;;; elint.el --- Lint Emacs Lisp -*- lexical-binding: t -*-

;; Copyright (C) 1997-2025 Free Software Foundation, Inc.

;; Author: Peter Liljenberg <petli@lysator.liu.se>
;; Maintainer: emacs-devel@gnu.org
;; Created: May 1997
;; Keywords: lisp

;; This file is part of GNU Emacs.

;; GNU Emacs 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 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs 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.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; This is a linter for Emacs Lisp.  Currently, it mainly catches
;; misspellings and undefined variables, although it can also catch
;; function calls with the wrong number of arguments.

;; To use it, call `elint-current-buffer' or `elint-defun' to lint a buffer
;; or defun.  The first call runs `elint-initialize' to set up some
;; argument data, which may take a while.

;; The linter will try to "include" any require'd libraries to find
;; the variables defined in those.  There is a fair amount of voodoo
;; involved in this, but it seems to work in normal situations.

;;; To do:

;; * Adding type checking.  (Stop that sniggering!)
;; * Make eval-when-compile be sensitive to the difference between
;;   functions and macros.
;; * Requires within function bodies.
;; * Handle defstruct.
;; * Prevent recursive requires.

;;; Code:

(defgroup elint nil
  "Linting for Emacs Lisp."
  :prefix "elint-"
  :group 'maint)

(defcustom elint-log-buffer "*Elint*"
  "The buffer in which to log lint messages."
  :type 'string
  :safe 'stringp
  :group 'elint)

(defcustom elint-scan-preloaded t
  "Non-nil means to scan `preloaded-file-list' when initializing.
Otherwise, just scan the DOC file for functions and variables.
This is faster, but less accurate, since it misses undocumented features.
This may result in spurious warnings about unknown functions, etc."
  :type 'boolean
  :safe 'booleanp
  :group 'elint
  :version "23.2")

(defcustom elint-ignored-warnings nil
  "If non-nil, a list of issue types that Elint should ignore.
This is useful if Elint has trouble understanding your code and
you need to suppress lots of spurious warnings.  The valid list elements
are as follows, and suppress messages about the indicated features:
  undefined-functions - calls to unknown functions
  unbound-reference   - reference to unknown variables
  unbound-assignment  - assignment to unknown variables
  macro-expansions    - failure to expand macros
  empty-let           - let-bindings with empty variable lists"
  :type '(choice (const :tag "Don't suppress any warnings" nil)
		 (repeat :tag "List of issues to ignore"
                         (choice (const :tag "Calls to unknown functions"
                                        undefined-functions)
                                 (const :tag "Reference to unknown variables"
                                        unbound-reference)
                                 (const :tag "Assignment to unknown variables"
                                        unbound-assignment)
                                 (const :tag "Failure to expand macros"
                                        macro-expansion)
                                 (const :tag "Let-binding with empty varlist"
                                        empty-let))))
  :safe (lambda (value) (or (null value)
			    (and (listp value)
				 (equal value
					(mapcar
					 (lambda (e)
					   (if (memq e
						     '(undefined-functions
						       unbound-reference
						       unbound-assignment
						       macro-expansion
						       empty-let))
					       e))
					 value)))))
  :version "23.2"
  :group 'elint)

(defcustom elint-directory-skip-re "\\(ldefs-boot\\|loaddefs\\)\\.el\\'"
  "If non-nil, a regexp matching files to skip when linting a directory."
  :type '(choice (const :tag "Lint all files" nil)
		 (regexp :tag "Regexp to skip"))
  :safe 'string-or-null-p
  :group 'elint
  :version "23.2")

;;;
;;; Data
;;;

(defconst elint-standard-variables
  ;; Most of these are defined in C with no documentation.
  ;; FIXME I don't see why they shouldn't just get doc-strings.
  '(vc-mode local-write-file-hooks activate-menubar-hook buffer-name-history
	    coding-system-history extended-command-history
	    yes-or-no-p-history)
  "Standard variables, excluding `elint-builtin-variables'.
These are variables that we cannot detect automatically for some reason.")

(defvar elint-builtin-variables nil
  "List of built-in variables.  Set by `elint-initialize'.
This is actually all those documented in the DOC file, which includes
built-in variables and those from dumped Lisp files.")

(defvar elint-autoloaded-variables nil
  "List of `loaddefs.el' variables.  Set by `elint-initialize'.")

(defvar elint-preloaded-env nil
  "Environment defined by the preloaded (dumped) Lisp files.
Set by `elint-initialize', if `elint-scan-preloaded' is non-nil.")

(defconst elint-unknown-builtin-args
  ;; encode-time allows extra arguments for use with decode-time.
  ;; For some reason, some people seem to like to use them in other cases.
  '((encode-time time &rest obsolescent-arguments))
  "Those built-ins for which we can't find arguments, if any.")

(defvar elint-extra-errors '(file-locked file-supersession ftp-error)
  "Errors without `error-message' or `error-conditions' properties.")

(defconst elint-preloaded-skip-re
  (regexp-opt '("loaddefs.el" "loadup.el" "cus-start" "language/"
		"eucjp-ms" "mule-conf" "/characters" "/charprop"
		"cp51932"))
  "Regexp matching elements of `preloaded-file-list' to ignore.
We ignore them because they contain no definitions of use to Elint.")

