[mh-e:bugs] #482 Incorrect usage of cl-flet

[Bill Wohler]

---

** [bugs:#482] Incorrect usage of cl-flet**

**Status:** open
**Milestone:** mh-e-8.7
**Created:** Mon Jan 18, 2016 06:02 AM UTC by Bill Wohler
**Last Updated:** Mon Jan 18, 2016 06:02 AM UTC
**Owner:** Bill Wohler


Katsumi Yamaoka <***@jpl.org> submitted Emacs bug#22317:
25.0.50; mh-e: wrong usage of cl-flet

Hi,

mh-e uses Gnus functions to render MIME messages and uses the
mh-cl-flet macro to modify some of them. Currently mh-e always
loads cl (see mh-acros.el), so both cl-flet and flet are available
and mh-cl-flet will become cl-flet:
,----
| ;; Emacs 24 renamed flet to cl-flet.
| (defalias 'mh-cl-flet
| (if (fboundp 'cl-flet)
| 'cl-flet
| 'flet))
`----
However, cl-flet is quite unlike flet, IIUC. For instance, if
cl-flet is used, the mh-cl-flet code in mh-display-emphasis
,----
| ;; (defun mh-display-emphasis ()
| ;; "Display graphical emphasis."
| ;; (when (and mh-graphical-emphasis-flag (mh-small-show-buffer-p))
| (mh-cl-flet
| ((article-goto-body ())) ; shadow this function to do nothing
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
| ;; ))
`----
will be expanded to
,----
| (progn
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
`----
whereas if flet is used, it will be expanded to:
,----
| (let* ((vnew (cl-function (lambda nil
| (cl-block article-goto-body))))
| (old (symbol-function 'article-goto-body)))
| (unwind-protect
| (progn
| (fset 'article-goto-body vnew)
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
| (fset 'article-goto-body old)))
`----
Note that the former doesn't achieve the original target, i.e.,
article-goto-body is not modified while running article-emphasize.

I don't know how it damages the behavior of mh-e, but I think it
should be fixed anyway. If mh-e keeps loading cl as ever,
mh-cl-flet can be:

(defalias 'mh-cl-flet 'flet)

Otherwise use this complete Emacs-Lisp style flet emulation macro
(a copy of gmm-flet that exists in only the Gnus git master):

(defmacro mh-cl-flet (bindings &rest body)
"Make temporary overriding function definitions.
This is an analogue of a dynamically scoped `let' that operates on
the function cell of FUNCs rather than their value cell.

\(fn ((FUNC ARGLIST BODY...) ...) FORM...)"
(require 'cl)
(if (fboundp 'cl-letf)
`(cl-letf ,(mapcar (lambda (binding)
`((symbol-function ',(car binding))
(lambda ,@(cdr binding))))
bindings)
,@body)
`(flet ,bindings ,@body)))
(put 'mh-cl-flet 'lisp-indent-function 1)
(put 'mh-cl-flet 'edebug-form-spec
'((&rest (sexp sexp &rest form)) &rest form))

I'm not the right person to install it since I'm not a mh-e user,
sorry.

Regards,



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[Bill Wohler]

- Description has changed:

