PATCH: cd -q (was Re: _canonical_path ...)

[Peter Stephenson <pws@csr.com>]

On Thu, 27 Mar 2008 11:25:06 +0000
Peter Stephenson <pws@csr.com> wrote:
> I thought unfunction was silent if a function didn't exist, as is now
> true of (and required for) unset, but apparently not.
> +_canonical_paths_pwd() {
> +  # Get the canonical directory name by changing to it.
> +  # To be run in a subshell.
> +  (( ${+functions[chpwd]} )) && unfunction chpwd
> +  setopt CHASE_LINKS
> +  cd $1 2>/dev/null && pwd
> +}

The more I think about this (and I'd really like to stop now), the more
wrong it seems to me that it's so hard to get the shell to cd without
side effects.  Indeed, the patch above is incomplete since it omits
the new chpwd_functions array, and I haven't work out a foolproof
way of suppressing the effect of chpwd without forking the shell.
chpwd will typically print a bogus directory to the terminal title
bar, which is to be avoided; but it can in principle do anything
and if we're not sticking around in the directory the interactive
environment really doesn't need to care about the cd.

Any comments about the following proposal, which adds the -q option
to all relevant functions?  If it looks OK, I'll change the function
above to unsetopt PUSHD_NO_DUPS and use pushd -q/popd -q to sanitize
the directory with REPLY=$PWD and remove the fork.

Index: Doc/Zsh/builtins.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/builtins.yo,v
retrieving revision 1.103
diff -u -r1.103 builtins.yo
--- Doc/Zsh/builtins.yo	1 Feb 2008 19:59:45 -0000	1.103
+++ Doc/Zsh/builtins.yo	27 Mar 2008 11:49:30 -0000
@@ -152,9 +152,9 @@
 module(cap)(zsh/cap)
 findex(cd)
 cindex(directories, changing)
-xitem(tt(cd) [ tt(-sLP) ] [ var(arg) ])
-xitem(tt(cd) [ tt(-sLP) ] var(old) var(new))
-item(tt(cd) [ tt(-sLP) ] {tt(PLUS())|tt(-)}var(n))(
+xitem(tt(cd) [ tt(-qsLP) ] [ var(arg) ])
+xitem(tt(cd) [ tt(-qsLP) ] var(old) var(new))
+item(tt(cd) [ tt(-qsLP) ] {tt(PLUS())|tt(-)}var(n))(
 Change the current directory.  In the first form, change the
 current directory to var(arg), or to the value of tt($HOME) if
 var(arg) is not specified.  If var(arg) is `tt(-)', change to the
@@ -189,6 +189,11 @@
 If the tt(PUSHD_MINUS) option is set, the meanings of `tt(PLUS())'
 and `tt(-)' in this context are swapped.
 
+If the tt(-q) (quiet) option is specified, the hook function tt(chpwd)
+and the functions in the array tt(chpwd_functions) are not called.
+This is useful for calls to tt(cd) that do not change the environment
+seen by an interactive user.
+
 If the tt(-s) option is specified, tt(cd) refuses to change the current
 directory if the given pathname contains symlinks.  If the tt(-P) option
 is given or the tt(CHASE_LINKS) option is set, symbolic links are resolved
@@ -795,7 +800,7 @@
 )
 prefix(noglob)
 findex(popd)
-item(tt(popd) [ {tt(PLUS())|tt(-)}var(n) ])(
+item(tt(popd) [ [-q] {tt(PLUS())|tt(-)}var(n) ])(
 Remove an entry from the directory stack, and perform a tt(cd) to
 the new top directory.  With no argument, the current top entry is
 removed.  An argument of the form `tt(PLUS())var(n)' identifies a stack
@@ -804,6 +809,11 @@
 pindex(PUSHD_MINUS, use of)
 If the tt(PUSHD_MINUS) option is set, the meanings of `tt(PLUS())' and
 `tt(-)' in this context are swapped.
+
+If the tt(-q) (quiet) option is specified, the hook function tt(chpwd)
+and the functions in the array tt($chpwd_functions) are not called,
+and the new directory stack is not printed.  This is useful for calls to
+tt(popd) that do not change the environment seen by an interactive user.
 )
 findex(print)
 xitem(tt(print) [ tt(-abcDilmnNoOpPrsz) ] [ tt(-u) var(n) ] [ tt(-f) var(format) ] [ tt(-C) var(cols) ])
@@ -935,9 +945,9 @@
 pindex(PUSHD_MINUS, use of)
 pindex(CDABLE_VARS, use of)
 pindex(PUSHD_SILENT, use of)
-xitem(tt(pushd) [ tt(-sLP) ] [ var(arg) ])
-xitem(tt(pushd) [ tt(-sLP) ] var(old) var(new))
-item(tt(pushd) [ tt(-sLP) ] {tt(PLUS())|tt(-)}var(n))(
+xitem(tt(pushd) [ tt(-qsLP) ] [ var(arg) ])
+xitem(tt(pushd) [ tt(-qsLP) ] var(old) var(new))
+item(tt(pushd) [ tt(-qsLP) ] {tt(PLUS())|tt(-)}var(n))(
 Change the current directory, and push the old current directory
 onto the directory stack.  In the first form, change the
 current directory to var(arg).
@@ -956,8 +966,14 @@
 from the right.  If the tt(PUSHD_MINUS) option is set, the meanings
 of `tt(PLUS())' and `tt(-)' in this context are swapped.
 
