Subject: bug#61205: 'function' in 3rd element of treesit-font-lock-feature-list

From: Dmitry Gutov <[email-masked]>
Date: Sun, 5 Feb 2023 01:44:40 +0200

On 04/02/2023 08:53, Eli Zaretskii wrote:
>> Date: Sat, 4 Feb 2023 05:36:15 +0200
>> From: Dmitry Gutov<[email-masked]>
>> Cc:[email-masked],[email-masked],[email-masked],[email-masked]
>>
>> Here's the updated patch in the meantime.
> Thanks, but please also update the doc string of
> treesit-font-lock-level.

Done.

>> Not sure what to do with 'type' highlighting in rust-ts-mode yet.
> What is the problem with that?

The nodes structure of a 'use' instruction has a lot of nesting, and at 
least a couple of variations, which would lead to a combinatoric 
increase in the number of queries.

Taking another look at the declarations, though, I wasn't sure I could 
understand the specific logic for choosing between font-lock-type-face 
and font-lock-constant-face.

It seemed heavily inspired by 
https://github.com/tree-sitter/tree-sitter-rust/blob/master/queries/highlights.scm, 
though. So what I did is reverted to those rules (in that area): the 
path segments that start with an uppercase char get highlighted with 
font-lock-type-face. The rest don't get highlighted at all. That's how 
Rust code looks at Github, so a fair number of developers must be okay 
with it.

(Github also highlights function calls, though.)

I'm also adding function parameter highlighting to rust and go modes.

See the attached patch. I suggest we install it in emacs-29, but then 
people are free to tweak the rules further.

diff --git a/doc/emacs/display.texi b/doc/emacs/display.texi
index 97732b65e32..a86c12a0db7 100644
--- a/doc/emacs/display.texi
+++ b/doc/emacs/display.texi
@@ -1159,11 +1159,11 @@ Parser-based Font Lock
 This level adds fontification of keywords, strings, and data types.
 @item Level 3
 This is the default level; it adds fontification of assignments,
-numbers, properties, etc.
+numbers, etc.
 @item Level 4
 This level adds everything else that can be fontified: operators,
 delimiters, brackets, other punctuation, function names in function
-calls, variables, etc.
+calls, property look ups, variables, etc.
 @end table
 
 @vindex treesit-font-lock-feature-list
diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index 2a164af26ea..7300074e5c6 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -774,8 +774,8 @@ c-ts-base-mode
   (setq-local treesit-font-lock-feature-list
               '(( comment definition)
                 ( keyword preprocessor string type)
-                ( assignment constant escape-sequence label literal property )
-                ( bracket delimiter error function operator variable))))
+                ( assignment constant escape-sequence label literal)
+                ( bracket delimiter error function operator property variable))))
 
 ;;;###autoload
 (define-derived-mode c-ts-mode c-ts-base-mode "C"
diff --git a/lisp/progmodes/go-ts-mode.el b/lisp/progmodes/go-ts-mode.el
index 95dcf653fc6..4b14e55281e 100644
--- a/lisp/progmodes/go-ts-mode.el
+++ b/lisp/progmodes/go-ts-mode.el
@@ -123,17 +123,26 @@ go-ts-mode--font-lock-settings
    :feature 'delimiter
    '((["," "." ";" ":"]) @font-lock-delimiter-face)
 
+   :language 'go
+   :feature 'definition
+   '((function_declaration
+      name: (identifier) @font-lock-function-name-face)
+     (method_declaration
+      name: (field_identifier) @font-lock-function-name-face)
+     (method_spec
+      name: (field_identifier) @font-lock-function-name-face)
+     (field_declaration
+      name: (field_identifier) @font-lock-property-face)
+     (parameter_declaration
+      name: (identifier) @font-lock-variable-name-face))
+
    :language 'go
    :feature 'function
    '((call_expression
       function: (identifier) @font-lock-function-name-face)
      (call_expression
       function: (selector_expression
-                 field: (field_identifier) @font-lock-function-name-face))
-     (function_declaration
-      name: (identifier) @font-lock-function-name-face)
-     (method_declaration
-      name: (field_identifier) @font-lock-function-name-face))
+                 field: (field_identifier) @font-lock-function-name-face)))
 
    :language 'go
    :feature 'keyword
@@ -221,11 +230,10 @@ go-ts-mode
     ;; Font-lock.
     (setq-local treesit-font-lock-settings go-ts-mode--font-lock-settings)
     (setq-local treesit-font-lock-feature-list
-                '(( comment)
+                '(( comment definition)
                   ( keyword string type)
-                  ( constant escape-sequence function label number
-                    property variable)
-                  ( bracket delimiter error operator)))
+                  ( constant escape-sequence label number)
+                  ( bracket delimiter error function operator property variable)))
 
