Validate font-lock rules when setting up tree-sitter major mode

When tree-sitter grammar make breaking changes, major modes
breaks completely: no highlighting is shown.  This new function
will run in treesit-major-mode-setup, validate each
font-lock features, and disable the ones that are not compatible
with the new grammar, so that the rest of the features still
work.  It also displays a warning explaining the situation,
which looks like this:

    Warning (treesit-font-lock-rules-mismatch): Emacs cannot
    compile every font-lock rules because a mismatch between the
    grammar and the rules.  This is most likely due to a
    mismatch between the font-lock rules defined by the major
    mode and the tree-sitter grammar.

    This error can be fixed by either downgrading the
    grammar (tree-sitter-c) on your system, or upgrading the
    major mode package.  The following are the temporarily
    disabled features:

    - `preprocessor' for c.

* lisp/treesit.el (treesit-validate-font-lock-rules): New function.
(treesit-major-mode-setup): Validate font-lock rules.

0 files changed, 0 insertions, 0 deletions