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PATCH: `try' syntax
- X-seq: zsh-workers 20036
- From: Peter Stephenson <pws@xxxxxxx>
- To: zsh-workers@xxxxxxxxxx (Zsh hackers list)
- Subject: PATCH: `try' syntax
- Date: Mon, 14 Jun 2004 12:23:38 +0100
- Mailing-list: contact zsh-workers-help@xxxxxxxxxx; run by ezmlm
Here's an experimental and possibly controversial (though, I think,
working) new syntax for running code protected from error and other
conditions in an internal block. Dave Yost suggested something like
this, but I've been missing it for a long time. Traps are too clumsy to
provide good protection against errors or interrupts.
The basic idea is:
:try
# Code here runs normally
:always
# Code here always gets run, even if there is a fatal
# error (unless it crashes the shell), or a return, break,
# or continue in the :try block.
#
# Optionally:
unset -e
# removes any error condition. Apart from that, after exiting
# the always block, the logic is as if it hadn't been present.
:tried
Thus it's a bit more like an unwind-protect in Lisp than exception
catching, which is why I deliberately avoided using `catch' in the
name. (The name `always' was probably suggested by Verilog but
it has a completely different meaning.)
The trickiest bit is the naming. I wanted something reasonably
memorable, but without polluting the name space, hence the names
with the colons in front. Note that `disable -r :try :always :tried'
works.
Index: Doc/Zsh/builtins.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/builtins.yo,v
retrieving revision 1.68
diff -u -r1.68 builtins.yo
--- Doc/Zsh/builtins.yo 21 May 2004 20:04:59 -0000 1.68
+++ Doc/Zsh/builtins.yo 14 Jun 2004 11:11:22 -0000
@@ -1472,8 +1472,10 @@
)
findex(unset)
cindex(parameters, unsetting)
-item(tt(unset) [ tt(-fmv) ] var(name) ...)(
-Each named parameter is unset.
+cindex(error condition, resetting)
+xitem(tt(unset) [ tt(-fmv) ] var(name) ...)
+item(tt(unset -e))(
+In the first form, each named parameter is unset.
Local parameters remain local even if unset; they appear unset within scope,
but the previous value will still reappear when the scope ends.
@@ -1490,6 +1492,11 @@
default behaviour.
tt(unset -f) is equivalent to tt(unfunction).
+
+tt(unset -e) may only be used in an tt(:always) block of a tt(:try)
+construct, as described in
+ifzman(the section em(Complex Commands) in zmanref(zshmisc))\
+ifnzman(noderef(Complex Commands))
)
findex(unsetopt)
cindex(options, unsetting)
Index: Doc/Zsh/grammar.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/grammar.yo,v
retrieving revision 1.8
diff -u -r1.8 grammar.yo
--- Doc/Zsh/grammar.yo 24 Jul 2001 13:16:09 -0000 1.8
+++ Doc/Zsh/grammar.yo 14 Jun 2004 11:11:26 -0000
@@ -250,6 +250,33 @@
there is a single var(word); otherwise, the parentheses will be treated as
forming a globbing pattern in that case.
)
+findex(:always)
+findex(:try)
+cindex(always blocks)
+cindex(try blocks)
+item(tt(:try) var(try-list) tt(:always) var(always-list) tt(:tried))(
+First var(try-list) is executed. Regardless of errors, or tt(break),
+tt(continue), or tt(return) commands encountered within var(try-list),
+var(always-list) is then executed. Execution then continues from the
+result of the execution of var(try-list); in other words, any error,
+or tt(break), tt(continue), or tt(return) command is treated in the
+normal way, as if the tt(:try) statement and tt(:always) block were not
+present.
+
+Newlines or semicolons may optionally appear between the tt(:try:)
+or tt(:always:) and the following list.
+
+The command `tt(unset -e)' may be used within the tt(:always) block to
+unset any error condition caused by the tt(:try) block. Hence the
+following idiom causes errors in var(commands...) to be ignored, without
+the need to run var(commands...) in a subshell.
+
+example(:try
+ var(commands)
+:always
+ unset -e
+:tried)
+)
cindex(timing)
findex(time)
item(tt(time) [ var(pipeline) ])(
Index: Functions/MIME/zsh-mime-setup
===================================================================
RCS file: /cvsroot/zsh/zsh/Functions/MIME/zsh-mime-setup,v
retrieving revision 1.1
diff -u -r1.1 zsh-mime-setup
--- Functions/MIME/zsh-mime-setup 14 Sep 2003 19:37:35 -0000 1.1
+++ Functions/MIME/zsh-mime-setup 14 Jun 2004 11:11:26 -0000
@@ -62,9 +62,8 @@
zstyle -a :mime: mailcap cap_files ||
cap_files=(~/.mailcap /etc/mailcap)
-TRAPEXIT() { unfunction mime-setup-add-type >&/dev/null; return 0; }
-
-mime-setup-add-type() {
+:try
+ mime-setup-add-type() {
local type suffix
local -a array
@@ -90,115 +89,117 @@
fi
fi
done
-}
+ }
-# Loop through files to find suffixes for MIME types.
