如何在主模式钩子中访问目录局部变量？ [英] How can I access directory-local variables in my major mode hooks?

问题描述

我已经定义了一个.dir-locals.el文件，其中包含以下内容：

 （（python-mode。 （cr / virtualenv-name。saas））））
  

在我的.emacs中我有以下函数来检索该值并提供一个virtualenv路径：

 （defun cr / virtualenv（）
（cond cr / virtualenv-name（格式％s /％svirtualenv-base cr / virtualenv-name））
（（getenvEMACS_VIRTUAL_ENV）（getenvEMACS_VIRTUAL_ENV））
（t /）$）
  

最后，在我的python-mode-hook列表中，我有这个钩子功能：

 （add-hook'python-mode-hook'cr / python-mode-shell-设置）
 
（defun cr / python-mode-shell-setup（）
（消息virtualenv-name is％scr / virtualenv-name）
（let （python-base（cr / virtualenv）））
（cond（（和（fboundp'ipython-shell-hook）（file-executable-p（concat python-base/ bin / ipython）））
（setq pyth on-python-command（concat python-base/ bin / ipython））
（setq py-python-command（concat python-base/ bin / ipython））
（setq py- python-command-args'（-colorsNoColor））
（t 
（setq python-python-command（concat python-base/ bin / python））
（setq py-python-command（concat python-base/ bin / python））
（setq py-python-command-args nil）））））
  

当我打开一个新的python文件，由 cr / python-mode-shell-setup 表示 cr / virtualenv-name 是 nil 。然而，当我C-h v的名字，我得到saas。

显然这里有一个加载订单问题;有没有办法让我的模式hook语句响应目录局部变量？

解决方案

这是因为正常模式调用（set-auto-mode）和（hack-local-variables）在该顺序。

然而 hack-local-variables-hook 是在本地变量有被处理，这使得一些解决方案：

1. 第一个是使Emacs为每个主要运行一个新的局部变量钩模式：

    （add-hook'hack-local-variables-hook'run-local- vars-mode-hook）
   （defun run-local-vars-mode-hook（）
   在处理了本地变量之后，为主模式运行挂钩
    run-hooks（intern（concat（symbol-name major-mode）-local-vars-hook））））
    
   （add-hook'python-mode-local-vars-hook' cr / python-mode-shell-setup）
     

   （您的ori第二个选项是使用可选的 LOCAL 参数 add-hook ，使指定的函数缓冲区本地。使用这种方式，你可以按照如下方式编写你的钩子：

    （add-hook'python-mode -hook'cr / python-mode-shell-setup）
    
   （defun cr / python-mode-shell-setup（）
   （add-hook'hack-local-variables-hook 
   （lambda（）（messagevirtualenv-name is％scr / virtualenv-name）
   （let（（python-base（cr / virtualenv）））
   （cond和（fboundp'ipython-shell-hook）（file-executable-p（concat python-base/ bin / ipython）））
   （setq python-python-command（concat python-base/ bin / ipython）
   （setq py-python-command（concat python-base/ bin / ipython））
   （setq py-python-command-args'（-colorsNoColor ））
   （t 
   （setq python-python-command（concat python-base/ bin / python））
   （setq py-python-command（concat python-base /箱/ python））
   （setq py-python-command-args nil）））））
    nil t））; buffer-local hack-local-variables-hook 
     

   首先运行 python-mode-hook ，并为当前缓冲区注册匿名函数 hack-local-variables-hook 只要;然后在处理局部变量后调用该函数。




2. Lindydancer的注释提示了第三种方法。它不像其他两个那么干净，但是证明是有趣的。我不喜欢引起（hack-local-variables）被调用两次的想法，但是我发现如果你设置了 local-启用本地变量缓冲区本地，它阻止（hack-local-variables）做任何事情，所以你可以这样做：

    （defun cr / python-mode-shell-setup（）
   （报告错误文件局部变量错误：％s
   （hack-local-variables）））
   （set（make-local-variable'local-enable-local-variables ）nil）
   （let（（python-base（cr / virtualenv）））
    ...））
     

   显然，修改正常的执行顺序有点，所以副作用可能是可能的。我担心如果文件中的局部变量注释设置了相同的主要模式，这可能会导致无限递归，但实际上并不是一个问题。

   
   
   

   局部变量头注释（例如 - * - mode：foo - * - ）由（set -auto-mode），所以这些都不错但是一个模式：foo 本地变量：评论似乎是一个问题，因为它由（hack-local-variables），所以如果模式是这样设置的，我以为会导致递归。

   
   
   

   练习我通过使用一个简单的函数作为模式来触发这个问题，这样做只是试图运行它的钩子;然而用正确模式进行测试没有出现问题，所以在现实中可能是安全的。我没有进一步研究（因为其他两个解决方案比这更清洁），但我猜想延迟模式钩子机制可能解释了吗？