Diff:

~~~~

--- old
+++ new
@@ -3,81 +3,80 @@

Hi,

-mh-e uses Gnus functions to render MIME messages and uses the
-mh-cl-flet macro to modify some of them. Currently mh-e always
-loads cl (see mh-acros.el), so both cl-flet and flet are available
-and mh-cl-flet will become cl-flet:
-,----
-| ;; Emacs 24 renamed flet to cl-flet.
-| (defalias 'mh-cl-flet
-| (if (fboundp 'cl-flet)
-| 'cl-flet
-| 'flet))
-`----
-However, cl-flet is quite unlike flet, IIUC. For instance, if
-cl-flet is used, the mh-cl-flet code in mh-display-emphasis
-,----
-| ;; (defun mh-display-emphasis ()
-| ;; "Display graphical emphasis."
-| ;; (when (and mh-graphical-emphasis-flag (mh-small-show-buffer-p))
-| (mh-cl-flet
-| ((article-goto-body ())) ; shadow this function to do nothing
-| (save-excursion
-| (goto-char (point-min))
-| (article-emphasize)))
-| ;; ))
-`----
+mh-e uses Gnus functions to render MIME messages and uses the mh-cl-flet macro to modify some of them. Currently mh-e always loads cl (see mh-acros.el), so both cl-flet and flet are available and mh-cl-flet will become cl-flet:
+
+ ,----
+ | ;; Emacs 24 renamed flet to cl-flet.
+ | (defalias 'mh-cl-flet
+ | (if (fboundp 'cl-flet)
+ | 'cl-flet
+ | 'flet))
+ `----
+
+However, cl-flet is quite unlike flet, IIUC. For instance, if cl-flet is used, the mh-cl-flet code in mh-display-emphasis
+
+ ,----
+ | ;; (defun mh-display-emphasis ()
+ | ;; "Display graphical emphasis."
+ | ;; (when (and mh-graphical-emphasis-flag (mh-small-show-buffer-p))
+ | (mh-cl-flet
+ | ((article-goto-body ())) ; shadow this function to do nothing
+ | (save-excursion
+ | (goto-char (point-min))
+ | (article-emphasize)))
+ | ;; ))
+ `----
+
will be expanded to
-,----
-| (progn
-| (save-excursion
-| (goto-char (point-min))
-| (article-emphasize)))
-`----
+
+ ,----
+ | (progn
+ | (save-excursion
+ | (goto-char (point-min))
+ | (article-emphasize)))
+ `----
+
whereas if flet is used, it will be expanded to:
-,----
-| (let* ((vnew (cl-function (lambda nil
-| (cl-block article-goto-body))))
-| (old (symbol-function 'article-goto-body)))
-| (unwind-protect
-| (progn
-| (fset 'article-goto-body vnew)
-| (save-excursion
-| (goto-char (point-min))
-| (article-emphasize)))
-| (fset 'article-goto-body old)))
-`----
-Note that the former doesn't achieve the original target, i.e.,
-article-goto-body is not modified while running article-emphasize.

-I don't know how it damages the behavior of mh-e, but I think it
-should be fixed anyway. If mh-e keeps loading cl as ever,
-mh-cl-flet can be:
+ ,----
+ | (let* ((vnew (cl-function (lambda nil
+ | (cl-block article-goto-body))))
+ | (old (symbol-function 'article-goto-body)))
+ | (unwind-protect
+ | (progn
+ | (fset 'article-goto-body vnew)
+ | (save-excursion
+ | (goto-char (point-min))
+ | (article-emphasize)))
+ | (fset 'article-goto-body old)))
+ `----

-(defalias 'mh-cl-flet 'flet)
+Note that the former doesn't achieve the original target, i.e.,article-goto-body is not modified while running article-emphasize.

-Otherwise use this complete Emacs-Lisp style flet emulation macro
-(a copy of gmm-flet that exists in only the Gnus git master):
+I don't know how it damages the behavior of mh-e, but I think it should be fixed anyway. If mh-e keeps loading cl as ever,mh-cl-flet can be:

-(defmacro mh-cl-flet (bindings &rest body)
- "Make temporary overriding function definitions.
-This is an analogue of a dynamically scoped `let' that operates on
-the function cell of FUNCs rather than their value cell.
+ (defalias 'mh-cl-flet 'flet)

-\(fn ((FUNC ARGLIST BODY...) ...) FORM...)"
- (require 'cl)
- (if (fboundp 'cl-letf)
- `(cl-letf ,(mapcar (lambda (binding)
- `((symbol-function ',(car binding))
- (lambda ,@(cdr binding))))
- bindings)
- ,@body)
- `(flet ,bindings ,@body)))
-(put 'mh-cl-flet 'lisp-indent-function 1)
-(put 'mh-cl-flet 'edebug-form-spec
- '((&rest (sexp sexp &rest form)) &rest form))
+Otherwise use this complete Emacs-Lisp style flet emulation macro (a copy of gmm-flet that exists in only the Gnus git master):

-I'm not the right person to install it since I'm not a mh-e user,
-sorry.
+ (defmacro mh-cl-flet (bindings &rest body)
+ "Make temporary overriding function definitions.
+ This is an analogue of a dynamically scoped `let' that operates on
+ the function cell of FUNCs rather than their value cell.
+
+ \(fn ((FUNC ARGLIST BODY...) ...) FORM...)"
+ (require 'cl)
+ (if (fboundp 'cl-letf)
+ `(cl-letf ,(mapcar (lambda (binding)
+ `((symbol-function ',(car binding))
+ (lambda ,@(cdr binding))))
+ bindings)
+ ,@body)
+ `(flet ,bindings ,@body)))
+ (put 'mh-cl-flet 'lisp-indent-function 1)
+ (put 'mh-cl-flet 'edebug-form-spec
+ '((&rest (sexp sexp &rest form)) &rest form))
+
+I'm not the right person to install it since I'm not a mh-e user,sorry.

Regards,