-# Earlier entries take precedence, so the files need to be listed
-# with the user's own first. This also means pre-existing
-# values in suffix_type_map are respected.
-for file in $type_files; do
+ # Loop through files to find suffixes for MIME types.
+ # Earlier entries take precedence, so the files need to be listed
+ # with the user's own first. This also means pre-existing
+ # values in suffix_type_map are respected.
+ for file in $type_files; do
[[ -r $file ]] || continue
# For once we rely on the fact that read handles continuation
# lines ending in backslashes, i.e. there's no -r.
while read line; do
- # Skip blank or comment lines.
- [[ $line = [[:space:]]#(\#*|) ]] && continue
-
- # There are two types of line you find in MIME type files.
- # The original simple sort contains the type name then suffixes
- # separated by whitespace. However, Netscape insists
- # on adding lines with backslash continuation with
- # key="value" pairs. So we'd better handle both.
- if [[ $line = *=* ]]; then
- # Gory.
- # This relies on the fact that a typical entry:
- # type=video/x-mpeg2 desc="MPEG2 Video" exts="mpv2,mp2v"
- # looks like a parameter assignment. However, we really
- # don't want to be screwed up by future extensions,
- # so we split the elements to an array and pick out the
- # ones we're interested in.
- type= exts=
-
- # Syntactically split line to preserve quoted words.
- array=(${(z)line})
- for elt in $array; do
- if [[ $elt = (type|exts)=* ]]; then
- eval $elt
- fi
- done
+ # Skip blank or comment lines.
+ [[ $line = [[:space:]]#(\#*|) ]] && continue
- # Get extensions by splitting on comma
- array=(${(s.,.)exts})
-
- [[ -n $type ]] && mime-setup-add-type $type $array
- else
- # Simple.
- mime-setup-add-type ${=line}
- fi
+ # There are two types of line you find in MIME type files.
+ # The original simple sort contains the type name then suffixes
+ # separated by whitespace. However, Netscape insists
+ # on adding lines with backslash continuation with
+ # key="value" pairs. So we'd better handle both.
+ if [[ $line = *=* ]]; then
+ # Gory.
+ # This relies on the fact that a typical entry:
+ # type=video/x-mpeg2 desc="MPEG2 Video" exts="mpv2,mp2v"
+ # looks like a parameter assignment. However, we really
+ # don't want to be screwed up by future extensions,
+ # so we split the elements to an array and pick out the
+ # ones we're interested in.
+ type= exts=
+
+ # Syntactically split line to preserve quoted words.
+ array=(${(z)line})
+ for elt in $array; do
+ if [[ $elt = (type|exts)=* ]]; then
+ eval $elt
+ fi
+ done
+
+ # Get extensions by splitting on comma
+ array=(${(s.,.)exts})
+
+ [[ -n $type ]] && mime-setup-add-type $type $array
+ else
+ # Simple.
+ mime-setup-add-type ${=line}
+ fi
done <$file
-done
-
+ done
+:always
+ unfunction mime-setup-add-type >&/dev/null
+:tried
# Loop through files to find handlers for types.
for file in $cap_files; do
- [[ -r $file ]] || continue
+ [[ -r $file ]] || continue
- # Oh, great. We need to preserve backslashes inside the line,
- # but need to manage continuation lines.
- while read -r line; do
- # Skip blank or comment lines.
- [[ $line = [[:space:]]#(\#*|) ]] && continue
-
- while [[ $line = (#b)(*)\\ ]]; do
- line=$match[1]
- read -r line2 || break
- line+=$line2
- done
-
- # Guess what, this file has a completely different format.
- # See mailcap(4).
- # The biggest unpleasantness here is that the fields are
- # delimited by semicolons, but the command field, which
- # is the one we want to extract, may itself contain backslashed
- # semicolons.
- if [[ $line = (#b)[[:space:]]#([^[:space:]\;]##)[[:space:]]#\;(*) ]]
- then
- # this is the only form we can handle, but there's no point
- # issuing a warning for other forms.
- type=$match[1]
- line=$match[2]
- # See if it has flags after the command.
