Commit b2790db0 authored by Noam Postavsky's avatar Noam Postavsky

Improve errors & warnings due to fancy quoted vars (Bug#32939)

Add some hints to the message for byte compiler free & unused variable
warnings, and 'void-variable' errors where the variable has confusable
quote characters in it.
* lisp/help.el (uni-confusables), uni-confusables-regexp): New
constants.
(help-command-error-confusable-suggestions): New function, added to
`command-error-function'.
(help-uni-confusable-suggestions): New function.
* lisp/emacs-lisp/bytecomp.el (byte-compile-variable-ref):
* lisp/emacs-lisp/cconv.el (cconv--analyze-use): Use it.

* lisp/emacs-lisp/lisp-mode.el
(lisp--match-confusable-symbol-character): New function.
(lisp-fdefs): Use it to fontify confusable characters with
font-lock-warning-face when they occur in symbol names.
* doc/lispref/modes.texi (Faces for Font Lock):
* doc/lispref/objects.texi (Basic Char Syntax): Recommend backslash
escaping of confusable characters, and mention new fontification.
* etc/NEWS: Announce the new fontification behavior.
* test/lisp/emacs-lisp/lisp-mode-tests.el (lisp-fontify-confusables):
New test.
parent 85f586f3
Pipeline #4192 failed with stage
in 56 minutes and 28 seconds
......@@ -3287,7 +3287,8 @@ assigned using the ordering as a guide.
@table @code
@item font-lock-warning-face
@vindex font-lock-warning-face
for a construct that is peculiar, or that greatly changes the meaning of
for a construct that is peculiar (e.g., an unescaped confusable quote
in an Emacs Lisp symbol like @samp{‘foo}), or that greatly changes the meaning of
other text, like @samp{;;;###autoload} in Emacs Lisp and @samp{#error}
in C.
......
......@@ -424,7 +424,11 @@ without a special escape meaning; thus, @samp{?\+} is equivalent to
characters. However, you must add a backslash before any of the
characters @samp{()[]\;"}, and you should add a backslash before any
of the characters @samp{|'`#.,} to avoid confusing the Emacs commands
for editing Lisp code. You can also add a backslash before whitespace
for editing Lisp code. You should also add a backslash before Unicode
characters which resemble the previously mentioned @acronym{ASCII}
ones, to avoid confusing people reading your code. Emacs will
highlight some non-escaped commonly confused characters such as
@samp{‘} to encourage this. You can also add a backslash before whitespace
characters such as space, tab, newline and formfeed. However, it is
cleaner to use one of the easily readable escape sequences, such as
@samp{\t} or @samp{\s}, instead of an actual whitespace character such
......
......@@ -2972,6 +2972,11 @@ and if the new behavior breaks your code please email
<32252@debbugs.gnu.org>. Because '%o' and '%x' can now format signed
integers, they now support the '+' and space flags.
+++
** In Emacs Lisp mode, symbols with confusable quotes are highlighted.
For example, the first character in '‘foo' would be highlighted in
'font-lock-warning-face'.
+++
** Omitting variables after '&optional' and '&rest' is now allowed.
For example '(defun foo (&optional))' is no longer an error. This is
......
......@@ -3428,7 +3428,10 @@ for symbols generated by the byte compiler itself."
(boundp var)
(memq var byte-compile-bound-variables)
(memq var byte-compile-free-references))
(byte-compile-warn "reference to free variable `%S'" var)
(let* ((varname (prin1-to-string var))
(suggestions (help-uni-confusable-suggestions varname)))
(byte-compile-warn "reference to free variable `%s'%s" varname
(if suggestions (concat "\n " suggestions) "")))
(push var byte-compile-free-references))
(byte-compile-dynamic-variable-op 'byte-varref var))))
......@@ -3444,7 +3447,10 @@ for symbols generated by the byte compiler itself."
(boundp var)
(memq var byte-compile-bound-variables)
(memq var byte-compile-free-assignments))
(byte-compile-warn "assignment to free variable `%s'" var)
(let* ((varname (prin1-to-string var))
(suggestions (help-uni-confusable-suggestions varname)))
(byte-compile-warn "assignment to free variable `%s'%s" varname
(if suggestions (concat "\n " suggestions) "")))
(push var byte-compile-free-assignments))
(byte-compile-dynamic-variable-op 'byte-varset var))))
......
......@@ -591,8 +591,10 @@ FORM is the parent form that binds this var."
(eq ?_ (aref (symbol-name var) 0))
;; As a special exception, ignore "ignore".
(eq var 'ignored))
(byte-compile-warn "Unused lexical %s `%S'"