-If the option tt(PUSHD_SILENT) is not set, the directory
-stack will be printed after a tt(pushd) is performed.
+If the tt(-q) (quiet) option is specified, the hook function tt(chpwd)
+and the functions in the array tt($chpwd_functions) are not called,
+and the new directory stack is not printed.  This is useful for calls to
+tt(pushd) that do not change the environment seen by an interactive user.
+
+If the option tt(-q) is not specified and the shell option tt(PUSHD_SILENT)
+is not set, the directory stack will be printed after a tt(pushd) is
+performed.
 
 The options tt(-s), tt(-L) and tt(-P) have the same meanings as for the
 tt(cd) builtin.
Index: Src/builtin.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/builtin.c,v
retrieving revision 1.188
diff -u -r1.188 builtin.c
--- Src/builtin.c	2 Mar 2008 21:21:53 -0000	1.188
+++ Src/builtin.c	27 Mar 2008 11:49:31 -0000
@@ -50,8 +50,8 @@
     BUILTIN("bg", 0, bin_fg, 0, -1, BIN_BG, NULL, NULL),
     BUILTIN("break", BINF_PSPECIAL, bin_break, 0, 1, BIN_BREAK, NULL, NULL),
     BUILTIN("bye", 0, bin_break, 0, 1, BIN_EXIT, NULL, NULL),
-    BUILTIN("cd", BINF_SKIPINVALID | BINF_SKIPDASH | BINF_DASHDASHVALID, bin_cd, 0, 2, BIN_CD, "sPL", NULL),
-    BUILTIN("chdir", BINF_SKIPINVALID | BINF_SKIPDASH | BINF_DASHDASHVALID, bin_cd, 0, 2, BIN_CD, "sPL", NULL),
+    BUILTIN("cd", BINF_SKIPINVALID | BINF_SKIPDASH | BINF_DASHDASHVALID, bin_cd, 0, 2, BIN_CD, "qsPL", NULL),
+    BUILTIN("chdir", BINF_SKIPINVALID | BINF_SKIPDASH | BINF_DASHDASHVALID, bin_cd, 0, 2, BIN_CD, "qsPL", NULL),
     BUILTIN("continue", BINF_PSPECIAL, bin_break, 0, 1, BIN_CONTINUE, NULL, NULL),
     BUILTIN("declare", BINF_PLUSOPTS | BINF_MAGICEQUALS | BINF_PSPECIAL, bin_typeset, 0, -1, 0, "AE:%F:%HL:%R:%TUZ:%afghi:%klmprtuxz", NULL),
     BUILTIN("dirs", 0, bin_dirs, 0, -1, 0, "clpv", NULL),
@@ -98,10 +98,10 @@
     BUILTIN("patdebug", 0, bin_patdebug, 1, -1, 0, "p", NULL),
 #endif
 
-    BUILTIN("popd", 0, bin_cd, 0, 1, BIN_POPD, NULL, NULL),
+    BUILTIN("popd", BINF_SKIPINVALID | BINF_SKIPDASH | BINF_DASHDASHVALID, bin_cd, 0, 1, BIN_POPD, "q", NULL),
     BUILTIN("print", BINF_PRINTOPTS, bin_print, 0, -1, BIN_PRINT, "abcC:Df:ilmnNoOpPrRsu:z-", NULL),
     BUILTIN("printf", 0, bin_print, 1, -1, BIN_PRINTF, NULL, NULL),
-    BUILTIN("pushd", BINF_SKIPINVALID | BINF_SKIPDASH | BINF_DASHDASHVALID, bin_cd, 0, 2, BIN_PUSHD, "sPL", NULL),
+    BUILTIN("pushd", BINF_SKIPINVALID | BINF_SKIPDASH | BINF_DASHDASHVALID, bin_cd, 0, 2, BIN_PUSHD, "qsPL", NULL),
     BUILTIN("pushln", 0, bin_print, 0, -1, BIN_PRINT, NULL, "-nz"),
     BUILTIN("pwd", 0, bin_pwd, 0, 0, 0, "rLP", NULL),
     BUILTIN("r", 0, bin_fc, 0, -1, BIN_R, "nrl", NULL),
@@ -788,7 +788,7 @@
 	unqueue_signals();
 	return 1;
     }
-    cd_new_pwd(func, dir);
+    cd_new_pwd(func, dir, OPT_ISSET(ops, 'q'));
 
     if (stat(unmeta(pwd), &st1) < 0) {
 	setjobpwd();
@@ -1087,7 +1087,7 @@
 
 /**/
 static void
-cd_new_pwd(int func, LinkNode dir)
+cd_new_pwd(int func, LinkNode dir, int quiet)
 {
     char *new_pwd, *s;
     int dirstacksize;
@@ -1127,7 +1127,7 @@
 
     if (isset(INTERACTIVE)) {
 	if (func != BIN_CD) {
-            if (unset(PUSHDSILENT))
+            if (unset(PUSHDSILENT) && !quiet)
 	        printdirstack();
         } else if (doprintdir) {
 	    fprintdir(pwd, stdout);
@@ -1138,7 +1138,8 @@
     /* execute the chpwd function */
     fflush(stdout);
     fflush(stderr);
-    callhookfunc("chpwd", NULL, 1);
+    if (!quiet)
+	callhookfunc("chpwd", NULL, 1);
 
     dirstacksize = getiparam("DIRSTACKSIZE");
     /* handle directory stack sizes out of range */

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070