~~~~




---

** [bugs:#482] Incorrect usage of cl-flet**

**Status:** open
**Milestone:** mh-e-8.7
**Created:** Mon Jan 18, 2016 06:02 AM UTC by Bill Wohler
**Last Updated:** Mon Jan 18, 2016 06:02 AM UTC
**Owner:** Bill Wohler


Katsumi Yamaoka <***@jpl.org> submitted Emacs bug#22317:
25.0.50; mh-e: wrong usage of cl-flet

Hi,

mh-e uses Gnus functions to render MIME messages and uses the mh-cl-flet macro to modify some of them. Currently mh-e always loads cl (see mh-acros.el), so both cl-flet and flet are available and mh-cl-flet will become cl-flet:

,----
| ;; Emacs 24 renamed flet to cl-flet.
| (defalias 'mh-cl-flet
| (if (fboundp 'cl-flet)
| 'cl-flet
| 'flet))
`----

However, cl-flet is quite unlike flet, IIUC. For instance, if cl-flet is used, the mh-cl-flet code in mh-display-emphasis

,----
| ;; (defun mh-display-emphasis ()
| ;; "Display graphical emphasis."
| ;; (when (and mh-graphical-emphasis-flag (mh-small-show-buffer-p))
| (mh-cl-flet
| ((article-goto-body ())) ; shadow this function to do nothing
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
| ;; ))
`----

will be expanded to

,----
| (progn
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
`----

whereas if flet is used, it will be expanded to:

,----
| (let* ((vnew (cl-function (lambda nil
| (cl-block article-goto-body))))
| (old (symbol-function 'article-goto-body)))
| (unwind-protect
| (progn
| (fset 'article-goto-body vnew)
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
| (fset 'article-goto-body old)))
`----

Note that the former doesn't achieve the original target, i.e.,article-goto-body is not modified while running article-emphasize.

I don't know how it damages the behavior of mh-e, but I think it should be fixed anyway. If mh-e keeps loading cl as ever,mh-cl-flet can be:

(defalias 'mh-cl-flet 'flet)

Otherwise use this complete Emacs-Lisp style flet emulation macro (a copy of gmm-flet that exists in only the Gnus git master):

(defmacro mh-cl-flet (bindings &rest body)
"Make temporary overriding function definitions.
This is an analogue of a dynamically scoped `let' that operates on
the function cell of FUNCs rather than their value cell.

\(fn ((FUNC ARGLIST BODY...) ...) FORM...)"
(require 'cl)
(if (fboundp 'cl-letf)
`(cl-letf ,(mapcar (lambda (binding)
`((symbol-function ',(car binding))
(lambda ,@(cdr binding))))
bindings)
,@body)
`(flet ,bindings ,@body)))
(put 'mh-cl-flet 'lisp-indent-function 1)
(put 'mh-cl-flet 'edebug-form-spec
'((&rest (sexp sexp &rest form)) &rest form))

I'm not the right person to install it since I'm not a mh-e user,sorry.

Regards,



---

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[Bill Wohler]

Katsumi had previously posted this in 2012-12-06:

Hi,

IMHO, isn't what you really want cl-letf, not cl-flet? Though it needs to have some accessories so as to work like flet.

;; This does not override `mm-handle-set-external-undisplayer'.
(progn (pp (macroexpand-all
'(mh-cl-flet
((mm-handle-set-external-undisplayer
(handle function)
(mh-handle-set-external-undisplayer folder handle function)))
(unwind-protect (mm-display-external part method)
(set-buffer-modified-p nil)))
)) nil)
=> (let ((--cl-mm-handle-set-external-undisplayer--
#'(lambda (handle function)
(mh-handle-set-external-undisplayer folder handle function))))
(unwind-protect
(mm-display-external part method)
(set-buffer-modified-p nil)))