(defvar elint-running)
(defvar elint-current-pos)	 ; dynamically bound in elint-top-form

;;;
;;; ADT: top-form
;;;

(defsubst elint-make-top-form (form pos)
  "Create a top form.
FORM is the form, and POS is the point where it starts in the buffer."
  (cons form pos))

(defsubst elint-top-form-form (top-form)
  "Extract the form from a TOP-FORM."
  (car top-form))

(defsubst elint-top-form-pos (top-form)
  "Extract the position from a TOP-FORM."
  (cdr top-form))

;;;
;;; ADT: env
;;;

(defsubst elint-make-env ()
  "Create an empty environment."
  (list (list nil) nil nil))

(defsubst elint-env-add-env (env newenv)
  "Augment ENV with NEWENV.
None of them is modified, and the new env is returned."
  (list (append (car env) (car newenv))
	(append (cadr env) (cadr newenv))
	(append (car (cdr (cdr env))) (car (cdr (cdr newenv))))))

(defsubst elint-env-add-var (env var)
  "Augment ENV with the variable VAR.
The new environment is returned, the old is unmodified."
  (cons (cons (list var) (car env)) (cdr env)))

(defsubst elint-env-add-global-var (env var)
  "Augment ENV with the variable VAR.
ENV is modified so VAR is seen everywhere.
ENV is returned."
  (nconc (car env) (list (list var)))
  env)

(defsubst elint-env-find-var (env var)
  "Non-nil if ENV contains the variable VAR.
Actually, a list with VAR as a single element is returned."
  (assq var (car env)))

(defsubst elint-env-add-func (env func args)
  "Augment ENV with the function FUNC, which has the arguments ARGS.
The new environment is returned, the old is unmodified."
  (list (car env)
	(cons (list func args) (cadr env))
	(car (cdr (cdr env)))))

(defsubst elint-env-find-func (env func)
  "Non-nil if ENV contains the function FUNC.
Actually, a list of (FUNC ARGS) is returned."
  (assq func (cadr env)))

(defsubst elint-env-add-macro (env macro def)
  "Augment ENV with the macro named MACRO.
DEF is the macro definition (a lambda expression or similar).
The new environment is returned, the old is unmodified."
  (list (car env)
	(cadr env)
	(cons (cons macro def) (car (cdr (cdr env))))))

(defsubst elint-env-macro-env (env)
  "Return the macro environment of ENV.
This environment can be passed to `macroexpand'."
  (car (cdr (cdr env))))

(defsubst elint-env-macrop (env macro)
  "Non-nil if ENV contains MACRO."
  (assq macro (elint-env-macro-env env)))

;;;
;;; User interface
;;;

;;;###autoload
(defun elint-file (file)
  "Lint the file FILE."
  (interactive "fElint file: ")
  (setq file (expand-file-name file))
  (or elint-builtin-variables
      (elint-initialize))
  (let ((dir (file-name-directory file)))
    (let ((default-directory dir))
      (elint-display-log))
    (elint-set-mode-line t)
    (with-current-buffer elint-log-buffer
      (unless (string-equal default-directory dir)
	(elint-log-message (format-message "\nLeaving directory `%s'"
                                           default-directory) t)
	(elint-log-message (format-message "Entering directory `%s'" dir) t)
	(setq default-directory dir))))
  (let ((str (format "Linting file %s" file)))
    (message "%s..." str)
    (or noninteractive
	(elint-log-message (format "\n%s at %s" str (current-time-string)) t))
    ;; elint-current-buffer clears log.
    (with-temp-buffer
      (insert-file-contents file)
      (let ((buffer-file-name file)
	    (max-lisp-eval-depth (max 1000 max-lisp-eval-depth)))
        (hack-local-variables)
	(with-syntax-table emacs-lisp-mode-syntax-table
	  (mapc 'elint-top-form (elint-update-env)))))
    (elint-set-mode-line)
    (message "%s...done" str)))

;; cf byte-recompile-directory.
;;;###autoload
(defun elint-directory (directory)
  "Lint all the .el files in DIRECTORY.
A complicated directory may require a lot of memory."
  (interactive "DElint directory: ")
  (let ((elint-running t))
    (dolist (file (directory-files directory t))
      ;; Bytecomp has emacs-lisp-file-regexp.
      (when (and (string-match "\\.el\\'" file)
		 (file-readable-p file)
		 (not (auto-save-file-name-p file)))
	(if (string-match elint-directory-skip-re file)
	    (message "Skipping file %s" file)
	  (elint-file file)))))
  (elint-set-mode-line))

;;;###autoload
(defun elint-current-buffer ()
  "Lint the current buffer.
If necessary, this first calls `elint-initialize'."
  (interactive)
  (or elint-builtin-variables
      (elint-initialize))
  (elint-clear-log (format "Linting %s" (or (buffer-file-name)
					    (buffer-name))))
  (elint-display-log)
  (elint-set-mode-line t)
  (mapc 'elint-top-form (elint-update-env))
  ;; Tell the user we're finished.  This is terribly kludgy: we set
    ;; elint-top-form-logged so elint-log-message doesn't print the
    ;; ** top form ** header...
  (elint-set-mode-line)
  (elint-log-message "\nLinting finished.\n" t))


;;;###autoload
(defun elint-defun ()
  "Lint the function at point.
If necessary, this first calls `elint-initialize'."
  (interactive)
  (or elint-builtin-variables
      (elint-initialize))
  (save-excursion
    (or (beginning-of-defun) (error "Lint what?"))
    (let ((pos (point))
	  (def (read (current-buffer))))
      (elint-display-log)
      (elint-update-env)
      (elint-top-form (elint-make-top-form def pos)))))

;;;
;;; Top form functions
;;;

(defvar elint-buffer-env nil
  "The environment of an elisp buffer.
Will be local in linted buffers.")