     (treesit-major-mode-setup)))
 
diff --git a/lisp/progmodes/rust-ts-mode.el b/lisp/progmodes/rust-ts-mode.el
index e317793d211..5722d037bba 100644
--- a/lisp/progmodes/rust-ts-mode.el
+++ b/lisp/progmodes/rust-ts-mode.el
@@ -155,6 +155,16 @@ rust-ts-mode--font-lock-settings
    :feature 'delimiter
    '((["," "." ";" ":" "::"]) @font-lock-delimiter-face)
 
+   :language 'rust
+   :feature 'definition
+   '((function_item name: (identifier) @font-lock-function-name-face)
+     (macro_definition "macro_rules!" @font-lock-constant-face)
+     (macro_definition (identifier) @font-lock-preprocessor-face)
+     (field_declaration name: (field_identifier) @font-lock-property-face)
+     (parameter pattern: (identifier) @font-lock-variable-name-face)
+     (parameter
+      pattern: (reference_pattern (identifier) @font-lock-variable-name-face)))
+
    :language 'rust
    :feature 'function
    '((call_expression
@@ -164,15 +174,12 @@ rust-ts-mode--font-lock-settings
         field: (field_identifier) @font-lock-function-name-face)
        (scoped_identifier
         name: (identifier) @font-lock-function-name-face)])
-     (function_item (identifier) @font-lock-function-name-face)
      (generic_function
       function: [(identifier) @font-lock-function-name-face
                  (field_expression
                   field: (field_identifier) @font-lock-function-name-face)
                  (scoped_identifier
                   name: (identifier) @font-lock-function-name-face)])
-     (macro_definition "macro_rules!" @font-lock-constant-face)
-     (macro_definition (identifier) @font-lock-preprocessor-face)
      (macro_invocation macro: (identifier) @font-lock-preprocessor-face))
 
    :language 'rust
@@ -208,20 +215,20 @@ rust-ts-mode--font-lock-settings
      (mod_item name: (identifier) @font-lock-constant-face)
      (primitive_type) @font-lock-type-face
      (type_identifier) @font-lock-type-face
-     (scoped_identifier name: (identifier) @font-lock-type-face)
-     (scoped_identifier path: (identifier) @font-lock-constant-face)
-     (scoped_identifier
-      (scoped_identifier
-       path: (identifier) @font-lock-constant-face))
+     ((scoped_identifier name: (identifier) @font-lock-type-face)
+      (:match "^[A-Z]" @font-lock-type-face))
+     ((scoped_identifier path: (identifier) @font-lock-type-face)
+      (:match "^[A-Z]" @font-lock-type-face))
+     ((scoped_identifier
+        (scoped_identifier
+         path: (identifier) @font-lock-type-face))
+      (:match "^[A-Z]" @font-lock-type-face))
      ((scoped_identifier
        path: [(identifier) @font-lock-type-face
               (scoped_identifier
                name: (identifier) @font-lock-type-face)])
       (:match "^[A-Z]" @font-lock-type-face))
      (scoped_type_identifier path: (identifier) @font-lock-constant-face)
-     (scoped_use_list
-      path: [(identifier) @font-lock-constant-face
-             (scoped_identifier (identifier) @font-lock-constant-face)])
      (type_identifier) @font-lock-type-face
      (use_as_clause alias: (identifier) @font-lock-type-face)
      (use_list (identifier) @font-lock-type-face))
@@ -317,11 +324,11 @@ rust-ts-mode
     ;; Font-lock.
     (setq-local treesit-font-lock-settings rust-ts-mode--font-lock-settings)
     (setq-local treesit-font-lock-feature-list
-                '(( comment)
+                '(( comment definition)
                   ( keyword string)
                   ( attribute builtin constant escape-sequence
-                    function number property type variable)
-                  ( bracket delimiter error operator)))
+                    number type)
+                  ( bracket delimiter error function operator property variable)))
 
     ;; Imenu.
     (setq-local treesit-simple-imenu-settings
diff --git a/lisp/treesit.el b/lisp/treesit.el
index 98f446a1456..2562e1286c7 100644
--- a/lisp/treesit.el
+++ b/lisp/treesit.el
@@ -585,9 +585,10 @@ treesit-font-lock-level
 Level 1 usually contains only comments and definitions.
 Level 2 usually adds keywords, strings, data types, etc.
 Level 3 usually represents full-blown fontifications, including
-assignments, constants, numbers and literals, properties, etc.
+assignments, constants, numbers and literals, etc.
 Level 4 adds everything else that can be fontified: delimiters,
-operators, brackets, punctuation, all functions and variables, etc.
+operators, brackets, punctuation, all functions, properties,
+variables, etc.
 
 In addition to the decoration level, individual features can be
 turned on/off by calling `treesit-font-lock-recompute-features'.