;; This does it.
(progn (pp (macroexpand-all
'(gmm-flet
((mm-handle-set-external-undisplayer
(handle function)
(mh-handle-set-external-undisplayer folder handle function)))
(unwind-protect (mm-display-external part method)
(set-buffer-modified-p nil)))
)) nil)
=> (let* ((vnew
#'(lambda (handle function)
(mh-handle-set-external-undisplayer folder handle function)))
(old (symbol-function 'mm-handle-set-external-undisplayer)))
(unwind-protect
(progn
(fset 'mm-handle-set-external-undisplayer vnew)
(unwind-protect
(mm-display-external part method)
(set-buffer-modified-p nil)))
(fset 'mm-handle-set-external-undisplayer old)))

Where the `gmm-flet' macro, that uses cl-letf, is now available only in Ma Gnus. Why it is not in the Emacs trunk is that I've removed it following RMS's statement:

http://thread.gmane.org/gmane.emacs.diffs/118608/focus=155306

As for Gnus such a macro is not necessary for the present if it is used with the Emacs version that bundles it, however I have no idea for MH-E better than overriding. :-<


---

** [bugs:#482] Incorrect usage of cl-flet**

**Status:** open
**Milestone:** mh-e-8.7
**Created:** Mon Jan 18, 2016 06:02 AM UTC by Bill Wohler
**Last Updated:** Mon Jan 18, 2016 06:04 AM UTC
**Owner:** Bill Wohler


Katsumi Yamaoka <***@jpl.org> submitted Emacs bug#22317:
25.0.50; mh-e: wrong usage of cl-flet

Hi,

mh-e uses Gnus functions to render MIME messages and uses the mh-cl-flet macro to modify some of them. Currently mh-e always loads cl (see mh-acros.el), so both cl-flet and flet are available and mh-cl-flet will become cl-flet:

,----
| ;; Emacs 24 renamed flet to cl-flet.
| (defalias 'mh-cl-flet
| (if (fboundp 'cl-flet)
| 'cl-flet
| 'flet))
`----

However, cl-flet is quite unlike flet, IIUC. For instance, if cl-flet is used, the mh-cl-flet code in mh-display-emphasis

,----
| ;; (defun mh-display-emphasis ()
| ;; "Display graphical emphasis."
| ;; (when (and mh-graphical-emphasis-flag (mh-small-show-buffer-p))
| (mh-cl-flet
| ((article-goto-body ())) ; shadow this function to do nothing
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
| ;; ))
`----

will be expanded to

,----
| (progn
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
`----

whereas if flet is used, it will be expanded to:

,----
| (let* ((vnew (cl-function (lambda nil
| (cl-block article-goto-body))))
| (old (symbol-function 'article-goto-body)))
| (unwind-protect
| (progn
| (fset 'article-goto-body vnew)
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
| (fset 'article-goto-body old)))
`----

Note that the former doesn't achieve the original target, i.e.,article-goto-body is not modified while running article-emphasize.

I don't know how it damages the behavior of mh-e, but I think it should be fixed anyway. If mh-e keeps loading cl as ever,mh-cl-flet can be:

(defalias 'mh-cl-flet 'flet)

Otherwise use this complete Emacs-Lisp style flet emulation macro (a copy of gmm-flet that exists in only the Gnus git master):

(defmacro mh-cl-flet (bindings &rest body)
"Make temporary overriding function definitions.
This is an analogue of a dynamically scoped `let' that operates on
the function cell of FUNCs rather than their value cell.

\(fn ((FUNC ARGLIST BODY...) ...) FORM...)"
(require 'cl)
(if (fboundp 'cl-letf)
`(cl-letf ,(mapcar (lambda (binding)
`((symbol-function ',(car binding))
(lambda ,@(cdr binding))))
bindings)
,@body)
`(flet ,bindings ,@body)))
(put 'mh-cl-flet 'lisp-indent-function 1)
(put 'mh-cl-flet 'edebug-form-spec
'((&rest (sexp sexp &rest form)) &rest form))

I'm not the right person to install it since I'm not a mh-e user,sorry.

Regards,



---

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[Bill Wohler]

Here is Katsumi's reply to my response on 2013-04-05:

Hi,

Thanks, Katsumi. I was simply trying to overcome a new deprecated
warning. When I have some time, I'll try to understand this more.