(defvar elint-buffer-forms nil
  "The top forms in a buffer.
Will be local in linted buffers.")

(defvar elint-last-env-time nil
  "The last time the buffers env was updated.
Is measured in buffer-modified-ticks and is local in linted buffers.")

;; This is a minor optimization.  It is local to every buffer, and so
;; does not prevent recursive requires.  It does not list the requires
;; of requires.
(defvar elint-features nil
  "List of all libraries this buffer has required, or that have been provided.")

(defun elint-update-env ()
  "Update the elint environment in the current buffer.
Don't do anything if the buffer hasn't been changed since this
function was called the last time.
Returns the forms."
  (if (and (local-variable-p 'elint-buffer-env (current-buffer))
	   (local-variable-p 'elint-buffer-forms (current-buffer))
	   (local-variable-p 'elint-last-env-time (current-buffer))
	   (= (buffer-modified-tick) elint-last-env-time))
      ;; Env is up to date
      elint-buffer-forms
    ;; Remake env
    (setq-local elint-buffer-forms (elint-get-top-forms))
    (setq-local elint-features nil)
    (setq-local elint-buffer-env (elint-init-env elint-buffer-forms))
    (if elint-preloaded-env
        ;; FIXME: This doesn't do anything!  Should we setq the result to
        ;; elint-buffer-env?
	(elint-env-add-env elint-preloaded-env elint-buffer-env))
    (setq-local elint-last-env-time (buffer-modified-tick))
    elint-buffer-forms))

(defun elint-get-top-forms ()
  "Collect all the top forms in the current buffer."
  (save-excursion
    (let (tops)
      (goto-char (point-min))
      (while (elint-find-next-top-form)
	(let ((elint-current-pos (point)))
	  ;; non-list check could be here too. errors may be out of seq.
	  ;; quoted check cannot be elsewhere, since quotes skipped.
	  (if (= (preceding-char) ?\')
	      ;; Eg cust-print.el uses ' as a comment syntax.
	      (elint-warning "Skipping quoted form `%c%.20s...'" ?\'
			   (read (current-buffer)))
	    (condition-case nil
		(setq tops (cons
			    (elint-make-top-form (read (current-buffer))
						 elint-current-pos)
			    tops))
	      (end-of-file
	       (goto-char elint-current-pos)
	       (error "Missing `)' in top form: %s"
		      (buffer-substring elint-current-pos
					(line-end-position))))))))
      (nreverse tops))))

(defun elint-find-next-top-form ()
  "Find the next top form from point.
Return nil if there are no more forms, t otherwise."
  (parse-partial-sexp (point) (point-max) nil t)
  (not (eobp)))

(defvar elint-env)			; from elint-init-env

(defun elint-init-form (form)
  "Process FORM, adding to ELINT-ENV if recognized."
  (cond
   ;; Eg nnmaildir seems to use [] as a form of comment syntax.
   ((not (listp form))
    (elint-warning "Skipping non-list form `%s'" form))
   ;; Add defined variable
   ((memq (car form) '(defvar defconst defcustom))
    (setq elint-env (elint-env-add-var elint-env (cadr form))))
   ;; Add function
   ((memq (car form) '(defun defsubst))
    (setq elint-env (elint-env-add-func elint-env (cadr form) (nth 2 form))))
   ;; FIXME needs a handler to say second arg is not a variable when we come
   ;; to scan the form.
   ((eq (car form) 'define-derived-mode)
    (setq elint-env (elint-env-add-func elint-env (cadr form) ())
	  elint-env (elint-env-add-var elint-env (cadr form))
	  elint-env (elint-env-add-var elint-env
				       (intern (format "%s-map" (cadr form))))))
   ((eq (car form) 'define-minor-mode)
    (setq elint-env (elint-env-add-func elint-env (cadr form) '(&optional arg))
	  ;; FIXME mode map?
	  elint-env (elint-env-add-var elint-env (cadr form))))
   ((and (eq (car form) 'easy-menu-define)
	 (cadr form))
    (setq elint-env (elint-env-add-func elint-env (cadr form) '(event))
	  elint-env (elint-env-add-var elint-env (cadr form))))
   ;; FIXME it would be nice to check the autoloads are correct.
   ((eq (car form) 'autoload)
    (setq elint-env (elint-env-add-func elint-env (cadr (cadr form)) 'unknown)))
   ((eq (car form) 'declare-function)
    (setq elint-env (elint-env-add-func
	       elint-env (cadr form)
	       (if (or (< (length form) 4)
		       (eq (nth 3 form) t)
		       (unless (stringp (nth 2 form))
			 (elint-error "Malformed declaration for `%s'"
				      (cadr form))
			 t))
		   'unknown
		 (nth 3 form)))))
   ((and (eq (car form) 'defalias) (listp (nth 2 form)))
    ;; If the alias points to something already in the environment,
    ;; add the alias to the environment with the same arguments.
    ;; FIXME symbol-function, eg backquote.el?
    (let ((def (elint-env-find-func elint-env (cadr (nth 2 form)))))
      (setq elint-env (elint-env-add-func elint-env (cadr (cadr form))
				    (if def (cadr def) 'unknown)))))
   ;; Add macro, both as a macro and as a function
   ((eq (car form) 'defmacro)
    (setq elint-env (elint-env-add-macro elint-env (cadr form)
				   (cons 'lambda (cddr form)))
	  elint-env (elint-env-add-func elint-env (cadr form) (nth 2 form))))
   ((and (eq (car form) 'put)
	 (= 4 (length form))
	 (eq (car-safe (cadr form)) 'quote)
	 (equal (nth 2 form) '(quote error-conditions)))
    (setq-local elint-extra-errors
                (cons (cadr (cadr form)) elint-extra-errors)))
   ((eq (car form) 'provide)
    (add-to-list 'elint-features (eval (cadr form))))
   ;; Import variable definitions
   ((memq (car form) '(require cc-require cc-require-when-compile))
    (let ((name (eval (cadr form)))
	  (file (eval (nth 2 form))))
      (unless (memq name elint-features)
	(add-to-list 'elint-features name)
	(setq elint-env (elint-add-required-env elint-env name file))))))
  elint-env)

