Properly canonicalize $SAGE_ROOT

[tornaria]

Currently, $SAGE_ROOT/sage uses (first among other alternate methods) readlink -n to detect the directory where the script lives (that's $SAGE_ROOT), but that is broken because

• It only works when $0 (the sage executable itself) is a symbolic link
• If the sage executable is a symbolic link, then readlink -n returns the link itself, not the canonicalized name. Example: if /usr/local/sage-4.7.1/sage is a symbolic link to sagefoo, then SAGE_ROOT would become sagefoo when '/usr/local/sage-4.7.1/sagefoo is intended.
• The symlink expansion may not be completely done, and $SAGE_ROOT could end up with a non-canonical dirname, which leads to issues with testing.
• The code to detect SAGE_ROOT inside sage-env does not canonicalize the pathname at all. This should be fixed as well. (The only case where sage-env is run without SAGE_ROOT being set is when testing Sage from the Makefile, i.e. when running make ptest or similar.)

Note that we should do this in a portable way, without using realpath, readlink -f or the likes.

See also #11704, which solves the same problem for DOT_SAGE.

Apply:

1. attachment: 5852_sage_root.patch to SAGE_ROOT
2. attachment: 5852_scripts.patch to local/bin
3. attachment: 5852_doc.patch and attachment: trac_5852-doc-referee.patch to devel/sage

Depends on #11926
Depends on #11959

CC: @nexttime @kini

Component: scripts

Author: Jeroen Demeyer

Reviewer: John Palmieri, Leif Leonhardy

Merged: sage-4.8.alpha3

Issue created by migration from https://trac.sagemath.org/ticket/5852

[tornaria]

comment:1

Patching $SAGE_ROOT/sage with this:

--- sage-3.4/sage.orig	2009-04-22 01:45:48.000000000 -0300
+++ sage-3.4/sage	2009-04-22 09:37:27.000000000 -0300
@@ -14,6 +14,7 @@
 fi
 
 if [ "$SAGE_ROOT" = "....." ];  then
+    SAGE_ROOT=`readlink -nf "$0" 2> /dev/null` || \
     SAGE_ROOT=`readlink -n "$0" 2> /dev/null` || \
     SAGE_ROOT=`realpath    "$0" 2> /dev/null` || \
     SAGE_ROOT="$0"

fixes the issue, since now $SAGE_ROOT is correct.

According to mabshoff, readlink -f doesn't work on some BSD; that's why I left the readlink -n test in the second line, but this should of course be tested on those BSD to make sure it doesn't cause a regression.

[tornaria]

On systems where "readlink -f" is supported, use that so the path for $SAGE_ROOT is fully canonicalized

[nthiery]

comment:2

Attachment: trac_5852.patch.gz

Replying to @tornaria:

Patching $SAGE_ROOT/sage with this:

--- sage-3.4/sage.orig	2009-04-22 01:45:48.000000000 -0300
+++ sage-3.4/sage	2009-04-22 09:37:27.000000000 -0300
@@ -14,6 +14,7 @@
 fi
 
 if [ "$SAGE_ROOT" = "....." ];  then
+    SAGE_ROOT=`readlink -nf "$0" 2> /dev/null` || \
     SAGE_ROOT=`readlink -n "$0" 2> /dev/null` || \
     SAGE_ROOT=`realpath    "$0" 2> /dev/null` || \
     SAGE_ROOT="$0"

fixes the issue, since now $SAGE_ROOT is correct.

According to mabshoff, readlink -f doesn't work on some BSD; that's why I left the readlink -n test in the second line, but this should of course be tested on those BSD to make sure it doesn't cause a regression.

I can confirm that it does not work on MacOS X.10.4.11 (e.g. Anne Schilling's machine)

A fix would be most welcome, as this makes sage -t make false reports of broken test files.

[nthiery]

comment:3

The readlink -f workaround is better than nothing, and should not make things worst for systems like BSD. I would vote for including it now, in waiting for a better solution.
Should I set a positive review?

Besides, what about adding a switch to sage -t to specify manually that the given file is inside or outside the sage source tree?

This would make a workaround for MacOX X, and also be occasionally be useful. For example, I often run tests from one sage source tree with another sage to compare the results.

[tornaria]

comment:4

Is there some equivalent of readlink -f that works in MacOS X?

[tornaria]

comment:5

Note that the version of readlink which is included in fink (in package debianutils) supports the -f switch, so a mac with fink doesn't suffer from this issue (asuming /sw/sbin is before /usr/bin in the search PATH).