varkind var)))
(let ((suggestions (help-uni-confusable-suggestions (symbol-name var))))
(byte-compile-warn "Unused lexical %s `%S'%s"
varkind var
(if suggestions (concat "\n " suggestions) "")))))
;; If it's unused, there's no point converting it into a cons-cell, even if
;; it's captured and mutated.
(`(,binder ,_ t t ,_)
......
......@@ -280,6 +280,19 @@ This will generate compile-time constants from BINDINGS."
`(face ,font-lock-warning-face
help-echo "This \\ has no effect"))))
(defun lisp--match-confusable-symbol-character (limit)
;; Match a confusable character within a Lisp symbol.
(catch 'matched
(while t
(if (re-search-forward uni-confusables-regexp limit t)
;; Skip confusables which are backslash escaped, or inside
;; strings or comments.
(save-match-data
(unless (or (eq (char-before (match-beginning 0)) ?\\)
(nth 8 (syntax-ppss)))
(throw 'matched t)))
(throw 'matched nil)))))
(let-when-compile
((lisp-fdefs '("defmacro" "defun"))
(lisp-vdefs '("defvar"))
......@@ -463,7 +476,10 @@ This will generate compile-time constants from BINDINGS."
(3 'font-lock-regexp-grouping-construct prepend))
(lisp--match-hidden-arg
(0 '(face font-lock-warning-face
help-echo "Hidden behind deeper element; move to another line?")))
help-echo "Hidden behind deeper element; move to another line?")))
(lisp--match-confusable-symbol-character
0 '(face font-lock-warning-face
help-echo "Confusable character"))
))
"Gaudy level highlighting for Emacs Lisp mode.")
......
......@@ -1507,6 +1507,55 @@ the same names as used in the original source code, when possible."
(let ((print-escape-newlines t))
(help--docstring-quote (format "%S" (help--make-usage fn arglist)))))
;; Just some quote-like characters for now. TODO: generate this stuff
;; from official Unicode data.
(defconst uni-confusables
'((#x2018 . "'") ;; LEFT SINGLE QUOTATION MARK
(#x2019 . "'") ;; RIGHT SINGLE QUOTATION MARK
(#x201B . "'") ;; SINGLE HIGH-REVERSED-9 QUOTATION MARK
(#x201C . "\"") ;; LEFT DOUBLE QUOTATION MARK
(#x201D . "\"") ;; RIGHT DOUBLE QUOTATION MARK
(#x201F . "\"") ;; DOUBLE HIGH-REVERSED-9 QUOTATION MARK
(#x301E . "\"") ;; DOUBLE PRIME QUOTATION MARK
(#xFF02 . "'") ;; FULLWIDTH QUOTATION MARK
(#xFF07 . "'") ;; FULLWIDTH APOSTROPHE
))
(defconst uni-confusables-regexp
(concat "[" (mapcar #'car uni-confusables) "]"))
(defun help-uni-confusable-suggestions (string)
"Return a message describing confusables in STRING."
(let ((i 0)
(confusables nil))
(while (setq i (string-match uni-confusables-regexp string i))
(let ((replacement (alist-get (aref string i) uni-confusables)))
(push (aref string i) confusables)
(setq string (replace-match replacement t t string))
(setq i (+ i (length replacement)))))
(when confusables
(format-message
(if (> (length confusables) 1)
"Found confusable characters: %s; perhaps you meant: `%s'?"
"Found confusable character: %s, perhaps you meant: `%s'?")
(mapconcat (lambda (c) (format-message "`%c'" c))
confusables ", ")
string))))
(defun help-command-error-confusable-suggestions (data _context _signal)
(pcase data
(`(void-variable ,var)
(let ((suggestions (help-uni-confusable-suggestions
(symbol-name var))))
(when suggestions
(princ (concat "\n " suggestions) t))))
(_ nil)))
(add-function :after command-error-function
#'help-command-error-confusable-suggestions)
(provide 'help)
......
......@@ -20,6 +20,10 @@
(require 'ert)
(require 'cl-lib)
(require 'lisp-mode)
(require 'faceup)
;;; Indentation
(defconst lisp-mode-tests--correctly-indented-sexp "\
\(a
......@@ -290,5 +294,27 @@ Expected initialization file: `%s'\"
(insert "\"\n")
(lisp-indent-region (point-min) (point-max))))
;;; Fontification
(ert-deftest lisp-fontify-confusables ()
"Unescaped 'smart quotes' should be fontified in `font-lock-warning-face'."
(with-temp-buffer
(dolist (ch
'(#x2018 ;; LEFT SINGLE QUOTATION MARK
#x2019 ;; RIGHT SINGLE QUOTATION MARK
#x201B ;; SINGLE HIGH-REVERSED-9 QUOTATION MARK
#x201C ;; LEFT DOUBLE QUOTATION MARK
#x201D ;; RIGHT DOUBLE QUOTATION MARK
#x201F ;; DOUBLE HIGH-REVERSED-9 QUOTATION MARK
#x301E ;; DOUBLE PRIME QUOTATION MARK
#xFF02 ;; FULLWIDTH QUOTATION MARK
#xFF07 ;; FULLWIDTH APOSTROPHE
))
(insert (format "«w:%c»foo \\%cfoo\n" ch ch)))
(let ((faceup (buffer-string)))
(faceup-clean-buffer)
(should (faceup-test-font-lock-buffer 'emacs-lisp-mode faceup)))))
(provide 'lisp-mode-tests)
;;; lisp-mode-tests.el ends here
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