(defun elint-init-env (forms)
  "Initialize the environment from FORMS."
  (let ((elint-env (elint-make-env))
	form)
    (while forms
      (setq form (elint-top-form-form (car forms))
	    forms (cdr forms))
      ;; FIXME eval-when-compile should be treated differently (macros).
      ;; Could bind something that makes elint-init-form only check
      ;; defmacros.
      (if (memq (car-safe form)
		'(eval-and-compile eval-when-compile progn prog1 prog2
				   with-no-warnings))
	  (mapc 'elint-init-form (cdr form))
	(elint-init-form form)))
    elint-env))

(defun elint-add-required-env (env name file)
  "Augment ENV with the variables defined by feature NAME in FILE."
  (condition-case err
      (let* ((libname (if (stringp file)
			  file
			(symbol-name name)))

	     ;; First try to find .el files, then the raw name
	     (lib1 (locate-library (concat libname ".el") t))
	     (lib (or lib1 (locate-library libname t))))
	;; Clear the messages :-/
	;; (Messes up the "Initializing elint..." message.)
;;;	(message nil)
	(if lib
	    (with-current-buffer (find-file-noselect lib)
	      ;; FIXME this doesn't use a temp buffer, because it
	      ;; stores the result in buffer-local variables so that
	      ;; it can be reused.
	      (elint-update-env)
	      (setq env (elint-env-add-env env elint-buffer-env)))
	      ;;; (with-temp-buffer
	      ;;; 	(insert-file-contents lib)
	      ;;; 	(with-syntax-table emacs-lisp-mode-syntax-table
	      ;;; 	  (elint-update-env))
	      ;;; 	(setq env (elint-env-add-env env elint-buffer-env))))
	      ;;(message "%s" (format "Elint processed (require '%s)" name))
	  (error "%s.el not found in load-path" libname)))
    (error
     (message "Can't get variables from require'd library %s: %s"
              name (error-message-string err))))
  env)

(defvar elint-top-form nil
  "The currently linted top form, or nil.")

(defvar elint-top-form-logged nil
  "Non-nil if the currently linted top form has been mentioned in the log buffer.")

(defun elint-top-form (form)
  "Lint a top FORM."
  (let ((elint-top-form form)
	(elint-top-form-logged nil)
	(elint-current-pos (elint-top-form-pos form)))
    (elint-form (elint-top-form-form form) elint-buffer-env)))

;;;
;;; General form linting functions
;;;

(defconst elint-special-forms
  '((let . elint-check-let-form)
    (let* . elint-check-let-form)
    (setq . elint-check-setq-form)
    (quote . elint-check-quote-form)
    (function . elint-check-quote-form)
    (cond . elint-check-cond-form)
    (lambda . elint-check-defun-form)
    (function . elint-check-function-form)
    (setq-default . elint-check-setq-form)
    (defalias . elint-check-defalias-form)
    (defun . elint-check-defun-form)
    (defsubst . elint-check-defun-form)
    (defmacro . elint-check-defun-form)
    (defvar . elint-check-defvar-form)
    (defconst . elint-check-defvar-form)
    (defcustom . elint-check-defcustom-form)
    (macro . elint-check-macro-form)
    (condition-case . elint-check-condition-case-form)
    (condition-case-unless-debug . elint-check-condition-case-form)
    (if . elint-check-conditional-form)
    (when . elint-check-conditional-form)
    (unless . elint-check-conditional-form)
    (and . elint-check-conditional-form)
    (or . elint-check-conditional-form)
    (require . elint-require-form))
  "Functions to call when some special form should be linted.")

