Preventing font-lock string match from going past end of line

Question

I have a custom mode to highlight my log files. In it, I attempt to highlight strings that are surrounded by double quotes("[^"]*"). In the files, there are sometimes lines with an odd number of double quotes. This results in many lines being treated as a string, up to the next line with a double quote.

The mode is defined by

(defun my--one-line-string-p (limit)
  "Match strings, but do not cross line boundaries"

  (when (search-forward "\"" limit 'no-error)
    (backward-char 1)
    (let ((end (min limit
                  (save-excursion
                    (end-of-line)
                    (point)))))
      (when
          (search-forward-regexp "\"[^\"]*\"" end 'no-error)
;;        (message "Found match from %d to %d" (match-beginning 0) (match-end 0))
        t
        )))
  )


(defvar my-log-file-mode-font-lock-defaults
  `((
     ("\\[WARN *\\].*" . font-lock-warning-face)
     ("\\[ERROR *\\].*" . 'my-error-face)
     (my--one-line-string-p . font-lock-string-face)
     ("{[^}
]+}" . font-lock-builtin-face)
     ("\\[akka://[^]]+\\]" . font-lock-doc-face)
     ("\\([a-zA-Z0-9]+\\)=\\([-a-zA-Z0-9:]+\\)"
      (1 font-lock-variable-name-face)
      (2 font-lock-constant-face))
     )))
;; log file mode
(define-derived-mode my-log-file-mode fundamental-mode
  "Log"
  "Major mode for viewing log files"

  (setq font-lock-defaults my-log-file-mode-font-lock-defaults)
)

font-lock-multiline is nil in the buffer.

font-lock-keywords is

 (t
 (("\\[WARN *\\].*" . font-lock-warning-face)
  ("\\[ERROR *\\].*" quote my-error-face)
  (my--one-line-string-p . font-lock-string-face)
  ("{[^}\n]+}" . font-lock-builtin-face)
  ("\\[akka://[^]]+\\]" . font-lock-doc-face)
  ("\\([a-zA-Z0-9]+\\)=\\([-a-zA-Z0-9:]+\\)"
   (1 font-lock-variable-name-face)
   (2 font-lock-constant-face)))
 ("\\[WARN *\\].*"
  (0 font-lock-warning-face))
 ("\\[ERROR *\\].*"
  (0 'my-error-face))
 (my--one-line-string-p
  (0 font-lock-string-face))
 ("{[^}\n]+}"
  (0 font-lock-builtin-face))
 ("\\[akka://[^]]+\\]"
  (0 font-lock-doc-face))
 ("\\([a-zA-Z0-9]+\\)=\\([-a-zA-Z0-9:]+\\)"
  (1 font-lock-variable-name-face)
  (2 font-lock-constant-face)))

It looks like an line with an unmatched double quote should not trigger highlighting, but it does.

I have these minor modes:

Enabled minor modes: Auto-Composition Auto-Compression Auto-Encryption Blink-Cursor Desktop-Save Diff-Auto-Refine Ede Electric-Indent File-Name-Shadow Flycheck Flycheck-Color-Mode-Line Font-Lock Global-Ede Global-Flycheck Global-Font-Lock Global-Semantic-Decoration Global-Semantic-Highlight-Func Global-Semantic-Idle-Breadcrumbs Global-Semantic-Idle-Completions Global-Semantic-Idle-Local-Symbol-Highlight Global-Semantic-Idle-Scheduler Global-Semantic-Idle-Summary Global-Semantic-Stickyfunc Global-Semanticdb Jdee-Etrace Line-Number Menu-Bar Mode-Icons Mouse-Wheel Pallet Schrute Semantic Shell-Dirtrack Show-Paren Tool-Bar Tooltip Which-Function Yas Yas-Global

Is there some other variable that I need to set to prevent multi-line string highlighting?

Answer 1

If you want to prevent multi-line matching then include \n (newline character) in the characters to exclude: "[^"\n]*".

Answer 2

The solution is to disable syntactical highlighting. Even though the regular expression suggested by Drew and the function that I originally had used only match a single line string, the syntax table will find multi-line strings.

To disable this, you need to set font-lock-keywords-only in the buffer. The way to do this that works is as the second element of font-lock-defaults.

(defvar my-log-file-mode-font-lock-defaults
  `((
     ("\\[WARN *\\].*" . font-lock-warning-face)
     ("\\[ERROR *\\].*" . 'my-error-face)
     (my--one-line-string-p . font-lock-string-face)
     ("{[^}
]+}" . font-lock-builtin-face)
     ("\\[akka://[^]]+\\]" . font-lock-doc-face)
     ("\\([a-zA-Z0-9]+\\)=\\([-a-zA-Z0-9:]+\\)"
      (1 font-lock-variable-name-face)
      (2 font-lock-constant-face))
     )
     t ;; <---- This is the addition
))