- if [[ $line = (#b)(([^\;\\]|\\\;|\\[^\;])#)\;(*) ]]; then
- line=$match[1]
- flags=$match[3]
- else
- flags=
- fi
- # Remove quotes from semicolons
- line=${line//\\\;/\;}
- # and remove any surrounding white space --- this might
- # make the handler empty.
- line=${${line##[[:space:]]#}%%[[:space:]]}
- if [[ -z $type_handler_map[$type] ]]; then
- if [[ -n $o_verbose ]]; then
- print -r "Adding handler for type $type:
+ # Oh, great. We need to preserve backslashes inside the line,
+ # but need to manage continuation lines.
+ while read -r line; do
+ # Skip blank or comment lines.
+ [[ $line = [[:space:]]#(\#*|) ]] && continue
+
+ while [[ $line = (#b)(*)\\ ]]; do
+ line=$match[1]
+ read -r line2 || break
+ line+=$line2
+ done
+
+ # Guess what, this file has a completely different format.
+ # See mailcap(4).
+ # The biggest unpleasantness here is that the fields are
+ # delimited by semicolons, but the command field, which
+ # is the one we want to extract, may itself contain backslashed
+ # semicolons.
+ if [[ $line = (#b)[[:space:]]#([^[:space:]\;]##)[[:space:]]#\;(*) ]]
+ then
+ # this is the only form we can handle, but there's no point
+ # issuing a warning for other forms.
+ type=$match[1]
+ line=$match[2]
+ # See if it has flags after the command.
+ if [[ $line = (#b)(([^\;\\]|\\\;|\\[^\;])#)\;(*) ]]; then
+ line=$match[1]
+ flags=$match[3]
+ else
+ flags=
+ fi
+ # Remove quotes from semicolons
+ line=${line//\\\;/\;}
+ # and remove any surrounding white space --- this might
+ # make the handler empty.
+ line=${${line##[[:space:]]#}%%[[:space:]]}
+ if [[ -z $type_handler_map[$type] ]]; then
+ if [[ -n $o_verbose ]]; then
+ print -r "Adding handler for type $type:
$line" >&2
- fi
- type_handler_map[$type]=$line
- type_flags_map[$type]=$flags
- if [[ -n $flags && -n $o_verbose ]]; then
- print -r " with flags $flags" >&2
- fi
- elif [[ -n $o_verbose ]]; then
- print -r "Skipping handler for already defined type $type:
+ fi
+ type_handler_map[$type]=$line
+ type_flags_map[$type]=$flags
+ if [[ -n $flags && -n $o_verbose ]]; then
+ print -r " with flags $flags" >&2
+ fi
+ elif [[ -n $o_verbose ]]; then
+ print -r "Skipping handler for already defined type $type:
$line" >&2
- if [[ -n $flags ]]; then
- print -r " with flags $flags" >&2
- fi
- fi
+ if [[ -n $flags ]]; then
+ print -r " with flags $flags" >&2
fi
- done <$file
+ fi
+ fi
+ done <$file
done
Index: Src/builtin.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/builtin.c,v
retrieving revision 1.121
diff -u -r1.121 builtin.c
--- Src/builtin.c 2 Jun 2004 22:14:25 -0000 1.121
+++ Src/builtin.c 14 Jun 2004 11:11:34 -0000
@@ -125,7 +125,7 @@
BUILTIN("unalias", 0, bin_unhash, 1, -1, 0, "ms", "a"),
BUILTIN("unfunction", 0, bin_unhash, 1, -1, 0, "m", "f"),
BUILTIN("unhash", 0, bin_unhash, 1, -1, 0, "adfms", NULL),
- BUILTIN("unset", BINF_PSPECIAL, bin_unset, 1, -1, 0, "fmv", NULL),
+ BUILTIN("unset", BINF_PSPECIAL, bin_unset, 0, -1, 0, "efmv", NULL),
BUILTIN("unsetopt", 0, bin_setopt, 0, -1, BIN_UNSETOPT, NULL, NULL),
BUILTIN("wait", 0, bin_fg, 0, -1, BIN_WAIT, NULL, NULL),
BUILTIN("whence", 0, bin_whence, 0, -1, 0, "acmpvfsw", NULL),
@@ -2614,6 +2614,23 @@
int match = 0, returnval = 0;
int i;
+ if (OPT_ISSET(ops,'e')) {
+ if (*argv) {
+ zwarnnam(name, "arguments not allowed with -e", NULL, 0);
+ return 1;
+ }
+ if (try_errflag < 0) {
+ zwarnnam(name, "-e can only be used in an :always block", NULL, 0);
