcome of this whole issue is that (defvar foo) syntax works fine if it is embedded in the source file being checked. But it fails if it is brought into the syntax check with a (require 'my-dcls) reference to an external file containing (defvar foo).

A value must be assigned to foo, such as (defvar foo nil), in the external file if the declaration is to remove free variable warnings in the source file being tested by Flycheck.

So for now, I conclude that there is no way in Emacs Lisp to "include" a reference list (with no values set in the declarations) of globally defined variables in each source file of a project.

So the choices are to live with the free variable warnings, embed declarations into every source file on the project (ugh), or ensure that all my globals are defined -- with values set -- in the external declarations file brought in by the (require 'my-dcls) statement. Of the three choices, #3 seems to be the best approach.

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