Unnecessary error for buffers containing a main function

[nordlow]

Flags sent to dmd should not contain -main flag if the current buffer contains a D main function.

This will inhibit the unneccessary error message:

3539     error    only one main allowed, -main switch added another main() (d-dmd-unittest)

This is preferrably solved by searching for a regexp matching a D main function definition such as

void main(string args[])

int the current buffer.

Here's a somewhat relaxed Emacs-Lisp regexp that works for me

(defcustom d-main-function-regexp "^\\(?:void\\|int\\)?[[:space:]]*main[[:space:]]*([[:space:]]*string[[:space:]]+"
  "Regexp matching C-style main function.")

[tom-tan]

I think it is not good idea to use original main function for unittest.
The main function may read a string from the standard input.
In that case, the unittest will wait for the user input and it never stops if we use original main.

Instead of that, it is better to enclose main function in version(!unittest) block as described in the document.

import std.stdio;

version(unittest) {}
else
void main()
{
    writeln("Hello!");
}

unittest
{
    assert(1+2 == 3);
}

[tom-tan]

I close this issue because using version(!unittest) is enough to avoid this issue.

[nordlow]

I would still like to have logic that only adds -main flag if d-main-function-regexp does not match contents of current buffer. Where can I most easily inject this without modifying flycheck.el itself?

[tom-tan]

You can directly modify the arguments by using put function.
Here is the example to remove -main from the arguments of d-dmd-unittest checker.

(let ((checker 'd-dmd-unittest))
  (put checker :flycheck-command
       (remove "-main" (flycheck-checker-arguments checker))))

"Defining new syntax checkers" section in Flycheck website will help you to modify the arguments.