(defun elint-form (form env &optional nohandler)
  "Lint FORM in the environment ENV.
Optional argument NOHANDLER non-nil means ignore `elint-special-forms'.
Returns the environment created by the form."
  (cond
   ((consp form)
    (let ((func (cdr (assq (car form) elint-special-forms))))
      (if (and func (not nohandler))
	  ;; Special form
	  (funcall func form env)

	(let* ((func (car form))
	       (args (elint-get-args func env))
	       (argsok t))
	  (cond
	   ((eq args 'undefined)
	    (setq argsok nil)
	    (or (memq 'undefined-functions elint-ignored-warnings)
		(elint-error "Call to undefined function: %s" func)))

	   ((eq args 'unknown) nil)

	   (t (setq argsok (elint-match-args form args))))

	  ;; Is this a macro?
	  (if (elint-env-macrop env func)
	      ;; Macro defined in buffer, expand it
	      (if argsok
		  ;; FIXME error if macro uses macro, eg bytecomp.el.
		  (condition-case nil
		      (elint-form
		       (macroexpand form (elint-env-macro-env env)) env)
		    (error
		     (or (memq 'macro-expansion elint-ignored-warnings)
			 (elint-error "Elint failed to expand macro: %s" func))
		     env))
		env)

	    (let ((fcode (if (symbolp func)
			     (if (fboundp func)
				 (indirect-function func))
			   func)))
	      (if (and (listp fcode) (eq (car fcode) 'macro))
		  ;; Macro defined outside buffer
		  (if argsok
		      (elint-form (macroexpand form) env)
		    env)
		;; Function, lint its parameters
		(elint-forms (cdr form) env))))))))
   ((symbolp form)
    ;; :foo variables are quoted
    (and (/= (aref (symbol-name form) 0) ?:)
	 (not (memq 'unbound-reference elint-ignored-warnings))
	 (elint-unbound-variable form env)
	 (elint-warning "Reference to unbound symbol: %s" form))
    env)

   (t env)))

(defun elint-forms (forms env)
  "Lint the FORMS, accumulating an environment, starting with ENV."
  ;; grumblegrumbletailrecursiongrumblegrumble
  (if (listp forms)
      (dolist (f forms env)
	(setq env (elint-form f env)))
    ;; Loop macro?
    (elint-error "Elint failed to parse form: %s" forms)
    env))

(defvar elint-bound-variable nil
  "Name of a temporarily bound symbol.")

(defun elint-unbound-variable (var env)
  "Return t if VAR is unbound in ENV."
  ;; #1063 suggests adding (symbol-file var) here, but I don't think
  ;; this is right, because it depends on what files you happen to have
  ;; loaded at the time, which might not be the same when the code runs.
  ;; It also suggests adding:
  ;; (numberp (get var 'variable-documentation))
  ;; (numberp (cdr-safe (get var 'variable-documentation)))
  ;; but this is not needed now elint-scan-doc-file exists.
  (not (or (memq var '(nil t))
	   (eq var elint-bound-variable)
	   (elint-env-find-var env var)
	   (memq var elint-builtin-variables)
	   (memq var elint-autoloaded-variables)
	   (memq var elint-standard-variables))))

;;;
;;; Function argument checking
;;;

(defun elint-match-args (arglist argpattern)
  "Match ARGLIST against ARGPATTERN."
  (let ((state 'all)
	(al (cdr arglist))
	(ap argpattern)
	(ok t))
    (while
	(cond
	 ((and (null al) (null ap)) nil)
	 ((eq (car ap) '&optional)
	  (setq state 'optional)
	  (setq ap (cdr ap))
	  t)
	 ((eq (car ap) '&rest)
	  nil)
	 ((or (and (eq state 'all) (or (null al) (null ap)))
	      (and (eq state 'optional) (and al (null ap))))
	  (elint-error "Wrong number of args: %s, %s" arglist argpattern)
	  (setq ok nil)
	  nil)
	 ((and (eq state 'optional) (null al))
	  nil)
	 (t (setq al (cdr al)
		  ap (cdr ap))
	    t)))
    ok))

(defvar elint-bound-function nil
  "Name of a temporarily bound function symbol.")

(defun elint-get-args (func env)
  "Find the args of FUNC in ENV.
Returns `unknown' if we couldn't find arguments."
  (let ((f (elint-env-find-func env func)))
    (if f
	(cadr f)
      (if (symbolp func)
	  (if (eq func elint-bound-function)
	      'unknown
	    (if (fboundp func)
		(let ((fcode (indirect-function func)))
		  (if (subrp fcode)
		      ;; FIXME builtins with no args have args = nil.
		      (or (get func 'elint-args) 'unknown)
		    (elint-find-args-in-code fcode)))
	      'undefined))
	(elint-find-args-in-code func)))))

(defun elint-find-args-in-code (code)
  "Extract the arguments from CODE.
CODE can be a lambda expression, a macro, or byte-compiled code."
  (let ((args (help-function-arglist code)))
    (if (listp args) args 'unknown)))

;;;
;;; Functions to check some special forms
;;;

(defun elint-check-cond-form (form env)
  "Lint a cond FORM in ENV."
  (dolist (f (cdr form))
    (if (consp f)
	(let ((test (car f)))
	  (cond ((equal test '(featurep (quote xemacs))))
		((equal test '(not (featurep (quote emacs)))))
		;; FIXME (and (boundp 'foo)
		((and (eq (car-safe test) 'fboundp)
		      (= 2 (length test))
		      (eq (car-safe (cadr test)) 'quote))
		 (let ((elint-bound-function (cadr (cadr test))))
		   (elint-forms f env)))
		((and (eq (car-safe test) 'boundp)
		      (= 2 (length test))
		      (eq (car-safe (cadr test)) 'quote))
		 (let ((elint-bound-variable (cadr (cadr test))))
		   (elint-forms f env)))
		(t (elint-forms f env))))
      (elint-error "cond clause should be a list: %s" f)))
  env)