What I wanted to say was that some mh-e functions that use mh-cl-flet for utilizing Gnus functions won't work as expected. For example,AFAIU, the function mh-display-with-external-viewer tries to substitute mm-handle-set-external-undisplayer with mh-handle-set-external-undisplayer while performing mm-display-external. Its mh-cl-flet form is expanded as folows:

(progn (pp (macroexpand-all (quote
(mh-cl-flet
((mm-handle-set-external-undisplayer
(handle function)
(mh-handle-set-external-undisplayer folder handle function)))
(unwind-protect (mm-display-external part method)
(set-buffer-modified-p nil)))
))) nil)
↓
(let ((--cl-mm-handle-set-external-undisplayer--
#'(lambda (handle function)
(mh-handle-set-external-undisplayer folder handle function))))
(unwind-protect
(mm-display-external part method)
(set-buffer-modified-p nil)))

However, as you can see, mh-handle-set-external-undisplayer will never be used. This is the case where mh-cl-flet is an alias to cl-flet, that happens under Emacs 24.3 and up. If it is an alias to flet, the expanded form will be:

(let* ((vnew
#'(lambda (handle function)
(progn
(mh-handle-set-external-undisplayer folder handle function))))
(old
(symbol-function 'mm-handle-set-external-undisplayer)))
(unwind-protect
(progn
(fset 'mm-handle-set-external-undisplayer vnew)
(unwind-protect
(mm-display-external part method)
(set-buffer-modified-p nil)))
(fset 'mm-handle-set-external-undisplayer old)))

This is what it should be, isn't it? For that purpose, cl-flet is a mischoice, cl-letf should be used instead. Here is a macro that uses cl-letf to emulate flet:

(defmacro gmm-flet (bindings &rest body)
"Make temporary overriding function definitions.
This is an analogue of a dynamically scoped `let' that operates on
the function cell of FUNCs rather than their value cell.

\(fn ((FUNC ARGLIST BODY...) ...) FORM...)"
(require 'cl)
(if (fboundp 'cl-letf)
`(cl-letf ,(mapcar (lambda (binding)
`((symbol-function ',(car binding))
(lambda ,@(cdr binding))))
bindings)
,@body)
`(flet ,bindings ,@body)))

With replacing mh-cl-flet with this, the form shown above will be expanded like the following:

(progn (pp (macroexpand-all (quote
(gmm-flet
((mm-handle-set-external-undisplayer
(handle function)
(mh-handle-set-external-undisplayer folder handle function)))
(unwind-protect (mm-display-external part method)
(set-buffer-modified-p nil)))
))) nil)
↓
(let* ((vnew
#'(lambda (handle function)
(mh-handle-set-external-undisplayer folder handle function)))
(old
(symbol-function 'mm-handle-set-external-undisplayer)))
(unwind-protect
(progn
(fset 'mm-handle-set-external-undisplayer vnew)
(unwind-protect
(mm-display-external part method)
(set-buffer-modified-p nil)))
(fset 'mm-handle-set-external-undisplayer old)))

Note that, gmm-flet exists only in the Gnus Git master, not the Emacs trunk. Maybe some Emacs core developers don't like it. Related readings: <https://lists.gnu.org/archive/html/emacs-devel/2012-12/msg00096.html> and the thread.

Anyway, the macro name mh-cl-flet had better be renamed into something like mh-flet, I think.


---

** [bugs:#482] Incorrect usage of cl-flet**

**Status:** open
**Milestone:** mh-e-8.7
**Created:** Mon Jan 18, 2016 06:02 AM UTC by Bill Wohler
**Last Updated:** Mon Jan 18, 2016 06:07 AM UTC
**Owner:** Bill Wohler


Katsumi Yamaoka <***@jpl.org> submitted Emacs bug#22317:
25.0.50; mh-e: wrong usage of cl-flet

Hi,

mh-e uses Gnus functions to render MIME messages and uses the mh-cl-flet macro to modify some of them. Currently mh-e always loads cl (see mh-acros.el), so both cl-flet and flet are available and mh-cl-flet will become cl-flet:

,----
| ;; Emacs 24 renamed flet to cl-flet.
| (defalias 'mh-cl-flet
| (if (fboundp 'cl-flet)
| 'cl-flet
| 'flet))
`----

However, cl-flet is quite unlike flet, IIUC. For instance, if cl-flet is used, the mh-cl-flet code in mh-display-emphasis

