Re: describe-function and advised C functions

[Tassilo Horn <tsdh@gnu.org>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>>  	 ;; If the function is advised, use the symbol that has the
>>  	 ;; real definition, if that symbol is already set up.
>>  	 (real-function
>>  	  (or (and advised
>> -		   (let ((origname (cdr (assq 'origname advised))))
>> -		     (and (fboundp origname) origname)))
>> +		   (let* ((f function)
>> +			  (advised-fn (advice--cdr (advice--symbol-function f))))
>> +		     (while (advice--p advised-fn)
>> +		       (setq f advised-fn)
>> +		       (setq advised-fn (advice--cdr (if (symbolp f)
>> +							 (advice--symbol-function f)
>> +						       f))))
>> +		     advised-fn))
>
> Here `f' is unnecessary (you can always replace it either with
> `function' or with `advised-fn').

Right.

> Doesn't this break the 80-columns limit?

Yes.  The new attached patch is at most 76 columns wide.

> Also, the (symbolp f) test is always nil since (advice--p advised-fn)
> can't be true at the same time.

Indeed.

> More important, for an advised macro, your `real-definition' will be
> a function (either a lambda expression or a byte-code-function-p).

Oh, yes.  I didn't test advising macros, but the new patch contains a
fix.

>> +	 (aliased (or (symbolp def)
>> +		      ;; advised & aliased
>> +		      (and (symbolp function)
>> +			   (symbolp real-function)
>> +			   (not (eq function real-function)))))
>
> Please capitalize and punctuate your comments.

Done.

> Also, why not use replace the `and' with
>
>    (and advised (symbolp real-function))

That's better.

>> +	 (real-def (cond
>> +		    (aliased (let ((f real-function))
>> +			       (while (and (fboundp f)
>> +					   (symbolp (symbol-function f)))
>> +				 (setq f (symbol-function f)))
>> +			       f))
>> +		    ((subrp def) (intern (subr-name def)))
>> +		    (t def)))
>
> Why do we need `subr-name'?

Later comes an `fboundp' check which errors when given a subr.

    (if (and aliased (not (fboundp real-def)))
	(princ ",\nwhich is not defined.  Please make a bug report.")

>> @@ -567,14 +577,14 @@
>>      ;; Print what kind of function-like object FUNCTION is.
>>      (princ (cond ((or (stringp def) (vectorp def))
>>  		  "a keyboard macro")
>> +		 (aliased
>> +		  (format "an alias for `%s'" real-def))
>>  		 ((subrp def)
>>  		  (if (eq 'unevalled (cdr (subr-arity def)))
>>  		      (concat beg "special form")
>>  		    (concat beg "built-in function")))
>>  		 ((byte-code-function-p def)
>>  		  (concat beg "compiled Lisp function"))
>> -		 (aliased
>> -		  (format "an alias for `%s'" real-def))
>>  		 ((eq (car-safe def) 'lambda)
>>  		  (concat beg "Lisp function"))
>>  		 ((eq (car-safe def) 'macro)
>
> Hmm... Why was this move necessary?  You'll probably want to add a
> comment explaining it.

Done so.  For the adviced macro thingy, I also had to move the macro
clause upwards and add (macrop function) check.

Bye,
Tassilo

--8<---------------cut here---------------start------------->8---
=== modified file 'lisp/help-fns.el'
--- lisp/help-fns.el	2013-06-15 01:12:05 +0000
+++ lisp/help-fns.el	2013-12-05 09:45:15 +0000
@@ -382,8 +382,6 @@
 			    (match-string 1 str))))
 	(and src-file (file-readable-p src-file) src-file))))))
 
-(declare-function ad-get-advice-info "advice" (function))
-
 (defun help-fns--key-bindings (function)
   (when (commandp function)
     (let ((pt2 (with-current-buffer standard-output (point)))
@@ -531,27 +529,34 @@
 
 ;;;###autoload
 (defun describe-function-1 (function)
-  (let* ((advised (and (symbolp function) (featurep 'advice)
-		       (ad-get-advice-info function)))
+  (let* ((advised (and (symbolp function)
+		       (featurep 'nadvice)
+		       (advice--p (advice--symbol-function function))))
 	 ;; If the function is advised, use the symbol that has the
 	 ;; real definition, if that symbol is already set up.
 	 (real-function
 	  (or (and advised
-		   (let ((origname (cdr (assq 'origname advised))))
-		     (and (fboundp origname) origname)))
+		   (let* ((advised-fn (advice--cdr
+				       (advice--symbol-function function))))
+		     (while (advice--p advised-fn)
+		       (setq advised-fn (advice--cdr advised-fn)))
+		     advised-fn))
 	      function))
 	 ;; Get the real definition.
 	 (def (if (symbolp real-function)
 		  (symbol-function real-function)
-		function))
-	 (aliased (symbolp def))
-	 (real-def (if aliased
-		       (let ((f def))
-			 (while (and (fboundp f)
-				     (symbolp (symbol-function f)))
-			   (setq f (symbol-function f)))
-			 f)
-		     def))
+		real-function))
+	 (aliased (or (symbolp def)
+		      ;; Advised & aliased function.
+		      (and advised (symbolp real-function))))
+	 (real-def (cond
+		    (aliased (let ((f real-function))
+			       (while (and (fboundp f)
+					   (symbolp (symbol-function f)))
+				 (setq f (symbol-function f)))
+			       f))
+		    ((subrp def) (intern (subr-name def)))
+		    (t def)))
 	 (file-name (find-lisp-object-file-name function def))
          (pt1 (with-current-buffer (help-buffer) (point)))
 	 (beg (if (and (or (byte-code-function-p def)
@@ -571,14 +576,20 @@
 		  (if (eq 'unevalled (cdr (subr-arity def)))
 		      (concat beg "special form")
 		    (concat beg "built-in function")))
-		 ((byte-code-function-p def)
-		  (concat beg "compiled Lisp function"))
+		 ;; Aliases are Lisp functions, so we need to check
+		 ;; aliases before functions.
 		 (aliased
 		  (format "an alias for `%s'" real-def))
+		 ((or (eq (car-safe def) 'macro)
+		      ;; For advised macros, def is a lambda
+		      ;; expression or a byte-code-function-p, so we
+		      ;; need to check macros before functions.
+		      (macrop function))
+		  (concat beg "Lisp macro"))
+		 ((byte-code-function-p def)
+		  (concat beg "compiled Lisp function"))
 		 ((eq (car-safe def) 'lambda)
 		  (concat beg "Lisp function"))
-		 ((eq (car-safe def) 'macro)
-		  (concat beg "Lisp macro"))
 		 ((eq (car-safe def) 'closure)
 		  (concat beg "Lisp closure"))
 		 ((autoloadp def)
--8<---------------cut here---------------end--------------->8---

Bye,
Tassilo