Bug with named dirs in prompt expansion

Bug with named dirs in prompt expansion

[Manuel Presnitz]

Dear all,

is it just me, or is there a bug in the "%~" prompt expansion:

$ export PS1='%~> '
~> zsh -f
~> cd /tmp
/tmp> fooo=$PWD
/tmp> : ~fooo
/tmp> foo=$PWD
/tmp> : ~foo
~foo> hash -d | grep tmp
foo=/tmp
fooo=/tmp
~foo>

I would expect that after ": ~fooo" the prompt changes to "~fooo>", but it doesn't.
With one "o" less it's working. But both variant, i.e. "fooo" and "foo", are listed in
the named dir hash, and "cd ~fooo" is working, too.

I seems to depend on the length of the path-string, because in /tmp1 this works:
/tmp1> fooo=$PWD
/tmp1> : ~fooo
~fooo>

But with one character more, i.e. length(namedir) > lentgh(tmp1), it fails again.

Although I use named dirs a lot, I never came about a problem in "real life",
probably because the named dir names are usually shorter than the path;
this issue was originally raised here: http://superuser.com/q/624603/195224
I tried to boil it down to a minimal example.

The behavior above is reproducable with

$ echo $ZSH_VERSION $ZSH_PATCHLEVEL `uname -mo`
4.3.10 Debian x86_64 GNU/Linux
and
5.0.2-dev-0 zsh-5.0.2-130-gc5d9abc i686 Cygwin

Thanks,
Manuel.

Re: Bug with named dirs in prompt expansion

[Phil Pennock]

On 2013-07-26 at 20:58 +0200, Manuel Presnitz wrote:
> is it just me, or is there a bug in the "%~" prompt expansion:

It's the documented, specified behaviour.  See zshexpn(1):

----------------------------8< cut here >8------------------------------
   Static named directories
[...]
       In  certain  circumstances  (in  prompts, for instance), when the shell
       prints a path, the path is checked to see if it has a  named  directory
       as  its  prefix.  If so, then the prefix portion is replaced with a `~'
       followed by the name of the directory.  The shortest way  of  referring
       to  the  directory is used, with ties broken in favour of using a named
       directory, except when the directory is / itself.  The parameters  $PWD
       and $OLDPWD are never abbreviated in this fashion.
----------------------------8< cut here >8------------------------------

> I would expect that after ": ~fooo" the prompt changes to "~fooo>", but it doesn't.

The idea of %~ is to find the shortest available name, for a condensed
representation so as to concisely convey to the user where they are.

> this issue was originally raised here: http://superuser.com/q/624603/195224

I've posted a reply.

-Phil

Re[2]: Bug with named dirs in prompt expansion

[Manuel Presnitz]

Phil Pennock hat am 26.07.2013 um 18:31 folgendes geschrieben:

> On 2013-07-26 at 20:58 +0200, Manuel Presnitz wrote:
> > is it just me, or is there a bug in the "%~" prompt expansion:
> 
> The idea of %~ is to find the shortest available name, for a condensed
> representation so as to concisely convey to the user where they are.

So, it's not a bug, but a feature -- I should have anticipated that.
Thanks for clarification!

For my apologies I want to quote the zshmisc manpage, which does
not mention that "shortening":

[ %~ 	As  %d  and  %/, but if the current working directory has a
[	named directory as its prefix, that part is replaced by a `~'
[	followed by the name of the directory.  If it starts with
[	$HOME, that part is replaced by a `~'.


Regards,
Manuel.

Re: Bug with named dirs in prompt expansion

[Phil Pennock]

On 2013-07-27 at 10:24 +0200, Manuel Presnitz wrote:
> For my apologies I want to quote the zshmisc manpage, which does
> not mention that "shortening":

Patches to the doc source are a good way to get involved with the
project.  :)  "See more details under Foo" would avoid violating DRY
while still making the content discoverable.

Re[4]: Bug with named dirs in prompt expansion

[Manuel Presnitz]

Phil Pennock hat am 27.07.2013 um 18:15 folgendes geschrieben:

> On 2013-07-27 at 10:24 +0200, Manuel Presnitz wrote:
> > For my apologies I want to quote the zshmisc manpage, which does
> > not mention that "shortening":
>
> Patches to the doc source are a good way to get involved with the
> project.  :)  "See more details under Foo" would avoid violating DRY
> while still making the content discoverable.

