Re: master 79d9f3982f: Add derived-mode test for bug#24176

[Stefan Monnier]

> +(ert-deftest test-add-font-lock ()
> +  (define-derived-mode mode-a fundamental-mode "mode-a"
> +    (font-lock-add-keywords nil `(("a" 0 'font-lock-keyword-face))))
> +  (define-derived-mode mode-b mode-a "mode-b"
> +    (font-lock-add-keywords nil `(("b" 0 'font-lock-builtin-face))))
> +  (define-derived-mode mode-c mode-b "mode-c"
> +    (font-lock-add-keywords nil `(("c" 0 'font-lock-constant-face))))
> +
> +  (with-temp-buffer
> +    (mode-c)
> +    (should (equal font-lock-keywords
> +                   '(t (("c" 0 'font-lock-constant-face)
> +                        ("b" 0 'font-lock-builtin-face)
> +                        ("a" 0 'font-lock-keyword-face))
> +                       ("c" (0 'font-lock-constant-face))
> +                       ("b" (0 'font-lock-builtin-face))
> +                       ("a" (0 'font-lock-keyword-face)))))))

An interesting other case is:

    (defvar mode-a-flk '(("a" 0 'font-lock-keyword-face)))
    (define-derived-mode mode-a fundamental-mode "mode-a"
      (setq-local font-lock-defaults '(mode-a-flk)))
    (define-derived-mode mode-b mode-a "mode-b"
      (font-lock-add-keywords nil `(("b" 0 'font-lock-builtin-face))))
    (defvar mode-c-flk '(("c" 0 'font-lock-keyword-face)))
    (define-derived-mode mode-c mode-b "mode-c"
      (setq-local font-lock-defaults '(mode-c-flk)))


-- Stefan