From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier via Users list for the GNU Emacs text editor Newsgroups: gmane.emacs.help Subject: Re: dynamic variables and advice Date: Thu, 03 Mar 2022 10:03:22 -0500 Message-ID: References: <20220303.121042.104668854711893143.enometh@meer.net> Reply-To: Stefan Monnier Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="6720"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:XCaSYGvFgW7ovRsNwIgdZwQJyAc= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Thu Mar 03 17:02:02 2022 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nPnty-0001bD-FF for geh-help-gnu-emacs@m.gmane-mx.org; Thu, 03 Mar 2022 17:02:02 +0100 Original-Received: from localhost ([::1]:39062 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nPntx-0001We-9M for geh-help-gnu-emacs@m.gmane-mx.org; Thu, 03 Mar 2022 11:02:01 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:42002) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nPmzL-0005uk-VH for help-gnu-emacs@gnu.org; Thu, 03 Mar 2022 10:03:33 -0500 Original-Received: from ciao.gmane.io ([116.202.254.214]:37406) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nPmzK-0001pp-6c for help-gnu-emacs@gnu.org; Thu, 03 Mar 2022 10:03:31 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1nPmzH-0003ah-SD for help-gnu-emacs@gnu.org; Thu, 03 Mar 2022 16:03:27 +0100 X-Injected-Via-Gmane: http://gmane.org/ Received-SPF: pass client-ip=116.202.254.214; envelope-from=geh-help-gnu-emacs@m.gmane-mx.org; helo=ciao.gmane.io X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Thu, 03 Mar 2022 10:59:33 -0500 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "help-gnu-emacs" Xref: news.gmane.io gmane.emacs.help:136339 Archived-At: > I was trying to use the add-function facility to make dired and friends > prompt only for directories. the naive approach with a lot of printf > debugging - > > #+begin_src elisp > (defvar read-file-name--directories-p nil > "dynamic variable which should be let-bound in an :around advice > and should be used in a :filter-args advice.") > > (defun read-file-name--maybe-filter-directories (args) > "filter-args advice for read-file-name." > (cl-destructuring-bind (prompt &optional dir default-filename > mustmatch initial predicate) > args > (let ((ret (list prompt dir default-filename mustmatch initial > (or predicate > (and read-file-name--maybe-filter-directories-p > #'file-directory-p))))) > (message "rfn-mfd: rfnmfd=%s this-command=%s ret=%s" > read-file-name--maybe-filter-directories-p this-command ret) > ret))) > > (advice-add 'read-file-name > :filter-args 'read-file-name--maybe-filter-directories) > > (defun rfnmfd-yes (oldfun &rest args) > "an around advice function which sets rfn-mfd-p to t" > (let ((read-file-name--mabe-filter-directories-p t)) > (message "rfnmfd-yes: begin") > (prog1 (apply oldfun args) > (message "rfnmfd-yes: done")))) > > (advice-add 'dired-read-dir-and-switches :around 'rfnmfd-yes) > #+end_src > > Now when I call M-x dired the around advice for > dired-read-dir-and-switches runs, and it binds > read-file-name--directories-p to t and eventually goes on to call > read-file-name where the filter-args advice kicks in. > > but in filter-args advice my dynamic variable is bound to nil and not > to t as I'd expect. > > How is my expectation wrong or what is actually happening? A typo, "maybe"? [ Pun intended. ] Stefan