bug#33475: [Wish list]: Display line and column numbers in warnings with `compile-defun'

[Alan Mackenzie <acm@muc.de>]

On Fri, Nov 23, 2018 at 17:58:39 +0000, Alan Mackenzie wrote:
> Hello, Emacs.

> At the moment, if a warning is displayed for a compilation started by
> `compile-defun', it appears something like:

>     Warning: assignment to free variable `foo'

> .  This is all very well, but it lacks the line and column number of the
> place of the warning, meaning one must search through the source and
> guess where the warning is.

> Why not output this information, much like is done in a batch
> compilation?  It would then look like:

>     Buffer winkler2.el:3:14:Warning: assignment to free variable `foo'

> .  This would save guessing and irritation.

> Here is a patch which achieves this:

[ .... ]

This patch was all very well, but was incomplete: hitting CR on such a
warning message in *Compile-Log* failed to move to the position in the
.el buffer, instead spuriously prompting for a file.

The following patch, incorporating the patch from my original post,
fixes this by amending compile.el to handle buffers as an alternative to
file names, creating emacs-lisp-compilation-mode, which extracts the
buffer from one of these warning messages, and calling this new mode
from byte-compile-log-file in place of compilation-mode.



diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index 0b8f8824b4..8312c0153e 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -1006,6 +1006,24 @@ byte-compile-eval-before-compile
 \f
 ;;; byte compiler messages
 
+(defun emacs-lisp-compilation-file-name-or-buffer (str)
+  "Return file name or buffer given by STR.
+If STR is a \"normal\" filename, just return it.
+If STR is something like \"Buffer foo.el\", return #<buffer foo.el>
+\(if it is still live) or the string \"foo.el\" otherwise."
+  (if (string-match "Buffer \\(.*\\)\\'" str)
+      (or (get-buffer (match-string-no-properties 1 str))
+          (match-string-no-properties 1 str))
+    str))
+
+(defconst emacs-lisp-compilation-parse-errors-filename-function
+  'emacs-lisp-compilation-file-name-or-buffer
+  "The value for `compilation-parse-errors-filename-function' for when
+we go into emacs-lisp-compilation-mode.")
+
+(define-compilation-mode emacs-lisp-compilation-mode "elisp-compile"
+  "The variant of `compilation-mode' used for emacs-lisp error buffers")
+
 (defvar byte-compile-current-form nil)
 (defvar byte-compile-dest-file nil)
 (defvar byte-compile-current-file nil)
@@ -1160,12 +1178,14 @@ byte-compile-warning-series
 ;; Return the position of the start of the page in the log buffer.
 ;; But do nothing in batch mode.
 (defun byte-compile-log-file ()
-  (and (not (equal byte-compile-current-file byte-compile-last-logged-file))
+  (and (not
+        (and (get-buffer byte-compile-log-buffer)
+             (equal byte-compile-current-file byte-compile-last-logged-file)))
        (not noninteractive)
        (with-current-buffer (get-buffer-create byte-compile-log-buffer)
 	 (goto-char (point-max))
 	 (let* ((inhibit-read-only t)
-		(dir (and byte-compile-current-file
+		(dir (and (stringp byte-compile-current-file)
 			  (file-name-directory byte-compile-current-file)))
 		(was-same (equal default-directory dir))
 		pt)
@@ -1180,7 +1200,7 @@ byte-compile-log-file
 	       (insert "\f\nCompiling "
 		       (if (stringp byte-compile-current-file)
 			   (concat "file " byte-compile-current-file)
-			 (concat "buffer "
+			 (concat "in buffer "
                                  (buffer-name byte-compile-current-file)))
 		       " at " (current-time-string) "\n")
 	     (insert "\f\nCompiling no file at " (current-time-string) "\n"))
@@ -1192,7 +1212,8 @@ byte-compile-log-file
 	   (setq byte-compile-last-logged-file byte-compile-current-file
 		 byte-compile-last-warned-form nil)
 	   ;; Do this after setting default-directory.
-	   (unless (derived-mode-p 'compilation-mode) (compilation-mode))
+	   (unless (derived-mode-p 'compilation-mode)
+             (emacs-lisp-compilation-mode))
 	   (compilation-forget-errors)
 	   pt))))
 
@@ -1981,7 +2002,7 @@ compile-defun
   (save-excursion
     (end-of-defun)
     (beginning-of-defun)
-    (let* ((byte-compile-current-file nil)
+    (let* ((byte-compile-current-file (current-buffer))
 	   (byte-compile-current-buffer (current-buffer))
 	   (byte-compile-read-position (point))
 	   (byte-compile-last-position byte-compile-read-position)
diff --git a/lisp/progmodes/compile.el b/lisp/progmodes/compile.el
index 7e7c18fb30..973d3a0146 100644
--- a/lisp/progmodes/compile.el
+++ b/lisp/progmodes/compile.el
@@ -83,7 +83,10 @@ compilation-first-column
 (defvar compilation-parse-errors-filename-function nil
   "Function to call to post-process filenames while parsing error messages.
 It takes one arg FILENAME which is the name of a file as found
-in the compilation output, and should return a transformed file name.")
+in the compilation output, and should return a transformed file name
+or a buffer, the one which was compiled.")
+;; Note: the compilation-parse-errors-filename-function need not save the
+;; match data.
 