+ return 1;
+ }
+ try_errflag = 0;
+ return 0;
+ }
+ if (!*argv) {
+ zwarnnam(name, "not enough arguments", NULL, 0);
+ return 1;
+ }
+
/* unset -f is the same as unfunction */
if (OPT_ISSET(ops,'f'))
return bin_unhash(name, argv, ops, func);
Index: Src/exec.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/exec.c,v
retrieving revision 1.64
diff -u -r1.64 exec.c
--- Src/exec.c 2 Jun 2004 22:14:25 -0000 1.64
+++ Src/exec.c 14 Jun 2004 11:11:39 -0000
@@ -137,10 +137,10 @@
/* Execution functions. */
-static int (*execfuncs[]) _((Estate, int)) = {
+static int (*execfuncs[WC_COUNT-WC_CURSH]) _((Estate, int)) = {
execcursh, exectime, execfuncdef, execfor, execselect,
execwhile, execrepeat, execcase, execif, execcond,
- execarith, execautofn
+ execarith, execautofn, exectry
};
/* structure for command builtin for when it is used with -v or -V */
Index: Src/hashtable.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/hashtable.c,v
retrieving revision 1.20
diff -u -r1.20 hashtable.c
--- Src/hashtable.c 2 Jun 2004 22:14:25 -0000 1.20
+++ Src/hashtable.c 14 Jun 2004 11:11:40 -0000
@@ -946,6 +946,9 @@
{NULL, "time", 0, TIME},
{NULL, "until", 0, UNTIL},
{NULL, "while", 0, WHILE},
+ {NULL, ":try", 0, TRY},
+ {NULL, ":always", 0, ALWAYS},
+ {NULL, ":tried", 0, TRIED},
{NULL, NULL, 0, 0}
};
Index: Src/loop.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/loop.c,v
retrieving revision 1.13
diff -u -r1.13 loop.c
--- Src/loop.c 2 Jun 2004 22:14:26 -0000 1.13
+++ Src/loop.c 14 Jun 2004 11:11:41 -0000
@@ -616,3 +616,64 @@
return lastval;
}
+
+/* Errflag from :try block, may be reset in :always block. */
+
+/**/
+int
+try_errflag = -1;
+
+/**/
+int
+exectry(Estate state, int do_exec)
+{
+ Wordcode end, always;
+ int endval;
+ int save_try_errflag, save_retflag, save_breaks, save_loops, save_contflag;
+
+ end = state->pc + WC_TRY_SKIP(state->pc[-1]);
+ always = state->pc + 1 + WC_TRY_SKIP(*state->pc);
+ state->pc++;
+ pushheap();
+ cmdpush(CS_TRY);
+
+ /* The :try clause */
+ execlist(state, 1, do_exec);
+
+ /* Don't record errflag here, may be reset. */
+ endval = lastval;
+
+ freeheap();
+
+ cmdpop();
+ cmdpush(CS_ALWAYS);
+
+ /* The :always clause. */
+ save_try_errflag = try_errflag;
+ try_errflag = errflag;
+ errflag = 0;
+ save_retflag = retflag;
+ retflag = 0;
+ save_breaks = breaks;
+ breaks = 0;
+ save_loops = loops;
+ loops = 0;
+ save_contflag = contflag;
+ contflag = 0;
+
+ state->pc = always;
+ execlist(state, 1, do_exec);
+
+ errflag = try_errflag;
+ try_errflag = save_try_errflag;
+ retflag = save_retflag;
+ breaks = save_breaks;
+ loops = save_loops;
+ contflag = save_contflag;
+
+ cmdpop();
+ popheap();
+ state->pc = end;
+
+ return endval || errflag;
+}
Index: Src/parse.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/parse.c,v
retrieving revision 1.44
diff -u -r1.44 parse.c
--- Src/parse.c 2 Jun 2004 22:14:26 -0000 1.44
+++ Src/parse.c 14 Jun 2004 11:11:43 -0000
@@ -760,7 +760,7 @@
}
/*
- * cmd : { redir } ( for | case | if | while | repeat |
+ * cmd : { redir } ( for | case | if | while | repeat | try
* subsh | funcdef | time | dinbrack | dinpar | simple ) { redir }
*/
@@ -819,6 +819,11 @@
par_repeat(complex);
cmdpop();
break;
+ case TRY:
+ cmdpush(CS_TRY);
+ par_try(complex);
+ cmdpop();
+ break;
case INPAR:
*complex = 1;
cmdpush(CS_SUBSH);
@@ -1330,6 +1335,49 @@
}
/*
+ * try : TRY list ALWAYS list TRIED
+ */
+
+/**/
+static void
+par_try(int *complex)