,----
| ;; (defun mh-display-emphasis ()
| ;; "Display graphical emphasis."
| ;; (when (and mh-graphical-emphasis-flag (mh-small-show-buffer-p))
| (mh-cl-flet
| ((article-goto-body ())) ; shadow this function to do nothing
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
| ;; ))
`----

will be expanded to

,----
| (progn
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
`----

whereas if flet is used, it will be expanded to:

,----
| (let* ((vnew (cl-function (lambda nil
| (cl-block article-goto-body))))
| (old (symbol-function 'article-goto-body)))
| (unwind-protect
| (progn
| (fset 'article-goto-body vnew)
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
| (fset 'article-goto-body old)))
`----

Note that the former doesn't achieve the original target, i.e.,article-goto-body is not modified while running article-emphasize.

I don't know how it damages the behavior of mh-e, but I think it should be fixed anyway. If mh-e keeps loading cl as ever,mh-cl-flet can be:

(defalias 'mh-cl-flet 'flet)

Otherwise use this complete Emacs-Lisp style flet emulation macro (a copy of gmm-flet that exists in only the Gnus git master):

(defmacro mh-cl-flet (bindings &rest body)
"Make temporary overriding function definitions.
This is an analogue of a dynamically scoped `let' that operates on
the function cell of FUNCs rather than their value cell.

\(fn ((FUNC ARGLIST BODY...) ...) FORM...)"
(require 'cl)
(if (fboundp 'cl-letf)
`(cl-letf ,(mapcar (lambda (binding)
`((symbol-function ',(car binding))
(lambda ,@(cdr binding))))
bindings)
,@body)
`(flet ,bindings ,@body)))
(put 'mh-cl-flet 'lisp-indent-function 1)
(put 'mh-cl-flet 'edebug-form-spec
'((&rest (sexp sexp &rest form)) &rest form))

I'm not the right person to install it since I'm not a mh-e user,sorry.

Regards,



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[Bill Wohler]

This will be my contribution to 8.7. I wonder if it'll fix some of the
weird display things we've been seeing.

Anyway, I don't fully follow Katsumi's message so if you know anything
about flet and can append some MH-E-specific advice to SF#482, that
would be great. Otherwise, I'll try to digest Katsumi's message as best
I can.

------------------------------------------------------------------------------------
[bugs:#482] Incorrect usage of cl-flet
Status: open
Milestone: mh-e-8.7
Created: Mon Jan 18, 2016 06:02 AM UTC by Bill Wohler
Last Updated: Mon Jan 18, 2016 06:02 AM UTC
Owner: Bill Wohler
25.0.50; mh-e: wrong usage of cl-flet
Hi,
mh-e uses Gnus functions to render MIME messages and uses the
mh-cl-flet macro to modify some of them. Currently mh-e always
loads cl (see mh-acros.el), so both cl-flet and flet are available
,----
| ;; Emacs 24 renamed flet to cl-flet.
| (defalias 'mh-cl-flet
| (if (fboundp 'cl-flet)
| 'cl-flet
| 'flet))
---- However, cl-flet is quite unlike flet, IIUC. For instance, if cl-flet is used,
the mh-cl-flet code in mh-display-emphasis ,---- | ;; (defun mh-display-emphasis ()
| ;; "Display graphical emphasis." | ;; (when (and mh-graphical-emphasis-flag
(mh-small-show-buffer-p)) | (mh-cl-flet | ((article-goto-body ())) ; shadow this
function to do nothing | (save-excursion | (goto-char (point-min)) |
(article-emphasize))) | ;; ))----
will be expanded to
,----
| (progn
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
---- whereas if flet is used, it will be expanded to: ,---- | (let* ((vnew
(cl-function (lambda nil | (cl-block article-goto-body)))) | (old (symbol-function
'article-goto-body))) | (unwind-protect | (progn | (fset 'article-goto-body vnew) |
(save-excursion | (goto-char (point-min)) | (article-emphasize))) | (fset
'article-goto-body old)))----
Note that the former doesn't achieve the original target, i.e.,
article-goto-body is not modified while running article-emphasize.
I don't know how it damages the behavior of mh-e, but I think it
should be fixed anyway. If mh-e keeps loading cl as ever,
(defalias 'mh-cl-flet 'flet)
Otherwise use this complete Emacs-Lisp style flet emulation macro
(defmacro mh-cl-flet (bindings &rest body)
"Make temporary overriding function definitions.
This is an analogue of a dynamically scoped `let' that operates on
the function cell of FUNCs rather than their value cell.
(fn ((FUNC ARGLIST BODY...) ...) FORM...)"
(require 'cl)
(if (fboundp 'cl-letf)
(cl-letf ,(mapcar (lambda (binding)((symbol-function ',(car binding))
bindings)
(put 'mh-cl-flet 'lisp-indent-function 1)
(put 'mh-cl-flet 'edebug-form-spec
'((&rest (sexp sexp &rest form)) &rest form))
I'm not the right person to install it since I'm not a mh-e user,
sorry.
Regards,
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[Bill Wohler]