(defun elint-check-defun-form (form env)
  "Lint a defun/defmacro/lambda FORM in ENV."
  (setq form (if (eq (car form) 'lambda) (cdr form) (cddr form)))
  (mapc (lambda (p)
	  (or (memq p '(&optional &rest))
	      (setq env (elint-env-add-var env p))))
	(car form))
  (elint-forms (cdr form) env))

(defun elint-check-defalias-form (form env)
  "Lint a defalias FORM in ENV."
  (let ((alias (cadr form))
	(target (nth 2 form)))
    (and (eq (car-safe alias) 'quote)
	 (eq (car-safe target) 'quote)
	 (eq (elint-get-args (cadr target) env) 'undefined)
	 (elint-warning "Alias `%s' has unknown target `%s'"
			(cadr alias) (cadr target))))
  (elint-form form env t))

(defun elint-check-let-form (form env)
  "Lint the let/let* FORM in ENV."
  (let ((varlist (cadr form)))
    (if (not varlist)
	(if (> (length form) 2)
	    ;; An empty varlist is not really an error.  Eg some cl macros
	    ;; can expand to such a form.
	    (progn
	      (or (memq 'empty-let elint-ignored-warnings)
		  (elint-warning "Empty varlist in let: %s" form))
	      ;; Lint the body forms
	      (elint-forms (cddr form) env))
	  (elint-error "Malformed let: %s" form)
	  env)
      ;; Check for (let (a (car b)) ...) type of error
      (if (and (= (length varlist) 2)
	       (symbolp (car varlist))
	       (listp (car (cdr varlist)))
	       (fboundp (car (car (cdr varlist)))))
	  (elint-warning "Suspect varlist: %s" form))
      ;; Add variables to environment, and check the init values
      (let ((newenv env))
	(mapc (lambda (s)
		(cond
		 ((symbolp s)
		  (setq newenv (elint-env-add-var newenv s)))
		 ((and (consp s) (<= (length s) 2))
		  (elint-form (cadr s)
			      (if (eq (car form) 'let)
				  env
				newenv))
		  (setq newenv
			(elint-env-add-var newenv (car s))))
		 (t (elint-error
		     "Malformed `let' declaration: %s" s))))
	      varlist)

	;; Lint the body forms
	(elint-forms (cddr form) newenv)))))

(defun elint-check-setq-form (form env)
  "Lint the setq FORM in ENV."
  (or (= (mod (length form) 2) 1)
      ;; (setq foo) is valid and equivalent to (setq foo nil).
      (elint-warning "Missing value in setq: %s" form))
  (let ((newenv env)
	sym val)
    (setq form (cdr form))
    (while form
      (setq sym (car form)
	    val (car (cdr form))
	    form (cdr (cdr form)))
      (if (symbolp sym)
	  (and (not (memq 'unbound-assignment elint-ignored-warnings))
	       (elint-unbound-variable sym newenv)
	       (elint-warning "Setting previously unbound symbol: %s" sym))
	(elint-error "Setting non-symbol in setq: %s" sym))
      (elint-form val newenv)
      (if (symbolp sym)
	  (setq newenv (elint-env-add-var newenv sym))))
    newenv))

(defun elint-check-defvar-form (form env)
  "Lint the defvar/defconst FORM in ENV."
  (if (or (= (length form) 2)
	  (= (length form) 3)
	  ;; Eg the defcalcmodevar macro can expand with a nil doc-string.
	  (and (= (length form) 4) (string-or-null-p (nth 3 form))))
          (elint-env-add-global-var (elint-form (nth 2 form) env)
			     (car (cdr form)))
    (elint-error "Malformed variable declaration: %s" form)
    env))

(defun elint-check-defcustom-form (form env)
  "Lint the defcustom FORM in ENV."
  (if (and (> (length form) 3)
	   ;; even no. of keyword/value args ?
	   (zerop (logand (length form) 1)))
      (elint-env-add-global-var (elint-form (nth 2 form) env)
				(car (cdr form)))
    (elint-error "Malformed variable declaration: %s" form)
    env))

(defun elint-check-function-form (form env)
  "Lint the function FORM in ENV."
  (let ((func (car (cdr-safe form))))
    (cond
     ((symbolp func)
      (or (elint-env-find-func env func)
	  ;; FIXME potentially bogus, since it uses the current
	  ;; environment rather than a clean one.
	  (fboundp func)
	  (elint-warning "Reference to undefined function: %s" form))
      env)
     ((and (consp func) (memq (car func) '(lambda macro)))
      (elint-form func env))
     ((stringp func) env)
     (t (elint-error "Not a function object: %s" form)
	env))))

(defun elint-check-quote-form (_form env)
  "Lint the quote FORM in ENV."
  env)

(defun elint-check-macro-form (form env)
  "Check the macro FORM in ENV."
  (elint-check-function-form (list (car form) (cdr form)) env))

(defun elint-check-condition-case-form (form env)
  "Check the `condition-case' FORM in ENV."
  (let ((resenv env))
    (if (< (length form) 3)
	(elint-error "Malformed condition-case: %s" form)
      (or (symbolp (cadr form))
	  (elint-warning "First parameter should be a symbol: %s" form))
      (setq resenv (elint-form (nth 2 form) env))
      (let ((newenv (elint-env-add-var env (cadr form)))
	    errlist)
	(dolist (err (nthcdr 3 form))
	  (setq errlist (car err))
	  (mapc (lambda (s)
		  (or (get s 'error-conditions)
		      (get s 'error-message)
		      (memq s elint-extra-errors)
		      (elint-warning
		       "Not an error symbol in error handler: %s" s)))
		(cond
		 ((symbolp errlist) (list errlist))
		 ((listp errlist) errlist)
		 (t (elint-error "Bad error list in error handler: %s"
				 errlist)
		    nil)))
	  (elint-forms (cdr err) newenv))))
    resenv))