Thanks for the encouragement. Before posting with [PATCH] subject,
I'd like to have a second opinion, because I do not understand the
expression "with ties broken in favour of " in the current doc. Perhaps
other non-native speakers have the same problem, so I simplyfied it very
much, but it can be completely wrong now:

Current doc (Static named directories in zshexpn):
[ In  certain  circumstances  (in  prompts, for instance), when the shell
[ prints a path, the path is checked to see if it has a  named  directory
[ as  its  prefix.  If so, then the prefix portion is replaced with a `~'
[ followed by the name of the directory.  The shortest way  of  referring
[ to  the  directory is used, with ties broken in favour of using a named
[ directory, except when the directory is / itself

My proposal:
[ When  the  shell  prints a path (e.g. when expanding %~ in prompts or
[ when printing the directory stack), the path is checked to see if it has a
[ named directory as its prefix.  If so, then the prefix portion is replaced
[ with a `~' followed by  the  name  of  the  directory.   The  shortest  way
[ of referring to the directory is used, so either the directory name or the full
[ path.

I also deleted the part "except when the directory is / itself". It seems
unnecessary to me, because a named directory (>= 2 chars) can never be
shorter than "/".

Is there another case, where this applies -- apart from expanding %~ and
printing the directory stack? (I tried to figure it out by grepping the source
code and the man pages, but I failed.)

Because the prompt expansion %~ is IMHO the most important case wherer
the "shell prints a path", I propose a small repetition (despite of DRY),
where as for "dirs" a reference is enough.

I also mentioned $HOME replacement first, this should be much more
common than named directories.

Current doc (SIMPLE PROMPT ESCAPES (%~) in zshmisc)
[ As %d and %/, but if the current working directory has a named                                                                            
[ directory as its prefix, that part is replaced by a `~' followed by                                                                            
[ the name of the directory.  If it starts with $HOME, that part is                                                                            
[ replaced by a `~'.

My proposal:
[ As %d and %/, but if the current working directory starts with
[ $HOME, that part is replaced by a `~'. Furthermore, if  it has  a  named
[ directory as its prefix, that part is replaced by a `~' followed by the name
[ of the directory, but only if the result is shorter compared to the full path;
[ see Dynamic and Static named directories in zshexpn(1).


Thanks,
Manuel.



----
diff --git a/Doc/Zsh/builtins.yo b/Doc/Zsh/builtins.yo
index 3623f9b..8e46a88 100644
--- a/Doc/Zsh/builtins.yo
+++ b/Doc/Zsh/builtins.yo
@@ -277,7 +277,9 @@ item(tt(-c))(
 clear the directory stack.
 )
 item(tt(-l))(
-print directory names in full instead of using of using tt(~) expressions.
+print directory names in full instead of using of using tt(~) expressions (\
+ifzman(see em(Dynamic) and em(Static named directories) in zmanref(zshexpn))\
+ifnzman(noderef(Filename Expansion))).
 )
 item(tt(-p))(
 print directory entries one per line.
diff --git a/Doc/Zsh/expn.yo b/Doc/Zsh/expn.yo
index e8d1ed2..9da46bd 100644
--- a/Doc/Zsh/expn.yo
+++ b/Doc/Zsh/expn.yo
@@ -1708,14 +1708,13 @@ Note that trailing slashes will be removed from the path to the directory
 It is also possible to define directory names using the tt(-d) option to the
 tt(hash) builtin.

-In certain circumstances (in prompts, for instance), when the shell
-prints a path, the path is checked to see if it has a named
-directory as its prefix.  If so, then the prefix portion
-is replaced with a `tt(~)' followed by the name of the directory.
-The shortest way of referring to the directory is used,
-with ties broken in favour of using a named directory,
-except when the directory is tt(/) itself.  The parameters tt($PWD) and
-tt($OLDPWD) are never abbreviated in this fashion.
+When the shell prints a path (e.g. when expanding tt(%~) in prompts or when
+printing the directory stack), the path is checked to see if it has a named
+directory as its prefix.  If so, then the prefix portion is replaced with a
+`tt(~)' followed by the name of the directory.
+The shortest way of referring to the directory is used, so either the directory
+name or the full path.
+The parameters tt($PWD) and tt($OLDPWD) are never abbreviated in this fashion.

 subsect(`=' expansion)

diff --git a/Doc/Zsh/prompt.yo b/Doc/Zsh/prompt.yo
index 8d79795..a6b9201 100644
--- a/Doc/Zsh/prompt.yo
+++ b/Doc/Zsh/prompt.yo
@@ -100,10 +100,13 @@ directory to show; zero means the whole path.  A negative integer
 specifies leading components, i.e. tt(%-1d) specifies the first component.
 )
 item(tt(%~))(
-As tt(%d) and tt(%/), but if the current working directory has a named
+As tt(%d) and tt(%/), but if the current working directory starts with
+tt($HOME), that part is replaced by a `tt(~)'. Furthermore, if it has a named
 directory as its prefix, that part is replaced by a `tt(~)' followed by
-the name of the directory.  If it starts with tt($HOME), that part is
-replaced by a `tt(~)'.
+the name of the directory, but only if the result is shorter compared
+to the full path;
+ifzman(see em(Dynamic) and em(Static named directories) in zmanref(zshexpn))\
+ifnzman(noderef(Filename Expansion)).
 )
 xitem(tt(%h))
 item(tt(%!))(