feature/tree-sitter 8083949861 4/5: treesit-font-lock-recompute-features now has two modes of operation

[Yuan Fu]

branch: feature/tree-sitter
commit 80839498614a3d898daabc2725fb814ce1e3ace0
Author: Yuan Fu <casouri@gmail.com>
Commit: Yuan Fu <casouri@gmail.com>

    treesit-font-lock-recompute-features now has two modes of operation
    
    1. Set activation of each feature (changes every feature)
    2. Add/remove features (only change those explicitly configured by
    ADD-LIST and REMOVE-LIST)
    
    This is useful for enabling/disabling certain features for all
    modes (without resetting others) by calling this function in
    prog-mode-hook
    
    * lisp/treesit.el (treesit-font-lock-recompute-features): See above
    description.
---
 lisp/treesit.el | 33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/lisp/treesit.el b/lisp/treesit.el
index abf5297edd..23c22f0785 100644
--- a/lisp/treesit.el
+++ b/lisp/treesit.el
@@ -694,16 +694,23 @@ name, it is ignored."
   "If non-nil, print debug messages when fontifying.")
 
 (defun treesit-font-lock-recompute-features (&optional add-list remove-list)
-  "Enable/disable font-lock settings according to decoration level.
+  "Enable/disable font-lock features.
 
-First compute the enabled features according to
-`treesit-font-lock-feature-list' and `font-lock-maximum-decoration',
-then, if ADD-LIST or REMOVE-LIST are not omitted, further add and
-remove features accordingly.
+Enable each feature in ADD-LIST, disable each feature in
+REMOVE-LIST.
+
+If both ADD-LIST and REMOVE-LIST are omitted, recompute each
+feature according to `treesit-font-lock-feature-list' and
+`font-lock-maximum-decoration'.  Let N be the value of
+`font-lock-maximum-decoration', features in the first Nth sublist
+of `treesit-font-lock-feature-list' are enabled, and the rest
+features are disabled.  If `font-lock-maximum-decoration' is t,
+all features in `treesit-font-lock-feature-list' are enabled, and
+the rest are disabled.
 
 ADD-LIST and REMOVE-LIST are each a list of feature symbols.  The
 same feature symbol cannot appear in both lists; the function
-signals the `treesit-font-lock-error' error if so."
+signals the `treesit-font-lock-error' error if that happens."
   (when-let ((intersection (cl-intersection add-list remove-list)))
     (signal 'treesit-font-lock-error
             (list "ADD-LIST and REMOVE-LIST contain the same feature"
@@ -717,13 +724,23 @@ signals the `treesit-font-lock-error' error if so."
                                 (>= level (1+ idx)))
                          append features))
          (features (cl-set-difference (cl-union base-features add-list)
-                                      remove-list)))
+                                      remove-list))
+         ;; If additive non-nil, we are configuring on top of the
+         ;; existing configuration, if nil, we are resetting
+         ;; everything according to `treesit-font-lock-feature-list'.
+         (additive (or add-list remove-list)))
     (cl-loop for idx = 0 then (1+ idx)
              for setting in treesit-font-lock-settings
              for feature = (nth 2 setting)
+             for current-value = (nth 1 setting)
              ;; Set the ENABLE flag for the setting.
              do (setf (nth 1 (nth idx treesit-font-lock-settings))
-                      (if (memq feature features) t nil)))))
+                      (cond
+                       ((not additive)
+                        (if (memq feature features) t nil))
+                       ((memq feature add-list) t)
+                       ((memq feature remove-list) nil)
+                       (t current-value))))))
 
 (defun treesit-fontify-with-override (start end face override)
   "Apply FACE to the region between START and END.