Don't fontify backquoted symbols as strings in process buffer

Author: lionel-

doc/newfeat.texi

@@ -4,6 +4,9 @@
 Changes and New Features in 19.04 (unreleased):
 @itemize @bullet
 
+@item ESS[R]: Backticked symbols in the process buffer are no
+longer fontified as strings.
+
 @item ESS[R]: @code{ess-command} now runs R code in a sandboxed environment.
 Use @code{.ess.environment()} to inspect the current environment.
 

lisp/ess-r-mode.el

@@ -375,7 +375,7 @@ namespace.")
                 'ess-operator-face)
             (if (cdr (assq 'ess-R-fl-keyword:%op% ess-R-font-lock-keywords))
                 'ess-%op%-face
-              'default)))
+              nil)))
          ((save-excursion
             (and (cdr (assq 'ess-R-fl-keyword:fun-defs ess-R-font-lock-keywords))
                  (ess-goto-char string-end)
@@ -389,11 +389,19 @@ namespace.")
                  (ess-looking-at "(")))
           ess-function-call-face)
          ((eq (nth 3 state) ?`)
-          'default)
+          nil)
          (t
           font-lock-string-face)))
     font-lock-comment-face))
 
+;; Don't fontify backquoted symbols as strings
+(defun inferior-ess-r-font-lock-syntactic-face-function (state)
+  (if (nth 3 state)
+      (if (eq (nth 3 state) ?`)
+          nil
+        font-lock-string-face)
+    font-lock-comment-face))
+
 (defvar ess-r--non-fn-kwds
   '("in" "else" "break" "next" "repeat"))
 
@@ -2387,6 +2395,7 @@ state.")
   :group 'ess-proc
   (ess-setq-vars-local ess-r-customize-alist)
   (setq-local ess-font-lock-keywords 'inferior-ess-r-font-lock-keywords)
+  (setq-local font-lock-syntactic-face-function #'ess-r-font-lock-syntactic-face-function)
   (setq-local comint-process-echoes (eql ess-eval-visibly t))
   (setq-local comint-prompt-regexp inferior-S-prompt)
   (setq-local syntax-propertize-function ess-r--syntax-propertize-function)

test/ess-test-r-mode.el

@@ -0,0 +1,26 @@
+;;; ess-test-r-mode.el --- ESS tests for R mode  -*- lexical-binding: t; -*-
+;;
+;; This file is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+;;
+;; This file is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+;;
+;; A copy of the GNU General Public License is available at
+;; https://www.r-project.org/Licenses/
+;;
+;;; Commentary:
+;;
+
+(etest-deftest-r test-ess-inferior-r-backticked ()
+  "Backticked symbols are not fontified as strings."
+  :case "¶`f¶oo¶`"
+  :eval (progn
+          (setq-local font-lock-syntactic-face-function
+                      'inferior-ess-r-font-lock-syntactic-face-function)
+          (font-lock-ensure)
+          (should (not (face-at-point)))))

test/run-tests

@@ -32,11 +32,12 @@
 (when (member "--org" argv)
   (load (expand-file-name "ess-test-org.el" ess-test-path) nil t))
 (when (member "--r-core" argv)
-  (load (expand-file-name "ess-test-rd.el" ess-test-path) nil t)
-  (load (expand-file-name "ess-test-r.el" ess-test-path) nil t)
-  (load (expand-file-name "ess-test-r-package.el" ess-test-path) nil t)
   (load (expand-file-name "ess-test-r-eval.el" ess-test-path) nil t)
+  (load (expand-file-name "ess-test-r-mode.el" ess-test-path) nil t)
+  (load (expand-file-name "ess-test-r-package.el" ess-test-path) nil t)
   (load (expand-file-name "ess-test-r-syntax.el" ess-test-path) nil t))
+  (load (expand-file-name "ess-test-r.el" ess-test-path) nil t)
+  (load (expand-file-name "ess-test-rd.el" ess-test-path) nil t)
 (when (member "--r-indent" argv)
   (load (expand-file-name "ess-test-indentation.el" ess-test-path) nil t))
 (when (member "--r-pkg" argv)