+{
+ int oecused = ecused, p, pp;
+
+ p = ecadd(0);
+ pp = ecadd(0);
+
+ do {
+ yylex();
+ } while (tok == SEPER);
+
+ par_save_list(complex);
+ ecbuf[pp] = WCB_TRY(ecused - 1 - pp);
+
+ incmdpos = 1;
+
+ while (tok == SEPER)
+ yylex();
+
+ if (tok != ALWAYS)
+ YYERRORV(oecused);
+
+ cmdpop();
+ cmdpush(CS_ALWAYS);
+ yylex();
+ par_save_list(complex);
+ while (tok == SEPER)
+ yylex();
+
+ incmdpos = 1;
+
+ if (tok != TRIED)
+ YYERRORV(oecused);
+ yylex();
+ ecbuf[p] = WCB_TRY(ecused - 1 - p);
+}
+
+/*
* subsh : ( INPAR | INBRACE ) list ( OUTPAR | OUTBRACE )
*/
Index: Src/prompt.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/prompt.c,v
retrieving revision 1.18
diff -u -r1.18 prompt.c
--- Src/prompt.c 28 May 2004 19:21:46 -0000 1.18
+++ Src/prompt.c 14 Jun 2004 11:11:44 -0000
@@ -49,7 +49,7 @@
/* parser states, for %_ */
-static char *cmdnames[] = {
+static char *cmdnames[CS_COUNT] = {
"for", "while", "repeat", "select",
"until", "if", "then", "else",
"elif", "math", "cond", "cmdor",
@@ -57,7 +57,8 @@
"case", "function", "subsh", "cursh",
"array", "quote", "dquote", "bquote",
"cmdsubst", "mathsubst", "elif-then", "heredoc",
- "heredocd", "brace", "braceparam",
+ "heredocd", "brace", "braceparam", ":try",
+ ":always"
};
/* The buffer into which an expanded and metafied prompt is being written, *
Index: Src/text.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/text.c,v
retrieving revision 1.13
diff -u -r1.13 text.c
--- Src/text.c 4 Feb 2003 11:23:05 -0000 1.13
+++ Src/text.c 14 Jun 2004 11:11:45 -0000
@@ -721,6 +721,31 @@
taddstr("))");
stack = 1;
break;
+ case WC_TRY:
+ if (!s) {
+ taddstr(":try");
+ /*
+ * skip location of end of first list, we will
+ * go all the way through it since we're just printing.
+ */
+ state->pc++;
+ tindent++;
+ taddnl();
+ tpush(code, 0);
+ } else if (!s->pop) {
+ tindent--;
+ taddnl();
+ taddstr(":always");
+ tindent++;
+ taddnl();
+ s->pop = 1;
+ } else {
+ tindent--;
+ taddnl();
+ taddstr(":tried");
+ stack = 1;
+ }
+ break;
case WC_END:
stack = 1;
break;
Index: Src/zsh.h
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/zsh.h,v
retrieving revision 1.56
diff -u -r1.56 zsh.h
--- Src/zsh.h 20 Apr 2004 12:11:16 -0000 1.56
+++ Src/zsh.h 14 Jun 2004 11:11:47 -0000
@@ -226,7 +226,10 @@
THEN, /* then */
TIME, /* time */
UNTIL, /* until */ /* 60 */
- WHILE /* while */
+ WHILE, /* while */
+ TRY, /* :try */
+ ALWAYS, /* :always */
+ TRIED /* :tried */
};
/* Redirection types. If you modify this, you may also have to modify *
@@ -580,6 +583,10 @@
#define WC_COND 17
#define WC_ARITH 18
#define WC_AUTOFN 19
+#define WC_TRY 20
+
+/* increment as necessary */
+#define WC_COUNT 21
#define WCB_END() wc_bld(WC_END, 0)
@@ -657,6 +664,9 @@
#define WC_REPEAT_SKIP(C) wc_data(C)
#define WCB_REPEAT(O) wc_bld(WC_REPEAT, (O))
+#define WC_TRY_SKIP(C) wc_data(C)
+#define WCB_TRY(O) wc_bld(WC_TRY, (O))
+
#define WC_CASE_TYPE(C) (wc_data(C) & 3)
#define WC_CASE_HEAD 0
#define WC_CASE_OR 1
@@ -1695,6 +1705,11 @@
#define CS_HEREDOCD 28
#define CS_BRACE 29
#define CS_BRACEPAR 30
+#define CS_TRY 31
+#define CS_ALWAYS 32
+
+/* Increment as necessary */
+#define CS_COUNT 33
/*********************
* Memory management *
--
Peter Stephenson <pws@xxxxxxx> Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK Tel: +44 (0)1223 692070
**********************************************************************
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