;; For the featurep parts, an alternative is to have
;; elint-get-top-forms skip the irrelevant branches.
(defun elint-check-conditional-form (form env)
  "Check the when/unless/and/or FORM in ENV.
Does basic handling of `featurep' tests."
  (let ((func (car form))
	(test (cadr form)))
    ;; Misses things like (and t (featurep 'xemacs))
    ;; Check byte-compile-maybe-guarded.
    (cond ((and (memq func '(when and))
		(eq (car-safe test) 'boundp)
		(= 2 (length test))
		(eq (car-safe (cadr test)) 'quote))
	   ;; Cf elint-check-let-form, which modifies the whole ENV.
	   (let ((elint-bound-variable (cadr (cadr test))))
	     (elint-form form env t)))
	  ((and (memq func '(when and))
		(eq (car-safe test) 'fboundp)
		(= 2 (length test))
		(eq (car-safe (cadr test)) 'quote))
	   (let ((elint-bound-function (cadr (cadr test))))
	     (elint-form form env t)))
	  ;; Let's not worry about (if (not (boundp...
	  ((and (eq func 'if)
		(eq (car-safe test) 'boundp)
		(= 2 (length test))
		(eq (car-safe (cadr test)) 'quote))
	   (let ((elint-bound-variable (cadr (cadr test))))
	     (elint-form (nth 2 form) env))
	   (dolist (f (nthcdr 3 form))
	     (elint-form f env)))
	  ((and (eq func 'if)
		(eq (car-safe test) 'fboundp)
		(= 2 (length test))
		(eq (car-safe (cadr test)) 'quote))
	   (let ((elint-bound-function (cadr (cadr test))))
	     (elint-form (nth 2 form) env))
	   (dolist (f (nthcdr 3 form))
	     (elint-form f env)))
	  ((and (memq func '(when and))	; skip all
		(or (null test)
		    (member test '((featurep (quote xemacs))
				   (not (featurep (quote emacs)))))
		    (and (eq (car-safe test) 'and)
			 (equal (car-safe (cdr test))
				'(featurep (quote xemacs)))))))
	  ((and (memq func '(unless or))
		(equal test '(featurep (quote emacs)))))
	  ((and (eq func 'if)
		(or (null test)
		    (member test '((featurep (quote xemacs))
				   (not (featurep (quote emacs)))))
		    (and (eq (car-safe test) 'and)
			 (equal (car-safe (cdr test))
				'(featurep (quote xemacs))))))
	   (dolist (f (nthcdr 3 form))
	     (elint-form f env)))	; lint the else branch
	  ((and (eq func 'if)
		(equal test '(featurep (quote emacs))))
	   (elint-form (nth 2 form) env)) ; lint the if branch
	  ;; Process conditional as normal, without handler.
	  (t
	   (elint-form form env t))))
  env)

(defun elint-require-form (form _env)
  "Load `require'd files."
  (pcase form
    (`(require ',x)
     (require x)))
  nil)

;;;
;;; Message functions
;;;

(defun elint-log (type string args)
  (elint-log-message (format "%s:%d:%s: %s"
			     (let ((f (buffer-file-name)))
			       (if f
				   (file-name-nondirectory f)
				 (buffer-name)))
			     (if (boundp 'elint-current-pos)
				 (save-excursion
				   (goto-char elint-current-pos)
				   (1+ (count-lines (point-min)
						    (line-beginning-position))))
			       0)	; unknown position
			     type
			     (apply #'format-message string args))))

(defun elint-error (string &rest args)
  "Report a linting error.
STRING and ARGS are thrown on `format' to get the message."
  (elint-log "Error" string args))

(defun elint-warning (string &rest args)
  "Report a linting warning.
See `elint-error'."
  (elint-log "Warning" string args))

(defun elint-output (string)
  "Print or insert STRING, depending on value of `noninteractive'."
  (if noninteractive
      (message "%s" string)
    (insert string "\n")))

(defun elint-log-message (errstr &optional top)
  "Insert ERRSTR last in the lint log buffer.
Optional argument TOP non-nil means pretend `elint-top-form-logged' is non-nil."
  (with-current-buffer (elint-get-log-buffer)
    (goto-char (point-max))
    (let ((inhibit-read-only t))
      (or (bolp) (newline))
      ;; Do we have to say where we are?
      (unless (or elint-top-form-logged top)
	(let* ((form (elint-top-form-form elint-top-form))
	       (top (car form)))
	  (elint-output (cond
			 ((memq top '(defun defsubst))
			  (format "\nIn function %s:" (cadr form)))
			 ((eq top 'defmacro)
			  (format "\nIn macro %s:" (cadr form)))
			 ((memq top '(defvar defconst))
			  (format "\nIn variable %s:" (cadr form)))
			 (t "\nIn top level expression:"))))
	(setq elint-top-form-logged t))
      (elint-output errstr))))