 ;;;###autoload
 (defvar compilation-process-setup-function nil
@@ -550,7 +553,8 @@ compilation-error-regexp-alist
 \(e.g. \"%s.c\") will be applied in turn to the recognized file
 name, until a file of that name is found.  Or FILE can also be a
 function that returns (FILENAME) or (RELATIVE-FILENAME . DIRNAME).
-In the former case, FILENAME may be relative or absolute.
+In the former case, FILENAME may be relative or absolute, or it may
+be a buffer.
 
 LINE can also be of the form (LINE . END-LINE) meaning a range
 of lines.  COLUMN can also be of the form (COLUMN . END-COLUMN)
@@ -944,10 +948,11 @@ compilation--loc->visited
 ;;   FILE-STRUCTURE is a list of
 ;;   ((FILENAME DIRECTORY) FORMATS (LINE LOC ...) ...)
 
-;; FILENAME is a string parsed from an error message.  DIRECTORY is a string
-;; obtained by following directory change messages.  DIRECTORY will be nil for
-;; an absolute filename.  FORMATS is a list of formats to apply to FILENAME if
-;; a file of that name can't be found.
+;; FILENAME is a string parsed from an error message, or the buffer which was
+;; compiled.  DIRECTORY is a string obtained by following directory change
+;; messages.  DIRECTORY will be nil for an absolute filename or a buffer.
+;; FORMATS is a list of formats to apply to FILENAME if a file of that name
+;; can't be found.
 ;; The rest of the list is an alist of elements with LINE as key.  The keys
 ;; are either nil or line numbers.  If present, nil comes first, followed by
 ;; the numbers in decreasing order.  The LOCs for each line are again an alist
@@ -1180,7 +1185,8 @@ compilation-internal-error-properties
   "Get the meta-info that will be added as text-properties.
 LINE, END-LINE, COL, END-COL are integers or nil.
 TYPE can be 0, 1, or 2, meaning error, warning, or just info.
-FILE should be (FILENAME) or (RELATIVE-FILENAME . DIRNAME) or nil.
+FILE should be (FILENAME) or (RELATIVE-FILENAME . DIRNAME) or (BUFFER) or
+nil.
 FMTS is a list of format specs for transforming the file name.
  (See `compilation-error-regexp-alist'.)"
   (unless file (setq file '("*unknown*")))
@@ -2493,12 +2499,14 @@ compilation-next-error-function
                  ;;            (setq timestamp compilation-buffer-modtime)))
                  )
       (with-current-buffer
-          (apply #'compilation-find-file
-                 marker
-                 (caar (compilation--loc->file-struct loc))
-                 (cadr (car (compilation--loc->file-struct loc)))
-                 (compilation--file-struct->formats
-                  (compilation--loc->file-struct loc)))
+          (if (bufferp (caar (compilation--loc->file-struct loc)))
+              (caar (compilation--loc->file-struct loc))
+            (apply #'compilation-find-file
+                   marker
+                   (caar (compilation--loc->file-struct loc))
+                   (cadr (car (compilation--loc->file-struct loc)))
+                   (compilation--file-struct->formats
+                    (compilation--loc->file-struct loc))))
         (let ((screen-columns
                ;; Obey the compilation-error-screen-columns of the target
                ;; buffer if its major mode set it buffer-locally.
@@ -2810,18 +2818,21 @@ compilation-get-file-structure
 		       (concat comint-file-name-prefix spec-directory))))))
 
 	;; If compilation-parse-errors-filename-function is
-	;; defined, use it to process the filename.
+	;; defined, use it to process the filename.  The result might be a
+	;; buffer.
 	(when compilation-parse-errors-filename-function
-	  (setq filename
-		(funcall compilation-parse-errors-filename-function
-			 filename)))
+          (save-match-data
+	    (setq filename
+		  (funcall compilation-parse-errors-filename-function
+			   filename))))
 
 	;; Some compilers (e.g. Sun's java compiler, reportedly) produce bogus
 	;; file names like "./bar//foo.c" for file "bar/foo.c";
 	;; expand-file-name will collapse these into "/foo.c" and fail to find
 	;; the appropriate file.  So we look for doubled slashes in the file
 	;; name and fix them.
-	(setq filename (command-line-normalize-file-name filename))
+	(if (stringp filename)
+            (setq filename (command-line-normalize-file-name filename)))
 
 	;; Store it for the possibly unnormalized name
 	(puthash file


-- 
Alan Mackenzie (Nuremberg, Germany).