Nope, it didn't.

I've taken the version of gmm-flet that Katsumi and replaced our
defalias with it. I also renamed it to mh-flet since mh-cl-flet was a
misnomer as it turns out.

I'll run with it a few days before checking it in to make sure I haven't
broken anything. I'll probably also check it onto the emacs-25 branch to
close Bug#22317 before merging it back to master.

Post by Bill Wohler
This will be my contribution to 8.7. I wonder if it'll fix some of the
weird display things we've been seeing.
Anyway, I don't fully follow Katsumi's message so if you know anything
about flet and can append some MH-E-specific advice to SF#482, that
would be great. Otherwise, I'll try to digest Katsumi's message as best
I can.

------------------------------------------------------------------------------------
[bugs:#482] Incorrect usage of cl-flet
Status: open
Milestone: mh-e-8.7
Created: Mon Jan 18, 2016 06:02 AM UTC by Bill Wohler
Last Updated: Mon Jan 18, 2016 06:02 AM UTC
Owner: Bill Wohler
25.0.50; mh-e: wrong usage of cl-flet
Hi,
mh-e uses Gnus functions to render MIME messages and uses the
mh-cl-flet macro to modify some of them. Currently mh-e always
loads cl (see mh-acros.el), so both cl-flet and flet are available
,----
| ;; Emacs 24 renamed flet to cl-flet.
| (defalias 'mh-cl-flet
| (if (fboundp 'cl-flet)
| 'cl-flet
| 'flet))
---- However, cl-flet is quite unlike flet, IIUC. For instance, if cl-flet is used,
the mh-cl-flet code in mh-display-emphasis ,---- | ;; (defun mh-display-emphasis ()
| ;; "Display graphical emphasis." | ;; (when (and mh-graphical-emphasis-flag
(mh-small-show-buffer-p)) | (mh-cl-flet | ((article-goto-body ())) ; shadow this
function to do nothing | (save-excursion | (goto-char (point-min)) |
(article-emphasize))) | ;; ))----
will be expanded to
,----
| (progn
| (save-excursion
| (goto-char (point-min))
| (article-emphasize)))
---- whereas if flet is used, it will be expanded to: ,---- | (let* ((vnew
(cl-function (lambda nil | (cl-block article-goto-body)))) | (old (symbol-function
'article-goto-body))) | (unwind-protect | (progn | (fset 'article-goto-body vnew) |
(save-excursion | (goto-char (point-min)) | (article-emphasize))) | (fset
'article-goto-body old)))----
Note that the former doesn't achieve the original target, i.e.,
article-goto-body is not modified while running article-emphasize.
I don't know how it damages the behavior of mh-e, but I think it
should be fixed anyway. If mh-e keeps loading cl as ever,
(defalias 'mh-cl-flet 'flet)
Otherwise use this complete Emacs-Lisp style flet emulation macro
(defmacro mh-cl-flet (bindings &rest body)
"Make temporary overriding function definitions.
This is an analogue of a dynamically scoped `let' that operates on
the function cell of FUNCs rather than their value cell.
(fn ((FUNC ARGLIST BODY...) ...) FORM...)"
(require 'cl)
(if (fboundp 'cl-letf)
(cl-letf ,(mapcar (lambda (binding)((symbol-function ',(car binding))
bindings)
(put 'mh-cl-flet 'lisp-indent-function 1)
(put 'mh-cl-flet 'edebug-form-spec
'((&rest (sexp sexp &rest form)) &rest form))
I'm not the right person to install it since I'm not a mh-e user,
sorry.
Regards,
------------------------------------------------------------------------------------
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----------------------------------------------------
----------------------------------------------------

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