How to fix coffee mode symbol?

Question

While trying to use highlight-symbol in coffee mode (especially, cjsx), it interprets Something and <Something as two different symbols, while I expect < to be not part of a symbol.

Tried to trace the problem, and found that this is probably due to thighatpt symbol receives incorrect data from syntax table for coffee mode. How to fix coffee mode's syntax table to allow highlighting all symbols correctly?

(but maybe I am totally wrong with the assessment, and highlight-symbol somehow adds < to the symbol by itself. But at least in C mode it handles "less than" correctly)

GNU Emacs 24.3.1, Coffee mode 0.6.2, highlight-symbol 20160102.1209

Answer 1

Put the cursor just before the < in <symbol and hit C-u C-x =. Look at the *Help* output - search for "syntax". If it says this:

syntax: _   which means: symbol

then the character < has symbol syntax. And yes, you will need to change its syntax in coffee mode, to make it something else (e.g. so that C-u C-x = says something like this:

syntax: (>  which means: open, matches >

See the Elisp manual, node Syntax Tables and its subnodes for details about setting the syntax the way you want.

You can add a function to the coffee mode hook (probably coffee-mode-hook) that invokes modify-syntax-entry to change the syntax of character ?<. (You might want to also change the syntax of >.)

Something like this:

(defun foo ()
  (modify-syntax-entry ?< "(>  ")   ; < opens, closed by >
  (modify-syntax-entry ?> ")<  "))  ; > closes, opened by <

(add-hook 'coffee-mode-hook 'foo)