(defun elint-clear-log (&optional header)
  "Clear the lint log buffer.
Insert HEADER followed by a blank line if non-nil."
  (let ((dir default-directory))
    (with-current-buffer (elint-get-log-buffer)
      (setq default-directory dir)
      (let ((inhibit-read-only t))
	(erase-buffer)
	(if header (insert header "\n"))))))

(defun elint-display-log ()
  "Display the lint log buffer."
  (let ((pop-up-windows t))
    (display-buffer (elint-get-log-buffer))
    (sit-for 0)))

(defun elint-set-mode-line (&optional on)
  "Set the `mode-line-process' of the Elint log buffer."
  (with-current-buffer (elint-get-log-buffer)
    (and (eq major-mode 'compilation-mode)
	 (setq mode-line-process
	       (list (if (or on (bound-and-true-p elint-running))
			 (propertize ":run" 'face 'compilation-warning)
		       (propertize ":finished" 'face 'compilation-info)))))))

(defun elint-get-log-buffer ()
  "Return a log buffer for elint."
  (or (get-buffer elint-log-buffer)
      (with-current-buffer (get-buffer-create elint-log-buffer)
	(or (eq major-mode 'compilation-mode)
	    (compilation-mode))
	(setq buffer-undo-list t)
	(current-buffer))))

;;;
;;; Initializing code
;;;

(defun elint-put-function-args (func args)
  "Mark function FUNC as having argument list ARGS."
  (and (symbolp func)
       args
       (not (eq args 'unknown))
       (put func 'elint-args args)))

;;;###autoload
(defun elint-initialize (&optional reinit)
  "Initialize elint.
If elint is already initialized, this does nothing, unless
optional prefix argument REINIT is non-nil."
  (interactive "P")
  (if (and elint-builtin-variables (not reinit))
      (message "Elint is already initialized")
    (message "Initializing elint...")
    (setq elint-builtin-variables (elint-scan-doc-file)
	  elint-autoloaded-variables (elint-find-autoloaded-variables))
    (mapc (lambda (x) (elint-put-function-args (car x) (cdr x)))
	  (elint-find-builtin-args))
    (if elint-unknown-builtin-args
	(mapc (lambda (x) (elint-put-function-args (car x) (cdr x)))
	      elint-unknown-builtin-args))
    (when elint-scan-preloaded
      (dolist (lib preloaded-file-list)
	;; Skip files that contain nothing of use to us.
	(unless (string-match elint-preloaded-skip-re lib)
	  (setq elint-preloaded-env
		(elint-add-required-env elint-preloaded-env nil lib)))))
    (message "Initializing elint...done")))


;; This includes all the built-in and dumped things with documentation.
(defun elint-scan-doc-file ()
  "Scan the DOC file for function and variables.
Marks the function with their arguments, and returns a list of variables."
  ;; Cribbed from help-fns.el.
  (let ((docbuf " *DOC*")
	vars sym args)
    (save-excursion
      (if (get-buffer docbuf)
	  (progn
	    (set-buffer docbuf)
	    (goto-char (point-min)))
	(set-buffer (get-buffer-create docbuf))
	(insert-file-contents-literally
	 (expand-file-name internal-doc-file-name doc-directory)))
      (while (re-search-forward "\^_\\([VF]\\)" nil t)
	(when (setq sym (intern-soft (buffer-substring (point)
						       (line-end-position))))
	  (if (string-equal (match-string 1) "V")
	      ;; Excludes platform-specific stuff not relevant to the
	      ;; running platform.
	      (if (boundp sym) (setq vars (cons sym vars)))
	    ;; Function.
	    (when (fboundp sym)
	      (when (re-search-forward "\\(^(fn.*)\\)?\^_" nil t)
		(backward-char 1)
		;; FIXME distinguish no args from not found.
		(and (setq args (match-string 1))
		     (setq args
			   (ignore-errors
			     (read
			      (replace-regexp-in-string "^(fn ?" "(" args))))
		     (elint-put-function-args sym args))))))))
    vars))

(defun elint-find-autoloaded-variables ()
  "Return a list of all autoloaded variables."
  (let (var vars)
    (with-temp-buffer
      (insert-file-contents (locate-library "loaddefs.el"))
      (while (re-search-forward "^(defvar \\([[:alnum:]_-]+\\)" nil t)
	(and (setq var (intern-soft (match-string 1)))
	     (boundp var)
	     (setq vars (cons var vars)))))
    vars))

(defun elint-find-builtins ()
  "Return a list of all built-in functions."
  (let (subrs)
    (mapatoms (lambda (s) (and (subrp (symbol-function s))
                          (push s subrs))))
    subrs))

(defun elint-find-builtin-args (&optional list)
  "Return a list of the built-in functions and their arguments.
If LIST is nil, call `elint-find-builtins' to get a list of all built-in
functions, otherwise use LIST.

Each function is represented by a cons cell:
\(function-symbol . args)
If no documentation could be found args will be `unknown'."
  (mapcar (lambda (f)
	    (let ((doc (documentation f t)))
	      (or (and doc
		       (string-match "\n\n(fn\\(.*)\\)\\'" doc)
		       (ignore-errors
			;; "BODY...)" -> "&rest BODY)".
			(read (replace-regexp-in-string
			       "\\([^ ]+\\)\\.\\.\\.)\\'" "&rest \\1)"
			       (format "(%s %s" f (match-string 1 doc)) t))))
		  (cons f 'unknown))))
	  (or list (elint-find-builtins))))

(provide 'elint)

;;; elint.el ends here
