GNU bug report logs - #23224
25.0.92; Can xref-find-references work without a "project"?

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From: Eli Zaretskii <eliz <at> gnu.org>
To: 23224 <at> debbugs.gnu.org
Subject: bug#23224: 25.0.92; Can xref-find-references work without a "project"?
Date: Tue, 05 Apr 2016 18:23:08 +0300

In an Emacs tree that is not under any VCS, type:

  emacs -Q
  M-x xref-find-references RET current_buffer RET

When prompted to choose a project directory, accept the default by
typing RET.  The result:

  No project found in ‘THE-DEFAULT-DIRECTORY/’

This is disappointing, since the default implementation of
xref-find-references is fully capable of producing the requested
results even if no project (in the project.el sense) was created in
the directory.

I think we shouldn't fail the operation in this case, but instead use
the directory specified by the user as the single project root.  The
proposed patch below implements this.  (I'm not married to the patch
as shown, so if someone comes up with a more elegant solution, I'd be
as happy.  The important part is that we should allow this command to
be usable even if no project infrastructure was created.)

--- lisp/progmodes/project.el~0	2016-01-31 06:43:03.000000000 +0200
+++ lisp/progmodes/project.el	2016-04-05 18:06:43.146022700 +0300
@@ -98,10 +98,12 @@
 that it is not applicable, or a project instance.")
 
 ;;;###autoload
-(defun project-current (&optional maybe-prompt dir)
+(defun project-current (&optional maybe-prompt dir noerror)
   "Return the project instance in DIR or `default-directory'.
 When no project found in DIR, and MAYBE-PROMPT is non-nil, ask
-the user for a different directory to look in."
+the user for a different directory to look in.
+Optional third argument NOERROR, if non-nil, means don't signal
+an error if no project is found in the specified directory."
   (unless dir (setq dir default-directory))
   (let ((pr (project--find-in-directory dir)))
     (cond
@@ -109,6 +111,8 @@
      (maybe-prompt
       (setq dir (read-directory-name "Choose the project directory: " dir nil t)
             pr (project--find-in-directory dir))
+      (if (and (not pr) noerror)
+          (setq pr dir))
       (unless pr
         (user-error "No project found in `%s'" dir))))
     pr))
--- lisp/progmodes/xref.el~0	2016-03-20 06:53:36.000000000 +0200
+++ lisp/progmodes/xref.el	2016-04-05 18:18:47.257475600 +0300
@@ -245,14 +245,19 @@
 
 The default implementation uses `semantic-symref-tool-alist' to
 find a search tool; by default, this uses \"find | grep\" in the
-`project-current' roots."
+`project-current' roots, falling back to the directory tree
+rooted at the directory specified by user."
   (cl-mapcan
    (lambda (dir)
      (xref-collect-references identifier dir))
-   (let ((pr (project-current t)))
-     (append
-      (project-roots pr)
-      (project-external-roots pr)))))
+   (let* ((pr (project-current t nil 'noerror))
+          (roots (ignore-errors (project-roots pr)))
+          (eroots (ignore-errors (project-external-roots pr))))
+     ;; If we didn't find any project files in PR, default to PR
+     ;; itself as the project's single root.
+     (if (and (null roots) (null eroots))
+         (setq roots (list (expand-file-name pr))))
+     (append roots eroots))))
 
 (cl-defgeneric xref-backend-apropos (backend pattern)
   "Find all symbols that match PATTERN.




In GNU Emacs 25.0.92.75 (i686-pc-mingw32)
 of 2016-04-04 built on HOME-C4E4A596F7
Repository revision: f501116ea896b20f195f5c841e8770d7fe0418b9
Windowing system distributor 'Microsoft Corp.', version 5.1.2600
Configured using:
 'configure --prefix=/d/usr --enable-checking=yes,glyphs --with-wide-int
 --with-modules 'CFLAGS=-O0 -gdwarf-4 -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS MODULES

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1255

Major mode: Message

Minor modes in effect:
  mml-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  auto-fill-function: message-do-auto-fill
  transient-mark-mode: t
  abbrev-mode: t

Recent messages:
Checking 167 files in d:/gnu/git/emacs/branch/lisp/emacs-lisp...
Checking 24 files in d:/gnu/git/emacs/branch/lisp/cedet...
Checking 57 files in d:/gnu/git/emacs/branch/lisp/calendar...
Checking 87 files in d:/gnu/git/emacs/branch/lisp/calc...
Checking 122 files in d:/gnu/git/emacs/branch/lisp/obsolete...
Checking for load-path shadows...done
Mark set [2 times]
Saved text from "From: eliz <at> HOME-C4E4A596F7.i-did-not-set"
Auto-saving...
Modification-flag cleared

Load-path shadows:
None found.

Features:
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text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote w32notify w32 multi-tty
make-network-process emacs)

Memory information:
((conses 16 95005 11151)
 (symbols 56 20730 0)
 (miscs 48 46 126)
 (strings 16 17838 6291)
 (string-bytes 1 448071)
 (vectors 16 12532)
 (vector-slots 8 432331 7162)
 (floats 8 167 313)
 (intervals 40 563 63)
 (buffers 856 13))

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