I have defined a .dir-locals.el file with the following content:

((python-mode . ((cr/virtualenv-name . "saas"))))

In my .emacs I have the following function to retrieve this value and provide a virtualenv path:

(defun cr/virtualenv ()
  (cond (cr/virtualenv-name (format "%s/%s" virtualenv-base cr/virtualenv-name))
        ((getenv "EMACS_VIRTUAL_ENV") (getenv "EMACS_VIRTUAL_ENV"))
        (t "~/.emacs.d/python")))

Finally, in my python-mode-hook list, I have this hook function:

(add-hook 'python-mode-hook 'cr/python-mode-shell-setup)

(defun cr/python-mode-shell-setup ()
  (message "virtualenv-name is %s" cr/virtualenv-name)
  (let ((python-base (cr/virtualenv)))
    (cond ((and (fboundp 'ipython-shell-hook) (file-executable-p (concat python-base "/bin/ipython")))
           (setq python-python-command (concat python-base "/bin/ipython"))
           (setq py-python-command (concat python-base "/bin/ipython"))
           (setq py-python-command-args '( "-colors" "NoColor")))
          (t
           (setq python-python-command (concat python-base "/bin/python"))
           (setq py-python-command (concat python-base "/bin/python"))
           (setq py-python-command-args nil)))))

When I open a new python file, the message logged by cr/python-mode-shell-setup indicates that cr/virtualenv-name is nil. However, when I C-h v the name, I get "saas" instead.

Obviously there's a load order issue here; is there a way to have my mode hook statements respond to directory-local variables?

解决方案

This happens because normal-mode calls (set-auto-mode) and (hack-local-variables) in that order.

However hack-local-variables-hook is run after the local variables have been processed, which enables some solutions:

1. The first is to make Emacs run a new "local variables hook" for each major mode:

   (add-hook 'hack-local-variables-hook 'run-local-vars-mode-hook)
   (defun run-local-vars-mode-hook ()
     "Run a hook for the major-mode after the local variables have been processed."
     (run-hooks (intern (concat (symbol-name major-mode) "-local-vars-hook"))))
   
   (add-hook 'python-mode-local-vars-hook 'cr/python-mode-shell-setup)
   

   (Your original function can be used unmodified, with that approach.)

2. A second option is to utilise the optional LOCAL argument to add-hook that makes the specified function buffer-local. With this approach you could write your hook as follows:

   (add-hook 'python-mode-hook 'cr/python-mode-shell-setup)
   
   (defun cr/python-mode-shell-setup ()
     (add-hook 'hack-local-variables-hook
               (lambda () (message "virtualenv-name is %s" cr/virtualenv-name)
                 (let ((python-base (cr/virtualenv)))
                   (cond ((and (fboundp 'ipython-shell-hook) (file-executable-p (concat python-base "/bin/ipython")))
                          (setq python-python-command (concat python-base "/bin/ipython"))
                          (setq py-python-command (concat python-base "/bin/ipython"))
                          (setq py-python-command-args '( "-colors" "NoColor")))
                         (t
                          (setq python-python-command (concat python-base "/bin/python"))
                          (setq py-python-command (concat python-base "/bin/python"))
                          (setq py-python-command-args nil)))))
               nil t)) ; buffer-local hack-local-variables-hook
   

   i.e. python-mode-hook runs first and registers the anonymous function with hack-local-variables-hook for the current buffer only; and that function is then called after the local variables have been processed.

3. Lindydancer's comment prompts a third approach. It's not nearly as clean as the other two, but proved interesting regardless. I didn't like the idea of causing (hack-local-variables) to be called twice, but I see that if you set the local-enable-local-variables buffer-locally, it prevents (hack-local-variables) from doing anything, so you could do this:

   (defun cr/python-mode-shell-setup ()
     (report-errors "File local-variables error: %s"
       (hack-local-variables)))
     (set (make-local-variable 'local-enable-local-variables) nil)
     (let ((python-base (cr/virtualenv)))
       ...))
   

   Obviously that modifies the normal sequence of execution a little, so side effects may be possible. I was worried that if the same major mode is set by a local variable comment in the file, this might cause infinite recursion, but that doesn't actually appear to be a problem.

   Local variable header comments (e.g. -*- mode: foo -*-) are handled by (set-auto-mode), so those are fine; but a mode: foo Local Variables: comment seems like it would be an issue as it is handled by (hack-local-variables), and so if the mode is set that way I thought it would cause recursion.

   In practice I was able to trigger the problem by using a simple function as a 'mode' which did nothing more than try to run its hooks; however testing with a 'proper' mode did not exhibit the problem, so it's probably safe in reality. I didn't look into this further (as the other two solutions are much cleaner than this), but I would guess the delayed mode hooks mechanism probably explains it?

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